Factors contributing to lower metabolic demand of eccentric compared with concentric cycling

Effects of Combined Endurance and Resistance Eccentric Training on Muscle Function and Functional Performance in Patients With Chronic Obstructive Pulmonary Disease: Randomized Controlled Trial

OBJECTIVE

To evaluate the adherence to treatment and efficacy of an eccentric-based training (ECC) program on peripheral muscle function and functional exercise capacity in patients with chronic obstructive pulmonary disease (COPD).

DESIGN

Prospective, assessor-blinded, randomized controlled trial.

SETTING

The cardiopulmonary rehabilitation unit of a tertiary subacute referral center.

PARTICIPANTS

Thirty (N=30) stable inpatients (mean age 68±8 years; FEV1 44±18% of predicted) with COPD were included in the study.

INTERVENTIONS

Inpatients were randomly assigned to 4 weeks of a combined endurance and resistance ECC (n=15) or conventional training (CON; n=15).

MAIN OUTCOME MEASURES

Quadriceps peak torque (PT) was the primary outcome measure for muscle function. Rate of force development (RFD), muscle activation and quality (quadriceps PT/leg lean mass), 6-min walk distance (6MWD), 4-meter gait speed (4mGS), 10-meter gait speed, 5-repetition sit-to-stand (5STS), dyspnea rate, and mortality risk were the secondary outcomes. Evaluations were performed at baseline and repeated after 4 weeks and 3 months of follow-up.

RESULTS

Quadriceps PT, RFD, and muscle quality improved by 17±23% (P<.001), 19±24%, and 16±20% (both P<.05) within the ECC group. Besides, a significant between-group difference for RFD (56±94 Nm/s, P=.038) was found after training. Both groups showed clinically relevant improvements in 6MWD, 4mGS, dyspnea rate, and mortality risk, with no significant differences between groups.

CONCLUSION

Combined endurance and resistance ECC improved lower limbs muscle function compared with CON in inpatients with COPD. In contrast, ECC did not further improve functional performance, dyspnea, and mortality risk. ECC may be of particular benefit to effect on skeletal muscle function in patients with COPD.

Eccentric cycling involves greater mental demand and cortical activation of the frontoparietal network

Eccentric, compared to concentric exercise, is proposed to involve different neuro-motor processing strategies and a higher level of mental demand. This study compared eccentric and concentric cycling at matched perceived effort and torque for the mental demand and related-cortical activation patterns. Nineteen men (30 ± 6 years) performed four different 5-min cycling conditions at 30 RPM on a semi-recumbent isokinetic cycle ergometer: (1) concentric at a moderate perceived effort (23 on the CR100® scale) without torque feedback; (2) concentric and (3) eccentric at the same average torque produced in the first condition; and (4) eccentric at the same moderate perceived effort than the first concentric condition. The conditions two to four were randomized. After each condition, mental demand was monitored using the NASA Task Load Index scale. Changes in oxy-(O2 Hb) and deoxy-(HHb) hemoglobin during exercise were measured over both prefrontal cortices and the right parietal lobe from a 15-probe layout using a continuous-wave NIRS system. Mental demand was significantly higher during eccentric compared to concentric cycling (+52%, p = 0.012) and when the exercise intensity was fixed by the torque rather than the perceived effort (+70%, p < 0.001). For both torque- or perceived effort-matched exercises, O2 Hb increased significantly (p < 0.001) in the left and right prefrontal cortices, and right parietal lobe, and HHb decreased in the left, and right, prefrontal cortices during eccentric compared to concentric cycling. This study supports that acute eccentric cycling, compared to concentric cycling, involves a higher mental demand, and frontoparietal network activation.

Cardiovascular Responses to Eccentric Cycling Based on Perceived Exertion Compared to Concentric Cycling, Effect of Pedaling Rate, and Sex

Interest in eccentric exercises has increased over the last decades due to its efficiency in achieving moderate-high intensity muscular work with reduced metabolic demands. However, individualizing eccentric exercises in rehabilitation contexts remains challenging, as concentric exercises mainly rely on cardiovascular parameters. To overcome this, perceived exertion could serve as an individualization tool, but the knowledge about cardiovascular responses to eccentric cycling based on perceived exertion are still scarce. For this purpose, the cardiorespiratory parameters of 26 participants were assessed during two 5 min bouts of concentric cycling at 30 and 60 rpm and two bouts of eccentric cycling at 15 and 30 rpm matched for rating of perceived exertion. With this method, we hypothesized higher exercise efficiency during eccentric cycling for a same perceived exertion. The results revealed significantly elevated heart rate and cardiac index at higher pedalling rates during concentric (p < 0.001), but not during eccentric cycling (p ≈ 1). Exercise efficiency was higher during concentric cycling (64%), decreasing with pedalling rate, while eccentric cycling exhibited increased work rates (82%), and increased by over 100% with higher pedalling rate. Hence, eccentric cycling, with lower cardiorespiratory work for the same perceived exertion, facilitates higher work rates in deconditioned populations. However, further studies are needed for effective individualization.

Behavioral Motor Performance

The human sensorimotor control system has exceptional abilities to perform skillful actions. We easily switch between strenuous tasks that involve brute force, such as lifting a heavy sewing machine, and delicate movements such as threading a needle in the same machine. Using a structure with different control architectures, the motor system is capable of updating its ability to perform through our daily interaction with the fluctuating environment. However, there are issues that make this a difficult computational problem for the brain to solve. The brain needs to control a nonlinear, nonstationary neuromuscular system, with redundant and occasionally undesired degrees of freedom, in an uncertain environment using a body in which information transmission is subject to delays and noise. To gain insight into the mechanisms of motor control, here we survey movement laws and invariances that shape our everyday motion. We then examine the major solutions to each of these problems in the three parts of the sensorimotor control system, sensing, planning, and acting. We focus on how the sensory system, the control architectures, and the structure and operation of the muscles serve as complementary mechanisms to overcome deviations and disturbances to motor behavior and give rise to skillful motor performance. We conclude with possible future research directions based on suggested links between the operation of the sensorimotor system across the movement stages. © 2024 American Physiological Society. Compr Physiol 14:5179-5224, 2024.

Acute physiological responses to eccentric cycling: a systematic review and meta-analysis

INTRODUCTION

Eccentric cycling (ECCCYC) has attracted considerable interest due to its potential applicability for exercise treatment/training of patients with poor exercise tolerance as well as healthy and trained individuals. Conversely, little is known about the acute physiological responses to this exercise modality, thus challenging its proper prescription. This study aimed to provide precise estimates of the acute physiological responses to ECCCYC in comparison to traditional concentric cycling (CONCYC).

EVIDENCE ACQUISITION

Searches were performed until November 2021 using the PubMed, Embase, and ScienceDirect databases. Studies that examined individuals' cardiorespiratory, metabolic, and perceptual responses to ECCCYC and CONCYC sessions were included. Bayesian multilevel meta-analysis models were used to estimate the population mean difference between acute physiological responses from ECCCYC and CONCYC bouts. Twenty-one studies were included in this review.

EVIDENCE SYNTHESIS

The meta-analyses showed that ECCCYC induced lower cardiorespiratory (i.e., V̇O2, V̇E, and HR), metabolic (i.e., [BLa]), and perceptual (i.e., RPE) responses than CONCYC performed at the same absolute power output, while greater cardiovascular strain (i.e., greater increases in HR, Q, MAP, [norepinephrine], and lower SV) was detected when compared to CONCYC performed at the same V̇O2.

CONCLUSIONS

The prescription of ECCCYC based on workloads used in the CONCYC sessions may be considered safe and, therefore, feasible for the rehabilitation of individuals with poor exercise tolerance. However, the prescription of ECCCYC based on the V̇O2 obtained during CONCYC sessions should be conducted with caution, especially in clinical settings, since there is a high probability of additional cardiovascular overload in this condition.

