Neuromuscular function after exercise-induced muscle damage: theoretical and applied implications

Effects of nociceptive and mechanosensitive afferents sensitization on central and peripheral hemodynamics following exercise-induced muscle damage

This study aims to test the separated and combined effects of mechanoreflex activation and nociception through exercise-induced muscle damage (EIMD) on central and peripheral hemodynamics before and during single passive leg movement (sPLM). Eight healthy young males undertook four experimental sessions, in which a sPLM was performed on the dominant limb while in each specific session the contralateral was: 1) in a resting condition (CTRL), 2) stretched (ST), 3) resting after EIMD called delayed onset muscle soreness (DOMS) condition, or 4) stretched after EIMD (DOMS + ST). EIMD was used to induce DOMS in the following 24-48 h. Femoral blood flow (FBF) was assessed using Doppler ultrasound whereas central hemodynamics were assessed via finger photoplethysmography. Leg vascular conductance (LVC) was calculated as FBF/mean arterial pressure (MAP). RR-intervals were analyzed in the time (root mean squared of successive intervals; RMSSD) and frequency domain [low frequency (LF)/high frequency (HF)]. Blood samples were collected before each condition and gene expression analysis showed increased fold changes for P2X4 and IL1β in DOMS and DOMS + ST compared with baseline. Resting FBF and LVC were decreased only in the DOMS + ST condition (-26 mL/min and -50 mL/mmHg/min respectively) with decreased RMSSD and increased LF/HF ratio. MAP, HR, CO, and SV were increased in ST and DOMS + ST compared with CTRL. Marked decreases of Δpeaks and AUC were observed for FBF (Δ: -146 mL/min and -265 mL respectively) and LVC (Δ: -8.66 mL/mmHg/min and ±1.7 mL/mmHg/min respectively) all P < 0.05. These results suggest that the combination of mechanoreflex and nociception resulted in decreased vagal tone and concomitant rise in sympathetic drive that led to increases in resting central hemodynamics with reduced limb blood flow before and during sPLM.NEW & NOTEWORTHY Exercise-induced muscle damage (EIMD) is a well-known model to study mechanical hyperalgesia and muscle peripheral nerve sensitizations. The combination of static stretching protocol on the damaged limb extensively increases resting central hemodynamics with reduction in resting limb blood flow and passive leg movement-induced hyperemia. The mechanism underlining these results may be linked to reduction of vagal tone with concomitant increase in sympathetic activity following mechano- and nociceptive activation.

Relationship Between Training Workloads, Match Workloads, and Match Performance in Elite Netball

PURPOSE

This study examined the relationships between training workloads, game workloads, and match performance in an elite netball team.

METHODS

Ten elite female netball athletes were monitored over a complete season. Training and game external workloads were determined through inertial movement units and expressed as absolute PlayerLoad (PL) and change of direction (COD). Monthly workload and training efficiency index were also calculated, which used internal workloads (session rating of perceived exertion and summated heart-rate zones). Game performance was assessed through a performance analysis statistic algorithm called NetPoints. To account for the influence of team game workloads on each other, the average workload for midcourt positions (avgMC) was calculated for each game. Data for each athlete were transformed into z scores, and linear mixed modeling was used to build models to examine the relationships between workloads and game performance.

RESULTS

Monthly PL, training efficiency index PL, and avgMC PL were statistically significant (P < .05) and positively related to game PL (z = 0.20-0.35, P < .001-.02). For game COD, statistically significant positive relationships were found between monthly COD (z = 0.29 [0.11], P = .01) and avgMC COD (z = 0.21 [0.09], P = .03). The models for NetPoints found significant negative relationships with monthly PL (z = 0.46 [0.12], P < .001) and COD (z = -0.36 [0.11], P = .01).

CONCLUSIONS

Higher monthly workloads are related to higher game workload; however, they are also related to decreases in match performance. Therefore, netball practitioners should consider that increases to training workload in a 4-week period prior to a game can influence game workloads and performance.

Repeated Bout Effect of Two Resistance Training Bouts on Bowling-Specific Performance in Male Cricketers

To examine the repeated bout effect (RBE) following two identical resistance bouts and its effect on bowling-specific performance in male cricketers. Male cricket pace bowlers (N = 10), who had not undertaken resistance exercises in the past six months, were invited to complete a familiarisation and resistance maximum testing, before participating in the study protocol. The study protocol involved the collection of muscle damage markers, a battery of anaerobic (jump and sprint), and a bowling-specific performance test at baseline, followed by a resistance training bout, and a retest of physical and bowling-specific performance at 24 h (T24) and 48 h (T48) post-training. The study protocol was repeated 7–10 days thereafter. Indirect markers of muscle damage were lower (creatine kinase: 318.7 ± 164.3 U·L⁻¹; muscle soreness: 3 ± 1), whilst drop jump was improved (~47.5 ± 8.1 cm) following the second resistance training bout when compared to the first resistance training bout (creatine kinase: 550.9 ± 242.3 U·L⁻¹; muscle soreness: 4 ± 2; drop jump: ~43.0 ± 9.7 cm). However, sport-specific performance via bowling speed declined (Bout 1: −2.55 ± 3.43%; Bout 2: 2.67 ± 2.41%) whilst run-up time increased (2.34 ± 3.61%; Bout 2: 3.84 ± 4.06%) after each bout of resistance training. Findings suggest that while an initial resistance training bout reduced muscle damage indicators and improved drop jump performance following a second resistance training bout, this RBE trend was not observed for bowling-specific performance. It was suggested that pace bowlers with limited exposure to resistance training should minimise bowling-specific practice for 1–2 days following the initial bouts of their resistance training program.

Are Measurement Instruments Responsive to Assess Acute Responses to Load in High-Level Youth Soccer Players?

Purpose

The aim of this study was to assess the short-term responsiveness of measurement instruments aiming at quantifying the acute psycho-physiological response to load in high-level adolescent soccer players.

Methods

Data were collected from 16 high-level male youth soccer players from the Under 15 age group. Players were assessed on two occasions during the week: after 2 days of load accumulation (“high load”) and after at least 48 h of rest. Measurements consisted of the Short Recovery and Stress Scale (SRSS), a countermovement jump (CMJ) and a sub-maximal run to assess exercise heart-rate (HRex) and heart-rate recovery (HRR60s). Training load was quantified using total distance and high-speed running distance to express external and sRPE training load to express internal load. It was expected that good instruments can distinguish reliably between high load and rest.

Results

Odd ratios (0.74–1.73) of rating one unit higher or lower were very low for athlete-reported ratings of stress and recovery of the SRSS. Standardized mean high load vs. rest differences for CMJ parameters were trivial to small (−0.31 to 0.34). The degree of evidence against the null hypothesis that changes are interchangeable ranged from p = 0.04 to p = 0.83. Moderate changes were observed for HRex (−0.62; 90% Cl −0.78 to −0.47; p = 3.24 × 10−9), while small changes were evident for HRR60s (0.45; 90% Cl 0.08–0.80; p = 0.04). Only small to moderate repeated-measures correlations were found between the accumulation of load and acute responses across all measurement instruments. The strongest relationships were observed between HRex and total distance (rm-r = −0.48; 90% Cl −0.76 to −0.25).

Conclusion

Results suggest that most of the investigated measurement instruments to assess acute psycho-physiological responses in adolescent soccer players have limited short-term responsiveness. This questions their potential usefulness to detect meaningful changes and manage subsequent training load and program adequate recovery.

Effect of 3 vs. 3 Soccer Small-Sided Game on Various Performance, Inflammatory, Muscle Damage and Hormonal Indicators in Semi-Professional Players

The purpose of this study was to examine the effect of a soccer small-sided game (SSG) on performance, inflammatory, muscle damage and hormonal indicators. Twenty-two male soccer players participated and were assigned to either experimental (EXP = 12) or control (CON = 10) groups. Subjective fatigue (RPE) and lactate (La¯) were measured during the SSG; vertical squat jump (SJ), 20-m sprint, creatine kinase (CK), interleukin-6 (IL-6), cortisol (C), and testosterone (T) were measured before (PRE), after (POST), 24 h, 48 h, and 72 h after the SSG in the EXP group. The heart rate during the SSG reached 92 ± 3% of their HRmax, whereas La¯ and RPE reached 13.02 ± 1.60 mmol·L−1 and 15 ± 1 after SSG, respectively. The IL-6, different among measurements (F (1.04, 11.50) = 504.82, p < 0.001), peaked (3.52 ± 0.43 pg·mL−1 [95%CI; 3.28−3.77]) after the SSG and returned to baseline 24 h later. The CK, different among measurements (F (1.76, 19.32) = 93.96, p < 0.001), peaked (536.58 ± 124.73U·L−1 [95%CI; 466.01−607.15]) 24 h after the SSG and remained significantly higher than PRE condition in POST and up to 72 h later. The T/C ratio, significantly different among measurements (F (1.73, 19.05) = 12.12, p < 0.001), was at its lowest (0.44 ± 0.16 [95%CI; 0.35−0.54]) immediately after the SSG (p < 0.05) and returned to baseline after 24 h. It seems that 48 h (at the most) after an SSG is adequate time for players to recover, and a high training load should be avoided sooner than 24 h after an SSG.

