Strength and power adaptations of the upper body following 20 training sessions on an eccentric arm-crank ergometer

PURPOSE

Eccentric strength training is an innovative and promising approach to improve exercise performance. However, most eccentric training studies in the past were performed with a focus on the lower extremities. The present study aimed to test the feasibility and effects on strength and power adaptations of a structured upper-body eccentric training program.

METHODS

Fourteen (median age (Q1-Q3) 29 years (27-32); 9 females, 5 males) healthy, regularly exercising individuals performed 20 progressive training sessions (2-3 sessions/week at 20-50% peak power for 8-14 min) on a symmetric eccentric arm-crank ergometer. Before and after the intervention, anaerobic peak power (PP) and maximal concentric aerobic power output (POmax) on an arm-crank ergometer as well as the one repetition maximum (1RM) for bench press were determined as main outcome parameters. A p-value ≤ 0.05 was considered statistically significant.

RESULTS

Significant improvements in PP (+ 4% (1-8), p = 0.007), POmax (+ 6% (0-8); p = 0.01), and 1RM (+ 12% (10-17); p < 0.001) were found. Exercise intensity was relatively low at 64% (55-70) of maximum heart rate.

CONCLUSIONS

Twenty progressive training sessions on a symmetric arm-crank ergometer are effective in inducing significant aerobic and anaerobic performance and strength improvements in the upper body. This intervention is safe and feasible, and can be performed at relatively low cardiovascular intensities. Therefore, this training method offers an interesting approach from elite sports to rehabilitation.

Pain quality patterns in delayed onset muscle soreness of the lower back suggest sensitization of fascia rather than muscle afferents: a secondary analysis study

Delayed onset muscle soreness (DOMS) of the lower back is considered a surrogate for acute low back pain (aLBP) in experimental studies. Of note, it is often unquestioningly assumed to be muscle pain. To date, there has not been a study analyzing lumbar DOMS in terms of its pain origin, which was the aim of this study. Sixteen healthy individuals (L-DOMS) were enrolled for the present study and matched to participants from a previous study (n = 16, L-PAIN) who had undergone selective electrical stimulation of the thoracolumbar fascia and the multifidus muscle. DOMS was induced in the lower back of the L-DOMS group using eccentric trunk extensions performed until exhaustion. On subsequent days, pain on palpation (100-mm analogue scale), pressure pain threshold (PPT), and the Pain Sensation Scale (SES) were used to examine the sensory characteristics of DOMS. Pain on palpation showed a significant increase 24 and 48 h after eccentric training, whereas PPT was not affected (p > 0.05). Factor analysis of L-DOMS and L-PAIN sensory descriptors (SES) yielded a stable three-factor solution distinguishing superficial thermal ("heat pain ") from superficial mechanical pain ("sharp pain") and "deep pain." "Heat pain " and "deep pain" in L-DOMS were almost identical to sensory descriptors from electrical stimulation of fascial tissue (L-PAIN, all p > 0.679) but significantly different from muscle pain (all p < 0.029). The differences in sensory description patterns as well as in PPT and self-reported DOMS for palpation pain scores suggest that DOMS has a fascial rather than a muscular origin.

MRI T2 mapping and shear wave elastography for identifying main pain generator in delayed-onset muscle soreness: muscle or fascia?

INTRODUCTION

The main generator of delayed onset muscle soreness (DOMS) is still unknown. This study aimed to clarify the main generator of DOMS.

METHODS

Twelve participants performed eccentric exercise (EE) on lower legs. MRI and ultrasound were used to assess changes of calf muscle and deep fascia before and after EE. These results were then compared to the muscle pain level.

RESULTS

Compared to baseline, muscle pain peaked at 24-48 h after EE (downstairs 22.25 ± 6.196, 57.917 ± 9.298, F = 291.168, p < 0.01; resting 5.833 ± 1.899, 5.083 ± 2.429, F = 51.678, p < 0.01). Shear wave speed (SWE) of the deep fascia and T2 values of the gastrocnemius muscle and deep fascia all increased and peaked at 48 h after EE (1.960 ± 0.130, F = 22.293; 50.237 ± 2.963, F = 73.172; 66.328 ± 2.968, F = 231.719, respectively, p < 0.01). These measurements were positively correlated with DOMS (downstairs: r = 0.46, 0.76, 0.87, respectively, p < 0.001; resting: r = 0.42, 0.70, 0.77, respectively, p < 0.001). There was a significant positive correlation between SWE and T2 values of deep fascia (r = 0.54, p < 0.01).

CONCLUSION

DOMS is a common result of muscle and fascia injuries. Deep fascia edema and stiffness play a crucial role in DOMS, which can be effectively evaluated MR-T2 and SWE.

CRITICAL RELEVANCE STATEMENT

Delayed-onset muscle soreness is a common result of muscle and deep fascia injuries, in which the edema and stiffness of the deep fascia play a crucial role. Both MRI and shear wave elastography can be effectively used to evaluate soft tissue injuries.

KEY POINTS

• The deep fascia is the major pain generator of delayed-onset muscle soreness. • There is a significant correlation between fascia injury and delayed-onset muscle soreness. • MRI and shear wave elastography are preferred methods for assessing fascia injuries.

[Multiple factors contributing to dysphagia : Extended tasks for the interprofessional team in the intensive care unit]

A stay in the intensive care unit (ICU) can be associated with complications and lead to secondary problems, known as post intensive care syndrome (PICS). They can prolong inpatient stays, increase ICU mortality and lead to long-term problems. One secondarily acquired problem in intensive care is dysphagia. This article highlights various influencing factors on dysphagia. Some require an extended interprofessional treatment concept that goes beyond strictly speech and swallowing therapist treatment.

Dose-response effect of L-citrulline on skeletal muscle damage after acute eccentric exercise: an in vivo study in mice

Background

Eccentric exercise may trigger mechanical stress, resulting in muscle damage that may decrease athletic performance. L-citrulline potentially prevents skeletal muscle damage after acute eccentric exercise. This study aimed to assess the dose-response effect of L-citrulline as a preventive therapy for skeletal muscle damage in mice after acute eccentric exercise.

Methods

This is a controlled laboratory in vivo study with a post-test-only design. Male mice (BALB/c, n = 25) were randomized into the following groups: a normal control (C1) (n = 5); a negative control (C2) with downhill running and placebo intervention (n = 5); treatment groups: T1 (n = 5), T2 (n = 5), and T3 (n = 5), were subjected to downhill running and 250, 500, and 1,000 mg/kg of L-citrulline, respectively, for seven days. Blood plasma was used to determine the levels of TNNI2 and gastrocnemius muscle tissue NOX2, IL-6, and caspase 3 using ELISA. NF-κB and HSP-70 expressions were determined by immunohistochemistry.

Results

Skeletal muscle damage (plasma TNNI2 levels) in mice after eccentric exercise was lower after 250 and 500 mg/kg of L-citrulline. Further, changes in oxidative stress markers, NOX2, were reduced after a 1,000 mg/kg dose. However, a lower level of change has been observed in levels of cellular response markers (NF-κB, HSP-70, IL-6, and caspase 3) after administration of L-citrulline doses of 250, 500, and 1,000 mg/kg.

Conclusion

L-citrulline may prevent skeletal muscle damage in mice after acute eccentric exercise through antioxidant effects as well as inflammatory and apoptotic pathways. In relation to dose-related effects, it was found that L-citrulline doses of 250, 500, and 1,000 mg/kg significantly influenced the expression of NF-κB and HSP-70, as well as the levels of IL-6 and caspase 3. Meanwhile, only doses of 250 and 500 mg/kg had an impact on TNNI2 levels, and the 1,000 mg/kg dose affected NOX2 levels.

Sodium salicylate ameliorates exercise-induced muscle damage in mice by inhibiting NF-kB signaling

BACKGROUND

Eccentric muscle contraction can cause muscle damage, which reduces the efficiency of exercise. Previous evidence suggested that Sodium salicylate (SS) could improve the repair of aged muscle. This study intends to investigate whether SS can impact skeletal muscle damage caused by eccentric exercise.

METHODS

Eccentric treadmill exercise was performed to induce muscle damage in mice. Plasma levels of muscle damage markers were estimated. RT-qPCR was employed for detecting mRNA levels of proinflammatory mediators in murine gastrocnemius muscle. Immunofluorescence staining of laminin/DAPI was utilized for quantifying centrally nucleated myofibers in the gastrocnemius muscle. Western blotting was implemented to examine protein levels of mitsugumin 53 (MG53), matrix metalloproteinase (MMP)-2/9, and NF-κB signaling-related markers.

RESULTS

SS administration reduced muscle damage marker production in the plasma and decreased the levels of proinflammatory mediators, MG53 and MMP-2/9 in mice after exercise. SS alleviated the severity of muscle damage in the gastrocnemius of mice after eccentric exercise. SS blocked NF-κB signaling pathway in the gastrocnemius muscle.

CONCLUSION

SS administration ameliorates skeletal muscle damage caused by eccentric exercise in the mouse model.

Longitudinal assessment of skeletal muscle functional mechanics in the DE50-MD dog model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD), caused by mutations in the dystrophin (DMD) gene, is associated with fatal muscle degeneration and atrophy. Patients with DMD have progressive reductions in skeletal muscle strength and resistance to eccentric muscle stretch. Using the DE50-MD dog model of DMD, we assessed tibiotarsal joint (TTJ) flexor and extensor force dynamics, and the resistance of dystrophic muscle to eccentric stretch. Male DE50-MD and wild-type (WT) dogs were analysed every 3 months until 18 months of age. There was an age-associated decline in eccentric contraction resistance in DE50-MD TTJ flexors that discriminated, with high statistical power, WT from DE50-MD individuals. For isometric contraction, at the majority of timepoints, DE50-MD dogs had lower maximum absolute and relative TTJ flexor force, reduced TTJ muscle contraction times and prolonged relaxation compared to those in WT dogs. Cranial tibial muscles, the primary TTJ flexor, of 18-month-old DE50-MD dogs had significant numbers of regenerating fibres as expected, but also fewer type I fibres and more hybrid fibres than those in WT dogs. We conclude that these parameters, in particular, the eccentric contraction decrement, could be used as objective outcome measures for pre-clinical assessment in DE50-MD dogs.