Connective Adaptive Resistance Exercise (CARE) Machines for Accentuated Eccentric and Eccentric-Only Exercise: Introduction to an Emerging Concept

Eccentric resistance exercise emphasizes active muscle lengthening against resistance. In the past 15 years, researchers and practitioners have expressed considerable interest in accentuated eccentric (i.e., eccentric overload) and eccentric-only resistance exercise as strategies for enhancing performance and preventing and rehabilitating injuries. However, delivery of eccentric resistance exercise has been challenging because of equipment limitations. Previously, we briefly introduced the concept of connected adaptive resistance exercise (CARE)-the integration of software and hardware to provide a resistance that adjusts in real time and in response to the individual's volitional force within and between repetitions. The aim of the current paper is to expand this discussion and explain the potential for CARE technology to improve the delivery of eccentric resistance exercise in various settings. First, we overview existing resistance exercise equipment and highlight its limitations for delivering eccentric resistance exercise. Second, we describe CARE and explain how it can accomplish accentuated eccentric and eccentric-only resistance exercise in a new way. We supplement this discussion with preliminary data collected with CARE technology in laboratory and non-laboratory environments. Finally, we discuss the potential for CARE technology to deliver eccentric resistance exercise for various purposes, e.g., research studies, rehabilitation programs, and home-based or telehealth interventions. Overall, CARE technology appears to permit completion of eccentric resistance exercise feasibly in both laboratory and non-laboratory environments and thus has implications for researchers and practitioners in the fields of sports medicine, physiotherapy, exercise physiology, and strength and conditioning. Nevertheless, formal investigations into the impact of CARE technology on participation in eccentric resistance exercise and clinical outcomes are still required.

Effect of Cadence on Physiological and Perceptual Responses during Eccentric Cycling at Different Power Outputs

INTRODUCTION

The effect of cadence in eccentric (ECC) cycling on physiological and perceptual responses is, to date, poorly understood. This study aimed to evaluate the effect of cadence during ECC cycling on muscular activation (EMG), oxygen consumption (V̇O 2 ), and perceived effort (PE) for two different levels of power output.

METHODS

Seventeen participants completed four sessions 1 wk apart: 1) determination of the maximal concentric peak power output (PPO) and familiarization with ECC cycling at five cadences (30, 45, 60, 75, and 90 rpm); 2) second familiarization with ECC cycling; 3) and 4) ECC cycling exercise consisting of 5 min at the five different cadences at either 40% or 60% PPO. PE was reported, and V̇O 2 and EMG of seven muscles were calculated over the exercise's last minute.

RESULTS

PE, V̇O 2 , and global lower limb muscles activation (EMG ALL ) showed an effect of cadence ( P < 0.001) and followed a curvilinear function. Both low and high cadences increased PE and V̇O 2 responses compared with intermediate cadences. Although muscle activation of vastus lateralis follows a U-shaped curve with cadence, it was greater at low cadence for rectus femoris and biceps femoris, greater at high cadence for tibialis anterior and gastrocnemius medialis, and was not altered for soleus. The estimated optimal cadence was greater (all P < 0.01) for V̇O 2 (64.5 ± 7.9 rpm) than PE (61.7 ± 9.4 rpm) and EMG ALL (55.9 ± 9.3 rpm), but power output had no effect on the optimal cadences.

CONCLUSIONS

The physiological and perceptual responses to changes in cadence during ECC cycling followed a U-shaped curve with an optimal cadence depending on the parameter considered.

Reliability and Variability of Lower Limb Muscle Activation as Indicators of Familiarity to Submaximal Eccentric Cycling

Submaximal eccentric (ECC) cycling exercise is commonly used in research studies. No previous study has specified the required time naïve participants take to familiarize with submaximal ECC cycling. Therefore, we designed this study to determine whether critical indicators of cycling reliability and variability stabilize during 15 min of submaximal, semi-recumbent ECC cycling (ECC cycling). Twenty-two participants, aged between 18–51 years, volunteered to complete a single experimental session. Each participant completed three peak eccentric torque protocol (PETP) tests, nine countermovement jumps and 15 min of submaximal (i.e., 10% peak power output produced during the PETP tests) ECC cycling. Muscle activation patterns were recorded from six muscles (rectus femoris, RF; vastus lateralis, VL; vastus medialis, VM; soleus, SOL; medial gastrocnemius, GM; tibialis anterior, TA), during prescribed-intensity ECC cycling, using electromyography (EMG). Minute-to-minute changes in the reliability and variability of EMG patterns were examined using intra-class correlation coefficient (ICC) and variance ratios (VR). Differences between target and actual power output were also used as an indicator of familiarization. Activation patterns for 4/6 muscles (RF, VL, VM and GM) became more consistent over the session, the RF, VL and VM increasing from moderate (ICC = 0.5–0.75) to good (ICC = 0.75–0.9) reliability by the 11th minute of cycling and the GM good reliability from the 1st minute (ICC = 0.79, ICC range = 0.70–0.88). Low variability (VR ≤ 0.40) was maintained for VL, VM and GM from the 8th, 8th and 1st minutes, respectively. We also observed a significant decrease in the difference between actual and target power output (χ214 = 30.895, p = 0.006, W = 0.105), expressed primarily between the 2nd and 3rd minute of cycling (Z = -2.677, p = 0.007). Indicators of familiarization during ECC cycling, including deviations from target power output levels and the reliability and variability of muscle activation patterns stabilized within 15 min of cycling. Based upon this data, it would be reasonable for future studies to allocate ∼ 15 min to familiarize naïve participants with a submaximal ECC cycling protocol.

A Short-Term Eccentric HIIT Induced Greater Reduction in Cardio-Metabolic Risk Markers in Comparison With Concentric HIIT in Sedentary Overweight Men

Background: Steady-state eccentric exercise training improves cardiometabolic risk (CMR) despite lesser cardiovascular demands compared with load-matched concentric training. Whether a high-intensity interval eccentric training is also effective reducing CMR is unknown. Aim: To compare the effects of a short-term high-intensity interval eccentric training (ECC-HIIT) with high-intensity interval concentric training (CONC-HIIT) on CMR in sedentary overweight men. Methods: Twenty men (age: 27.9 ± 5.3y, body massindex: 29.1 ± 3.1 kg·m-2) were randomly assigned to ECC-HIIT (n = 10) or CONC-HIIT (n = 10) delivered as six sessions, including 4 x 5:2 min work-to-rest ratio, at 80% peak concentric power output. Heart rate (HR), rate of perceived exertion (RPE) and muscle soreness weremonitored during training sessions. Training effects on lipid profile, insulin sensitivity (HOMA-IR), body composition, thigh circumference, isometric knee extensors maximal strength, resting systolic and diastolic blood pressure (SBP and DBP) were determined. Results: Average training HR and RPE were -29%and -50%lower in ECC-HIIT in comparison with CONC-HIIT. Muscle soreness was initially greater after ECC-HIIT compared with CONC-HIIT. Significant changes in total and low-density lipoprotein cholesterol (-7.0 ± 8.7%; p = .02 and -6.3 ± 14.4%; p = .03), SBP (-9.8 ± 7.8%; p = .002), and maximal thigh circumference (+2.5 ± 3.1%; p = .02) were observed following ECC-HIIT. No changes in any CMR marker were observed after CONC-HIIT. Moderate-to-large training effect sizes were obtained in thigh circumference, SBP, total cholesterol and low-density lipoprotein cholesterol in response to ECC-HIIT. Conclusion: A two-week ECC-HIIT was well-tolerated and induced rapid onset improvements in cholesterol and blood pressure compared to conventional CONC-HIIT in sedentary overweight men.