Heavy-intensity cycling and running work-rate associated to VO2max affects isokinetic strength, the dynamic control ratio but not the conventional H:Q ratio

BACKGROUND: Bilateral strength asymmetry and fatigue predispose athletes to various injuries and conventional methods appear to be poor predictors of lower extremity muscular performance under NF conditions. OBJECTIVE: The purpose of the study was to compare the conventional Hcon/Qcon (HQR) ratio and the dynamic control ratio (DCR: Hecc/Qcon) under non-fatiguing (NF) and fatiguing (F) conditions and verify the effects of heavy-intensity constant running and cycling exercise on the isokinetic performance. METHODS: Twenty healthy male participants performed running and cycling VO2max at work-rate associated with the achievement of VO2max (TTE). Isokinetic muscle strength performance was tested at 60 and 180∘/s before and after these sessions with 48-hour intervals. Quadriceps (QFR) and hamstring (HFR) muscle fatigue rates were also calculated during these sessions. Blood lactate concentration was measured before and two-minutes after running and cycling TTE. RESULTS: No between-condition differences were found for the HQR while the DCR decreased significantly at 180∘/s following cycling and running sessions (p< 0.05). Cycling TTE was positively correlated with in dominant (r= 0.535, p= 0.015) and non-dominant (r= 0.446, p= 0.048) QFR. Positive correlations were also found between running TTE and dominant (r= 0.500, p= 0.25) and non-dominant (r= 0.465, p= 0.039) HFR. CONCLUSIONS: The DCR obtained at fast angular velocities following a strenuous exercise seems to be the best indicator of muscle performance while its assessment under F conditions reveals higher ratios compared to NF conditions and conventional methods.

Acute physiological and perceptual responses to a netball specific training session in professional female netball players

The 24 h responses to professional female netball-specific training were examined. British Superleague players (n = 14) undertook a 90-min on-court training session incorporating key movement, technical, and scenario-specific match-play drills. Perceptual (mood, fatigue, soreness), neuromuscular (countermovement jump peak power output [PPO], PPO relative to mass [PPOrel], jump height [JH]), endocrine (salivary cortisol [C], testosterone [T] concentrations) and biochemical (creatine kinase concentrations [CK]) markers were assessed at baseline (immediately before; Pre), and immediately, two and 24 hours after (+0h, +2h, +24h) training. Session (sRPE) and differential (dRPE) ratings of perceived exertion were recorded at +0h. Identification of clear between time-point differences were based on the 95% confidence interval (CI) for mean differences relative to baseline values not overlapping. At +0h, C (raw unit mean difference from baseline; 95% CI: 0.16; 0.06 to 0.25 μg·dl^-1), T (32; 20 to 45 pg⋅ml^–1), CK (39; 28 to 50 u·L^-1), PPOrel (2.4; 0.9 to 3.9 W·kg^-1) and PPO (169; 52 to 286 W) increased. At +2h, fatigue (15; 7 to 24 AU), CK (49; 38 to 60 u·L^-1), and soreness (14; 3 to 25 AU) increased, while T (-24; -37 to -11 pg⋅ml^–1) and mood (-20; -27 to -12 AU) reduced. At +24h, CK increased (25; 13 to 36 u·L^-1) whereas PPOrel (-1.6; -3.2 to -0.1 W·kg^-1) and JH (-0.02; -0.03 to -0.08 m) reduced. Responses were variable specific, and recovery of all variables did not occur within 24h. The residual effects of the prior stimulus should be accounted for in the planning of training for professional female netball players.

The efficacy of intermittent pneumatic compression and negative pressure therapy on muscle function, soreness and serum indices of muscle damage: a randomized controlled trial

BACKGROUND

The study aimed to assess whether intermittent pneumatic compression (IPC) and intermittent negative pressure (INP) would attenuate the muscle damaging effects of eccentric exercise.

METHODS

Forty-five healthy males were recruited. Immediately post, 24 and 48 h post eccentric exercise consisting of 100 drop jumps, volunteers randomly received 30-min sessions of intermittent pneumatic compression (IPC, n = 15) or intermittent negative pressure (INP, n = 15), or sham microcurrent (PT, n = 15). Creatine kinase (CK), lactate dehydrogenase (LDH), isokinetic muscle strength, soreness and active flexion of the knee joint were measured after every therapy session.

RESULTS

No significant intergroup differences were observed in biochemical or functional measurements. However, there was an increase in muscle soreness (P < 0.05), CK and LDH activity (P < 0.05), and a reduction in muscle strength (P < 0.05) and range of active knee flexion (P < 0.05).

CONCLUSIONS

The prescription of IPC and INP did not attenuate the reduction of markers to muscle function or pain perception up to 48 h after muscle damaging exercise. Future research should focus on the potential impact of treatment frequency and duration on muscle recovery. Trial registration The study was retrospectively registered in the Australian New Zealand Clinical Trials Registry (ANZCTR); The trial registration number: ACTRN12621001294842; date of registration: 24/09/2021.

Potential Relevance of Bioactive Peptides in Sports Nutrition

Bioactive peptides are physiologically active peptides mostly derived from proteins following gastrointestinal digestion, fermentation or hydrolysis by proteolytic enzymes. It has been shown that bioactive peptides can be resorbed in their intact form and have repeatedly been shown to have a positive effect on health-related parameters such as hypertension, dyslipoproteinemia, inflammation and oxidative stress. In recent years, there has been increasing evidence that biologically active peptides could also play an important role in sports nutrition. Current studies have shown that bioactive peptides could have a positive impact on changes in body composition and muscular performance, reduce muscle damage following exercise and induce beneficial adaptions within the connective tissue. In the following overview, potential mechanisms as well as possible limitations regarding the sports-related effect of bioactive peptides and their potential mechanisms are presented and discussed. In addition, practical applications will be discussed on how bioactive peptides can be integrated into a nutritional approach in sports to enhance athletic performance as well as prevent injuries and improve the rehabilitation process.

Effect of heat pre-conditioning on recovery following exercise-induced muscle damage

This study investigated the influence of heat pre-conditioning on the recovery of muscle torque, microvascular function, movement economy and stride mechanics following exercise-induced muscle damage (EIMD). Twenty male participants were equally assigned to a control (CON) and an experimental group (HEAT), and performed a 30-min downhill run (DHR) to elicit EIMD. HEAT group received three consecutive days of heat exposure (45.1 ​± ​3.2 ​min of hot water immersion at 42 ​°C) prior to DHR. Microvascular function (near-infrared spectroscopy), maximal voluntary contraction (MVC) torque of the knee extensors, as well as two treadmill-based steady-state runs performed below (SSR-1) and above (SSR-2) the first ventilatory threshold were assessed prior to DHR and repeated for four consecutive days post-DHR (D1-POST to D4-POST). The decline in MVC torque following EIMD was attenuated in HEAT compared with CON at D1-POST (p ​= ​0.037), D3-POST (p ​= ​0.002) and D4-POST (p ​= ​0.022). Muscle soreness increased in both CON and HEAT, but was significantly attenuated in HEAT compared with CON at D2-POST (p ​= ​0.024) and D3-POST (p ​= ​0.013). Microvascular function decreased in CON from D1-POST to D3-POST (p ​= ​0.009 to 0.018), and was lower compared with HEAT throughout D1-POST to D3-POST (p ​= ​0.003 to 0.017). Pre-heat treatment decreased the magnitude of strength loss and muscle soreness, as well as attenuated the decline in microvascular function following EIMD. Heat treatment appears a promising pre-conditioning strategy when embarking on intensified training periods or competition.

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Three days of heat pre-conditioning decreases the extent of strength loss, soreness and microvascular function after EIMD.

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Pre heat treatment might be a promising preconditioning tool prior to intensified training periods or competition.

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Heat tretament may positively impact activities of daily living, training quality and adherence to training programs.

Comparison between cryotherapy and photobiomodulation in muscle recovery: a systematic review and meta-analysis

The purpose of this study is to compare the effect of photobiomodulation therapy (PBMT) and cryotherapy (CRT) on muscle recovery outcomes. These searches were performed in PubMed, PEDro, CENTRAL, and VHL (which includes the Lilacs, Medline, and SciELO database) from inception to June 2021. We included randomized clinical trials involved healthy human volunteers (> 18 years) underwent an intervention of PBMT and CRT, when used in both isolated form post-exercise. Standardized mean differences (SMD) or mean difference (MD) with 95% confidence interval were calculated and pooled in a meta-analysis for synthesis. The risk of bias and quality of evidence were assessed through Cochrane risk-of-bias tool and GRADE system. Four articles (66 participants) with a high to low risk of bias were included. The certainty of evidence was classified as moderate to very low. PBMT was estimated to improve the muscle strength (SMD = 1.73, CI 95% 1.33 to 2.13, I² = 27%, p < 0.00001), reduce delayed onset muscle soreness (MD: - 25.69%, CI 95% - 34.42 to - 16.97, I² = 89%, p < 0.00001), and lower the concentration of biomarkers of muscle damage (SMD =  - 1.48, CI 95% - 1.93 to - 1.03, I² = 76%, p < 0,00,001) when compared with CRT. There was no difference in oxidative stress and inflammatory levels. Based on our findings, the use of PBMT in muscle recovery after high-intensity exercise appears to be beneficial, provides a clinically important effect, and seems to be the best option when compared to CRT.