Effect of CO2 and H2 gas mixture in cold water immersion on recovery after eccentric loading

Background

The findings of previous studies support the efficacy of cold water immersion (CWI) with carbon dioxide (CO2) in enhancing muscle blood flow and maintaining aerobic performance efficiency. We hypothesize that the addition of hydrogen gas (H2), known for its antioxidant properties and role in inflammation regulation, to C-CWI can enhance recovery after eccentric exercise.

Subjects

and Methods: Thirty-four healthy subjects performed a knee-extensor eccentric exercise. They were randomly allocated into four groups: control, CWI, CO2-rich CWI (C-CWI), and CO2 + H2 gas mixture CWI (CH-CWI). In the three CWI groups, all subjects were immersed in the appropriate bath at 20 °C for 20 min immediately after 60 repetitions of eccentric exercise. Before exercise and after 48 h of recovery, the subjects' maximal voluntary isometric contraction torque (MVC-ISO), maximal voluntary concentric (MVC-CON) contraction torque, countermovement jump (CMJ) height, knee flexion range of motion (ROM), muscle soreness, and muscle thickness were measured.

Results

In the CH-CWI group only, the MVC-ISO, CMJ height, and ROM did not decrease significantly post-exercise, whereas all of these decreased in the other three groups. Muscle soreness at palpation, contraction, and stretching significantly increased post-exercise in all groups. Echo intensity and tissue hardness did not increase significantly in the CH-CWI group.

Conclusions

CH-CWI stimulated recovery from impairments in MVC-ISO torque, CMJ height, knee-flexion ROM, tissue hardness, and echo intensity. These findings indicate that CH-CWI can promote recovery after eccentric exercise.

Recovery kinetics following eccentric exercise is volume-dependent

The present study compared the effect of 75 vs 150 vs 300 intensity-matched eccentric contractions on muscle damage and performance recovery kinetics. Ten healthy males participated in a randomized, cross-over study consisted of 4 experimental trials (ECC75, ECC150, ECC300 and Control - no exercise) with a 4-week washout period in-between. Performance and muscle damage, inflammatory and oxidative stress markers were evaluated at baseline, post-exercise, 24, 48 and 192 hours following each exercise protocol. Concentric and eccentric peak torque decreased similarly in ECC150 and ECC300 during the first 48 h of recovery (p < 0.05) but remained unaffected in ECC75. Countermovement jump indices decreased post-exercise and at 24 h in ECC150 and ECC300, with ECC300 inducing a more pronounced reduction (p < 0.05). Creatine kinase increased until 48 h of recovery in all trials and remained elevated up to 192 h only in ECC300 (p < 0.05). Delayed onset of muscle soreness increased, and knee-joint range of motion decreased in a volume-dependent manner during the first 48 h (p < 0.05). Likewise, a volume-dependent decline of glutathione and a rise of protein carbonyls was observed during the first 48 h of recovery (p < 0.05). Collectively, our results indicate that muscle damage and performance recovery following eccentric exercise is volume dependent, at least in lower limbs.

Sensory, functional and electromyographic variables show different recovery patterns over a seven day period following exercise-induced pain in the hamstrings

BACKGROUND

Delayed-onset muscle soreness (DOMS) is common after unaccustomed exercises and can restrict performance if intense physical activities are performed while the muscle is still sore. This study aimed to evaluate the recovery process following exercise-induced DOMS over a seven-day period by evaluating sensory, functional, and electromyographic parameters.

METHODS

Twenty-four healthy males participated in four experimental sessions (Day-0, Day-2, Day-4, Day-7). Pain perception, pressure pain sensitivity, active range of motion, maximal isometric strength, and muscle activity of the hamstrings during the maximal isometric contraction were assessed bilaterally at each session. A single-leg deadlift eccentric exercise (5-sets of 20-reps) was performed at the end of Day-0 to induce DOMS in the dominant leg.

FINDINGS

At Day-2, the DOMS-side showed increased pain sensitivity and decreased active range of motion, strength and muscle activity compared to Day-0 (P < 0.015). Muscle activity on the DOMS-side reached similar values than at baseline on Day-4, whereas pain perception, pressure pain sensitivity, maximal isometric strength, and active range of motion had returned to the baseline state on Day-7. No changes over time were observed on the control-side, showing all variables an excellent reliability between values at Day-0 and Day-7 (Intraclass Correlation Coefficient > 0.90).

INTERPRETATION

Surface electromyographic values during a maximal isometric contraction recover faster than the other parameters. Given the heterogeneous path of altered variables towards DOMS recovery, trainers and clinicians should consider a multimodal assessment, including quantitative sensory and functional measures in addition to the subjective perception of recovery.

Increased muscle force does not induce greater stretch-induced damage to calf muscles during work-matched heel drop exercise

PURPOSE

To investigate the effect of muscle force during active stretch on quantitative and qualitative indicators of exercise-induced muscle damage (EIMD) in the medial gastrocnemius (MG) muscle.

METHODS

Twelve recreationally active volunteers performed two trials of an eccentric heel drop exercise. Participants performed a single bout of low-load (body weight) and high-load (body weight + 30% body weight) exercises on separate legs. The total mechanical work output for each condition was matched between legs. Before, two hours and 48 h after each bout of eccentric exercise, electrically stimulated triceps surae twitch torque, muscle soreness, MG active fascicle length at maximum twitch torque and muscle passive stiffness were collected. Triceps surae electromyographic (EMG) activity, MG fascicle stretch and MG muscle-tendon unit (MTU) length were measured during the eccentric tasks.

RESULTS

The high-load condition increased triceps surae muscle activity by 6-9%, but reduced MG fascicle stretch (p < 0.001). MTU stretch was similar between conditions. The greater muscle force during stretch did not give rise to additional torque loss (5 vs 6%) or intensify muscle soreness.

CONCLUSIONS

Adding 30% body weight during eccentric contractions has a modest impact on exercise-induced muscle damage in the medial gastrocnemius muscle. These results suggest that muscle load may not be an important determinant of stretch-induced muscle damage in the human MG muscle. The muscle investigated does exhibit large pennation angles and high series elastic compliance; architectural features that likely buffer muscle fibres against stretch and damage.

Clinical effectiveness of pulsed electromagnetic field therapy as an adjunct treatment to eccentric exercise for Achilles tendinopathy: a randomised controlled trial

BACKGROUND

The Achilles tendon is the largest and strongest tendon in the human body. Achilles tendinopathy (AT) is a common clinical problem with Achilles overuse. Eccentric exercise is often used as an initial treatment for these patients. Most patients with AT experienced moderate to severe pain, limiting the incentive to perform eccentric exercise. It is difficult for them to complete eccentric exercise for 3 months consecutively to obtain significant improvements. Using PEMF as an adjunct, there could be immediate pain relief and improved response to eccentric exercise by modulating the mechanical properties of the Achilles tendon. Participants may experience less pain while performing eccentric exercises to increase compliance with the rehabilitation programme.

METHODS

This prospective randomised double-blinded, placebo-controlled trial aims to investigate the treatment effects of PEMF for participants with AT. All participants are randomised into two groups: the intervention group (n = 20; active PEMF treatment and eccentric exercise) and the control group (n = 20; sham treatment and eccentric exercise). Researchers perform self-reported, functional and ultrasonographic outcomes during baseline assessment, 4 weeks, 8 weeks follow-ups, and 3 and 6 months follow-ups after the commencement of the PEMF treatment.

DISCUSSION

AT is a common clinical condition affecting athletes and sedentary populations. It is essential to investigate treatment adjuncts to improve rehabilitation outcomes for these patients. This trial may demonstrate the effectiveness of PEMF in relieving pain, improving function, and restoring mechanical changes of the tendon in participants with AT.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05316961. Registered on 7th April 2022.

Effects of cold water immersion and protein intake combined recovery after eccentric exercise on exercise performance in elite soccer players

The purpose of this study is to analyze the effects of the combined recovery method of cold water immersion (CWI) and protein supplement intake after eccentric exercise that causes muscle fatigue in elite soccer players. Eleven semiprofessional soccer players participated in this study. Participants were divided into CWI group, combined protein and CWI group (PCWI), and passive resting group (CON). The participants completed the eccentric exercise for one hour and performed one of three recovery methods. The muscle strength of the quadriceps and hamstring muscles significantly decreased at 48-hr postexercise compared to before exercise in all recovery groups (P<0.05), with no significantly different between the recovery groups. The time required to sprint 40 m was significantly longer in all groups at 24 hr and 48 hr after exercise than before exercise (P<0.05). The vertical jump height was significantly decreased at 48 hr after exercise compared to before exercise in the CON and CWI groups (P<0.05). The muscle soreness values were higher at 6 hr, 24 hr, and 48 hr after exercise than before exercise in all groups (P<0.001). The perceived recovery quality was reduced after exercise in the PCWI (P<0.01) and CON groups (P<0.001) compared to before exercise; it was unchanged in the CWI group. The recovery quality decreased at 6 hr, 24 hr, and 48 hr after exercise in all recovery groups (P<0.01). In conclusion, the combined recovery method was less effective than CWI alone for the recovery of exercise performance.

Eccentric exercise-induced muscle weakness amplifies the history dependence of force

INTRODUCTION

Following active lengthening or shortening contractions, isometric steady-state torque is increased (residual force enhancement; rFE) or decreased (residual force depression; rFD), respectively, compared to fixed-end isometric contractions at the same muscle length and level of activation. Though the mechanisms underlying this history dependence of force have been investigated extensively, little is known about the influence of exercise-induced muscle weakness on rFE and rFD.