Corticospinal Excitability Is Lower During Eccentric Than Concentric Cycling in Men

How corticospinal excitability changes during eccentric locomotor exercise is unknown. In the present study, 13 volunteers performed 30-min strenuous concentric and eccentric cycling bouts at the same power output (60% concentric peak power output). Transcranial magnetic and electrical femoral nerve stimulations were applied at exercise onset (3rd min) and end (25th min). Motor-evoked potentials (MEPs) amplitude was measured for the rectus femoris (RF) and vastus lateralis (VL) muscles with surface electromyography (EMG) and expressed as a percentage of maximal M-wave amplitude (M_MAX). EMG amplitude 100 ms prior to MEPs and the silent period duration were calculated. There was no change in any neural parameter during the exercises (all P > 0.24). VL and RF M_MAX were unaffected by exercise modality (all P > 0.38). VL MEP amplitude was greater (26 ± 11.4 vs. 15.2 ± 7.7% M_MAX; P = 0.008) during concentric than eccentric cycling whereas RF MEP amplitude was not different (24.4 ± 10.8 vs. 17.2 ± 9.8% M_MAX; P = 0.051). While VL EMG was higher during concentric than eccentric cycling (P = 0.03), RF EMG showed no significant difference (P = 0.07). Similar silent period durations were found (RF: 120 ± 30 ms; VL: 114 ± 27 ms; all P > 0.61), but the silent period/MEP ratio was higher during eccentric than concentric cycling for both muscles (all P < 0.02). In conclusion, corticospinal excitability to the knee extensors is lower and relative silent period longer during eccentric than concentric cycling, yet both remained unaltered with time.

The time course of different neuromuscular adaptations to short-term downhill running training and their specific relationships with strength gains

Purpose

Due to its eccentric nature, downhill running (DR) training has been suggested to promote strength gains through neuromuscular adaptations. However, it is unknown whether short-term chronic DR can elicit such adaptations.

Methods

Twelve untrained, young, healthy adults (5 women, 7 men) took part in 4 weeks’ DR, comprising 10 sessions, with running speed equivalent to 60–65% maximal oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max, assessed at weeks 0 and 4). Isometric and isokinetic knee-extensor maximal voluntary torque (MVT), vastus lateralis (VL) muscle morphology/architecture (anatomical cross-sectional area, ACSA; physiological CSA, PCSA; volume; fascicle length, L_f; pennation angle, PA) and neuromuscular activation (VL EMG) were assessed at weeks 0, 2 and 4.

Results

MVT increased by 9.7–15.2% after 4 weeks (p < 0.01). VL EMG during isometric MVT increased by 35.6 ± 46.1% after 4 weeks (p < 0.05) and correlated with changes in isometric MVT after 2 weeks (r = 0.86, p = 0.001). VL ACSA (+2.9 ± 2.7% and +7.1 ± 3.5%) and volume (+2.5 ± 2.5% and +6.6 ± 3.2%) increased after 2 and 4 weeks, respectively (p < 0.05). PCSA (+3.8 ± 3.3%), PA (+5.8 ± 3.8%) and L_f (+2.7 ± 2.2%) increased after 4 weeks (p < 0.01). Changes in VL volume (r = 0.67, p = 0.03) and PCSA (r = 0.71, p = 0.01) correlated with changes in concentric MVT from 2 to 4 weeks. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max (49.4 ± 6.2 vs. 49.7 ± 6.3 mL·kg⁻¹·min⁻¹) did not change after 4 weeks (p = 0.73).

Conclusion

Just 4 weeks’ moderate-intensity DR promoted neuromuscular adaptations in young, healthy adults, typically observed after high-intensity eccentric resistance training. Neural adaptations appeared to contribute to most of the strength gains at 2 and 4 weeks, while muscle hypertrophy seemed to contribute to MVT changes from 2 to 4 weeks only.

Modeling the Metabolic Reductions of a Passive Back-Support Exoskeleton

Despite several attempts to quantify the metabolic savings resulting from the use of passive back-support exoskeletons (BSEs), no study has modeled the metabolic change while wearing an exoskeleton during lifting. The objectives of this study were to: 1) quantify the metabolic reductions due to the VT-Lowe's exoskeleton during lifting; and 2) provide a comprehensive model to estimate the metabolic reductions from using a passive BSE. In this study, 15 healthy adults (13M, 2F) of ages 20 to 34 years (mean=25.33, SD=4.43) performed repeated freestyle lifting and lowering of an empty box and a box with 20% of their bodyweight. Oxygen consumption and metabolic expenditure data were collected. A model for metabolic expenditure was developed and fitted with the experimental data of two prior studies and the without-exoskeleton experimental results. The metabolic cost model was then modified to reflect the effect of the exoskeleton. The experimental results revealed that VT-Lowe's exoskeleton significantly lowered the oxygen consumption by ~9% for an empty box and 8% for a 20% bodyweight box, which corresponds to a net metabolic cost reduction of ~12% and ~9%, respectively. The mean metabolic difference (i.e., without-exo minus with-exo) and the 95% confidence interval were 0.36 and (0.2-0.52) [Watts/kg] for 0% bodyweight, and 0.43 and (0.18-0.69) [Watts/kg] for 20% bodyweight. Our modeling predictions for with-exoskeleton conditions were precise, with absolute freestyle prediction errors of <2.1%. The model developed in this study can be modified based on different study designs, and can assist researchers in enhancing designs of future lifting exoskeletons.

A Semi-recumbent Eccentric Cycle Ergometer Instrumented to Isolate Lower Limb Muscle Contractions to the Appropriate Phase of the Pedal Cycle

Eccentric (ECC) cycling is used in rehabilitation and sports conditioning settings. We present the construction and mode of operation of a custom-built semi-recumbent ECC cycle designed to limit the production of lower limb muscle activity to the phase of the pedal cycle known to produce ECC contractions. A commercially available semi-recumbent frame and seat (Monarch, 837E Semi-recumbent Bike, Sweden) were used to assemble the ergometer. An electrical drive train system was constructed using individual direct drive servo motors. To avoid active muscle activation occurring during the non-ECC pedaling phase of cycling, a “trip” mechanism was integrated into the drivetrain system using a servo-driven regenerative braking mechanism based on the monitoring of the voltage produced over and above a predetermined threshold produced by the motors. The servo drive internal (DC bus) voltage is recorded and internally monitored during opposing (OPP) and non-opposing (N-OPP) phases of the pedal cycle. To demonstrate that the cycle functions as desired and stops or “trips” when it is supposed to, we present average (of 5 trials) muscle activation patterns of the principal lower limb muscles for regular ECC pedal cycles in comparison with one pedal cycle during which the muscles activated outside the desired phase of the cycle for a sample participant. This semi-recumbent ECC cycle ergometer has the capacity to limit the occurrence of muscle contraction only to the ECC phase of cycling. It can be used to target that mode of muscle contraction more precisely in rehabilitation or training studies.

Effects of eccentric vs concentric cycling training on patients with moderate COPD

PURPOSE

The present study compared the effects of eccentric cycling (ECC) and conventional concentric cycling (CONC) training on muscle function, body composition, functional performance, and quality of life (QOL) of patients with moderate chronic obstructive pulmonary disease (COPD).

METHODS

Twenty patients (age: 69.6 ± 10.1 years, forced expiratory volume in 1-s: 73.2 ± 11.4% of predicted) were randomly allocated to ECC (n = 10) or CONC (n = 10) group. They performed 12 weeks of ECC or CONC training at similar perceived exertion. The workload, heart rate (HR), blood oxygen saturation (SpO₂), and dyspnea were monitored during cycling. Outcomes measures included maximal voluntary isometric contraction (MVC) strength of the knee extensors, rate of force development (RFD), lower limb fat-free (LLFFM) and fat (LLFM) mass, 6-min walking test (6MWT), timed up-and-go test (TUG), stairs ascending (SAWT) and descending walking time (SDWT), and QOL assessed by the Saint George's respiratory questionnaire.

RESULTS

ECC produced on average threefold greater (P < 0.001) workload (211.8 ± 106.0 kJ) than CONC (78.1 ± 62.6 kJ) over 34 training sessions. ECC showed 1.5 ± 2.1% greater SpO₂, 24.7 ± 4.1% lower HR, and 64.4 ± 29.6% lower dyspnea in average than CONC (P < 0.001). ECC increased LLFFM (4.5 ± 6.2%; P = 0.03), while CONC decreased LLFM (3.3 ± 6.4%; P = 0.04) after training. Both ECC and CONC reduced (P < 0.05) SAWT (- 16.1 ± 9.3% vs - 10.1 ± 14.4%) and SDWT (- 12.2 ± 12.6% vs - 14.4 ± 14.7%), and improved (P < 0.05) QOL (33.4 ± 38.8 vs 26.1 ± 36.6%) similarly, but only ECC improved (P < 0.05) RFD (69-199%), TUG (13.6 ± 13.6%), and 6MWT (25.3 ± 27.7%).