Preliminary Investigations Into the Effect of Exercise-Induced Muscle Damage on Systemic Extracellular Vesicle Release in Trained Younger and Older Men

Background: Exercise-induced muscle damage (EIMD) results in transient muscle inflammation, strength loss, and muscle soreness and may cause subsequent exercise avoidance. Research has recently proven that skeletal muscle can also release extracellular vesicles (EVs) into the circulation following a bout of exercise. However, EV’s potential role, including as a biomarker, in the response to eccentric resistance exercise stimulus remains unclear.

Methods: Twelve (younger, n=7, 27.0±1.5years and older, n=5, 63.0±1.0years) healthy, physically active males, undertaking moderate, regular physical activity (3–5 times per week) performed a unilateral high intensity eccentric exercise protocol. Venous plasma was collected for assessment of EVs and creatine kinase (CK) prior to EIMD, immediately after EIMD, and 1–72h post-EIMD, and maximal voluntary isometric contraction (MVIC) and delayed onset muscle soreness (DOMS) were assessed at all time points, except 1 and 2h post-EIMD.

Results: A significant effect of both time (p=0.005) and group (p<0.001) was noted for MVIC, with younger participants’ MVIC being higher throughout. Whilst a significant increase was observed in DOMS in the younger group (p=0.014) and in the older group (p=0.034) following EIMD, no significant differences were observed between groups. CK was not different between age groups but was altered following the EIMD (main effect of time p=0.026), with increased CK seen immediately post-, at 1 and 2h post-EIMD. EV count tended to be lower in older participants at rest, relative to younger participants (p=0.056), whilst EV modal size did not differ between younger and older participants pre-EIMD. EIMD did not substantially alter EV modal size or EV count in younger or older participants; however, the alteration in EV concentration (ΔCount) and EV modal size (ΔMode) between post-EIMD and pre-EIMD negatively associated with CK activity. No significant associations were noted between MVIC or DOMS and either ΔCount or ΔMode of EVs at any time point.

Conclusion: These findings suggest that profile of EV release, immediately following exercise, may predict later CK release and play a role in the EIMD response. Exercise-induced EV release profiles may therefore serve as an indicator for subsequent muscle damage.

Neuromuscular responses to isometric, concentric and eccentric contractions of the knee extensors at the same torque-time integral

PURPOSE

The present study compared isometric, concentric and eccentric contractions at the same torque-time integral for changes in neuromuscular fatigue and muscle damage parameters.

METHOD

Healthy men (18-24 years) were placed to either isometric (ISO), concentric (CONC), or eccentric (ECC) group (n = 11/group) that performed corresponding contractions of the knee extensors to exert the same amount of torque-time integral (24,427 ± 291 Nm·s). Changes in maximal voluntary contraction (MVC) torque, voluntary activation, evoked torque at 10 Hz and 100 Hz and its ratio, M-wave amplitude, and muscle soreness were assessed immediately before and after, 1 h, 1 day and 2 days after each exercise, and were compared among the groups.

RESULTS

MVC torque decreased immediately after ISO (- 17.0 ± 8.3%), CONC (- 21.7 ± 11.5%) and ECC (- 26.2 ± 15.6%) similarly (p = 0.35), but the decrease sustained longer (p < 0.05) for ECC (2 days post-exercise: - 12.9 ± 14.8%) and ISO (- 5.5 ± 7.9%) than CONC (+ 5.0 ± 11.0%). Muscle soreness developed after ECC (25.1 ± 19.8 mm) and ISO (17.5 ± 21.0 mm) similarly (p = 0.15). Voluntary activation decreased immediately (- 3.7 ± 6.6%) and 1 h post-exercise (- 4.7 ± 7.6%) for all groups similarly. Electrically evoked forces decreased greater immediately (- 30.1 ± 15.6%) and 1 h post-exercise (- 35.0 ± 12.8%) for ECC than others, and the decrease in 10/100 Hz ratio was also greater immediately (- 30.5 ± 12.6%) and 1 h after ECC (- 23.8 ± 10.3%) than others.

CONCLUSION

ISO, CONC and ECC with the same torque-time integral produced similar neuromuscular fatigue at immediately post-exercise, but the force loss was longer-lasting after ISO and ECC than CONC, and the changes in peripheral fatigue parameters were the greatest after ECC, suggesting greater muscle damage.

Acute and prolonged effects of the simulated physical demands of a futsal match on lower limb muscle power and strength, sprint performance and muscle soreness

BACKGROUND: Prolonged fatigue effects may be a concern after futsal matches mainly because of the actions performed by futsal players (e.g., sprinting, jumping) that usually involve the stretch-shortening cycle (SSC). However, there no studies analyzed the prolonged effects of futsal-specific fatigue and how futsal players can recover from performance tasks. OBJECTIVE: To analyze the acute and prolonged effects of a protocol that simulates specific physical demands of futsal on countermovement-jump, sprint performance, muscle strength and muscle soreness. METHODS: Fifteen amateur futsal male athletes (18.3 ± 3.8 years) performed a futsal intermittent running protocol (FIRP) and were assessed for (moment production, sprint and jumping performance and muscle soreness) at pre, during half-time, immediately after, post 24 and 48 hours after the FIRP. Analysis of variance (repeated measures) was used to compare variable means over time. RESULTS: The main results indicated a decrement in the CMJ height (p= 0.03) and an increase of 10 m and 20 m sprint times (p= 0.01–p< 0.01, respectively) during half-time and the post FIRP. There was a decrement in eccentric peak moment of the knee extensors (p= 0.02) and flexors (p< 0.01) until 48h post protocol and a decrement in concentric peak moment of the flexors (p< 0.01) post protocol. Athletes reported muscle soreness in the hamstrings (p= 0.03) post and 24 h after the FIRP. CONCLUSION: FIRP induced acute effects in the jump and sprint performances only. On the other hand, the knee moment production capability (mainly eccentric) suffered acute and also prolonged effects of the FIRP accompanied by delayed muscle soreness in the hamstring muscles.

Local vibration therapy increases oxygen re-saturation rate and maintains muscle strength following exercise-induced muscle damage

CONTEXT

Exercise induced muscle damage (EIMD) is associated with transient reductions in strength and athletic performance. Studies conclude aetiology is due in part to muscle micro vascular damage and disruption of blood flow. Previous research on vibration therapy reports modulation in muscle blood flow, oxygenation and strength.

OBJECTIVE

The aim of this study was to observe if local vibration therapy (VT) alleviates the impairments and haemodynamic changes associated with EIMD.

DESIGN

Controlled laboratory study.

SETTING

Laboratory and public gymnasium.

PATIENTS OR OTHER PARTICIPANTS

Ten healthy participants (6 males: 4 females; age: 38±15 yrs; height: 1.72±0.48 m; mass 72.0±10.4 kg) were randomized into experimental (VT) and control (CON) groups.

INTERVENTIONS

Both groups performed 10 sets of 10 eccentric wrist flexions at 70% of 1-repetition maximum to induce muscle damage. Subsequent assessment of wrist flexor strength and flexor carpus ulnaris (FCU) muscle oxygen saturation (SmO2) occurred at 1-, 24- and 48 hr-post exercise. VT group underwent 10 min of local VT (45 Hz) starting 1 hr-post exercise and applied twice daily (separated by 8 hrs) for 48 hrs during habitual waking hours. CON group received no local VT.

MAIN OUTCOME MEASURE(S)

Grip strength, resting muscle oxygen (SmO2), muscle oxygen de-saturation and re-saturation rate.

RESULTS

No difference in grip strength observed pre EIMD, but the VT group demonstrated greater strength at 1 hr (P=0.004), 24 hr (P=0.031) and 48 hr (P=0.021) post EIMD compared to controls. No difference in SmO2 re-saturation over time (P>0.05), but the VT group had a greater re-saturation rate compared to controls at 1 hr (P=0.007, d = 2.6), 24 hr (P=0.001 d = 3.1) and 48 hr (P=0.035, d = 1.7) post EIMD.

CONCLUSIONS

Local VT successfully attenuated the effects of EIMD and increased SmO2 re-saturation in FCU muscles. Including local VT as part of a recovery protocol post-EIMD could be beneficial for rehabilitation and athletic training purposes.

Effects of Beetroot Supplementation on Recovery After Exercise-Induced Muscle Damage: A Systematic Review

CONTEXT

Beetroots have antioxidant and anti-inflammatory properties, which may help attenuate inflammation and oxidative stress, enhancing recovery from exercise-induced muscle damage (EIMD).

OBJECTIVE

To evaluate the effects of beetroot supplementation on oxidative stress, inflammation, and recovery after EIMD.