PURPOSE

Assess rFE and rFD in the dorsiflexors at 20%, 60%, and 100% maximal voluntary torque (MVC) and activation matching, and electrically stimulated at 20% MVC, prior to, 1 h following, and 24 h following 150 maximal eccentric dorsiflexion contractions.

METHODS

Twenty-six participants (13 male, 24.7 ± 2.0y; 13 female, 22.5 ± 3.6y) were seated in a dynamometer with their right hip and knee angle set to 110° and 140°, respectively, with an ankle excursion set between 0° and 40° plantar flexion (PF). MVC torque, peak twitch torque, and prolonged low frequency force depression were used to assess eccentric exercise-induced neuromuscular impairments. History-dependent contractions consisted of a 1 s isometric (40°PF or 0°PF) phase, a 1 s shortening or lengthening phase (40°/s), and an 8 s isometric (0°PF or 40°PF) phase.

RESULTS

Following eccentric exercise; MVC torque was decreased, prolonged low frequency force depression was present, and both rFE and rFD increased for all maximal and submaximal conditions.

CONCLUSIONS

The history dependence of force during voluntary torque and activation matching, and electrically stimulated contractions is amplified following eccentric exercise. It appears that a weakened neuromuscular system amplifies the magnitude of the history-dependence of force.

Eccentric and concentric exercises induce different adaptions in adipose tissue biology

Alterations in adipose tissue (AT) metabolism related to inflammation and adipokine's production lead to perturbations in its capacity to store lipids and release fatty acids (FA) during feeding/fasting transition or during exercise. Exercise has a beneficial effect on AT metabolism, but conventional trainings are not always suitable for patients with functional limitations. Dynamic eccentric (ECC) exercise prevents the accumulation of AT and may then overcome those limitations. Consequently, this study aimed at investigating AT's adaptations after ECC training. Nine-week-old male rats were randomly assigned to a control sedentary or three-trained groups for which treadmill slopes modulated exercise oxygen consumption (VO₂) and mechanical work (n = 15 per group): (1) + 15% uphill-concentric group (CONC), (2) - 15% downhill group (ECC15, same mechanical work as CONC) and (3) - 30% downhill group (ECC30, same VO₂, or oxygen cost as CONC). Body composition and energy expenditure (EE) were measured before and after 8 weeks of training. Subcutaneous AT was collected to study total FA profile and gene expression. Higher total EE was driven by lean mass gain in trained animals. In AT, there was a decrease in arachidonic acid with CONC or ECC15 training. Increased adiponectin, leptin, lipases, Glut4 and Igf1 mRNA levels in ECC15 group suggested major metabolic adaption in AT. In conclusion, ECC could induce beneficial modifications in AT fatty acid profile and the expression of key genes related to metabolism and insulin sensitivity.

Physical modalities with eccentric exercise are no better than eccentric exercise alone in the treatment of chronic achilles tendinopathy: A systematic review and meta-analysis

BACKGROUND

To investigate the available evidence and conduct a systematic review with meta-analysis to determine the effectiveness of physical modalities combined with eccentric exercise (PMEE) with eccentric exercise (EE) alone for improvements in pain and function in individuals with chronic Achilles tendinopathy (AT) at short-term (4 weeks) and long-term (12-16 weeks) follow-ups.

MATERIALS AND METHODS

A systematic literature review identified 8 papers (from 6404 possible inclusions) that allowed the comparison of PMEE with EE alone, in the treatment of chronic AT. We extracted the mean and standard deviations for Victorian Institute of Sports Assessment Achilles Tendinopathy (VISA-A), Numerical Pain Rating Scale (NPRS), and load-induced pain (NRS). Standardized mean difference (SMD) of the included variables was presented, and all the studies had low risk of bias.

RESULTS

Non-significant results were achieved for short-term (pooled SMD = 0.03; 95% CI= -0.46 to 0.53, p = 0.89, I2 = 60%) and long- term follow-ups (pooled SMD =0.43; 95% CI= -0.05 to 0.92, p = 0.08, I2 = 82%) of VISA-A. Short-term (pooled SMD = -0.16; 95% CI= -0.72 to 0.40, p = 0.57, I2 = 40%) and long-term (pooled SMD = -0.39;95% CI= -1.11 to 0.32, p = 0.28, I2 = 62%) follow-up analysis of NPRS and long-term(pooled SMD = -0.46; 95% CI= -1.08 to 0.15, p = 0.14, I2 = 74%) follow-up of load induced pain also demonstrated non-significant improvements when comparing two groups.

CONCLUSION

Meta- analysis of the results published in the 8 papers that met theinclusion criteria showed no significant differences between PMEE and EE, in terms of load-induced pain (NRS) and numerical pain rating scales (NPRS) at 4 and 12-16 weeks. Thus, the meta-analysis reflects the other cited published work that PMEE shows no greater advantage than EE in the treatment of Chronic Achilles Tendinopathy.

Downhill running affects the late but not the early phase of the rate of force development

Purpose

This study aimed to evaluate the acute changes in the knee extensors maximum voluntary isometric contraction force (MVIC), rate of force development (RFD), and rate of EMG rise (RER) following a bout of downhill running.

Methods

MVIC and RFD at 0–50, 50–100, 100–200, and 0–200 ms were determined in thirteen men (22 ± 2 yr) before and after 30 min of downhill running (speed: 10 km h⁻¹; slope: − 20%). Vastus lateralis maximum EMG (EMG_max) and RER at 0–30, 0–50, and 0–75 ms were also recorded.

Results

MVIC, RFD_0–200, and EMG_max decreased by ~ 25% [Cohen’s d = − 1.09 (95% confidence interval: − 1.88/− 0.24)], ~ 15% [d = − 0.50 (− 1.26/0.30)], and ~ 22% [d = − 0.37 (− 1.13/0.42)] (all P < 0.05), respectively. RFD_100–200 was also reduced [− 25%; d = − 0.70 (− 1.47/0.11); P < 0.001]. No change was observed at 0–50 ms and 50–100 ms (P ≥ 0.05). RER values were similar at each time interval (all P > 0.05).

Conclusion

Downhill running impairs the muscle capacity to produce maximum force and the overall ability to rapidly develop force. No change was observed for the early phase of the RFD and the absolute RER, suggesting no alterations in the neural mechanisms underlying RFD. RFD_100–200 reduction suggests that impairments in the rapid force-generating capacity are located within the skeletal muscle, likely due to a reduction in muscle–tendon stiffness and/or impairments in the muscle contractile apparatus. These findings may help explain evidence of neuromuscular alterations in trail runners and following prolonged duration races wherein cumulative eccentric loading is high.

Eccentric exercise improves joint flexibility in adults: A systematic review update and meta-analysis

BACKGROUND

Eccentric exercise is thought to improve joint flexibility, but the size of the effect is not known. We aimed to quantify the overall effect of eccentric exercise on joint flexibility in adults.

DESIGN

Systematic review, meta-analysis.

DATA SOURCES

AMED, CINAHL, MEDLINE, EMBASE, SportDiscus.

PARTICIPANTS

Adults.

INTERVENTION

Eccentric exercise compared to no intervention or to a different intervention.

OUTCOME MEASURES

Joint range of motion or muscle fascicle length.

DATA EXTRACTION AND SYNTHESIS

Descriptive data of included trials and estimates of effect sizes were extracted. Standardised mean differences (SMD) of range of motion or fascicle length outcomes were meta-analysed using random effects models. Overall quality of evidence was assessed using the GRADE scale.

RESULTS

32 trials (1122 participants, 108 lost to follow-up) were included in the systematic review. The mean (SD) PEDro score was 5.2 (1.3). Four trials reported insufficient data for meta-analysis. Data from 27 trials (911 participants, 82 lost to follow-up) were meta-analysed. Eccentric exercise improved joint flexibility in adults (pooled random effects Hedges' g SMD = 0.54, 95% CI 0.34 to 0.74). The true effect size is different across studies and 50% of the variance in observed effects is estimated to reflect variance in true effects rather than sampling error (I² = 50%, Q = 67.6, d.f. = 34, p = 0.001). Overall quality of evidence ranged from 'low' to 'high'.

CONCLUSION

Eccentric exercise improves joint flexibility in adults. The overall standardised mean effect of eccentric exercise was moderately large, and the narrow width of the 95% confidence interval indicates the effect was estimated with good precision.

REGISTRATION

Open Science Foundation (https://osf.io/mkdqr); PROSPERO registration CRD42020151303.

Investigating the effects of neuromobilization in lateral epicondylitis

STUDY DESIGN

Randomized controlled study.

INTRODUCTION

Lateral epicondylitis (LE) causes pain and loss of function in the affected limb. Different exercises have been used for the treatment of LE. In recent years, the technique of neuromobilization has been frequently used to treat tendinopathy. However, there is no study that demonstrates the effects of neuromobilization techniques on patients with LE.

PURPOSE OF THE STUDY

The aim of the present study was to determine the effects of neuromobilization techniques on pain, grip strength, and functional status in LE patients and to compare them with conservative rehabilitation treatment.

METHODS

A total of 40 patients (26 females and 14 males; age: 42.80 ± 8.91 years) with a history of LE participated in the study. The patients were randomly assigned to two groups: the neuromobilization group and the control group. The neuromobilization group completed a 6-week conservative rehabilitation and radial nerve mobilization program, whereas the control group received conservative rehabilitation therapy only. Both groups underwent a 7-day weekly conservative home rehabilitation program. Pain severity, grip strength, pinch strength, joint motions, and upper extremity functional level were assessed before treatment, at the third week after treatment, and at the sixth week after treatment.

RESULTS

There was a significant decrease in all pain scores in favor of the neuromobilization group at week 6 after treatment (at rest: P = .001, effect size (ES) = 0.84; at night: P = .001, ES = 0.91 and during activity: P = .004, ES = 1.06). No significant differences were found for grip strength, pinch strength, joint motions, and functional level in the neuromobilization group, although trends toward better improvement were observed.

CONCLUSIONS

Radial nerve mobilization techniques are more effective on pain than conservative rehabilitation therapy in LE patients, and this effect continues after treatment.