CONCLUSION

These results suggest that ECC training with less cardio-pulmonary demands was more effective in increasing functional performance and muscle mass for COPD patients than CONC training.

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.

Skeletal muscle and cerebral oxygenation levels during and after submaximal concentric and eccentric isokinetic exercise

The aim was to investigate the potential differences in muscle (vastus lateralis) and cerebral (prefrontal cortex) oxygenation levels as well as in the number of repetitions and total work output between isokinetic eccentric and concentric exercise at a moderate relative intensity until exhaustion. Ten recreationally active young men underwent two isokinetic exercise sessions either concentric or eccentric, one on each randomly selected leg. The protocols were performed at 60°/s and an intensity corresponding to 60% of the maximal voluntary contraction (MVC) of each contraction type. Concentric torque was significantly lower compared to eccentric torque in both peak values and at values corresponding to 60% of MVC [230 ± 18 Nm vs. 276 ± 19 Nm (P = .014) and 137 ± 12 Nm vs. 168 ± 11 Nm, respectively (P = .010)]. The participants performed 40% more contractions during eccentric compared to concentric exercise [122 ± 15 vs. 78 ± 7, respectively]. No differences were found in the levels of oxyhaemoglobin, deoxyhemoglobin, total haemoglobin and tissue saturation index when eccentric and eccentric exercise regimes were compared (all P > .05). Our results demonstrate that eccentric exercise of moderate intensity leads to greater resistance to fatigue and more work output compared to concentric exercise, despite the comparable muscle and cerebral oxygenation levels.

Analysis of Fractal Correlation Properties of Heart Rate Variability during an Initial Session of Eccentric Cycling

Eccentric cycling (ECC) has attracted attention as a method to improve muscle strength and aerobic fitness in populations unable to tolerate conventional methods. However, agreement on exercise prescription targets have been problematic. The current report is an initial exploration of a potentially useful tool, a nonlinear heart rate (HR) variability (HRV) index based on the short-term scaling exponent alpha1 of detrended fluctuation analysis (DFA a1), which has been previously shown to correspond to exercise intensity. Eleven male volunteers performed 45 min of concentric (CON) cycling and ECC separated by 1 month. Work rates were matched for HR (~50% of the maximal HR) during the first 5 min and remained stable thereafter. HRV, HR, oxygen consumption (VO2), and cycling power were monitored and evaluated at elapsed times of 10 (T10) and 45 (T45) minutes duration. HR significantly increased between ECC T10 and ECC T45 (p = 0.003, d = 1.485), while DFA a1 significantly decreased (p = 0.004, d = 1.087). During CON, HR significantly increased (p < 0.001 d = 1.570) without significant DFA a1 change (p = 0.48, d = 0.22). Significantly higher HR was observed at T45 in ECC than in CON (p = 0.047, d = 1.059). A session of unaccustomed ECC lead to decreased values of DFA a1 at T45 in comparison to that seen with CON at similar VO2. ECC lead to altered autonomic nervous system balance as reflected by the loss of correlation properties compared to CON.

Acute and Delayed Effects of Time-Matched Very Short "All Out" Efforts in Concentric vs. Eccentric Cycling

BACKGROUND

To the authors' knowledge, there have been no studies comparing the acute responses to "all out" efforts in concentric (isoinertial) vs. eccentric (isovelocity) cycling.

METHODS

After two familiarization sessions, 12 physically active men underwent the experimental protocols consisting of a 2-min warm-up and 8 maximal efforts of 5 s, separated by 55 s of active recovery at 80 rpm, in concentric vs. eccentric cycling. Comparisons between protocols were conducted during, immediately after, and 24-h post-sessions.

RESULTS

Mechanical (Work: 82,824 ± 6350 vs. 60,602 ± 8904 J) and cardiometabolic responses (mean HR: 68.8 ± 6.6 vs. 51.3 ± 5.7% HRmax, lactate: 4.9 ± 2.1 vs. 1.8 ± 0.6 mmol/L) were larger in concentric cycling (p < 0.001). The perceptual responses to both protocols were similarly low. Immediately after concentric cycling, vertical jump was potentiated (p = 0.028). Muscle soreness (VAS; p = 0.016) and thigh circumference (p = 0.045) were slightly increased only 24-h after eccentric cycling. Serum concentrations of CK, BAG3, and MMP-13 did not change significantly post-exercise.

CONCLUSIONS

These results suggest the appropriateness of the eccentric cycling protocol used as a time-efficient (i.e., ~60 kJ in 10 min) and safe (i.e., without exercise-induced muscle damage) alternative to be used with different populations in future longitudinal interventions.

Reliability of a Protocol to Elicit Peak Measures Generated by the Lower Limb for Semi-recumbent Eccentric Cycling

Semi-recumbent eccentric (ECC) cycling is increasingly used in studies of exercise with healthy and clinical populations. However, workloads are generally prescribed using measures obtained during regular concentric cycling. Therefore, the purpose of the study was to quantify the reliability of measures derived from a protocol that elicited peak ECC torque produced by the lower limb in a semi-recumbent position. Experiments were carried out on a dynamometer in a seated, semi-recumbent position identical to that of a custom-built ECC cycle, a modified Monark recumbent cycle. Thirty healthy participants completed two testing sessions. Each session comprised three series of six repetitions of a peak ECC torque protocol (PETP) on an isokinetic dynamometer. Absolute and relative reliability of peak torque, power, angle of peak torque, and work (recorded for each repetition) was determined using coefficient of variation (CV) and intraclass correlation coefficient (ICC), respectively. Ratings of perceived exertion (RPE), muscle soreness, and perceived effort (PE) were recorded pre-PETP, immediately post-PETP, and 1-min post each PETP. The protocol showed absolute reliability values <15% for mean peak (CV = 10.6-12.1) torque, power (CV = 10.4-12.3), angle of peak torque (CV = 1.2-1.4), and work (CV = 9.7-12.1). Moderate to high between-test relative reliability is reported for mean and highest torque (ICC = 0.84-0.95; ICC = 0.88-0.98), power (ICC = 0.84-0.94; ICC = 0.89-0.98), and work (ICC = 0.84-0.93; ICC = 0.88-0.98), respectively. Within-session peak torque, peak power, and peak work showed high relative reliability for mean (ICC = 0.92-0.95) and highest (ICC = 0.92-0.97) values. Overall, the PETP test provides a reliable way of determining peak ECC torque specific to semi-recumbent ECC cycling that may be used to prescribe workloads for this form of exercise.

Skeletal Muscle-Adipose Tissue-Tumor Axis: Molecular Mechanisms Linking Exercise Training in Prostate Cancer

Increased visceral adiposity may influence the development of prostate cancer (PCa) aggressive tumors and cancer mortality. White adipose tissue (WAT), usually referred to as periprostatic adipose tissue (PPAT), surrounds the prostatic gland and has emerged as a potential mediator of the tumor microenvironment. Exercise training (ET) induces several adaptations in both skeletal muscle and WAT. Some of these effects are mediated by ET-induced synthesis and secretion of several proteins, known as myo- and adipokines. Together, myokines and adipokines may act in an endocrine-like manner to favor communication between skeletal muscle and WAT, as they may work together to improve whole-body metabolic health. This crosstalk may constitute a potential mechanism by which ET exerts its beneficial role in the prevention and treatment of PCa-related disorders; however, this has not yet been explored. Therefore, we reviewed the current evidence on the effects of skeletal muscle–WAT–tumor crosstalk in PCa, and the potential mediators of this process to provide a better understanding of underlying ET-related mechanisms in cancer.

Changes in pulmonary and plasma oxidative stress and inflammation following eccentric and concentric cycling in stable COPD patients

PURPOSE

The purpose of this study was to compare pulmonary and plasma markers of oxidative stress and inflammation after concentric and eccentric cycling bouts in individuals with chronic obstructive pulmonary disease (COPD).

