Characterization of performance fatigability during a self-paced exercise

Pacing during a high-intensity cycling time trial (TT) appears to prevent premature task failure, but the performance fatigability during a self-paced exercise is currently unknown. Therefore, the current study characterized the time course of performance fatigability during a 4-km TT. Eleven male cyclists performed three separated TTs in a crossover, counterbalanced design. The TTs lasted until the end of the fast-start (FS; 600 ± 205 m), even-pace (EP; 3,600 ± 190 m), and end-spurt (ES; 4,000 m) phases. Performance fatigability was characterized by using isometric maximal voluntary contractions (IMVCs), whereas the muscle activation [i.e., voluntary activation (VA)] and contractile function of knee extensors [e.g., peak torque of potentiated twitches (TwPt)] were evaluated using electrically evoked contractions performed before and 1 min after each specific part of the trial. Gas exchange, power output (PO), and electromyographic activity (EMG) were also recorded. EMG/PO showed an abrupt increase followed by a continuous decrease toward the end of FS, resulting in a drop in IMVC (−12%), VA (−8%), and TwPt (−23%). EMG/PO was stable during EP, with no additional drop on IMVC, VA, or TwPt (−12%, −6%, and −22%, respectively). EMG/PO increased abruptly during the ES, but there was no change in IMVCs, VA, or TwPt (−13%, −8%, and −26%, respectively). These findings demonstrate that the performance fatigability during a self-paced exercise is characterized by a large drop in contractile function and muscle activation at the beginning of the trial (i.e., FS), without additional change during the middle and end phases (i.e., EP and ES). NEW & NOTEWORTHY The time course of performance fatigability throughout a self-paced exercise is currently unknown. The results showed that a large amount of muscle activation and contractile function impairments are attained early on a self-paced exercise (first ∼15% of the total time trial distance) and maintained throughout the test. This novel finding characterizes the performance fatigability from a contractile function and muscle activation perspective, which brings new insights for future studies focused on real-world exercise training and competition.

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Slight power output manipulations around the maximal lactate steady state have an impact on fatigue in females and males.

Journal of Applied Physiology ◽

10.1152/japplphysiol.00892.2020 ◽

2021 ◽

Author(s):

Rafael de Almeida Azevedo ◽

Jonas Forot ◽

Danilo Iannetta ◽

Martin J. MacInnis ◽

Guillaume Y. Millet ◽

...

Keyword(s):

Steady State ◽

Power Output ◽

Contractile Function ◽

Femoral Nerve ◽

Peak Torque ◽

Knee Extensors ◽

Time To Exhaustion ◽

Maximal Lactate Steady State ◽

Subsequent Performance ◽

Single Twitch

Neuromuscular fatigue (NMF) and exercise performance are affected by exercise intensity and sex differences. However, whether slight changes in power output (PO) below and above the maximal lactate steady-state (MLSS) impact NMF and subsequent performance (time to exhaustion, TTE) is unknown. Purpose: This study compared NMF and TTE in females and males in response to exercise performed at MLSS, 10 W below (MLSS-10) and above (MLSS+10). Methods: Twenty participants (9 females) performed three 30-min constant-PO exercise bouts followed (1 min delay) by a TTE at 80% of the peak-PO. NMF was characterized by isometric maximal voluntary contractions (IMVC) and femoral nerve electrical stimulation of knee extensors [e.g. peak torque of potentiated high-frequency (Db100) and single twitch (TwPt)] before and immediately after the constant-PO and TTE bouts. Results: IMVC declined less after MLSS-10 (-18±10%) compared to MLSS (-26±14%) and MLSS+10 (-31±11%) (all p<0.05), and the Db100 decline was greater after MLSS+10 (-24±14%) compared to the other intensities (MLSS-10: -15±9%; MLSS: -18±11%) (all p<0.05). Females showed smaller reductions in IMVC and TwPt compared to males after constant-PO bouts (all p<0.05), this difference being not dependant on intensity. TTE was negatively impacted by increasing the PO in the constant-PO (p<0.001), with no differences in end-exercise NMF (p>0.05). Conclusion: Slight changes in PO around MLSS elicited great changes in the reduction of maximal voluntary force and impairments in contractile function. Although NMF was lower in females compared to males, the changes in PO around the MLSS impacted both sexes similarly.