Neuromuscular, biomechanical, and energetic adjustments following repeated bouts of downhill running

PURPOSE

This study used downhill running as a model to investigate the repeated bout effect (RBE) on neuromuscular performance, running biomechanics, and metabolic cost of running.

METHODS

Ten healthy recreational male runners performed two 30-min bouts of downhill running (DR1 and DR2) at a -20% slope and 2.8 m/s 3 weeks apart. Neuromuscular fatigue, level running biomechanics during slow and fast running, and running economy parameters were recorded immediately before and after the downhill bouts, and at 24 h, 48 h, 72 h, 96 h, and 168 h thereafter (i.e., follow-up days).

RESULTS

An RBE was confirmed by attenuated muscle soreness and serum creatine kinase rise after DR2 compared to DR1. An RBE was also observed in maximum voluntary contraction (MVC) force loss and voluntary activation where DR2 resulted in attenuated MVC force loss and voluntary activation immediately after the run and during follow-up days. The downhill running protocol significantly influenced level running biomechanics; an RBE was observed in which center of mass excursion and, therefore, lower-extremity compliance were greater during follow-up days after DR1 compared to DR2. The observed changes in level running biomechanics did not influence the energy cost of running.

CONCLUSION

This study demonstrated evidence of adaptation in neural drive as well as biomechanical changes with the RBE after DR. The higher neural drive resulted in attenuated MVC force loss after the second bout. It can be concluded that the RBE after downhill running manifests as changes to global and central fatigue parameters and running biomechanics without substantially altering the energy cost of running.

The Effect of Ankle Position on Peak Eccentric Force during The Nordic Hamstring Exercise

Peak eccentric force during the Nordic hamstring exercise (NHE) is recognized as a predictive factor for hamstring strain injury (HSI). During the NHE, the knee flexor muscles are eccentrically contracting to resist the knee joint extension. Therefore, it is thought that the action of the gastrocnemius muscle, and thus the ankle position, influences peak eccentric force during the NHE. However, the effect of ankle position on peak eccentric force during the NHE remains unclear. Therefore, we investigated the effect of ankle position on peak eccentric force during the NHE in a cohort of 50 healthy young male rugby players (mean age, 18.7 ± 1.2 years; mean body mass, 81.7 ± 15.2 kg; height, 1.72 ± 0.06 m) with no history of HSI. Each participant performed NHE strength testing with the ankle dorsiflexed or plantarflexed position and was instructed to fall forward as far as possible within 3 s. Peak eccentric force, reported relative to body mass (N/kg), of both legs was recorded, and the mean values of both legs were compared in both ankle positions. The mean peak eccentric force was significantly greater with the ankle plantarflexed position than the dorsiflexed position (3.8 ± 1.1 vs. 3.5 ± 1.1 N/kg, respectively, p = 0.049). These results indicate that ankle position should be carefully considered when measuring peak eccentric force during the NHE and performing NHE training.

Inflammatory response of the peripheral neuroendocrine system following downhill running

Exploring the relationship between exercise inflammation and the peripheral neuroendocrine system is essential for understanding how acute or repetitive bouts of exercise can contribute to skeletal muscle adaption. In severe damage, some evidence demonstrates that peripheral neuroendocrine receptors might contribute to inflammatory resolution, supporting the muscle healing process through myogenesis. In this sense, the current study aimed to evaluate two classic peripheral neuronal receptors along with skeletal muscle inflammation and adaptation parameters in triceps brachii after exercise. We euthanized C57BL (10 to 12 weeks old) male mice before, and one, two, and three days after a downhill running protocol. The positive Ly6C cells, along with interleukin-6 (IL-6), nuclear factor kappa B (NF-κB), glucocorticoid receptor (GR), α7 subunits of the nicotinic acetylcholine receptor (nAChRs), and myonuclei accretion were analyzed. Our main results demonstrated that nAChRs increased with the inflammatory and myonuclei accretion responses regardless of NF-κB and GR protein expression. These results indicate that increased nAChR may contribute to skeletal muscle adaption after downhill running in mice.

Whole-body vibration decreases delayed onset muscle soreness following eccentric exercise in elite hockey players: a randomised controlled trial

BACKGROUND

Delayed onset muscle soreness (DOMS) is a common non-structural muscle injury which can disrupt training and impair performance in elite athletes. Vibration therapy reduces inflammation and improves neuromuscular efficiency, leading to reductions in pain and stiffness, and may be effective for the prevention or treatment of DOMS. However, the effect of whole-body vibration (WBV) used after sport in elite athletes has not been reported.

METHODS

A randomised, controlled trial was performed. Participants were elite (national or international level) hockey players and underwent an eccentric exercise protocol previously shown to produce clinical DOMS. After exercise, one group underwent static stretching with WBV therapy, and the other performed stretching only. Baseline and serial post-exercise pain scores and measurements of quadriceps tightness were obtained.

RESULTS

Eleven participants were recruited into each study arm. There were no significant differences in baseline group characteristics. Participants receiving WBV had significant reductions in both pain (p = 0.04) and quadriceps tightness (p = 0.02) compared with stretching only.

CONCLUSIONS

Post-exercise WBV is effective in elite hockey players to reduce DOMS after eccentric exercise. Elite athletes in multi-sprint sports are at risk of DOMS during training and competition, and its reduction could contribute to reduced injury risk and improved performance. This treatment modality is favourable because it can be incorporated with minimal disruption into the recovery section of existing training regimes. These findings may also be extrapolated to other multi-sprint sports.

Effectiveness of eccentric-biased exercise interventions in reducing the incidence of falls and improving functional performance in older adults: a systematic review

Aim

To systematically review the literature on the effectiveness of eccentric exercise interventions in reducing falls and improving the functional performance in older adults.

Findings

The existing literature was of mixed quality and suggested that eccentric exercises can be as effective as conventional exercises in improving functional performance in healthy older adults. There was limited evidence focussing on the aspect of incidence of falls.

Message

Eccentric exercises may be as effective as conventional exercises in improving geriatric function, although evidence remains limited. More research is needed to explore any adverse effects of such exercises in older adults.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41999-021-00571-8.

Background

Exercise has been known to preserve and enhance functional performance in older adults. Eccentric exercise involves muscle contractions characterised by unique features such as lengthening of the muscle–tendon complex by a greater opposing force.

Aims

To systematically review randomised-controlled trials (RCTs) investigating the effectiveness of eccentric exercises in reducing the incidence of falls and improving the functional performance in older adults.

Key methods

We conducted a systematic review of RCTs following the PRISMA-P guidelines. Searches were completed in the Cochrane Central Register of Controlled Trials, Embase, CINAHL, Medline, and Global Health CABI. We included RCTs reporting at least one of the following outcomes—falls, Berg balance scale, timed-up and go test, chair stand test, stair climb test, maximal walking speed, and minute walking distance. Two reviewers screened papers for eligibility and assessed the quality of included papers using the Cochrane Collaborative risk-of-bias tool for randomised trials. Data were extracted by a single reviewer and cross-checked by the second reviewer. A narrative synthesis was undertaken, given the high level of heterogeneity across studies.

Results

Ten studies were assessed as eligible for inclusion in the review. Overall, eccentric exercises were as effective as conventional resistance exercises in improving the selected outcomes by most studies. Additionally, when pre-exercise and post-eccentric exercise functional performance measures were compared, there was a statistically significant improvement in nearly all measures. The quality of trials was mixed (one high, four moderate, two low–moderate, and three low risk of bias).

Conclusions

Our systematic review suggests that eccentric exercises can be as effective as conventional exercises in older adults. Evidence suggests that such exercise interventions can lead to an improvement in geriatric function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41999-021-00571-8.

Electromyographic analysis of select eccentric-focused rotator cuff exercises

Background: Eccentric-focused rotator cuff exercises are clinically useful in rehabilitation; however, to what extent these exercises activate shoulder musculature is unknown.Purpose: Investigate peak electromyographic (EMG) activity of shoulder musculature during eccentric-focused rotator cuff exercises to inform clinical decision-making.Methods: Surface EMG activity was measured in 15 healthy subjects from 5 muscles of the dominant shoulder: supraspinatus, infraspinatus, upper trapezius, lower trapezius, and middle deltoid. Subjects performed 5 exercises: short-to-long scaption, sit-to-stand scaption, standing external rotation (ER), sidelying ER, and sidelying horizontal adduction. The effects of exercise and muscle on peak EMG activity were analyzed using two-way repeated-measures ANOVA and followed with post-hoc pairwise comparisons.Results: Significant exercise-by-muscle interaction effect was found (p < .001). Short-to-long and sit-to-stand scaption elicited higher activity in supraspinatus and middle deltoid compared to other exercises (p < .05); however, no effect of muscle was found for these exercises (p > .05). Infraspinatus and lower trapezius demonstrated higher activity compared to other muscles during standing ER, sidelying ER, and sidelying horizontal adduction (p < .05).Conclusion: Eccentric-focused exercises sufficiently activate the rotator cuff and is effective for use in rehabilitation. Caution must be taken as some exercises do not target specific musculature.