METHODS

Ten patients with moderate COPD level (68.3 ± 9.1 years; forced expiratory volume in 1 s = 68.6 ± 20.4% of predicted) performed 30 min of moderate-intensity concentric (CONC-M: 50% maximum concentric cycling power output; PO_max) and eccentric cycling (ECC-M: 50% PO_max), and high-intensity eccentric cycling (ECC-H: 100% PO_max) in a randomised order. Cardiometabolic demand was monitored during cycling. Indirect markers of muscle damage were assessed before, immediately after, 24 and 48 h after cycling (muscle strength, muscle soreness and creatine kinase activity). Plasma oxidative stress (malondialdehyde: MDA), antioxidant (glutathione peroxidase activity: GPx) and inflammatory markers (IL-6, TNF-α) were measured before and 5 min after cycling. Exhaled breath condensate (EBC) samples were collected before and 15 min after cycling and analysed for hydrogen peroxide (H₂O₂), nitrites (NO^2-) and pH.

RESULTS

Cardiometabolic demand was 40-50% lesser for ECC-M than CONC-M and ECC-H. Greater muscle damage was induced after ECC-H than ECC-M and CONC-M. MDA decreased immediately after CONC-M (- 28%), ECC-M (- 14%), and ECC-H (- 17%), while GPx remained unchanged. IL-6 increased only after ECC-H (28%), while TNF-α remained unchanged after exercise. Pulmonary H₂O₂, NO^2- and pH remained unchanged after exercise.

CONCLUSION

These results suggest that only moderate muscle damage and inflammation were induced after high-intensity eccentric cycling, which did not induce pulmonary or plasmatic increases in markers of oxidative stress.

TRIAL REGISTRATION NUMBER

Trial registration number: DRKS00009755.

Elevated body temperature contributes to the increased heart rate response during eccentric compared to concentric cycling when matched for oxygen consumption

A cardiovascular requirement to facilitate thermal homeostasis may partly contribute to the elevated heart rate during eccentric cycling. This study compared the body temperature response to a bout of eccentric (ECC) and concentric (CON) cycling to account for the difference in heart rate. Eight (N = 8) aerobically trained males (age 35 y [SD 8], peak oxygen consumption 3.82 L.min^-1 [SD 0.79]) completed an ECC cycling trial (60% PPO) followed by an oxygen consumption/duration matched CON trial (30   ∘ C , 35% RH) on a separate day. Trial termination was determined as an elevation in aural temperature, a surrogate of deep body temperature, by +0.5   ∘ C during ECC. Mean skin (8-sites) and body temperature (weighting of 80:20 for auditory canal and mean skin temperature) were calculated. Matching the oxygen consumption between the trials increased external work during ECC cycling (CON: 71 [SD 14] ECC: 194 [SD 38] W, p < 0.05) and elevated aural temperature (+0.5   ∘ C ) by 20 min 32 s [SD 9 min 19 s] in that trial. The peak rate of rise in aural temperature was significantly greater in ECC (CON: 0.012 [SD 0.007] ECC: 0.031 [SD 0.002] ^oC.s^-1, p < 0.05). Aural, mean skin and body temperature were significantly higher during the ECC trial (p < 0.05) and this was accompanied by elevated mean heart rate (CON: 103 [SD 14] ECC: 118 [SD 12] b.min^-1, p < 0.05) and thermal discomfort (p < 0.05). Moderate load eccentric cycling imposes an elevated thermal strain when compared to concentric cycling. This requirement for dissipating heat, in part, explains the elevated heart rate during eccentric cycling.

Greater decrements in neuromuscular function following interval compared to continuous eccentric cycling

Our aim was to determine the demands and consequences of a single session of continuous (CONT) or interval (INT) eccentric cycling. Fourteen healthy males performed 'work-matched' CONT and INT eccentric cycling in a cross over design. Measures of maximal voluntary contraction (MVC), resting twitch force, voluntary activation (VA), muscle soreness and creatine kinase (CK) were taken at baseline, immediately post, and 24, 48 and 72 h post the first exercise bout. The second bout was used to characterise within session demands. Decreases in MVC (INT 19%, CONT 13%), twitch force (INT 31%, CONT 18%), and VA (INT 10%, CONT 6%) were observed immediately post session (p < 0.05). Reductions in twitch force were greater after INT (p < 0.05) and lasted 48 h. Muscle soreness was greater following INT, versus CONT (p < 0.05), although no differences in CK were observed. Metabolic demands (% of V̇O_2peak and [BLa]) were greater during INT vs. CONT (32 ± 6% 28 ± 6%; p < 0.001), [BLa] (1.0 ± 0.4 vs. 0.8 ± 0.2 mmol·L^-1; p < 0.001) and RPE (12 ± 1 vs. 11 ± 1; p < 0.001), respectively. Total time under tension was 48% greater in CONT compared to INT (p < 0.001), whereas average torque (during exercise) was 40% greater during INT compared to CONT (p < 0.001). Interval eccentric cycling exacerbates muscle soreness, decrements in muscle function and lengthens recovery compared to a work matched continuous bout, which is attributable to increased force rather than time under tension.

Fast-Velocity Eccentric Cycling Exercise Causes Greater Muscle Damage Than Slow Eccentric Cycling

This study aims to investigate muscle damage occurring in the early and recovery phases after fast-velocity and slow-velocity eccentric cycling. Eleven untrained men (age, 20.0 ± 1.7 years; height, 171.3 ± 6.8 cm; weight, 61.8 ± 7.7 kg; and %body fat, 13.2 ± 2.9%) performed slow-velocity maximal isokinetic eccentric cycling (slow-velocity; 30°/s) with one leg and fast-velocity (fast-velocity; 210°/s) isokinetic eccentric cycling with the other leg. Changes in maximal voluntary isokinetic concentric contraction (MVCC) torque at velocities of 30 and 210°/s, range of motion (ROM), and muscle soreness were assessed by pressure using a digital muscle stiffness instrument; thigh circumference, muscle echo intensity, and muscle stiffness were assessed before exercise, and immediately after exercise, 1 day, and 4 days after exercise. Comparing with the results obtained for slow-velocity cycling (post: 215.9 ± 32.3 Nm, day 1: 192.9 ± 47.4 Nm, day 4: 184.3 ± 47.2 Nm) and before exercise, MVCC after fast-velocity cycling significantly decreased at immediately (160.4 ± 43.5 Nm), 1 day (143.6 ± 54.1 Nm), and 4 days (150.1 ± 44.5 Nm) after exercise (p < 0.05). Significant increase in muscle soreness for vastus lateralis was observed after fast-velocity cycling (41.2 ± 16.9 mm) compared with slow-velocity cycling (23.7 ± 12.2 mm) 4 days after exercise (p < 0.05). However, no significant difference in muscle soreness was observed for rectus femoris and vastus medialis at any time points after exercise. In addition, no significant differences were observed in the ROM, thigh circumference, muscle echo intensity, and muscle stiffness. In conclusion, fast-velocity eccentric cycling causes a decrease in muscle strength and an increase in soreness as compared to slow-velocity eccentric cycling.

Metabolic Demand and Indirect Markers of Muscle Damage After Eccentric Cycling With Blood Flow Restriction

Purpose: To compare the effects of a single bout of eccentric cycling (ECC) and eccentric cycling with blood flow restriction (ECC_BFR) on the changes in cardio-metabolic demand and indirect markers of muscle damage in healthy men. Method: Twenty-one young men (24.0 ± 3.2 y) were randomly allocated in two groups to perform a 30-min eccentric cycling bout with or without blood flow restriction. Oxygen consumption, heart rate, rate of perceived exertion and mean arterial blood pressure were monitored during cycling. Blood lactate was measured before and after cycling. Maximal voluntary isometric knee extensor strength and muscle damage were measured before, immediately after and 1-4 days after each eccentric cycling bout. Results: Oxygen consumption, heart rate, rate of perceived exertion and mean arterial blood pressure were similar between bouts. Blood lactate concentrations increased in both groups (p < .01), with ECC_BFR showing 60% greater blood lactate concentration than eccentric cycling (p < .01). Maximal voluntary isometric knee extensor strength decreased 19-7% until 48 h and decreased 16-7% until 72 h after ECC and ECC_BFR, respectively. Muscle soreness and pressure pain threshold remained elevated until 72 h after ECC and until 96 h after ECC_BFR. Conclusion: These results show that ECC_BFR induces similar cardiovascular stress, greater lactate production and longer time to recover than ECC alone. Thus, BFR can be safely implemented with eccentric cycling.