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The Effect of Heating and Cooling on Time Course of Voluntary and Electrically Induced Muscle Force Variation

Medicina ◽

10.3390/medicina47010006 ◽

2011 ◽

Vol 47 (1) ◽

pp. 6 ◽

Cited By ~ 3

Author(s):

◽

Keyword(s):

Muscle Fatigue ◽

Time Course ◽

Muscle Force ◽

Peak Torque ◽

Voluntary Contraction ◽

Knee Extensors ◽

Lower Body ◽

Heating And Cooling ◽

Force Variation ◽

Voluntary Contractions

The aim of this study was to investigate the effect of heating and cooling on time course of voluntary and electrically induced muscle force variation. Material and Methods. Ten volunteers performed 50 maximal voluntary and electrically induced contractions of the knee extensors at an angle of 120 degrees under the control conditions and after passive lower body heating and cooling in the control, heating, and cooling experiments. Peak torque, torque variation, and half-relaxation time were assessed during the exercise. Results. Passive lower body heating increased muscle and core temperatures, while cooling lowered muscle temperature, but did not affect core temperature. We observed significantly lower muscle fatigue during voluntary contraction compared with electrically induced contractions. Body heating (opposite to cooling) increased involuntarily induced muscle force, but caused greater electrically induced muscle fatigue. In the middle of the exercise, the coefficient of correlation for electrically induced muscle torque decreased significantly as compared with the beginning of the exercise, while during maximal voluntary contractions, this relation for torque remained significant until the end of the exercise. Conclusion. It was shown that time course of voluntary contraction was more stable than in electrically induced contractions.

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Pacing Strategy, Muscle Fatigue, and Technique in 1500-m Speed-Skating and Cycling Time Trials

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2014-0603 ◽

2016 ◽

Vol 11 (3) ◽

pp. 337-343 ◽

Cited By ~ 27

Author(s):

Inge K. Stoter ◽

Brian R. MacIntosh ◽

Jared R. Fletcher ◽

Spencer Pootz ◽

Inge Zijdewind ◽

...

Keyword(s):

Muscle Fatigue ◽

Blood Lactate ◽

National Level ◽

Time Trial ◽

Voluntary Activation ◽

Slow Start ◽

Speed Skating ◽

Fast Start ◽

Start Trial ◽

Cycling Time

Purpose:To evaluate pacing behavior and peripheral and central contributions to muscle fatigue in 1500-m speed-skating and cycling time trials when a faster or slower start is instructed.Methods:Nine speed skaters and 9 cyclists, all competing at regional or national level, performed two 1500-m time trials in their sport. Athletes were instructed to start faster than usual in 1 trial and slower in the other. Mean velocity was measured per 100 m. Blood lactate concentrations were measured. Maximal voluntary contraction (MVC), voluntary activation (VA), and potentiated twitch (PT) of the quadriceps muscles were measured to estimate central and peripheral contributions to muscle fatigue. In speed skating, knee, hip, and trunk angles were measured to evaluate technique.Results:Cyclists showed a more explosive start than speed skaters in the fast-start time trial (cyclists performed first 300 m in 24.70 ± 1.73 s, speed skaters in 26.18 ± 0.79 s). Both trials resulted in reduced MVC (12.0% ± 14.5%), VA (2.4% ± 5.0%), and PT (25.4% ± 15.2%). Blood lactate concentrations after the time trial and the decrease in PT were greater in the fast-start than in the slow-start trial. Speed skaters showed higher trunk angles in the fast-start than in the slow-start trial, while knee angles remained similar.Conclusions:Despite similar instructions, behavioral adaptations in pacing differed between the 2 sports, resulting in equal central and peripheral contributions to muscle fatigue in both sports. This provides evidence for the importance of neurophysiological aspects in the regulation of pacing. It also stresses the notion that optimal pacing needs to be studied sport specifically, and coaches should be aware of this.