DATA SOURCES

SPORTDiscus, PubMed, Web of Science, and Scopus databases were searched, and hand-searching was performed by looking to relevant studies that were cited in other studies.

STUDY SELECTION

For a study to be included in this review, the following inclusion criteria had to be met: (1) research conducted with human participants, (2) original articles in peer-reviewed publications, (3) original studies that had investigated beetroot supplementation intervention on muscle damage and recovery, (4) research conducted with 1 control/placebo group, and (5) articles published from inception to October 2020.

STUDY DESIGN

Systematic review using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement.

LEVEL OF EVIDENCE

Level 3.

DATA EXTRACTION

Two of the 4 authors independently extracted data and assessed the methodological quality of the articles with the PEDro scale. All discrepancies were resolved through a consensus meeting.

RESULTS

A total of 9 studies were included in this review. The methodological quality of the included studies ranged from moderate to high. Most of the studies found a better recovery of functional variables and muscle soreness, but improvements in markers of muscle damage, inflammation, and oxidative stress were not reported.

CONCLUSION

The existing evidence suggests that a short-term beetroot supplementation has the potential to accelerate recovery of functional measures and muscle soreness, but further research is needed to clarify if a longer supplementation period (with some days before exercise and some days after) could also promote recovery of markers of muscle damage, inflammation, and oxidative stress.

Peripheral Alterations Affect the Loss in Force after a Treadmill Downhill Run

Downhill running has an important effect on performance in trail running competitions, but it is less studied than uphill running. The purpose of this study was to investigate the cardiorespiratory response during 15 min of downhill running (DR) and to evaluate the neuromuscular consequences in a group of trail runners. Before and after a 15-min DR trial (slope: −25%) at ~60% of maximal oxygen consumption (V̇O₂max), we evaluated maximal voluntary contraction torque (MVCt) and muscle contractility in a group of seventeen trail running athletes. Additionally, during the DR trial, we measured V̇O₂ and heart rate (HR). V̇O₂ and HR increased as a function of time, reaching +19.8 ± 15.9% (p < 0.001; ES: 0.49, medium) and +15.3 ± 9.9% (p < 0.001; ES: 0.55, large), respectively, in the last minute of DR. Post-exercise, the MVCt decreased (−22.2 ± 12.0%; p < 0.001; ES = 0.55, large) with respect to the pre-exercise value. All the parameters related to muscle contractility were impaired after DR: the torque evoked by a potentiated high frequency doublet decreased (−28.5 ± 12.7%; p < 0.001; ES: 0.61, large), as did the torque response from the single-pulse stimulation (St, −41.6 ± 13.6%; p < 0.001; ES: 0.70, large) and the M-wave (−11.8 ± 12.1%; p < 0.001; ES: 0.22, small). We found that after 15 min of DR, athletes had a decreased MVCt, which was ascribed mainly to peripheral rather than central alterations. Additionally, during low-intensity DR exercise, muscle fatigue and exercise-induced muscle damage may contribute to the development of O₂ and HR drift.

Amino Acids and Their Metabolites for Improving Human Exercising Performance

Achieving adequate nutrition for exercising humans is especially important for improving both muscle mass and metabolic health. One of the most common misunderstandings in the fitness industry is that the human body has requirements for dietary whole protein and that exercising individuals must consume only whole protein to meet their physiological needs. This view, however, is incorrect. Instead, humans at rest or during exercise have requirements for dietary amino acids (AAs), and dietary protein is a source of AAs in the body. The requirements for AAs must be met each day to avoid a negative nitrogen balance in individuals with moderate or intense physical activity. By properly meeting increased requirements for AAs through increased intake of high-quality protein (the source of AAs) plus supplemental AAs, athletes can improve their overall athletic performance. AAs or metabolites that are of special importance for exercising individuals include arginine, branched-chain AAs, creatine, glycine, taurine, and glutamine. The AAs play vital roles as both substrates for protein synthesis and molecules for regulating blood flow and nutrient metabolism. The functional roles of AAs include the maintenance of cell and tissue integrity; stimulation of mechanistic target of rapamycin and AMP-activated protein kinase cell signaling pathways; energy sources for the small intestine, cells of the immune system, and skeletal muscle; antioxidant and anti-inflammatory reactions; production of neurotransmitters; modulation of acid-base balance in the body. All of those roles are crucial for the overall goal of improving exercise performance. Therefore, adequate intakes of proteinogenic AAs and their functional metabolites, especially those noted in this review, are essential for optimal human health (including optimum muscle mass and function) and should be a primary goal of exercising individuals.

Effects of omega-3 supplementation on muscle damage after resistance exercise in young women: a randomized placebo-controlled trial

BACKGROUND

Omega-3 is a nutritional strategie that have been used to recover muscles from exercise-induced muscle damage in a preventive perspective.

AIM

To verify whether omega-3 (ω-3) supplementation after a session of resistance exercise facilitates muscle recovery in women undergoing a balanced diet.

METHODS

This clinical trial was registered under the number NCT02839525. Thirty healthy women (22.2 ± 3.3 years) participated in this double-blinded, placebo-controlled trial. They were randomly distributed into ω-3 (n=15) and placebo (n=15) groups. They ingested ω-3 fish oil (3200 mg/day) or placebo (olive oil) at the dinner after the exercise bout (10 sets of 10 unilateral eccentric contractions in a knee extension chair), as well as at lunch for the three subsequent days. In addition, both groups followed a balanced diet along the four days. Muscle soreness and maximal isometric and isokinetic voluntary contractions were assessed immediately before, and 24, 48, and 72 hours after the resistance exercise.

MAIN FINDINGS

There was no significant group-time interaction for any outcome. Participants presented increased levels of muscle soreness and reduced muscle strength capacity along the three days after exercise. There was no difference between placebo and ω-3 groups.

CONCLUSION

Supplementation of ω-3 fish oil for three days after resistance exercise provided no additional benefits compared to placebo supplementation on recovery of healthy young women following a balanced diet.

Immediate Effects of Acupuncture on Force and Delayed Onset of Muscle Soreness

Background: The ability to produce force is critical to several daily activities. Strategies to reduce delayed onsent muscle soreness (DOMS) and restore force-generating properties that occur in response to training and impair physical performance have been proposed. Acupuncture has been proposed to accelerate recovery and optimize muscle functioning. It was to determine the effects of acupuncture on DOMS and on the muscle force production capacity. Methods: Thirty physically active volunteers (26.3 ± 3.1 years old, 1.70 ± 0.08 m, 66.5 ± 12.6 kg) were allocated in a control (CG; n = 10), placebo (PG; n = 10), and acupuncture (AG; n = 10) groups. The groups were subjected to an exercise protocol to induce DOMS and were assessed for muscle force, threshold, and rate of perceived pain and activation of the biceps brachialis muscle before (PRE) and 20 minutes after (POST) a single acupuncture session using a mixed model analysis. Results: The threshold and rate of perceived pain were reduced in the AG (P < 0.05) but remained unchanged in the other groups (P > 0.05). Muscle activation also showed larger changes in the AG in comparison with the other groups (P < 0.05). No changes in the ability to produce force were found after acupuncture in any groups (P > 0.05). Conclusions: Acupuncture may reduce discomfort and improve muscle activation but was not effective to promote force improvement and/or restore the force-generating properties. It may be speculated that muscle disruption may have played a role and did not allow participants to restore their muscular performance. Rebec Number; RBR-8bh5k7 (www.ensaiosclinicos.gov.br/rg/RBR-8bh5k7); Clinical Trial Registry (UTN No.: U1111-1234-9553).

Does Branched-Chain Amino Acids (BCAAs) Supplementation Attenuate Muscle Damage Markers and Soreness after Resistance Exercise in Trained Males? A Meta-Analysis of Randomized Controlled Trials

Previous studies have reported the positive effects of branched-chain amino acids (BCAAs) supplementation on lowering plasma markers of muscle damage and subjective soreness after resistance exercise. However, a variety of factors can potentially moderate its efficacy. This meta-analysis aimed to summarize the evidence regarding the effect of BCAAs supplementation on plasma muscle damage markers and soreness after resistance exercise in only trained males, by considering the plasma lactate dehydrogenase (LDH) and creatine kinase (CK). Randomized controlled trials were identified through a computerized literature search for the period 2010–2020. The pooled data were analyzed with the random-effects model and heterogeneity using I². Cochrane Collaboration tools was used for the assessment of risk of bias. Nine studies met the inclusion criteria. A positive effect was found for CK at <24, 24, and 48 h after exercise and for muscle soreness at <24 h only. However, the positive effect was not evident for plasma LDH at any follow-up time. Different outcomes for post-exercise responses may suggest that BCAAs supplementation can attenuate muscle damage and ameliorate muscle soreness after resistance exercise in trained males.