Moving forward with backward pedaling: a review on eccentric cycling

PURPOSE

There is a profound gap in the understanding of the eccentric cycling intensity continuum, which prevents accurate exercise prescription based on desired physiological responses. This may underestimate the applicability of eccentric cycling for different training purposes. Thus, we aimed to summarize recent research findings and screen for possible new approaches in the prescription and investigation of eccentric cycling.

METHOD

A search for the most relevant and state-of-the-art literature on eccentric cycling was conducted on the PubMed database. Literature from reference lists was also included when relevant.

RESULTS

Transversal studies present comparisons between physiological responses to eccentric and concentric cycling, performed at the same absolute power output or metabolic load. Longitudinal studies evaluate responses to eccentric cycling training by comparing them with concentric cycling and resistance training outcomes. Only one study investigated maximal eccentric cycling capacity and there are no investigations on physiological thresholds and/or exercise intensity domains during eccentric cycling. No study investigated different protocols of eccentric cycling training and the chronic effects of different load configurations.

CONCLUSION

Describing physiological responses to eccentric cycling based on its maximal exercise capacity may be a better way to understand it. The available evidence indicates that clinical populations may benefit from improvements in aerobic power/capacity, exercise tolerance, strength and muscle mass, while healthy and trained individuals may require different eccentric cycling training approaches to benefit from similar improvements. There is limited evidence regarding the mechanisms of acute physiological and chronic adaptive responses to eccentric cycling.

Changes in Urinary Titin Fragment in Response to Different Types of Dynamic Eccentric Exercises

The urinary level of the titin fragment has been considered a non-invasive and sensitive biomarker for muscle damage in clinical cases. However, there is little evidence regarding changes in the urinary titin fragment in response to exercise-induced muscle damage. In this study, we aimed to investigate whether the urinary titin fragment reflects the magnitude of muscle damage induced by two lower-limb eccentric exercises. In this study, healthy young male subjects performed drop jump (n=9) and eccentric ergometer exercise (n=9). Blood and urine samples were collected at various time points before and after the exercises. Although perceived muscle soreness assessed by sit-to-stand tasks was increased at 24 h and 48 h after both drop jump and the eccentric ergometer exercise groups, the pressure pain threshold was not changed. Changes of the urinary titin fragment, plasma myomesin 3 fragments, creatine kinase (CK), and myoglobin (Mb) after the eccentric exercises were increased but not statistically significant. Meanwhile, we found that the changes in the urinary titin fragment levels in response to both drop jump and the eccentric ergometer exercise were correlated with those of plasma CK and Mb levels. These results provide evidence that the urinary titin fragment level is a non-invasive biomarker reflecting the magnitude of eccentric exercise-induced muscle damage.

Leg Muscle Activity and Perception of Effort before and after Four Short Sessions of Submaximal Eccentric Cycling

Background: This study tested muscle activity (EMG) and perception of effort in eccentric (ECC) and concentric (CON) cycling before and after four sessions of both. Methods: Twelve volunteers naïve to ECC cycling attended the laboratory six times. On day 1, they performed a CON cycling peak power output (PPO) test. They then carried-out four sessions comprising two sets of 1 to 1.5-min cycling bouts at 5 intensities (30, 45, 60, 75, and 90% PPO) in ECC and CON cycling. On day 2 and day 6 (two weeks apart), EMG root mean square of the vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), and soleus (SOL) muscles, was averaged from 15 to 30 s within each 1-min bout and perception of effort was asked after 45 s. Results: Before the four cycling sessions, while VL EMG was lower in ECC than CON cycling, most variables were not different. Afterwards, ECC cycling exhibited lower RF EMG at 75 and 90% PPO (all p < 0.02), lower VL and BF EMG at all exercise intensities (all p < 0.02), and inferior SOL EMG (all p < 0.04) except at 45% PPO (p = 0.07). Perception of effort was lower in ECC cycling at all exercise intensities (all p < 0.03) but 60% PPO (p = 0.11). Conclusions: After four short sessions of ECC cycling, the activity of four leg muscles and perception of effort became lower in ECC than in CON cycling at most of five power outputs, while they were similar before.

Impact of Rest-Redistribution on Fatigue During Maximal Eccentric Knee Extensions

Redistributing long inter-set rest intervals into shorter but more frequent rest intervals generally maintains concentric performance, possibly due to improved energy store maintenance. However, eccentric actions require less energy than concentric actions, meaning that shorter but more frequent sets may not affect eccentric actions to the same degree as concentric actions. Considering the increased popularity of eccentric exercise, the current study evaluated the effects of redistributing long inter-set rest periods into shorter but more frequent rest periods during eccentric only knee extensions. Eleven resistance-trained men performed 40 isokinetic unilateral knee extensions at 60°·s-1 with 285 s of total rest using traditional sets (TS; 4 sets of 10 with 95 s inter-set rest) and rest-redistribution (RR; 20 sets of 2 with 15 s inter-set rest). Before and during exercise, muscle oxygenation was measured via near-infrared spectroscopy, and rating of perceived exertion (RPE) was recorded after every 10th repetition. There were no differences between protocols for peak torque (RR, 241.58±47.20 N; TS, 231.64±48.87 N; p=0.396) or total work (RR, 215.26±41.47 J; TS, 209.71±36.02 J; p=0.601), but moderate to large effect sizes existed in later repetitions (6,8,10) with greater peak torque during RR (d=0.66-1.19). For the entire session, RR had moderate effects on RPE (RR, 5.73±1.42; TS, 6.09±1.30; p=0.307; d=0.53) and large effects on oxygen saturation (RR, 5857.4±310.0; TS, 6495.8±273.8; p=0.002, d=2.13). Therefore, RR may maintain peak torque or total work during eccentric exercise, improve oxygen utilization at the muscle, and reduce the perceived effort.

Physiological response to eccentric and concentric cycling in patients with chronic obstructive pulmonary disease

We aimed to compare the cardiorespiratory, metabolic, and perceptual responses to high- and moderate-intensity eccentric cycling versus moderate-intensity concentric cycling in chronic obstructive pulmonary disease (COPD) patients. Ten patients with moderate COPD (forced expiratory volume in 1 s (FEV₁) = 68.6% ± 20.4% of predicted; 68.3 ± 9.1 years) performed 30 min of moderate-intensity concentric (CONC-M: 50% maximum workload; W_max), moderate-intensity eccentric (ECC-M: 50% W_max), and high-intensity eccentric (ECC-H: 100% W_max) cycling. Average power output, oxygen consumption (V̇O₂), minute ventilation (VE), respiratory frequency (f_R), oxygen saturation (SpO₂), heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), rate of perceived exertion (RPE), and dyspnea were measured during cycling. Compared with CONC-M, lower V̇O₂ (-52% ± 14%), VE (-47% ± 16%), f_R (-21% ± 14%), HR (-14% ± 16%), SBP (-73% ± 54%), RPE (-36% ± 26%), and dyspnea (-41% ± 37%) were found during ECC-M. During ECC-H, a similar metabolic demand to CONC-M was found. However, average power output was 117% ± 79% higher during ECC-H. Eccentric cycling can be safely performed by COPD patients and induced lower cardiorespiratory, metabolic, and perceptual responses than concentric exercise when performed at the same workload. Novelty Moderate- and high-intensity eccentric cycling can be performed by COPD patients. Moderate-intensity eccentric cycling showed lower cardiorespiratory, metabolic, and perceptual demand than concentric cycling at the same workload in COPD patients. Even at double workload, eccentric cycling induces lower cardiorespiratory, metabolic, and perceptual demand than moderate-intensity concentric cycling.

