scholarly journals Power reserve following ramp-incremental cycling to exhaustion: implications for muscle fatigue and function

2018 ◽  
Vol 125 (2) ◽  
pp. 304-312 ◽  
Author(s):  
Michael D. Hodgson ◽  
Daniel A. Keir ◽  
David B. Copithorne ◽  
Charles L. Rice ◽  
John M. Kowalchuk
Keyword(s):  
Muscle Fatigue ◽  
Power Output ◽  
Voluntary Activation ◽  
Time To Exhaustion ◽  
Maximal Velocity ◽  
Distribution Analysis ◽  
Incremental Test ◽  
Cycling Exercise ◽  
Specific Level ◽  
Peripheral Muscle

In ramp-incremental cycling exercise, some individuals are capable of producing power output (PO) in excess of that produced at their limit of tolerance (LoT) whereas others cannot. This study sought to describe the 1) prevalence of a “power reserve” within a group of young men ( n = 21; mean ± SD: age 25 ± 4 yr; V̇o2max 45 ± 8 ml·kg−1·min−1); and 2) muscle fatigue characteristics of those with and without a power reserve. “Power reserve” (ΔPReserve) was determined as the difference between peak PO achieved during a ramp-incremental test to exhaustion and maximal, single-leg isokinetic dynamometer power determined within 45 s of completing the ramp-incremental test. Between-group differences in pre- vs. postexercise changes in voluntary and electrically stimulated single-leg muscle force production measures (maximal voluntary contraction torque, voluntary activation, maximal isotonic velocity and isokinetic power; 1-, 10-, 50-Hz torque; and 10/50-Hz ratio), V̇o2max, and constant-PO cycling time-to-exhaustion also were assessed. Frequency distribution analysis revealed a dichotomy in the prevalence of a power reserve within the sample resulting in two groups: 1) “No Reserve” (NRES: power reserve <5%; n = 10) and 2) “Reserve” (RES: power reserve >15%; n = 11). At the LoT, all participants had achieved V̇o2max. Muscle fatigue was evident in both groups, although the NRES group had greater reductions ( P < 0.05) in 10-Hz peak torque (PT), 10/50 Hz ratio, and maximal velocity. Time to the LoT during the constant PO test was 22 ± 16% greater ( P < 0.05) in RES (116 ± 19 s; PO = 317 ± 52 W) than in NRES (90 ± 23 s; PO = 337 ± 71 W), despite similar ramp-incremental exercise durations and V̇o2max between groups. Compared with the RES group, the NRES group accrued greater peripheral muscle fatigue at the LoT, suggesting that the mechanisms contributing to exhaustion in a ramp-incremental protocol are not uniform. NEW & NOTEWORTHY This study demonstrates that the mechanisms associated with the limit of tolerance during ramp-incremental cycling exercise differ between those who are capable of generating power output in excess of that at exercise termination vs. those who are not. Those without a “power reserve” exhibit greater peripheral muscle fatigue and reduced muscle endurance, supporting the hypothesis that exhaustion occurs at a specific level of neuromuscular fatigue. In contrast, those with a power reserve likely are limited by other mechanisms.

Plyometric Training Does Not Affect Central and Peripheral Muscle Fatigue Differently in Prepubertal Girls and Boys

2010 ◽  
Vol 22 (4) ◽  
pp. 547-556 ◽  
Author(s):  
Albertas Skurvydas ◽  
Marius Brazaitis
Keyword(s):  
Muscle Fatigue ◽  
Central Fatigue ◽  
Quadriceps Muscle ◽  
Voluntary Activation ◽  
Peripheral Fatigue ◽  
Plyometric Training ◽  
Peripheral Muscle ◽  
Before And After ◽  
Voluntary Contractions ◽  
Prepubertal Girls