Palmitoylethanolamide: A Natural Compound for Health Management

All nations which have undergone a nutrition transition have experienced increased frequency and falling latency of chronic degenerative diseases, which are largely driven by chronic inflammatory stress. Dietary supplementation is a valid strategy to reduce the risk and severity of such disorders. Palmitoylethanolamide (PEA) is an endocannabinoid-like lipid mediator with extensively documented anti-inflammatory, analgesic, antimicrobial, immunomodulatory and neuroprotective effects. It is well tolerated and devoid of side effects in animals and humans. PEA's actions on multiple molecular targets while modulating multiple inflammatory mediators provide therapeutic benefits in many applications, including immunity, brain health, allergy, pain modulation, joint health, sleep and recovery. PEA's poor oral bioavailability, a major obstacle in early research, has been overcome by advanced delivery systems now licensed as food supplements. This review summarizes the functionality of PEA, supporting its use as an important dietary supplement for lifestyle management.

Moderate intensity cycling is better than running on recovery of eccentric exercise-induced muscle damage

OBJECTIVE

To compare the effects of moderate intensity running and cycling on markers of exercise-induced muscle damage in men.

STUDY DESIGN

Randomized controlled trial.

SETTING

Laboratory.

PARTICIPANTS

Thirty volunteers were randomized in three groups [running (RG; n = 10), cycling (CG; n = 10) and control (CON; n = 10)] and were evaluated at baseline, post 24, 48 and 72 h of knee extensors' muscle damage protocol. CON performed passive recovery, while RG and CG performed active recovery immediately after the protocol, as well as 24 h and 48 h afterwards.

MAIN OUTCOMES

(i) maximal voluntary isometric contraction (MVIC); (ii) delayed-onset muscle soreness (DOMS); (iii) plasma creatine kinase (CK) and lactate dehydrogenase (LDH) levels.

RESULTS

No group-by-time interaction was found in any outcome evaluated (p > 0.05). All groups presented decreases in MVIC and increases in DOMS (p < 0.001), without differences in CK and LDH. Compared with CON, exercise groups presented likely beneficial effects for LDH, while only CG had a likely beneficial effect for DOMS. Lastly, CG presented likely/very likely beneficial effects for MVIC and DOMS compared to RG.

CONCLUSION

Although the null hypothesis analysis did not find differences, the magnitude-based inference analysis suggested that moderate intensity cycling have likely beneficial effects on knee extensor muscle recovery after eccentric exercise protocol.

Muscle Damage and Performance after Single and Multiple Simulated Matches in University Elite Female Soccer Players

The present study aimed to compare changes in muscle damage and performance parameters after playing single versus multiple soccer matches to examine fixture congestion effects on performance. Twelve elite female university soccer players performed single, three and six consecutive 90-min bouts of the Loughborough Intermittent Shuttle Test (LIST) with ≥12-weeks between conditions in a pseudo-randomized order. Heart rate, blood lactate, rating of perceived exertion and covering distance in each LIST were examined. Changes in several types of muscle damage (e.g., maximal voluntary isometric torque of the knee extensors: MVC-KE) and performance measures (e.g., Yo-Yo Intermittent Recovery Test level 1: YYIR1) were taken before each LIST, 1 h, and 1–5 d after the last LIST. The total distance covered during the LIST was shorter (p < 0.05) in the 2nd–3rd, or 2nd–6th LISTs when compared with the 1st LIST. Changes (p < 0.05) in all measures were observed after the LIST, and the greatest changes were observed after the six than after the three LISTs followed by one LIST (e.g., largest changes in MVC-KE: −26 > −20 > −14%; YYIR1: −31 > −26 > −11%). Many of the variables did not recover to the baseline for 5 d after six LISTs. These suggest that fixture congestion induces greater muscle damage and performance decline than a single match.

Criterion Validity of a MARG Sensor to Assess Countermovement Jump Performance in Elite Basketballers

ABSTRACT

Staunton, CA, Stanger, JJ, Wundersitz, DW, Gordon, BA, Custovic, E, and Kingsley, MI. Criterion validity of a MARG sensor to assess countermovement jump performance in elite basketballers. J Strength Cond Res 35(3): 797-803, 2021-This study assessed the criterion validity of a magnetic, angular rate, and gravity (MARG) sensor to measure countermovement jump (CMJ) performance metrics, including CMJ kinetics before take-off, in elite basketballers. Fifty-four basketballers performed 2 CMJs on a force platform with data simultaneously recorded by a MARG sensor located centrally on the player's back. Vertical accelerations recorded from the MARG sensor were expressed relative to the direction of gravity. Jumps were analyzed by a blinded assessor and the best jump according to the force platform was used for comparison. Pearson correlation coefficients (r) and mean bias with 95% ratio limits of agreement (95% RLOA) were calculated between the MARG sensor and the force platform for jumps performed with correct technique (n = 44). The mean bias for all CMJ metrics was less than 3%. Ninety-five percent RLOA between MARG- and force platform-derived flight time and jump height were 1 ± 7% and 1 ± 15%, respectively. For CMJ performance metrics before takeoff, impulse displayed less random error (95% RLOA: 1 ± 13%) when compared with mean concentric power and time to maximum force displayed (95% RLOA: 0 ± 29% and 1 ± 34%, respectively). Correlations between MARG and force platform were significant for all CMJ metrics and ranged from large for jump height (r = 0.65) to nearly perfect for mean concentric power (r = 0.95). Strong relationships, low mean bias, and low random error between MARG and force platform suggest that MARG sensors can provide a practical and inexpensive tool to measure impulse and flight time-derived CMJ performance metrics.

Neuromuscular fatigue and recovery after strenuous exercise depends on skeletal muscle size and stem cell characteristics

Hamstring muscle injury is highly prevalent in sports involving repeated maximal sprinting. Although neuromuscular fatigue is thought to be a risk factor, the mechanisms underlying the fatigue response to repeated maximal sprints are unclear. Here, we show that repeated maximal sprints induce neuromuscular fatigue accompanied with a prolonged strength loss in hamstring muscles. The immediate hamstring strength loss was linked to both central and peripheral fatigue, while prolonged strength loss was associated with indicators of muscle damage. The kinematic changes immediately after sprinting likely protected fatigued hamstrings from excess elongation stress, while larger hamstring muscle physiological cross-sectional area and lower myoblast:fibroblast ratio appeared to protect against fatigue/damage and improve muscle recovery within the first 48 h after sprinting. We have therefore identified novel mechanisms that likely regulate the fatigue/damage response and initial recovery following repeated maximal sprinting in humans.

Resistance Training Affects Neuromuscular Fatigue But Not Efficiency in Elite Rowers

PURPOSE

To investigate how resistance training (RT) in a regular training program affects neuromuscular fatigue (NMF) and gross efficiency (EGROSS) in elite rowers.

METHODS

Twenty-six elite male rowers performed 4 RT sessions within 10 days. At baseline and after the first and fourth RT, EGROSS and NMF were established. From breathing gas, EGROSS was determined during submaximal rowing tests. Using a countermovement jump test, NMF was assessed by jump height, flight time, flight-to-contraction-time ratio, peak power, and time to peak power. Muscle soreness was assessed using a 10-cm-long visual analog scale.

RESULTS

No significant differences were found for EGROSS (P = .565, ω2 = .032). Muscle soreness (P = .00, ω2 = .500) and time to peak power (P = .08, ω2 = 0.238) were higher compared with baseline at all test moments. Flight-to-contraction-time ratio, jump height, and peak power after the fourth RT differed from baseline (P < .05, ω2 = .36, ω2 = .38, and ω2 = .31) and from results obtained after the first RT (P < .05, ω2 = .36, ω2 = .47, and ω2 = .22).

CONCLUSIONS

RT in general does not influence EGROSS, but large individual differences (4.1%-14.8%) were observed. NMF is affected by RT, particularly after multiple sessions. During periods of intensified RT, imposed external load for low-intensity endurance training need not be altered, but rowers are recommended to abstain from intensive endurance training. Individual monitoring is strongly recommended.

Six weeks of Jilin ginseng root supplementation attenuates drop jump-related muscle injury markers in healthy female college students

BACKGROUND

Eccentric muscle contraction is an inherent component of numerous sporting movements but can result in muscle fatigue and injury, especially when engaging in unfamiliar exercise, which requires pharmacological intervention. Jilin ginseng root (GS) has been used to protect muscles and reduce the risk of exercise injury.

AIM OF THE STUDY

In this study, we sought to examine and demonstrate the effectiveness of using GS in preventing muscle stiffness and reducing the risk of exercise injury in women.

METHODS

Twenty females were randomly assigned to GS and placebo groups. Body composition, serum biochemistry index, kinematics, and endurance exercise tests were measured at two time point presupplementation and 6 weeks after supplementation. The major compounds of GS were characterized using a high-performance liquid chromatograph with a gradient delivery system (HPLC).

RESULTS

After 6 weeks of supplementation, the GS group exhibited significant increases in the serum levels of free fatty acids and glucose as well as greater maximum oxygen consumption (VO2 max, mL min-1 kg-1) compared with the placebo group in an exhaustive biking test. Following drop jump tests, the jump height and reactive strength index were increased in the GS group after completing 70 DJs. In addition, subjects in the GS group also showed decreased knee and ankle stiffness in DJs, leading to reduced fatigue associated with eccentric movement.