The Acute Physiological Responses of Eccentric Cycling During the Recovery Periods of a High Intensity Concentric Cycling Interval Session

Eccentric and concentric exercise is associated with disparate acute and chronic responses. We uniquely interspersed workload equivalent eccentric cycling during each recovery period of a high intensity interval training (HIIT) cycling trial to determine acute cardiopulmonary, thermal and psycho-physiological responses. Twelve males [age 28 years (SD 6), peak oxygen consumption 48 mL ⋅ kg^–1 ⋅ min^–1 (SD 6)] completed two high intensity interval cycling trials [4 × 5 min, 60% peak power output (PPO)] separated by 7–10 days. The CON_R trial required participants to cycle concentrically during each recovery period (5 min, 30% PPO). The ECC_R trial modified the recovery to be eccentric cycling (5 min, 60% PPO). High intensity workload (CON_R: 187 ± 17; ECC_R: 187 ± 21 W), oxygen consumption (CON_R: 2.55 ± 0.17; ECC_R: 2.68 ± 0.20 L ⋅ min^–1), heart rate (CON_R: 165 ± 7; ECC_R: 171 ± 10 beats ⋅ min^–1) and RPE legs (CON_R: 15 ± 3; ECC_R: 15 ± 3) were equivalent between trials. Eccentric cycling recovery significantly increased external workload (CON_R: 93 ± 18; ECC_R: 196 ± 24 W, P < 0.01) yet lowered oxygen consumption (CON_R: 1.51 ± 0.18; ECC_R: 1.20 ± 0.20 L ⋅ min^–1, P < 0.05) while heart rate (CON_R: 132 ± 13; ECC_R: 137 ± 12 beats ⋅ min^–1) and RPE of the legs (CON_R: 11 ± 7; ECC_R: 12 ± 7) remained equivalent. There was no significant difference in the aural temperature between the trials (ECC_R: 37.3 ± 0.1°C; CON_R: 37.4 ± 0.1°C, P > 0.05), yet during recovery periods mean skin temperature was significantly elevated in the ECC_R (ECC_R: 33.9 ± 0.2°C; CON_R: 33.3 ± 0.2°C, P < 0.05). Participants preferred ECC_R (10/12) and rated the ECC_R as more achievable (82.8 ± 11.4 mm) than CON_R (79.4 ± 15.9 mm, P < 0.01). In conclusion, eccentric cycling during the recovery period of a HIIT training session, offers a novel approach to concurrent training methodology. The unique cardiopulmonary and skeletal muscle responses facilitate the achievement of both training stimuli within a single exercise bout.

Ultrasound imaging to assess skeletal muscle architecture during movements: a systematic review of methods, reliability, and challenges

B-mode ultrasound is often used to quantify muscle architecture during movements. Our objectives were to 1) systematically review the reliability of fascicle length (FL) and pennation angles (PA) measured using ultrasound during movements involving voluntary contractions; 2) systematically review the methods used in studies reporting reliability, discuss associated challenges, and provide recommendations to improve the reliability and validity of dynamic ultrasound measurements; and 3) provide an overview of computational approaches for quantifying fascicle architecture, their validity, agreement with manual quantification of fascicle architecture, and advantages and drawbacks. Three databases were searched until June 2019. Studies among healthy human individuals aged 17-85 yr that investigated the reliability of FL or PA in lower-extremity muscles during isoinertial movements and that were written in English were included. Thirty studies (n = 340 participants) were included for reliability analyses. Between-session reliability as measured by coefficient of multiple correlations (CMC), and coefficient of variation (CV) was FL CMC: 0.89-0.96; CV: 8.3% and PA CMC: 0.87-0.90; CV: 4.5-9.6%. Within-session reliability was FL CMC: 0.82-0.99; CV: 0.0-6.7% and PA CMC: 0.91; CV: 0.0-15.0%. Manual analysis reliability was FL CMC: 0.89-0.96; CV: 0.0-15.9%; PA CMC: 0.84-0.90; and CV: 2.0-9.8%. Computational analysis FL CMC was 0.82-0.99, and PA CV was 14.0-15.0%. Eighteen computational approaches were identified, and these generally showed high agreement with manual analysis and high validity compared with phantoms or synthetic images. B-mode ultrasound is a reliable method to quantify fascicle architecture during movement. Additionally, computational approaches can provide a reliable and valid estimation of fascicle architecture.

Global Corticospinal Excitability as Assessed in A Non-Exercised Upper Limb Muscle Compared Between Concentric and Eccentric Modes of Leg Cycling

This study investigated the effects of eccentric (ECC) and concentric (CON) semi-recumbent leg cycling on global corticospinal excitability (CSE), assessed through the activity of a non-exercised hand muscle. Thirteen healthy male adults completed two 30-min bouts of moderate intensity ECC and CON recumbent cycling on separate days. Power output (POutput), heart rate (HR) and cadence were monitored during cycling. Global CSE was assessed using transcranial magnetic stimulation to elicit motor-evoked potentials (MEP) in the right first dorsal interosseous muscle before (‘Pre’), interleaved (at 10 and 20 mins, t10 and t20, respectively), immediately after (post, P0), and 30-min post exercise (P30). Participants briefly stopped pedalling (no more than 60 s) while stimulation was applied at the t10 and t20 time-points of cycling. Mean POutput, and rate of perceived exertion (RPE) did not differ between ECC and CON cycling and HR was significantly lower during ECC cycling (P = 0.01). Group mean MEP amplitudes were not significantly different between ECC and CON cycling at P0, t10, t20, and P30 and CON (at P > 0.05). Individual participant ratios of POutput and MEP amplitude showed large variability across the two modes of cycling, as did changes in slope of stimulus-response curves. These results suggest that compared to ‘Pre’ values, group mean CSE is not significantly affected by low-moderate intensity leg cycling in both modes. However, POutput and CSE show wide inter-participant variability which has implications for individual neural responses to CON and ECC cycling and rates of adaptation to a novel (ECC) mode. The study of CSE should therefore be analysed for each participant individually in relation to relevant physiological variables and account for familiarisation to semi-recumbent ECC leg cycling.

Activation of protein synthesis, regeneration, and MAPK signaling pathways following repeated bouts of eccentric cycling

The aim of this study was to examine the activation of skeletal muscle signaling pathways related to protein synthesis and the gene expression of regeneration/degradation markers following repeated bouts of eccentric cycling. Nine untrained men (25.4 ± 1.9 yr) performed two 30-min eccentric cycling bouts (ECC1, ECC2) at 85% of maximal concentric workload, separated by 2 wk. Muscle biopsies were taken from the vastus lateralis before and 2 h after each bout. Indirect markers of muscle damage were assessed before and 24-48 h after exercise. Changes in the Akt/mammalian target of rapamycin (mTOR)/rbosomal protein S6 kinase 1 (S6K1)/ribosomal protein S6 (rpS6) and MAPK signaling pathways were measured by Western blot and changes in mRNA expression of IL-6 and IL-1β, and myogenic regulatory factors (MRFs) were measured by real-time PCR. ECC1 induced greater increases in indirect markers of muscle damage compared with ECC2. Phosphorylation of S6K1 and rpS6 increased after both exercise bouts (P < 0.05), whereas phosphorylation of mTOR increased after ECC2 only (P = 0.03). Atrogin-1 mRNA expression decreased after ECC1 and ECC2 (P < 0.05) without changes in muscle RING-finger protein-1 mRNA. Basal mRNA levels of myoblast determination protein-1 (MyoD), MRF4, and myogenin were higher 2 wk after ECC1 (P < 0.05). MRF4 mRNA increased after ECC1 and ECC2 (P < 0.05), whereas MyoD mRNA expression increased only after ECC1 (P = 0.03). Phosphorylation of JNK and p38 MAPK increased after both exercise bouts (P < 0.05), similar to IL-6 and IL-1β mRNA expression. All together, these results suggest that differential regulation of the mTOR pathway and MRF expression could mediate the repeated bout effect observed between an initial and secondary bout of eccentric exercise.