Expression of tissue remodelling, inflammation- and angiogenesis-related factors after eccentric exercise in humans

Eccentric exercise has been extensively used as a model to study the contraction-induced muscle damage and its consequent processes. This study aimed at examining molecular responses associated with tissue remodelling, inflammation and angiogenesis in skeletal muscle during the recovery period after eccentric exercise in humans. Ten healthy men performed 50 maximal eccentric muscle actions with the knee extensors and muscle biopsies were collected from the vastus lateralis before and 6 h, 48 h and 120 h post eccentric exercise. Real Time-PCR was utilized to investigate alterations in gene expression of various tissue remodelling-, inflammation- and angiogenesis-related factors: uPA, uPA-R, TGF-β1, MMP-9, TNF-α, IL-6, IL-8, VEGF, VEGFR-2, HIF-1a, Ang-1, Ang-2 and Tie-2. The uPA/uPA-R system exhibited a similar time-expression pattern increasing 6 h post exercise (p < 0.05), while the other tissue remodelling factors TGF-β1 and MMP-9 did not change significantly over time. Transcriptional responses of inflammatory factors TNF-α and IL-8 increased significantly and peaked 6 h post eccentric exercise (p < 0.05), while IL-6 exhibited a similar, though not statistically significant, expression profile (p > 0.05). Similarly, the expression of angiopoietin receptor Tie-2 showed an early increase only at 6 h after the completion of exercise (p < 0.05), while the other angiogenic factors failed to reach statistical significance due a high interindividual variability in the gene expression responses. The early transcriptional upregulation of tissue remodelling, inflammation- and angiogenesis-related factors post eccentric exercise may indicate the acute intramuscular activation of these processes functionally related to muscle damage-induced adaptation.

[TGF-β1/ERK/CTGF pathway involved in effect of acupuncture on exercise-induced skeletal muscle fibrosis]

OBJECTIVE

To observe the changes of the skeletal muscle fibrosis and changes of transforming growth factor-β1(TGF-β1)/ extracellular signal-regulated kinase (ERK) / connective tissue growth factor (CTGF)pathway in rats after long-term eccentric exercise and acupuncture intervention, so as to explore the mechanism of acupuncture in regulating exercise-induced skeletal muscle fibrosis.

METHODS

A total of 30 male SD rats were randomly divided into normal control, exercise and acupuncture group, with 10 rats in each group. The rat model of skeletal muscle fibrosis was established by eccentric exercise for 3 weeks. After exercise trained every time, the rats of the acupuncture group received acupuncture stimulation by holding the acupuncture needle to obliquely and longitudinally penetrate the ventral part of triceps of the lower leg along its lateral side, followed by retaining the needle for 2 min. Changes of the collagen fibers in each group was observed by scanning electron microscope. The expressions of Collagen Ⅰ, TGF-β1, phosphated (p)-ERK/ERK and CTGF proteins were detected by Western blot.

RESULTS

After 3 weeks of eccentric exercise and acupuncture, the fibrosis and deposition of collagen fibers in the exercise group were significantly higher than that in the normal control group,the degree of fibrosis in the acupuncture group was significantly lower than that in the exercise group. Compared with the normal control group, the expression levels of Collagen Ⅰ, TGF-β1, CTGF and p-ERK/ERK in the exercise group was significantly higher (P<0.01，P<0.05). After EA interventions, the increased levels of the above indicators were significantly reversed (P<0.05，P<0.01) apart from p-ERK/ERK which had a downward trend, but the difference was not statistically significant.

CONCLUSION

The accumulation of chronic sports injury can lead to the deposition of collagen fibers in skeletal muscle, which leads to the fibrosis of skeletal muscle. Acupuncture can inhibit skeletal muscle fibrosis via down-regulating TGF-β1/ERK/CTGF signaling pathway.

The torque-frequency relationship is impaired similarly following two bouts of eccentric exercise: No evidence of a protective repeated bout effect

High-intensity eccentric exercise can lead to muscle damage and weakness. The 'repeated bout effect' (RBE) can attenuate these impairments when performing a subsequent bout. The influence of eccentric exercise-induced muscle damage on low-frequency force production is well-characterized; however, it is unclear how eccentric exercise and the RBE affect torque production across a range of stimulation frequencies (i.e., the torque-frequency relationship). We investigated the influence of an initial (Bout 1) and repeated bout (Bout 2) of eccentric exercise on the elbow flexor torque-frequency relationship. Eleven males completed two bouts of high-intensity eccentric elbow flexions, 4 weeks apart. Torque-frequency relationships were constructed at baseline and 0.5, 24, 48, 72, 96, and 168 h following both bouts via percutaneous stimulation at 1, 6, 10, 20, 30, 40, 50, and 100 Hz. Serum creatine kinase activity, self-reported muscle soreness, and isometric maximum voluntary contraction torque indirectly inferred the presence of muscle damage following Bout 1, and attenuation of muscle damage following Bout 2. Torque amplitude at all stimulation frequencies was impaired 30 min following eccentric exercise, however, torque at lower (1-10 Hz) and higher frequencies (40-100 Hz) recovered within 24 h while torque across the middle frequency range (20-30 Hz) recovered by 48 h. No between-bout differences were detected in absolute or normalized torque at any stimulation frequency, indicating no protective RBE on the elbow flexor torque-frequency relationship.

The Myotendinous Junction-A Vulnerable Companion in Sports. A Narrative Review

The incidence of strain injuries continues to be high in many popular sports, especially hamstring strain injuries in football, despite a documented important effect of eccentric exercise to prevent strains. Studies investigating the anatomical properties of these injuries in humans are sparse. The majority of strains are seen at the interface between muscle fibers and tendon: the myotendinous junction (MTJ). It has a unique morphology with a highly folded muscle membrane filled with invaginations of collagen fibrils from the tendon, establishing an increased area of force transmission between muscle and tendon. There is a very high rate of remodeling of the muscle cells approaching the MTJ, but little is known about how the tissue adapts to exercise and which structural changes heavy eccentric exercise may introduce. This review summarizes the current knowledge about the anatomy, composition and adaptability of the MTJ, and discusses reasons why strain injuries can be prevented by eccentric exercise.

Urinary N-terminal fragment of titin: A surrogate marker of serum creatine kinase activity after exercise-induced severe muscle damage

We aimed to evaluate whether changes in the noninvasively assessed urinary N-terminal fragment of titin (U-titin) concentration may be associated with those of serum creatine kinase (CK) activity, transverse relaxation time (T₂), maximal voluntary contraction (MVC) torque, range of motion (ROM), and muscle soreness, following high-intensity eccentric exercise. Twenty-eight healthy young men performed 30 maximal isokinetic (120°/s) eccentric elbow flexor contractions using an isokinetic dynamometer. U-titin concentration, serum CK activity, T₂, MVC torque, ROM, and muscle soreness were measured before and after a maximum of 4 days. Both U-titin concentration and serum CK activity increased post-exercise in a similar manner, though the former elevated slightly earlier (p < 0.05). The peak values of log U-titin concentration following eccentric exercise were strongly correlated with those of log serum CK activity (r = 0.90, p < 0.05) and T₂ (r = 0.84, p < 0.05). There were moderate correlations between peak values of U-titin concentration and those of MVC torque (r = 0.69, p < 0.05) and ROM decline rate (r = 0.45, p < 0.05). These results suggest that in healthy young men, the non-invasive marker, U-titin, may be used as a serum CK surrogate following exercise-induced severe muscle damage.

Safety, Feasibility, and Efficacy of an Eccentric Exercise Intervention in People with Multiple Sclerosis with Ankle Contractures

Background

The primary aim of this study was to investigate the safety and feasibility of an eccentric exercise program for people with multiple sclerosis (MS) who have ankle contractures, ie, reduced ankle range of motion (ROM). Secondary aims were to explore the efficacy of this eccentric exercise on ankle joint ROM and functional mobility.

Methods

Five adults with MS with ankle contractures (three women and two men; mean ± SD age, 50.8 ± 9.4; MS duration, 7.6 ± 5.6 years) completed two eccentric exercise training sessions (10-45 minutes) per week for 12 weeks. The training involved walking backward downhill on an inclined treadmill (gradient, 10°-14°) at a self-selected pace. The intervention was assessed for safety (adverse events), feasibility (recruitment rates, adherence rates, enjoyment levels, difficulty, and discomfort), and clinical outcomes, including passive/active ankle ROM and distance walked in 6 minutes.

Results

There were no adverse events during or after the eccentric exercise training. There was a 100% adherence rate. All participants enjoyed the training and experienced low levels of muscle soreness/discomfort. The training program improved passive/active ankle ROM in all participants; however, improvements did not translate to improvements in walking for all participants.

Conclusions

Walking backward and downhill is a safe and feasible training modality for people with MS with ankle contractures. Clinical outcomes (greater passive/active ankle ROM) after this eccentric exercise training were evident. However, translation to clinically meaningful changes in walking function requires further examination.

Exercise-induced muscle damage: multi-parametric MRI quantitative assessment

BACKGROUND

To explore the value of magnetic resonance quantitative analysis using diffusion tensor imaging, T2 mapping, and intravoxel incoherent motion in the evaluation of eccentric exercise-induced muscle damage and to compare the effects of various eccentric exercise modes at different time points in rats.

METHODS

A total of 174 Sprague-Dawley male rats were randomly divided into five groups: control, once-only exercise, continuous exercise, intermittent exercise, and once-fatigue exercise groups. Each experimental group was divided into seven time-subgroups: 0.5 h, 24 h, 48 h, 72 h, 96 h, 120 h and 168 h after exercise. The quadriceps femoris muscles were then scanned using magnetic resonance imaging. The apparent diffusion coefficient and fractional anisotropy values of diffusion tensor imaging, T2 values of T2 mapping, D and D* values of intravoxel incoherent motion and optical density values of desmin were measured. Associations among different eccentric exercise programmes, magnetic resonance imaging findings, and histopathological results were evaluated. Dunnett's test, two-way repeated measures analysis of variance, and Pearson correlation analysis were used for statistical analysis.

RESULTS

Diffusion tensor imaging showed that the number of muscle fibre bundles decreased to varying degrees with different time points and eccentric exercises. Apparent diffusion coefficient values of the exercise groups showed a trend that first increased and then decreased, the opposite of fractional anisotropy. The specimens in all eccentric exercise programmes showed high signal T2 values after exercise, the highest among which was in the once-fatigue exercise group. D and D* in the experimental groups were significantly higher than those in the control group at 0.5-48 h after exercise. The apparent diffusion coefficient, fractional anisotropy, T2, D and D* values correlated with the optical density values of desmin.