CONCLUSIONS

GS supplementation leads to ameliorates drop jump muscle stiffness and fatigue in females and is to be used as a nutrient supplement to reduce the risk of musculoskeletal system injuries when performing drop jumps.

Acute and Delayed Effects of Fatigue on Ground Reaction Force, Lower Limb Stiffness and Coordination Asymmetries During a Landing Task

Landing is a critical phase of movement for injury occurrence, in which lower limbs should be used equally to better absorb the shock. However, it has been suggested that fatigue can lead to the appearance of asymmetries. The aim of this study was to verify the acute and delayed effects of fatigue on the lower limb asymmetry indexes of peak ground reaction force, leg stiffness and intra-limb coordination during a landing task. Fifteen physically active men performed a fatigue protocol composed of 14 sets of 10 continuous vertical jumps, with a one-minute rest interval between the sets. A step-off landing task was performed before, immediately after, 24 h and 48 h after the fatigue protocol. Two force plates and a video analysis system were used. The symmetry index equation provided the asymmetry indexes. For statistical analysis, ANOVA and effect size analysis were utilized. Inferential statistics did not show the effect of fatigue in the asymmetry indexes for any variable or condition (p > .05). Moderate effect sizes were observed for peak ground reaction force (0.61) and leg stiffness (0.61) immediately after the application of the protocol. In conclusion, fatigue does not seem to significantly change the asymmetries of lower limbs, especially regarding intra-limb coordination. The moderate effects observed for peak ground reaction force and leg stiffness asymmetries suggest that these variables may be acutely affected by fatigue.

Considerations in interpreting neuromuscular state in elite level Australian Rules football players

OBJECTIVES

Examine the influence of test modality, season stage, match load and physical qualities on the interpretation of neuromuscular function (NF) post Australian Rules Football (ARF) matches.

DESIGN

Repeated measures design.

METHODS

Thirty-two elite ARF players' NF was assessed 72h following competitive matches (7±2) via the counter movement jump (CMJ) and isometric mid-thigh pull (IMTP). Influence of season stage, external load parameters (GPS; 10Hz) and moderating influences of lower body strength (LBS), lower body power (LBP) and intermittent exercise capacity upon NF recovery were assessed using linear mixed effects models.

RESULTS

Moderate negative seasonal trends were evident for both rate of force development (RFD) 0-100ms (d=-0.86, 95%, CI: ±0.57) and 0-200ms (d=-0.76, CI: ±0.64). Significant but trivial effects of match load were observed between one standardised unit increase in high speed running (HSR) versus CMJ: Force at zero velocity (d=0.12, CI: ±0.12), and sum of high intensity accelerations and CMJ: Eccentric deceleration RFD (d=-0.18, CI: ±0.14). Accounting for baseline LBS better explained (weight of evidence: W=87%) seasonal trends observed in IMTP: peak force, with lower LBS showing greater capacity for improvement. Positive moderating influences were observed with baseline LBS and LBP (W=91 & 75%) on CMJ: eccentric mean power responses to HSR, and CMJ: jump height responses to very-HSR, respectively.

CONCLUSIONS

Interpretation of athlete NF responses is complicated by the inconsistent and interacting influence of contextual factors (assessment modality, stage of season, load), in-particular higher baseline LBS and LBP may improve acute load related responses of NF.

Effects of Power-Oriented Resistance Training With Heavy vs. Light Loads on Muscle-Tendon Function in Older Adults: A Study Protocol for a Randomized Controlled Trial

Background

Power-oriented resistance training (PRT) is one of the most effective exercise programs to counteract neuromuscular and physical function age-related declines. However, the optimal load that maximizes these outcomes or the load-specific adaptations induced on muscle power determinants remain to be better understood. Furthermore, to investigate whether these adaptations are potentially transferred to an untrained limb (i.e., cross-education phenomenon) could be especially relevant during limb-immobilization frequently observed in older people (e.g., after hip fracture).

Methods

At least 30 well-functioning older participants (>65 years) will participate in a within-person randomized controlled trial. After an 8-week control period, the effects of two 12-week PRT programs using light vs. heavy loads will be compared using an unilateral exercise model through three study arms (light-load PRT vs. non-exercise; heavy-load PRT vs. non-exercise; and light- vs. heavy- load PRT). Muscle-tendon function, muscle excitation and morphology and physical function will be evaluated to analyze the load-specific effects of PRT in older people. Additionally, the effects of PRT will be examined on a non-exercised contralateral limb.

Discussion

Tailored exercise programs are largely demanded given their potentially greater efficiency preventing age-related negative consequences, especially during limb-immobilization. This trial will provide evidence supporting the use of light- or heavy-load PRT on older adults depending on individual needs, improving decision making and exercise program efficacy.

Clinical Trial Registration

NCT03724461 registration data: October 30, 2018.

Altered Drop Jump Landing Biomechanics Following Eccentric Exercise-Induced Muscle Damage

Limited research exists in the literature regarding the biomechanics of the jump-landing sequence in individuals that experience symptoms of muscle damage. The present study investigated the effects of knee localized muscle damage on sagittal plane landing biomechanics during drop vertical jump (DVJ). Thirteen regional level athletes performed five sets of 15 maximal eccentric voluntary contractions of the knee extensors of both legs at 60°/s. Pelvic and lower body kinematics and kinetics were measured pre- and 48 h post-eccentric exercise. The examination of muscle damage indicators included isometric torque, muscle soreness, and serum creatine kinase (CK) activity. The results revealed that all indicators changed significantly following eccentric exercise (p < 0.05). Peak knee and hip joint flexion as well as peak anterior pelvic tilt significantly increased, whereas vertical ground reaction force (GRF), internal knee extension moment, and knee joint stiffness significantly decreased during landing (p < 0.05). Therefore, the participants displayed a softer landing pattern following knee-localized eccentric exercise while being in a muscle-damaged state. This observation provides new insights on how the DVJ landing kinematics and kinetics alter to compensate the impaired function of the knee extensors following exercise-induced muscle damage (EIMD) and residual muscle soreness 48 h post-exercise.

Ten Days of Curcumin Supplementation Attenuates Subjective Soreness and Maintains Muscular Power Following Plyometric Exercise

Curcumin has become a popular product used to decrease inflammation and enhance recovery from exercise.

PURPOSE

To determine the effects of curcumin supplementation on delayed onset muscle soreness and muscle power following plyometric exercise.

METHODS

Participants (n = 22; five females, 17 males) consumed either curcumin (500 mg) or placebo twice daily for 10 days (6 days pre, day of and 3 days post exercise). Participants completed 5 x 20 drop jumps on day 7. Blood sampling and recovery tests were assessed at pre-supplementation, 24-hours and immediately pre-exercise, and immediately post-, 24, 48 and 72-hours post-exercise. Blood markers included serum creatine kinase (CK) and erythrocyte sedimentation rate (ESR), while soreness was measured during a squat and post vertical jump.

RESULTS

Both groups experienced muscle damage post-exercise with elevated CK (403 ± 390 ul; p < 0.01), soreness with squatting (38 ± 29 mm; p < 0.01), and vertical jump (36 ± 30 mm; p < 0.01). Soreness was greater in placebo vs. curcumin 48 h and 72 h post-exercise (p < 0.01); however, CK was not significantly different between groups (p = 0.28) despite being >200 IU·L^-1 greater 24 hr post exercise in placebo vs. curcumin. ESR was significantly greater immediately post-exercise (6.3 ± 5.6 vs. 3.4 ± 2.6 mm/hr; p = 0.03), however these were within the normal range for this test and not significantly different between groups (p = 0.25). Vertical jump decreased over time in the placebo, but not curcumin group (19.8 ± 4.8 vs. 21.4 ± 3.2 in; p = 0.01).

CONCLUSION

These data suggest curcumin reduces soreness and maintains muscular power following plyometric exercise.

The neuromuscular, physiological, endocrine and perceptual responses to different training session orders in international female netball players

AbstractThe 20 h responses of International female netball players to training days requiring two sessions (netball and strength, separated by two hours) ordered alternatively were examined. Eleven players completed strength followed by netball training two hours later (STR-NET), with the order reversed (NET-STR) on a separate day. Well-being, neuromuscular performance (jump height [JH], peak power output [PPO], peak velocity [PV]) and endocrine function (testosterone, cortisol concentrations) were measured before sessions one (PreS1) and two (PreS2), immediately after sessions one (IPS1) and two (IPS2), and 20 h post session one (20P). Session and differential ratings of perceived exertion (upper-body, cognitive/technical [RPE-T], lower-body, breathlessness) were collected, and accelerometry and heart rate measured netball load. Identification of clear between-order differences was based on the nonoverlap of the 95% confidence interval (95%CI) for mean differences relative to baseline. Compared to PreS1, greater increases in JH (percentage difference between trials; 95%CI: 9%; 4-14%), PPO (5%; 2-8%), PV (3%; 1-5%) and cortisol concentration (45%; 1-88%), and a greater decrease for testosterone/cortisol ratio (-35%; -72 to -2%) occurred at PreS2 in NET-STR. At 20P, greater decreases in JH (10%; 5-15%), PPO (4%; 1-8%) and PV (4%; 2-6%) were observed following STR-NET. No differences existed for well-being, whilst RPE-T was greater (15 AU; 3-26 AU) for strength training during NET-STR. Session order influenced neuromuscular and endocrine responses in International female netball players, highlighting session ordering as a key consideration when planning training.