HSP72 expression is specific to skeletal muscle contraction type

Exercise is capable of inducing the cellular stress response and increasing skeletal muscle heat shock protein (HSP) content. HSPs function as molecular chaperones and play roles in facilitating protein folding thereby contributing to muscle proteostasis. To determine the relationship between muscle contraction types, muscle damage, and HSP content, one tibialis anterior (TA) muscle from male Sprague-Dawley rats (n = 5/group) was electrically stimulated while actively lengthening (LC), shortening (SC), or remaining to stagnate (IC) for 15 repetitions (3 sets of five). Two additional LC groups underwent 5 and 10 repetitions. Maximal tetanic tension (MTT) was recorded prior to (pre) and at 5 min after (post) the last contraction. Twenty-four hours after stimulation, TA muscles were removed, processed, and assessed for damage and for HSP25 and HSP72 content. Post-MTT was significantly decreased following 15 LCs, (24%; p < 0.05) but not following 15 SCs or 15 ICs. Post-MTT was also decreased by 8% (p < 0.05), and 18% (p < 0.05) for muscles subjected to 5 and 10 LCs, respectively. HSP72 content increased after all LCs conditions but not following ICs or SCs. HSP25 content remained unchanged following all contractions. Similarly, muscle damage was observed only after LCs and not after other contraction types. In conclusion, muscle HSP72 content can be increased with as few as 5 maximal lengthening contractions and appears to be related to muscle damage. This may have important implications for muscle rehabilitation and exercise training programs.

Neuromuscular and Perceptual Responses to Sub-Maximal Eccentric Cycling

Objective

Eccentric (ECC) cycle-ergometers have recently become commercially-available, offering a novel method for rehabilitation training. Many studies have reported that ECC cycling enables the development of higher levels of muscular force at lower cardiorespiratory and metabolic loads, leading to greater force enhancements after a training period. However, fewer studies have focused on the specific perceptual and neuromuscular changes. As the two latter aspects are of major interest in clinical settings, this review aimed to present an overview of the current literature centered on the neuromuscular and perceptual responses to submaximal ECC cycling in comparison to concentric (CON) cycling.

Design

Narrative review of the literature.

Results

At a given mechanical workload, muscle activation is lower in ECC than in CON while the characteristics of the musculo-articular system (i.e., muscle-tendon unit, fascicle, and tendinous tissue length) are quite similar. At a given heart rate or oxygen consumption, ECC cycling training results in greater muscular hypertrophy and strength gains than CON cycling. On the contrary, CON cycling training seems to enhance more markers of muscle aerobic metabolism than ECC cycling performed at the same heart rate intensity. Data concerning perceptual responses, and neuromuscular mechanisms leading to a lower muscle activation (i.e., neural commands from cortex to muscular system) at a given mechanical workload are scarce.

Conclusion

Even though ECC cycling appears to be a very useful tool for rehabilitation purposes the perceptual and neural commands from cortex to muscular system during exercise need to be further studied.

Eccentric cycling is more efficient in reducing fat mass than concentric cycling in adolescents with obesity

The benefits of eccentric (ECC) training on fat mass (FM) remain underexplored. We hypothesized that in obese adolescents, ECC cycling training is more efficient for decreasing whole-body FM percentage compared to concentric (CON) performed at the same oxygen consumption (VO₂ ). Twenty-four adolescents aged 13.4 ± 1.3 years (BMI > 90th percentile) were randomized to ECC or CON. They performed three cyclo-ergometer sessions per week (30 min per session) for 12 weeks: two habituation, 5 at 50% VO_2peak , and 5 at 70% VO_2peak . Anthropometric measurements, body composition, maximal incremental CON tests, strength tests, and blood samples were assessed pre- and post-training. Whole-body FM percentage decreased significantly after compared to pretraining in both groups, though to a larger extent in the ECC group (ECC: -10% vs CON: -4.2%, P < 0.05). Whole-body lean mass (LM) percentage increased significantly in both groups after compared to pretraining, with a greater increase in the ECC group (ECC: 3.8% vs CON: 1.5%, P <0.05). The improvements in leg FM and LM percentages were greater in the ECC group (-6.5% and 3.0%, P = 0.01 and P < 0.01). Quadriceps isometric and isokinetic ECC strength increased significantly more in the ECC group (28.3% and 21.3%, P < 0.05). Both groups showed similar significant VO_2peak improvement (ECC: 15.4% vs CON: 10.3%). The decrease in homeostasis model assessment of insulin resistance index was significant in the ECC group (-19.9%). In conclusion, although both ECC and CON cycling trainings are efficient to decrease FM, ECC induces greater FM reduction, strength gains, and insulin resistance improvements and represents an optimal modality to recommend for obese adolescents.

Microvascular permeability of skeletal muscle after eccentric contraction-induced muscle injury: in vivo imaging using two-photon laser scanning microscopy

Via modulation of endothelial integrity and vascular permeability in response to damage, skeletal muscle microvessels play a crucial permissive role in tissue leukocyte invasion. However, direct visual evidence of altered microvascular permeability of skeletal muscle has not been technically feasible, impairing mechanistic understanding of these responses. Two-photon laser scanning microscopy (TPLSM) allows three-dimensional in vivo imaging of skeletal muscle microcirculation. We hypothesized that the regulation of microvascular permeability in vivo is temporally related to acute inflammatory and regenerative processes following muscle injury. To test our hypothesis, tibialis anterior muscles of anesthetized male Wistar rats were subjected to eccentric contractions (ECCs) via electrical stimulation. The skeletal muscle microcirculation was imaged by an intravenously infused fluorescent dye (rhodamine B isothiocyanate-dextran) to assess microvascular permeability via TPLSM 1, 3, and 7 days after ECC. Immunohistochemistry on serial muscle sections was performed to determine the proportion of VEGF-A-positive muscle fibers in the damaged muscle. Compared with control rats, the volumetrically determined interstitial leakage of fluorescent dye (5.1 ± 1.4, 5.3 ± 1.2 vs. 0.51 ± 0.14 μm3 × 106; P < 0.05, days 1 and 3, respectively, vs. control) and percentage of VEGF-A-positive fibers in the damaged muscle (10 ± 0.4%, 22 ± 1.1% vs. 0%; days 1 and 3, respectively, vs. control) were significantly higher on days 1 and 3 after ECC. The interstitial leakage volume returned to control by day 7. These results suggest that microvascular hyperpermeability assessed by in vivo TPLSM imaging is associated with ECC-induced muscle damage and increased VEGF expression.

NEW & NOTEWORTHY This investigation employed a novel in vivo imaging technique for skeletal muscle microcirculation using two-photon laser scanning microscopy that enabled microvascular permeability to be assessed by four-dimensional image analysis. By combining in vivo imaging and histological analysis, we found the temporal profile of microvascular hyperpermeability to be related to that of eccentric contraction-induced skeletal muscle injury and pronounced novel myocyte VEGF expression.

Performance determinants of fixed gear cycling during criteriums

Nowadays, fixed gear competitions on outdoor circuits such as criteriums are regularly organized worldwide. To date, no study has investigated this alternative form of cycling. The purpose of the present study was to examine fixed gear performance indexes and to characterize physiological determinants of fixed gear cyclists. This study was carried out in two parts. Part 1 (n = 36) examined correlations between performance indexes obtained during a real fixed gear criterium (time trial, fastest laps, averaged lap time during races, fatigue indexes) and during a sprint track time trial. Part 2 (n = 9) examined correlations between the recorded performance indexes and some aerobic and anaerobic performance outputs (VO_2max, maximal aerobic power, knee extensor and knee flexor maximal voluntary torque, vertical jump height and performance during a modified Wingate test). Results from Part 1 indicated significant correlations between fixed gear final performance (i.e. average lap time during the finals) and single lap time (time trial, fastest lap during races and sprint track time trial). In addition, results from Part 2 revealed significant correlations between fixed gear performance and aerobic indicators (VO_2max and maximal aerobic power). However, no significant relationship was obtained between fixed gear cycling and anaerobic qualities such as strength. Similarly to traditional cycling disciplines, we concluded that fixed gear cycling is mainly limited by aerobic capacity, particularly criteriums final performance. However, specific skills including technical competency should be considered.