CONCLUSIONS

Diffusion tensor imaging, T2 mapping, and intravoxel incoherent motion technology accurately reflect the degree of skeletal muscle damage and recovery associated with eccentric exercise. The degree of muscle damage was the lowest in the continuous exercise group and the highest in the once-fatigue exercise group, which may provide more information and guidance for the formulation of physical and athletic training programmes.

The effect of acute and repeated ischemic preconditioning on recovery following exercise-induced muscle damage

OBJECTIVES

The aim of this investigation was to determine if acute or repeated applications of ischemic preconditioning (IPC) could enhance the recovery process, following exercise induced muscle damage (EIMD).

DESIGN

Randomized control trial.

METHODS

Twenty-three healthy males were familiarised with the muscle damaging protocol (five sets of 20 drop jumps from a 0.6 m box) and randomly allocated to one of three groups: SHAM (3 × 5 min at 20 mmHg), Acute IPC (3 × 5 min at 220 mmHg) and Repeated IPC (3 days x 3 × 5 min at 220 mmHg). The indices of muscle damage measured included creatine kinase concentration ([CK]), thigh swelling, delayed onset muscle soreness, counter movement jumps (CMJ) and maximal voluntary isometric contraction (MVIC).

RESULTS

Both acute and repeated IPC improved recovery in MVIC versus SHAM. Repeated IPC led to a faster MVIC recovery at 48 h (101.5%) relative to acute IPC (92.6%) and SHAM (84.4%) (P <  0.05). Less swelling was found for both acute and repeated IPC vs. SHAM (P <  0.05) but no group effects were found for CMJ, soreness or [CK] responses (P >  0.05).

CONCLUSION

Taken together, repeated IPC can enhance recovery time of MVIC more than an acute application, and both reduce swelling following EIMD, relative to a SHAM condition.

An acute eccentric exercise increases circulating myomesin 3 fragments

Discovery of blood biomarkers to evaluate exercise-induced muscle damage have attracted many researchers and coaches. This study aimed to determine changes in circulating myomesin 3 fragments as a novel biomarker for exercise-induced muscle damage. Nine healthy males performed 10 sets of 40 repetitions of one-leg calf-raise exercise by the load corresponding to the half of their body weight. Muscle symptoms were evaluated by a visual analog scale (VAS). Blood samples were collected before and 2, 4, 24, 48, 72, and 96 h post-exercise. Plasma myomesin 3 fragments levels were significantly increased at 96 h after the eccentric exercise. The myomesin 3 fragments levels were correlated with other biomarkers of muscle damage and the muscle symptoms. These results suggest that the circulating myomesin 3 fragments levels are potential biomarkers reflecting eccentric exercise-induced muscle damage.

The effect of Omega-3 polyunsaturated fatty acid supplementation on exercise-induced muscle damage

Background

Exercise-induced muscle damage (EIMD) results in transient muscle inflammation, strength loss, muscle soreness and may cause subsequent exercise avoidance. Omega-3 (n-3) supplementation may minimise EIMD via its anti-inflammatory properties, however, its efficacy remains unclear.

Methods

Healthy males (n = 14, 25.07 ± 4.05 years) were randomised to 3 g/day n-3 supplementation (N-3, n = 7) or placebo (PLA, n = 7). Following 4 weeks supplementation, a downhill running protocol (60 min, 65% V̇O₂max, − 10% gradient) was performed. Creatine kinase (CK), interleukin (IL)-6 and tumour necrosis factor (TNF)-α, perceived muscle soreness, maximal voluntary isometric contraction (MVIC) and peak power were quantified pre, post, and 24, 48 and 72 h post-EIMD.

Results

Muscle soreness was significantly lower in N-3 vs PLA group at 24 h post-EIMD (p = 0.034). IL-6 was increased in PLA (p = 0.009) but not in N-3 (p = 0.434) following EIMD, however, no significant differences were noted between groups. Peak power was significantly suppressed in PLA relative to pre-EIMD but not in N-3 group at 24 h post-EIMD. However, no significant difference in peak power output was observed between groups. MVIC, CK and TNF-α were altered by EIMD but did not differ between groups.

Conclusion

N-3 supplementation for 4 weeks may successfully attenuate minor aspects of EIMD. Whilst not improving performance, these findings may have relevance to soreness-associated exercise avoidance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12970-020-00405-1.

Changes in plasma hydroxyproline and plasma cell-free DNA concentrations after higher- versus lower-intensity eccentric cycling

PURPOSE

We examined changes in plasma creatine kinase (CK) activity, hydroxyproline and cell-free DNA (cfDNA) concentrations in relation to changes in maximum voluntary isometric contraction (MVIC) torque and delayed-onset muscle soreness (DOMS) following a session of volume-matched higher- (HI) versus lower-intensity (LI) eccentric cycling exercise.

METHODS

Healthy young men performed either 5 × 1-min HI at 20% of peak power output (n = 11) or 5 × 4-min LI eccentric cycling at 5% of peak power output (n = 9). Changes in knee extensor MVIC torque, DOMS, plasma CK activity, and hydroxyproline and cfDNA concentrations before, immediately after, and 24-72 h post-exercise were compared between groups.

RESULTS

Plasma CK activity increased post-exercise (141 ± 73.5%) and MVIC torque decreased from immediately (13.3 ± 7.8%) to 48 h (6.7 ± 13.5%) post-exercise (P < 0.05), without significant differences between groups. DOMS was greater after HI (peak: 4.5 ± 3.0 on a 10-point scale) than LI (1.2 ± 1.0). Hydroxyproline concentration increased 40-53% at 24-72 h after both LI and HI (P < 0.05). cfDNA concentration increased immediately after HI only (2.3 ± 0.9-fold, P < 0.001), with a significant difference between groups (P = 0.002). Lack of detectable methylated HOXD4 indicated that the cfDNA was not derived from skeletal muscle. No significant correlations were evident between the magnitude of change in the measures, but the cfDNA increase immediately post-exercise was correlated with the maximal change in heart rate during exercise (r = 0.513, P = 0.025).

CONCLUSION

Changes in plasma hydroxyproline and cfDNA concentrations were not associated with muscle fiber damage, but the increased hydroxyproline in both groups suggests increased collagen turnover. cfDNA may be a useful metabolic-intensity exercise marker.

Apoptotic response to acute and chronic exercises in rat skeletal muscle: Eccentric & sprint interval

AIMS

Apoptosis is a type of cell death that is vital for tissue homeostasis. Exercise can lead to initial stimulation of apoptotic regulator genes. We investigated their response to an acute exercise and their adaptations to chronic exercise training with an emphasis on eccentric and sprint interval exercises.

MAIN METHODS

Male Sprague Dawley rats were randomly assigned to five groups (n = 8): acute eccentric exercise (AEE), acute sprint interval exercise (ASE), chronic eccentric exercise (CEE), chronic sprint interval exercise (CSE) and control (C). The AEE group underwent downhill running (at -16° slope) at 16 m/min 18 sets. The ASE group run for 7 sets and the speed increased gradually to 70-80 m/min. The chronic groups were implemented for 9 weeks. The CEE run 1 set for 15 min at -4° slope that increased gradually to 90 min at -16°. The CSE sprinted 1 min with 2-5 min rest. The mRNA in soleus (slow-twitch muscle) and super vastus lateralis (SVL) (fast-twitch muscle) muscles was analyzed by real-time RT-PCR.

KEY FINDINGS

According to the gene expression level in soleus muscle, apoptotic responses to acute and chronic sprint interval exercise as well as towards chronic eccentric exercise were clearly evident. But in SVL muscle, the only acute eccentric exercise group showed significance increase in apoptotic factors.

SIGNIFICANCE

these results revealed the apoptotic response to the exercise depends on the type and intensity of exercise and also on the sensitivity and susceptibility of the muscle.

The effect of vitamin D supplementation on the muscle damage after eccentric exercise in young men: a randomized, control trial

Background

Vitamin D contributes to the optimal functioning of muscles. This study was designed to determine the modulating effect of vitamin D supplementation on the degree of muscle cell damage caused by eccentric exercise in young men.

Methods

60 male volunteers (20–24 years old) taking part in this study were divided in two groups - with suboptimal (S) and optimal (O;) 25(OH)D plasma levels. These groups were randomly subdivided into groups with vitamin D supplementation (experimental: SE and OE) and controls (SC and OC). Before the supplementation (Test I) and after 3 months (Test II), participants were subjected to two rounds of eccentric exercise tests on a declined treadmill (running speed corresponded 60% VO2peak determined in each subject in incremental exercise test). During each test, blood samples used for determination of 25(OH)D, Il-1β, myoglobin (Mb) levels and CK, LDH activity were taken at three timepoints: before the test, 1 h and 24 h after it ended.

After distribution normality testing (Saphiro-Wilk test), statistical analyses were performed. Non-parametric: Kruskal-Wallis test and the Wilcoxon test were applied, and the Dunn-Bonferroni test as a post-hoc test.

Results

In all groups, after 3 months, higher concentrations of 25(OH)D were indicated (SE p = 0.005; SC p = 0.018; OE p = 0.018; OC p = 0.028). SE and SC groups showed higher baseline concentrations of Il-1β and significantly higher concentrations of this interleukin after 1 h compared to groups with an optimal 25(OH)D level. After supplementation, the SE group reacted with a similar jump in concentration of Il-1β as the OC and OE groups. The change after 1 h after exercise in Test II was significantly different from that from Test I (p = 0.047) in SE group. Lower Mb concentrations indicated 1 h after exercise in Test II for SC and SE groups were indicated. CK activity did not differentiate the studied groups. Plasma calcium and phosphate disorders were also not indicated.

Conclusions

The study has shown that vitamin D doses determined from the plasma concentration of 25(OH)D of individuals to match their specific needs can significantly reduce muscle cell damage induced by eccentric exercise.