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The influence of ice slushy on voluntary contraction force following exercise-induced hyperthermia

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2013-0394 ◽

2014 ◽

Vol 39 (7) ◽

pp. 781-786 ◽

Cited By ~ 3

Author(s):

Catriona A. Burdon ◽

Christopher S. Easthope ◽

Nathan A. Johnson ◽

Phillip G. Chapman ◽

Helen O’Connor

Keyword(s):

Muscle Activation ◽

Force Production ◽

Central Fatigue ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Peripheral Fatigue ◽

Knee Extensors ◽

Central Component ◽

Induced Hyperthermia ◽

Exercise Induced

This study aimed to investigate the effect of exercise-induced hyperthermia on central fatigue and force decline in exercised and nonexercised muscles and whether ingestion of ice slushy (ICE) ameliorates fatigue. Eight participants (5 males, 3 females) completed 45 s maximal voluntary isometric contractions (MVIC) with elbow flexors and knee extensors at baseline and following an exercise-induced rectal temperature (Trec) of 39.3 ± 0.2 °C. Percutaneous electrical muscle stimulation was superimposed at 15, 30 and 44 s during MVICs to assess muscle activation. To increase Trec to 39.3 °C, participants cycled at 60% maximum power output for 42 ± 11 min in 40 °C and 50% relative humidity. Immediately prior to each MVIC, participants consumed 50 g of ICE (–1 °C) or thermoneutral drink (38 °C, CON) made from 7.4% carbohydrate beverage. Participants consumed water (19 °C) during exercise to prevent hypohydration. Voluntary muscle force production and activation in both muscle groups were unchanged at Trec 39.3 °C with ICE (knee extensors: 209 ± 152 N) versus CON (knee extensors: 255 ± 157 N, p = 0.19). At Trec 39.3 °C, quadriceps mean force (232 ± 151 N) decreased versus baseline (302 ± 180 N, p < 0.001) and mean voluntary activation was also decreased (by 15% ± 11%, p < 0.001). Elbow flexor mean force decreased from 179 ± 67 N to 148 ± 65 N when Trec was increased to 39.3 °C (p < 0.001) but mean voluntary activation was not reduced at 39.3 °C (5% ± 25%, p = 0.79). After exercise-induced hyperthermia, ICE had no effect on voluntary activation or force production; however, both were reduced from baseline in the exercised muscle group. Peripheral fatigue was greater than the central component and limited the ability of an intervention designed to alter central fatigue.

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Neuromuscular fatigue during a long-duration cycling exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00880.2001 ◽

2002 ◽

Vol 92 (4) ◽

pp. 1487-1493 ◽

Cited By ~ 131

Author(s):

Romuald Lepers ◽

Nicola A. Maffiuletti ◽

Ludovic Rochette ◽

Julien Brugniaux ◽

Guillaume Y. Millet

Keyword(s):

Time Course ◽

Muscle Activation ◽

Mechanical Response ◽

Vastus Lateralis ◽

Quadriceps Muscle ◽

Voluntary Contraction ◽

Vastus Lateralis Muscle ◽

Electromyographic Activity ◽

Cycling Exercise ◽

M Wave

The effects of prolonged cycling on neuromuscular parameters were studied in nine endurance-trained subjects during a 5-h exercise sustained at 55% of the maximal aerobic power. Torque during maximal voluntary contraction (MVC) of the quadriceps muscle decreased progressively throughout the exercise ( P < 0.01) and was 18% less at the end of exercise compared with the preexercise value. Peak twitch torque, contraction time, and total area of mechanical response decreased significantly ( P < 0.05) after the first hour of exercise. In contrast, changes in M-wave characteristics were significant only after the fourth hour of the exercise. Significant reductions ( P < 0.05) in electromyographic activity normalized to the M wave occurred after the first hour for the vastus lateralis muscle but only at the end of the exercise for the vastus medialis muscle. Muscle activation level, assessed by the twitch interpolation technique, decreased by 8% ( P < 0.05) at the end of the exercise. The results suggest that the time course is such that the contractile properties are significantly altered after the first hour, whereas excitability and central drive are more impaired toward the latter stages of the 5-h cycling exercise.