Exercise-induced muscle damage: mechanism, assessment and nutritional factors to accelerate recovery

There have been a multitude of reviews written on exercise-induced muscle damage (EIMD) and recovery. EIMD is a complex area of study as there are a host of factors such as sex, age, nutrition, fitness level, genetics and familiarity with exercise task, which influence the magnitude of performance decrement and the time course of recovery following EIMD. In addition, many reviews on recovery from exercise have ranged from the impact of nutritional strategies and recovery modalities, to complex mechanistic examination of various immune and endocrine signaling molecules. No one review can adequately address this broad array of study. Thus, in this present review, we aim to examine EIMD emanating from both endurance exercise and resistance exercise training in recreational and competitive athletes and shed light on nutritional strategies that can enhance and accelerate recovery following EIMD. In addition, the evaluation of EIMD and recovery from exercise is often complicated and conclusions often depend of the specific mode of assessment. As such, the focus of this review is also directed at the available techniques used to assess EIMD.

Muscular and Physical Response to an Agility and Repeated Sprint Tests According to the Level of Competition in Futsal Players

The aim of this study was to evaluate the neuromuscular response to an agility and repeated sprint ability (RSA) test according to the level of competition in futsal players. A total of 33 players from two elite teams and one amateur team participated in the study. The participants completed an agility t-test, a 30 m-speed test, and a RSA test. A countermovement jump (CMJ) test and a tensiomyography test of the rectus femoris (RF) and biceps femoris (BF) of both legs were carried out before and after the tests. RSA test revealed better sprint times in elite players compared to amateurs in the seven bouts, as well as in the 30 m sprint and in the agility test (p < 0.05). Before the tests, elite players showed higher sustain time (Ts) in RF (+31.03 ms; ES: 0.76) and BF (+28.73 ms; ES: 0.73), higher half-relaxation time (Tr) in BF (+20.79 ms; ES: 0.94), and lower delay time (Td) in BF (−2 ms; ES: 1.19) compared to amateur players. However, post-test values did not present any significant differences (p > 0.05). In conclusion, elite players showed greater performance in the RSA test, in the 30 m tests and in the agility test compared to amateur players. The contractile properties were not a key factor in the RSA performance of the futsal players.

Aging and Recovery After Resistance-Exercise-Induced Muscle Damage: Current Evidence and Implications for Future Research

Aging is anecdotally associated with a prolonged recovery from resistance training, though current literature remains equivocal. This brief review considers the effects of resistance training on indirect markers of muscle damage and recovery (i.e., muscle soreness, blood markers, and muscle strength) in older males. With no date restrictions, four databases were searched for articles relating to aging, muscle damage, and recovery. Data from 11 studies were extracted for review. Of these, four reported worse symptoms in older compared with younger populations, while two have observed the opposite, and the remaining studies (n = 6) proposed no differences between age groups. It appears that resistance training can be practiced in older populations without concern for impaired recovery. To improve current knowledge, researchers are urged to utilize more ecologically valid muscle-damaging bouts and investigate the mechanisms which underpin the recovery of muscle soreness and strength after exercise in older populations.

Downhill Running: What Are The Effects and How Can We Adapt? A Narrative Review

Downhill running (DR) is a whole-body exercise model that is used to investigate the physiological consequences of eccentric muscle actions and/or exercise-induced muscle damage (EIMD). In a sporting context, DR sections can be part of running disciplines (off-road and road running) and can accentuate EIMD, leading to a reduction in performance. The purpose of this narrative review is to: (1) better inform on the acute and delayed physiological effects of DR; (2) identify and discuss, using a comprehensive approach, the DR characteristics that affect the physiological responses to DR and their potential interactions; (3) provide the current state of evidence on preventive and in-situ strategies to better adapt to DR. Key findings of this review show that DR may have an impact on exercise performance by altering muscle structure and function due to EIMD. In the majority of studies, EIMD are assessed through isometric maximal voluntary contraction, blood creatine kinase and delayed onset muscle soreness, with DR characteristics (slope, exercise duration, and running speed) acting as the main influencing factors. In previous studies, the median (25th percentile, Q1; 75th percentile, Q3) slope, exercise duration, and running speed were - 12% (- 15%; - 10%), 40 min (30 min; 45 min) and 11.3 km h-1 (9.8 km h-1; 12.9 km h-1), respectively. Regardless of DR characteristics, people the least accustomed to DR generally experienced the most EIMD. There is growing evidence to suggest that preventive strategies that consist of prior exposure to DR are the most effective to better tolerate DR. The effectiveness of in-situ strategies such as lower limb compression garments and specific footwear remains to be confirmed. Our review finally highlights important discrepancies between studies in the assessment of EIMD, DR protocols and populations, which prevent drawing firm conclusions on factors that most influence the response to DR, and adaptive strategies to DR.

Power loss is attenuated following a second bout of high-intensity eccentric contractions due to the repeated bout effect's protection of rate of torque and velocity development

High-intensity unaccustomed eccentric contractions result in weakness and power loss because of fatigue and muscle damage. Through the repeated bout effect (RBE), adaptations occur, then damage and weakness are attenuated following a subsequent bout. However, it is unclear whether the RBE protects peak power output. We investigated the influence of the RBE on power production and estimated fatigue- and damage-induced neuromuscular impairments following repeated high-intensity eccentric contractions. Twelve healthy adult males performed 5 sets of 30 maximal eccentric elbow flexions and repeated an identical bout 4 weeks later. Recovery was tracked over 7 days following both bouts. Reduced maximum voluntary isometric contraction torque, and increased serum creatine kinase and self-reported soreness indirectly inferred muscle damage. Peak isotonic power, time-dependent measures - rate of velocity development (RVD) and rate of torque development (RTD) - and several electrophysiological indices of neuromuscular function were assessed. The RBE protected peak power, with a protective index of 66% 24 h after the second eccentric exercise bout. The protection of power also related to preserved RVD (R² = 0.61, P < 0.01) and RTD (R² = 0.39, P < 0.01). Furthermore, the RBE's protection against muscle damage permitted the estimation of fatigue-associated neuromuscular performance decrements following eccentric exercise. Novelty: The repeated bout effect protects peak isotonic power. Protection of peak power relates to preserved rates of torque and velocity development, but more so rate of velocity development. The repeated bout effect has little influence on indices of neuromuscular fatigue.

Prolonging the duration of cooling does not enhance recovery following a marathon

Runners commonly utilize cryotherapy as part of their recovery strategy. Cryotherapy has been ineffective in mitigating signs and symptoms of muscle damage following marathon running and is limited by its duration of application. Phase change material (PCM) packs can prolong the duration of cooling. This study aimed to test the efficacy of prolonging the duration of cooling using PCM on perceptual recovery, neuromuscular function, and blood markers following a marathon run. Thirty participants completed a marathon run and were randomized to receive three hours of 15°C PCM treatment covering the quadriceps or recover without an intervention (control). Quadriceps soreness, strength, countermovement jump (CMJ) height, creatine kinase (CK), and high sensitivity C-reactive protein (hsCRP) were recorded at baseline, 24, 48, and 72 hours after the marathon. Following the marathon, strength decreased in both groups (P < .0001), with no difference between groups. Compared to baseline, strength was reduced 24 (P = .004) and 48 hours after the marathon (P = .008) in the control group, but only 24 hours (P = .028) in the PCM group. Soreness increased (P < .0001) and CMJ height decreased (P < .0001) in both groups, with no difference between groups. Compared to baseline, CMJ height was not reduced on any days in the PCM group but was reduced in the control group 24 (P < .0001) and 48 hours (P = .003) after the marathon. CK and hsCRP increased in both groups (P < .0001). Although the marathon run induced significant muscle damage, prolonging the duration of cooling using PCM did not accelerate the resolution of any dependent variables.

The effectiveness of low intensity exercise and blood flow restriction without exercise on exercise induced muscle damage: A systematic review

OBJECTIVE

To investigate the evidence and provide clinical recommendations for low intensity exercises(LIE) and blood flow restriction(BFR) without exercise on reducing the effects of exercise induced muscle damage(EIMD).

METHOD

PubMed, Embase, Web of science, and PEDro(Physiotherapy Evidence Database) were searched up to December 2019 for studies that included LIE or BFR without exercise and their effect on EIMD.

RESULTS

Out of 3192 studies, 23 were included with 17 on LIE and 6 on BFR without exercise. 11 studies demonstrated positive effects for LIE on EIMD, with two level 2 and nine level 3 studies. Two level 2 and two level 3 studies found benefits for BFR without exercise on reducing the negative effects of EIMD, while two level 2 studies found did not find benefits for BFR without exercise.