Whey protein supplementation does not accelerate recovery from a single bout of eccentric exercise

The current double blind, randomized, placebo-controlled trial with two parallel groups aimed to assess the impact of whey protein supplementation on recovery of muscle function and muscle soreness following eccentric exercise. During a 9-day period, forty recreationally active males received twice daily supplementation with either whey protein (PRO; 60 g/day) or an iso-energetic amount of carbohydrate (CON). Muscle function and soreness were assessed before, and 0, 3, 24, 48, and 72 h after performing 100 drop jumps. Recovery of isometric maximal voluntary contraction (MVC) did not significantly differ between groups (timextreatment, P = 0.56). In contrast, the recovery of isokinetic MVC at 90°·s^-1 was faster in CON as opposed to PRO (timextreatment interaction, P = 0.044). Recovery of isokinetic MVC at 180°·s^-1 was also faster in CON as opposed to PRO (timextreatment interaction, P = 0.011). Recovery of countermovement jump performance did not differ between groups (timextreatment interaction, P = 0.52). Muscle soreness, CK and CRP showed a transient increase over time (P < 0.001), with no differences between groups. In conclusion, whey protein supplementation does not accelerate recovery of muscle function or attenuate muscle soreness and inflammation during 3 days of recovery from a single bout of eccentric exercise.

Cole-impedance parameters representing biceps tissue bioimpedance in healthy adults and their alterations following eccentric exercise

The purpose of this study is to identify if participation in an eccentric exercise protocol altered the Cole-impedance model parameters that represent localized bicep tissue bioimpedance. This supports continued efforts to identify which features of tissue bioimpedance may be effective markers to non-invasively identify skeletal muscle damage. Here, the Cole-impedance model parameters that best fit the localized electrical impedance of exercised (using an eccentric stimulus) and unexercised biceps of 6 participants (collected before, immediately after and at 24 h, 48 h, 72 h and 96 h) are determined using a numerical optimization technique. Statistical tests comparing the pre-exercise and post-exercise model parameters report significant decreases in R ∞ and R 1 with significant increases in C at 72 h and 96 h post-exercise for exercised biceps (aligning with noted periods of peak swelling). These changes in R ∞ , R 1 , and C were not observed in the unexercised biceps. These results support that the C parameter of the Cole-impedance model fit to bioimpedance data may be a suitable marker for identifying skeletal muscle damage.

Eccentric exercise and delayed onset muscle soreness reduce the variability of active cervical movements

People with acute neck pain commonly present with restricted neck movement. However, it is unknown whether the presence of acute pain affects the quality of neck movement, specifically neck movement variability. We examined the effects of acute neck muscle soreness induced via eccentric exercise in healthy volunteers, on the variability of neck movement by examining changes in parameters of the helical axis during active neck movements. An experimental, single-arm repeated measures study recruited 32 healthy participants, male and female, aged between 18 and 55 years. Repetitive active neck movements (flexion-extension, bilateral lateral flexion and bilateral rotation) were performed at different speeds, either at full range of motion (RoM) or restricted to 45° RoM at baseline, pre-exercise (T0), immediately following eccentric neck exercise (T1), 24 h (T2) and 48 h post-exercise (T3). The mean distance (MD) and mean angle (MA) parameters of the helical axis were extracted to quantify movement variability. MD, measured during movements performed at full RoM, reduced significantly at T2 compared to T0 (P = 0.001) regardless of direction or speed of movement. MA was significantly lower at T2 and T3 compared to T1 (P = 0.029 and P = 0.033, respectively). When RoM was restricted to 45°, significantly lower MD values were observed at T3 compared to T1 (P = 0.034), and significantly lower MA values were measured at T3 compared to T0, T1 and T2 (all P < 0.0001). This study uniquely demonstrates that neck movement variability is reduced immediately after, 24 h and 48 h after eccentric exercise, indicating that acute neck muscle soreness modifies the quality of neck movement.

Validity and reliability of force-velocity outcome parameters in flywheel squats

Our study was designed to check the reliability of force-velocity (F-v) relationship outcome measures using flywheel (FW) squats. The main objectives at the primary level were to test intra-session reliability of mechanical parameters for ten equidistant FW loads, and at the secondary level, to test reliability and validity of the F-v relationship outcome measures in case any possible reduction in used loads and number of loads - compared to the 10-load method as a reference - is administered. Twenty-six subjects performed two sets of five squats with FW loads in the range 0.025-0.25 kg∙m2. Averaging six consecutive repetitions obtained ICC2.k > 0.9 for mean force and mean velocity results. Consecutively averaged parameters at the primary level showed excellent inter-set reliability (ICC2.1 > 0.9). The inverse F-v relationship was strong (R2 = 0.96). At the secondary level, Bland-Altman statistics showed decreasing bias and limits of agreement in combination with more loads. Theoretical maximal force and power showed smaller bias as F-v slope and theoretical maximal velocity for three loads or more. Four loads (0.025, 0.075, 0.225 and 0.25 kg∙m2) lowered bias to a 5% in relation to the reference F-v slope. In conclusion, six repetitions are required to obtain trustworthy force and velocity results. The results will contribute to standardising the methodology for assessing the mechanical capacities of leg muscles using FW resistance. Moreover, assessing individual F-v profile with reduced protocol may be a less fatiguing tool for prescribing exercise intensity and for assessing training adaptations.

Physiological factors determining downhill vs uphill running endurance performance

OBJECTIVES

Recent studies investigated the determinants of trail running performance (i.e., combining uphill (UR) and downhill running sections (DR)), while the possible specific physiological factors specifically determining UR vs DR performances (i.e., isolating UR and DR) remain presently unknown. This study aims to determine the cardiorespiratory responses to outdoor DR vs UR time-trial and explore the determinants of DR and UR performance in highly trained runners.

DESIGN

Randomized controlled trial.

METHODS

Ten male highly-trained endurance athletes completed 5-km DR and UR time-trials (average grade: ±8%) and were tested for maximal oxygen uptake, lower limb extensor maximal strength, local muscle endurance, leg musculotendinous stiffness, vertical jump ability, explosivity/agility and sprint velocity. Predictors of DR and UR performance were investigated using correlation and commonality regression analyses.

RESULTS

Running velocity was higher in DR vs UR time-trial (20.4±1.0 vs 12.0±0.5km·h^-1, p<0.05) with similar average heart rate (95±2% vs 94±2% maximal heart rate; p>0.05) despite lower average V̇O₂ (85±8% vs 89±7% V̇O_2max; p<0.05). Velocity at V̇O_2max (vV̇O_2max) body mass index (BMI) and maximal extensor strength were significant predictors of UR performance (r²=0.94) whereas vV̇O_2max, leg musculotendinous stiffness and maximal extensor strength were significant predictors of DR performance (r²=0.84).

CONCLUSIONS

Five-km UR and DR running performances are both well explained by three independent predictors. If two predictors are shared between UR and DR performances (vV̇O_2max and maximal strength), their relative contribution is different and, importantly, the third predictor appears very specific to the exercise modality (BMI for UR vs leg musculotendinous stiffness for DR).

Muscle activation during leg-press exercise with or without eccentric overload

PURPOSE

This study sought to investigate the electromyographic activity of the vastus lateralis (VL) muscle during concentric-eccentric exercise using a new concept leg press machine enabling a preset overloading in the eccentric phase.

METHODS

Ten young males familiar with resistive exercise were recruited for this study. Tests were performed on a Leg-press Biostrength® (Technogym S.p.A., Italy). The load was set to 70% and 80% of one-repetition maximum (1-RM). The participants performed 2 sets of 6 repetitions at each relative load with (ECC +) and without (ISOW) an eccentric overload equivalent to 150% of the concentric load. A metronome was employed to maintain the selected cadence. Sets were separated by a 5-min rest. Surface electromyography (EMG) of VL was recorded and integrated (iEMG).

RESULTS

Results showed a higher iEMG in ECC + with respect to ISOW at both intensities (+ 29% for 70% 1-RM, p < 0.01 and + 31% for 80% 1-RM, p < 0.001). No statistically significant differences were detected between concentric and eccentric phase in both ECC + conditions.

CONCLUSIONS

Training with a 150% eccentric overload provides a ~ 30% greater motor unit recruitment of the VL muscle in leg press exercise. Moreover, the results show that the eccentric overloading provided by the Biostrength® machine enables training at the same level of neural activation of the concentric phase. Hence, the derecruitment of motor units, normally observed during the eccentric phase when using conventional training machines, was overcome using the Biostrength® machine; this observation seems particularly important for maximizing neuromuscular responses to strength training.

The effect of vitamin D supplementation on serum total 25(OH) levels and biochemical markers of skeletal muscles in runners

Background

The beneficial adaptation of skeletal muscle function to strenuous exercise is partially attributable to the improvement of vitamin D status. The present study aimed to evaluate the effects of a 3-week vitamin D supplementation on serum 25(OH)D levels and skeletal muscle biomarkers (i.e. troponin, myoglobin, creatine kinase and lactic dehydrogenase) of endurance runners.

Methods

A double-blind placebo-controlled study design was used and vitamin D supplementation was compared to a non-treatment control group. Twenty-four runners, competitors of the ultra-marathons held during the National Running Championships, were randomly assigned into two groups supplemented with the dose of 2000 IU vitamin D or placebo for three weeks. All subjects participated in three exercise protocols: (a) incremental exercise test (to determine the maximum oxygen uptake and the intensity of eccentric exercise), (b) eccentric exercise before and (c) after two dietary protocols. Venous blood samples were drawn at rest, immediately after the exercise and after 1 h and 24 h of recovery in order to estimate serum 25(OH)D levels, skeletal muscle biomarkers, proinflammatory cytokines and tumor necrosis factor-alpha (TNF-α) levels. A two-way ANOVA was used to test main effects and their interactions and Pearson correlation coefficients were analyzed to determine the effects of inter-variable relationships.