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Swing- and support-related muscle actions differentially trigger human walk–run and run–walk transitions

Journal of Experimental Biology ◽

10.1242/jeb.204.13.2277 ◽

2001 ◽

Vol 204 (13) ◽

pp. 2277-2287 ◽

Cited By ~ 11

Author(s):

Boris I. Prilutsky ◽

Robert J. Gregor

Keyword(s):

Muscle Activation ◽

Rectus Femoris ◽

Swing Phase ◽

Knee Extensors ◽

Electromyographic Activity ◽

Sense Of Effort ◽

Leg Muscles ◽

Transition Speed ◽

Walking Speeds ◽

Preferred Transition Speed

SUMMARY There has been no consistent explanation as to why humans prefer changing their gait from walking to running and from running to walking at increasing and decreasing speeds, respectively. This study examined muscle activation as a possible determinant of these gait transitions. Seven subjects walked and ran on a motor-driven treadmill for 40s at speeds of 55, 70, 85, 100, 115, 130 and 145% of the preferred transition speed. The movements of subjects were videotaped, and surface electromyographic activity was recorded from seven major leg muscles. Resultant moments at the leg joints during the swing phase were calculated. During the swing phase of locomotion at preferred running speeds (115, 130, 145%), swing-related activation of the ankle, knee and hip flexors and peaks of flexion moments were typically lower (P<0.05) during running than during walking. At preferred walking speeds (55, 70, 85%), support-related activation of the ankle and knee extensors was typically lower during stance of walking than during stance of running (P<0.05). These results support the hypothesis that the preferred walk–run transition might be triggered by the increased sense of effort due to the exaggerated swing-related activation of the tibialis anterior, rectus femoris and hamstrings; this increased activation is necessary to meet the higher joint moment demands to move the swing leg during fast walking. The preferred run–walk transition might be similarly triggered by the sense of effort due to the higher support-related activation of the soleus, gastrocnemius and vastii that must generate higher forces during slow running than during walking at the same speed.

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Age-related differences in performance and fatigability during an isometric quadriceps intermittent fatigue test

10.1101/2021.09.19.460938 ◽

2021 ◽

Author(s):

Giorgio Varesco ◽

Eric Luneau ◽

Léonard Féasson ◽

Thomas Lapole ◽

Vianney Rozand

Keyword(s):

Older Adults ◽

Contractile Function ◽

Age Groups ◽

Femoral Nerve ◽

Voluntary Activation ◽

Knee Extensors ◽

Men And Women ◽

Very Old ◽

Old Adults ◽

Age Related

AbstractThe aim of the present study was to investigate age-related differences in fatigability induced by an isometric quadriceps intermittent fatiguing test in young (<35 years old), old (>60 years old) and very old (>80 years old) men and women. Maximal force loss, contractile function and voluntary activation of the knee extensors were evaluated throughout an isometric fatiguing test using femoral nerve magnetic stimulations. Older adults performed more contractions (index of relative performance) than young (P = 0.046) and very old adults (P = 0.007), without differences between young and very old adults. Total work (absolute performance) was greater for young and old adults compared to very old adults (P < 0.001), without differences between young and old adults. At exhaustion, force loss was greater for young (−28 ± 9%) compared to old adults (−19 ± 8%), but not very old adults (−23 ± 8%). The response to femoral nerve stimulation decreased similarly at exhaustion for the three age groups, indicating similar alteration in contractile function with age. No impairment in voluntary activation was observed. Impairments in neuromuscular parameters were similar for men and women. This study showed that older adults were less fatigable than young adults during an isometric intermittent fatiguing task of the knee extensors. This greater fatigue resistance was not maintained in very old adults independent of sex. Fatigability at exhaustion was likely due to impairments in contractile function for the three age groups.