CONCLUSION

Moderate to low levels of evidence supported LIE, particularly in the form of protective low load eccentric exercise, in reducing the negative effects of EIMD. Conflicting moderate to low levels of evidence was found regarding BFR without exercise. There does seem to be potential benefit for BFR without exercise in untrained individuals. Clinicians can provide clinical recommendations as LIE and BFR without exercise reducing EIMD.

Influence of Weekly Workload on Physical, Biochemical and Psychological Characteristics in Professional Rugby Union Players Over a Competitive Season

Dubois, R, Lyons, M, Paillard, T, Maurelli, O, and Prioux, J. Influence of weekly workload on physical, biochemical and psychological characteristics in professional rugby union players over a competitive season. J Strength Cond Res 34(2): 527-545, 2020-This study aimed to (a) quantify the physical workload (P-WL) during training and games throughout the professional rugby season and (b) analyze the influence of the season period and weekly-WL, at short (acute) and moderate (chronic) terms, on physical, biochemical, and psychological responses during the season. Physiological (physical and biochemical) responses to P-WL were analyzed by examining changes in the individual Z score of the Yo-Yo intermittent recovery test (YYIRT), submaximal aerobic tests (5'/5'-test), strength tests, countermovement jump tests, blood sampling, and "recovery-stress" scores (RESTq) in 14 professional players (26.9 ± 1.9 years). Changes throughout the season were analyzed using a linear mixed model to identify changes in P-WL, whereas repeated-measures analysis of variance was used to analyze changes in physiological responses across the season. The relationship between P-WL and physiological responses was analyzed using Pearson's correlation coefficient (r). The results showed that the preseason period comprised the highest level of P-WL compared with all other blocks across the season (p < 0.001). The acute P-WL, acute competitive-WL, and number of impacts seemed to be the WL parameters, which most influenced the physiological responses (changes in testosterone [T], cortisol [C], T/C ratio, IGF-1/C ratio, strength, and RESTq index). The chronic P-WL, particularly conditioning-WL, induced positive changes in fitness characteristics (YYIRT and 5'/5'-test). Finally, this study provides information to players and coaches alike as to the influence of P-WL on as well as adaptations in physiological and psychological indices throughout a playing season. This information can greatly inform the training and preparation of future players in different levels.

A Randomized Controlled Pilot Study Comparing the Efficacy of Pulsed Radiofrequency Combined With Exercise Versus Exercise Alone in Pain Relief and Functional Improvement for Chronic Knee Osteoarthritis

OBJECTIVES

To compare the long-term efficacy between pulsed radiofrequency (PRF) combined with passive stretching (PRF-PS) exercise and PS exercise alone in reducing pain and improving quadriceps muscle strength and knee function.

METHODS

Sixty-two participants were randomly assigned with a 1:1 allocation to the PRF-PS exercise group or the PS exercise group. Level of pain, muscle strength, and knee function were assessed from baseline to the first, third, and sixth months after treatment using the VAS, peak torque (PT), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), respectively.

RESULTS

There were no significant differences at baseline between the 2 groups. Compared to exercise alone, participants achieved superior efficacy with PRF-PS in pain relief, improvement of muscle strength, and knee function. Moreover, the improvement of all variables was maintained for a longer period of time in the PRF-PS group. The reduction in participants' VAS pain intensity scores was superior for PRF-PS vs. PS with overall estimation (adjusted mean difference: -1.85 cm; 95% confidence interval [CI] -2.25, -1.45 cm; P = 0.000). The increase in participants' PT scores was superior for PRF-PS vs. PS with overall estimation (adjusted mean difference: 15.53 N. m; 95% CI 7.07, 23.98 N. m; P = 0.000; and 12.62 N. m; 95% CI 0.96, 24.28 N. m; P = 0.000 for PT 60 degrees/s and PT 180 degrees/s, respectively). The reduction in participants' WOMAC scores was superior for PRF-PS vs. PS with overall estimation (adjusted mean difference: -16.43; 95% CI -22.22, -10.64; P = 0.000).

DISCUSSION

The improvement in pain relief and knee function might be associated with restoration of muscle strength after PRF-PS exercise by overcoming muscle inhibition.

Local Heat Therapy to Accelerate Recovery After Exercise-Induced Muscle Damage

The prolonged impairment in muscle strength, power, and fatigue resistance after eccentric exercise has been ascribed to a plethora of mechanisms, including delayed muscle refueling and microvascular and mitochondrial dysfunction. This review explores the hypothesis that local heat therapy hastens functional recovery after strenuous eccentric exercise by facilitating glycogen resynthesis, reversing vascular derangements, augmenting mitochondrial function, and stimulating muscle protein synthesis.

Nutritional interventions for reducing the signs and symptoms of exercise-induced muscle damage and accelerate recovery in athletes: current knowledge, practical application and future perspectives

PURPOSE

This review provides an overview of the current knowledge of the nutritional strategies to treat the signs and symptoms related to EIMD. These strategies have been organized into the following sections based upon the quality and quantity of the scientific support available: (1) interventions with a good level of evidence; (2) interventions with some evidence and require more research; and (3) potential nutritional interventions with little to-no-evidence to support efficacy.

METHOD

Pubmed, EMBASE, Scopus and Web of Science were used. The search terms 'EIMD' and 'exercise-induced muscle damage' were individually concatenated with 'supplementation', 'athletes', 'recovery', 'adaptation', 'nutritional strategies', hormesis'.

RESULT

Supplementation with tart cherries, beetroot, pomegranate, creatine monohydrate and vitamin D appear to provide a prophylactic effect in reducing EIMD. β-hydroxy β-methylbutyrate, and the ingestion of protein, BCAA and milk could represent promising strategies to manage EIMD. Other nutritional interventions were identified but offered limited effect in the treatment of EIMD; however, inconsistencies in the dose and frequency of interventions might account for the lack of consensus regarding their efficacy.

CONCLUSION

There are clearly varying levels of evidence and practitioners should be mindful to refer to this evidence-base when prescribing to clients and athletes. One concern is the potential for these interventions to interfere with the exercise-recovery-adaptation continuum. Whilst there is no evidence that these interventions will blunt adaptation, it seems pragmatic to use a periodised approach to administering these strategies until data are in place to provide and evidence base on any interference effect on adaptation.

Relationships Between External- and Internal-Workload Variables in an Elite Female Netball Team and Between Playing Positions

PURPOSE

To examine relationships between external- and internal-workload variables in an elite female netball team, with consideration of positional differences.

METHODS

Nine elite female netball athletes had their weekly workloads monitored across their preseason and competition phases of a season. Internal workload was determined using summated heart-rate (HR) zones and session ratings of perceived exertion (sRPE), whereas external workload was determined using inertial movement units and included absolute PlayerLoad (PL), relative PL (PL per minute), accelerations (ACCEL), decelerations (DECEL), jumps, changes of direction (COD), high-intensity events, medium-intensity events, low-intensity events, PL in the forward direction, PL in the sideways direction, and PL in the vertical direction. Relationships between external- and internal-workload variables in the team and relative to playing position were examined.

RESULTS

Across the team, the strongest external workloads that correlated with summated HR zones were PL (r = .65), COD (r = .64), ACCEL (r = .61), and DECEL (r = .61). The strongest external workloads that correlated with sRPE were COD (r = .79), followed by jumps (r = .76), ACCEL (r = .75), and DECEL (r = .75). For all positions, except-goal shooter, the strongest correlation was between PL and sRPE (r = .88-.94). In the goal-shooter position, the strongest correlation was between summated HR zones and DECEL (r = .89).

CONCLUSIONS

The inertial movement unit-derived external-workload variables are strongly related to common internal-workload variables. In particular, COD and sRPE appear to provide a good monitoring combination of external and internal training loads for elite netball players.

Individualized Whole-Body Vibration: Neuromuscular, Biochemical, Muscle Damage and Inflammatory Acute Responses

Objective. We aimed to investigate the acute residual hormonal, biochemical, and neuromuscular responses to a single session of individualized whole-body vibration (WBV) while maintaining a half-squat position. Methods. Twenty male sport science students voluntarily participated in the present study and were randomly assigned to an individualized WBV group (with the acceleration load determined for each participant) or an isometric group (ISOM). A double-blind, controlled parallel study design with repeated measures was employed. Results. Testosterone and growth hormone increased significantly over time in the WBV group (P < .05 and P < .01, respectively; effect size [ES] ranged from 1.00 to 1.23), whereas cortisol increased over time in both groups (P < .01; ES ranged from 1.04 and 1.36). Interleukin-6 and creatine kinase increased significantly over time only in the WBV group (P < .05; ES = 1.07). The maximal voluntary contraction decreased significantly over time in the ISOM group (P = .019; ES = 0.42), whereas in the WBV group, the decrease did not reach a significant level (P = .05). The ratio of electromyographic activity and power decreased significantly over time in the WBV group (P < .01; ES ranged from 0.57 to 0.72). Conclusion. Individualized WBV increased serum hormonal concentrations, muscle damage, and inflammation to levels similar to those induced by resistance training and hypertrophy exercises.