Results

Significant differences between pre- and post-intervention in baseline 25(OH)D levels were observed (34.9 ± 4.7 versus 40.3 ± 4.9 ng/ml, p = 0.02) in supplemented group. A higher post intervention 25(OH)D level was observed after vitamin D diet compared to placebo (40.3 ± 4.9 versus 31.8 ± 4.2 ng/mL, respectively; p < 0.05). The vitamin D supplementation decreased post-exercise (TN max) and 1 h post-exercise troponin (p = 0.004, p = 0.03, respectively), 1 h post-exercise myoglobin concentration (p = 0.01) and TNF-α levels(p < 0.03). 24 h post exercise creatine kinase activity was significantly lower in supplemented group compared to placebo (p < 0.05). A negative correlation was observed between post exercise 25(OH)D levels and myoglobin levels (r = − 0.57; p = 0.05), and 25(OH)D levels and TNFα (r = − 0.58; p = 0.05) in vitamin D supplemented group.

Conclusions

Three weeks of vitamin D supplementation had a positive effect on serum 25(OH)D levels in endurance trained runners and it caused a marked decrease in post-exercise biomarkers levels. We concluded that vitamin D supplementation might play an important role in prevention of skeletal muscle injuries following exercise with eccentric muscle contraction in athletes.

BILATERAL SENSORY DEFICITS AND WIDESPREAD HYPERALGESIA OCCUR FOLLOWING INDUCED DELAYED ONSET MUSCLE SORENESS OF THE QUADRICEPS

BACKGROUND

Unaccustomed eccentric exercise during sport or training may lead to delayed onset muscle soreness (DOMS), which has been demonstrated to influence postural control, potentially resulting in further injury. Afferent sensory input is critical to effective postural control, but little is known about somatosensory changes at the knee following induction of DOMS of the quadriceps muscle. The 'soreness' or hyperalgesia associated with DOMS has been postulated to occur because of damage to/inflammation of the exercised muscle, however, effects on central nociceptive mechanisms, which are known to induce altered postural responses, have been less studied.

PURPOSE/HYPOTHESIS

It was hypothesized that DOMS of the quadriceps muscle would result in widespread hyperalgesia and hypoesthesia at the knee. Therefore, the purpose of this study was to investigate the effects of DOMS on knee somatosensory changes in asymptomatic healthy participants.

STUDY DESIGN

Quasi-experimental cohort study.

METHODS

Thirty participants (15 males and 15 females) took part in the study. Eccentric exercise consisted of 10 sets of 10 maximum eccentric quadriceps contractions performed with the dominant knee. Outcome measures consisted of pain intensity (Visual Analog Scale), pressure pain threshold (PPT), vibration perception threshold (VPT) and proprioception, measured via threshold to detection of passive motion (TDPM) at the knee, at three different assessment time points: (1) pre-eccentric exercise; (2) immediately and (3) 48 hours post-eccentric exercise.

RESULTS

Not surprisingly, pain intensity increased and PPT of the vastus medialis and rectus femoris muscles decreased (hyperalgesia) immediately post-exercise on the exercised limb. However, at 48 hours, hyperalgesia was demonstrated at other lower extremity muscles, including bilaterally at the tibialis anterior muscles, and also at the hand. Evidence of hypoesthesia was also demonstrated. VPT and TDPM increased (worsened) ipsilaterally both immediately and 48 hours after exercise, and TDPM increased bilaterally at 48 hours. Females demonstrated greater impairment in TDPM than males at 48 hours. Expanding distribution of hyperalgesia, ipsilaterally impaired VPT and bilaterally impaired proprioception were demonstrated in the presence of DOMS.

DISCUSSION/CONCLUSION

Inflammation from unaccustomed eccentric exercise may induce neuroplastic changes in nociceptive pathways resulting in wider distribution of pain and hypoesthesia. Futures studies examining the effect of DOMS related somatosensory changes on postural control may be warranted.

LEVEL OF EVIDENCE

3.

To Compare the Effect of Eccentric Exercises and Isometric Exercises for Achilles Tendinitis in Skaters

Background

Achilles tendinitis is one of the commonest injuries that happen to skaters. Roller skates traditionally have four wheels onto axles, one under the ball of the foot and one under the heel. Skaters have to maintain a closed kinematics chain which involves continuous trunk and hip flexion along with knee flexion and ankle dorsiflexion. It creates angular tension and strain in the muscles and tendons which can lead to different types of musculotendinous injuries. As not many studies has not been done on the prospect in India this study was done with a objective to compare the effect eccentric exercise and isometric exercise on Achilles tendinitis for skaters.

Methods

A Quasi-experimental study with 40 subjects of the age group between 15 and 25 was administered the VISA-A Questionnaire and VAS as outcome measures. A sample size of 40 was separated into two groups of 20 participants each into Group A (eccentric) and Group B (isometric). Pre-test and post-test were done using the VISA-A questionnaire and VAS Scale in the Study period- 4 weeks.

Results

There was a significant difference during the comparison between pre-test and post-test values (p < 0.005) of isometric exercise and eccentric exercise by VISA-A questionnaire and VAS scale but there was insignificance during the comparison of post-test values (p > 0.005) of the same.

Conclusion

The study concludes that there is a significant improvement in Achilles tendinitis when assessed with VISA-A questionnaire and VAS Scale for both the exercise; that is, eccentric and isometric, individually but it isn’t statistically significant enough to choose one method of intervention over the other.

Age-specific differences in the time-frequency representation of surface electromyographic data recorded during a submaximal cyclic back extension exercise: a promising biomarker to detect early signs of sarcopenia

PURPOSE

Motivated by the goal of developing new methods to detect early signs of sarcopenia, we investigated if surface electromyographic (SEMG) data recorded during the performance of cyclic, submaximal back extensions are marked by age-specific differences in their time and frequency characteristics. Furthermore, day-to-day retest reliability of the EMG measures was examined.

METHODS

A total of 86 healthy volunteers used a back dynamometer to perform a series of three maximal voluntary contractions (MVC) consisting of isometric back extensions, followed by an isometric back extension at 80% MVC, and finally 25 slow cyclic back extensions at 50% MVC. SEMG data was recorded bilaterally at L1, L2, and L5 from the iliocostalis lumborum, longissimus, and multifidus muscles, respectively. Tests were repeated two days and six weeks later. A linear mixed-effects model with fixed effects "age, sex, test number" and the random effect "person" was performed to investigate age-specific differences in both the initial value and the time-course (as defined by the slope of the regression line) of the root mean square (RMS-SEMG) values and instantaneous median frequency (IMDF-SEMG) values calculated separately for the shortening and lengthening phases of the exercise cycles. Generalizability Theory was used to examine reliability of the EMG measures.

RESULTS

Back extensor strength was comparable in younger and older adults. The initial value of RMS-SEMG and IMDF-SEMG as well as the RMS-SEMG time-course did not significantly differ between the two age groups. Conversely, the IMDF-SEMG time-course showed more rapid changes in younger than in older individuals. Absolute and relative reliability of the SEMG time-frequency representations were comparable in older and younger individuals with good to excellent relative reliability but variable absolute reliability levels.

CONCLUSIONS

The IMDF-SEMG time-course derived from submaximal, cyclic back extension exercises performed at moderate effort showed significant differences in younger vs. older adults even though back extension strength was found to be comparable in the two age groups. We conclude that the SEMG method proposed in this study has great potential to be used as a biomarker to detect early signs of sarcopenic back muscle function.

The effect of varying intensities of lower limb eccentric muscle contractions on left ventricular function

Purpose

The effect of eccentric (ECC) resistance exercise (RE) on myocardial mechanics is currently unknown.

Method

This study investigated ECC RE at varying intensities on left ventricular (LV) function using LV strain (ε), wall stress and haemodynamic parameters. Twenty-four healthy male volunteers completed ECC leg extensions at 20%, 50% and 80% of their ECC maximal voluntary contraction (MVC), whilst receiving echocardiograms. Global longitudinal ɛ, strain rate (SR), longitudinal tissue velocity, heart rate (HR), blood pressure (BP), mean arterial pressure (MAP), LV wall stress and rate pressure product (RPP) were assessed at baseline and during exercise.

Results

Left ventricular global ɛ, systolic SR and wall stress remained unchanged throughout. Systolic blood pressure (sBP), MAP and RPP increased at 80% and 50% intensities compared to rest (P < 0.01). Eccentric RE increased HR and peak late diastolic SR at all intensities compared to rest (P < 0.02).

Conclusion

The findings suggest acute ECC RE may not alter main parameters of LV function, supporting future potential for wider clinical use. However, future studies must investigate the impact of multiple repetitions and training on LV function.

Eccentric exercise and dietary restriction inhibits M1 macrophage polarization activated by high-fat diet-induced obesity

AIMS

Obesity induce low-grade inflammation and elicit insulin resistance (IR), exercise training accompanied by a low-fat diet has been prescribed as part of the treatment for managing obesity and IR. The purpose of this study is to evaluate the effect of eccentric exercise accompanied by a low-fat diet on glycolipid metabolism, exercise capacity, and macrophage polarization in obesity-induced IR mice.

MATERIALS AND METHODS

Mice were fed with 60% high fat diet (HFD) for 12 weeks and subsequently treated with eccentric exercise or/and dietary restriction for 8 weeks. Related biochemical index were examined both before and during intervention to evaluate the ability of glycolipid metabolism. Exercise capacity was measured to verify the results of biochemical index. At 12 weeks and 12 + 8 weeks, infiltration was observed by H&E staining in adipose tissue, and macrophage polarization was detected by Immunofluorescence staining and ELISA.

KEY FINDING

1) obesity-induced IR model was established by HFD fed for 12 weeks accompanied by impaired exercise ability and increased M1 macrophage, 2) eccentric exercise accompanied by a low-fat diet markedly rescued obesity-induced IR and improved exercise capacity, 3) eccentric exercise accompanied by a low-fat diet markedly inhibited M1 macrophage polarization and activated M2 macrophage.

SIGNIFICANCE

Eccentric exercise accompanied by a low-fat diet rescued obesity-induced IR and improved exercise capacity, which were associated with the inhibition of M1 macrophage polarization and the activation of M2 macrophage. These indicate that macrophage polarization provides the potential target of intervention for inflammation and IR in obesity.