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Exercise-Induced Muscle Damage and Recovery in Young and Middle-Aged Males with Different Resistance Training Experience

Sports ◽

10.3390/sports7060132 ◽

2019 ◽

Vol 7 (6) ◽

pp. 132 ◽

Cited By ~ 4

Author(s):

John Fernandes ◽

Kevin Lamb ◽

Craig Twist

Keyword(s):

Resistance Training ◽

Muscle Damage ◽

Peak Power ◽

Time Course ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Knee Extensors ◽

Middle Aged ◽

Training Experience ◽

Exercise Induced

This study compared the time course of recovery after a squatting exercise in trained young (YG; n = 9; age 22.3 ± 1.7 years) and trained (MT; n = 9; 39.9 ± 6.2 years) and untrained (MU; n = 9; age 44.4 ± 6.3 years) middle-aged males. Before and at 24 and 72 h after 10 × 10 squats at 60% one-repetition maximum (1RM), participants provided measurements of perceived muscle soreness (VAS), creatine kinase (CK), maximal voluntary contraction (MVC), voluntary activation (VA), and resting doublet force of the knee extensors and squatting peak power at 20% and 80% 1RM. When compared to the YG males, the MT experienced likely and very likely moderate decrements in MVC, resting doublet force, and peak power at 20% and 80% 1RM accompanied by unclear differences in VAS, CK, and VA after the squatting exercise. MU males, compared to MT, experienced greater alterations in peak power at 20% and 80% 1RM and VAS. Alterations in CK, MVC, VA, and resting doublet force were unclear at all time-points between the middle-aged groups. Middle-aged males experienced greater symptoms of muscle damage and an impaired recovery profile than young resistance trained males. Moreover, regardless of resistance training experience, middle-aged males are subject to similar symptoms after muscle-damaging lower-body exercise.

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Contractile speed and EMG changes during fatigue of sustained maximal voluntary contractions

Journal of Neurophysiology ◽

10.1152/jn.1983.50.1.313 ◽

1983 ◽

Vol 50 (1) ◽

pp. 313-324 ◽

Cited By ~ 336

Author(s):

B. Bigland-Ritchie ◽

R. Johansson ◽

O. C. Lippold ◽

J. J. Woods

Keyword(s):

Nerve Stimulation ◽

Maximal Voluntary Contraction ◽

Time Course ◽

Muscle Activation ◽

Neuromuscular Block ◽

Voluntary Contraction ◽

Percentage Change ◽

Electromyographic Activity ◽

Excitation Rate ◽

Voluntary Contractions

Measurements were made from the human adductor pollicis muscle of force, contractile speed, and electromyographic activity (EMG) before, during, and after maximal isometric voluntary contractions sustained for 60 s. The use of brief test periods of maximal nerve stimulation with single shocks or trains of shocks enabled various muscle mechanical properties to be studied throughout each contraction. Electrical activity was measured after rectification and smoothing of the surface potentials and also by counting the total number of potentials per unit time from a population of motor units using fine wire intramuscular electrodes. During a 60-s maximal voluntary contraction, the force fell by 30-50%. Throughout the experiment the voluntary force matched that produced by supramaximal tetanic nerve stimulation. This indicated that, with sufficient practice, full muscle activation could be maintained by voluntary effort. However, the amplitude of the smoothed, rectifed EMG and the rate of spike counts declined. Since no evidence for neuromuscular block was found, the decline in EMG and spike counts was attributed to a progressive reduction of the neural drive from the central nervous system, despite maintained maximum effort. After the prolonged voluntary contractions twitch duration was prolonged, mainly as a result of slowing in relaxation rate. Twitch summation in unfused tetani increased. Both the maximum rate of relaxation and the time course of force decay declined by 50-70%. Similar changes were seen in both voluntary contractions and in test periods of stimulation. The percentage change in muscle contractile speed measured by these parameters approximately equaled the percentage change in the surface EMG measured simultaneously. It is concluded that 1) during a 60-s sustained maximal voluntary contraction there is a progressive slowing of contraction speed such that the excitation rate required to give maximal force generation is reduced, 2) the simultaneous decline in EMG may be due to a continuous reduction in motoneuron discharge rate, and 3) the EMG decline may not necessarily contribute to force loss.

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