The aim of the study was to evaluate the effect of plyometric training (PT) on central and peripheral (muscle) fatigue in prepubertal girls and boys. The boys (n = 13, age 10.3 ± 0.3 years) and girls (n = 13, age, 10.2 ± 0.3 years) performed continuous 2-min maximal voluntary contractions (MVCs) before and after 16 high-intensity PT sessions. PT comprised two training sessions per week of 30 jumps in each session with 20 s between jumps. The greatest effect of PT was on excitation–contraction coupling, (twitch force increased by 323% in boys and 21% in girls) and height of a counter–movement jump (increased by 37% in boys and 38% in girls). In contrast, the quadriceps voluntary activation index, central activation ratio, and MVC did not change significantly after PT. The thickness of the quadriceps muscle increased by 9% in boys and 14% in girls after PT. In conclusion, boys and girls demonstrated similar changes in indicators of central fatigue (50–60% decrease) and peripheral fatigue (45–55% decrease) after MVC before and after PT.

scholarly journals A Comparative Study of EMG Indices in Muscle Fatigue Evaluation Based on Grey Relational Analysis during All-Out Cycling Exercise

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Lejun Wang ◽  
Yuting Wang ◽  
Aidi Ma ◽  
Guoqiang Ma ◽  
Yu Ye ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Power Output ◽  
Vastus Lateralis ◽  
Wavelet Packet ◽  
Vastus Lateralis Muscle ◽  
Cycling Exercise ◽  
Warm Up ◽  
Wavelet Packet Transformation ◽  
Fatigue Evaluation ◽  
Grey Relational

The increased popularization of cycling has brought an increase in cycling-related injuries, which has been suggested to be associated with muscle fatigue. However, it still remains unclear on the utility of different EMG indices in muscle fatigue evaluation induced by cycling exercise. In this study, ten cyclist volunteers performed a 30-second all-out cycling exercise after a warm-up period. Surface electromyography (sEMG) from vastus lateralis muscle (VL) and power output and cadence were recorded and EMG RMS, MF and MPF based on Fourier Transform, MDF and MNF based on wavelet packet transformation, and C(n) based on Lempel–Ziv complexity algorithm were calculated. Utility of the indices was compared based on the grey rational grade of sEMG indices and power output and cadence. The results suggested that MNF derived from wavelet packet transformation was significantly higher than other EMG indices, indicating the potential application for fatigue evaluation induced by all-out cycling exercise.

On the Implication of Dietary Nitrate Supplementation for the Hemodynamic and Fatigue Response to Cycling Exercise

2021 ◽  
Author(s):  
Taylor S. Thurston ◽  
Joshua C. Weavil ◽  
Thomas J. Hureau ◽  
Jayson R. Gifford ◽  
Vincent P. Georgescu ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Femoral Nerve ◽  
Voluntary Activation ◽  
Peak Power Output ◽  
Cycling Exercise ◽  
Dietary Nitrate ◽  
Task Failure ◽  
Nitrate Supplementation ◽  
The Impact ◽  
Cycling Time

This study investigated the impact of dietary nitrate supplementation on peripheral hemodynamics, the development of neuromuscular fatigue, and time to task failure during cycling exercise. Eleven recreationally active male participants (27±5 years, VO2max: 42±2ml/kg/min) performed two experimental trials following 3 days of either dietary nitrate-rich beetroot juice (4.1mmol NO3-/day; DNS) or placebo (PLA) supplementation in a blinded, counterbalanced order. Exercise consisted of constant-load cycling at 50, 75, and 100 W (4-min each) and, at ~80% of peak power output (218±12W), to task-failure. All participants returned to repeat the shorter of the two trials performed to task-failure, but with the opposite supplementation regime (ISO-time comparison). Mean arterial pressure (MAP), leg blood flow (QL; Doppler ultrasound), leg vascular conductance (LVC), and pulmonary gas exchange were continuously assessed during exercise. Locomotor muscle fatigue was determined by the change in pre- to post-exercise quadriceps twitch-torque (∆Qtw) and voluntary activation (∆VA; electrical femoral nerve stimulation). Following DNS, plasma [nitrate] (~670 vs ~180 nmol) and [nitrite] (~775 vs ~11 nmol) were significantly elevated compared to PLA. Unlike PLA, DNS lowered both QL and MAP by ~8% (P<0.05), but did not alter LVC (P=0.31). VO2 across work rates, as well as cycling time to task-failure (~7min) and locomotor muscle fatigue following the ISO-time comparison were not different between the two conditions (∆Qtw ~42%, ∆VA ~4%). Thus, despite significant hemodynamic changes, DNS did not alter the development of locomotor muscle fatigue and, ultimately, cycling time to task failure.

Similar maximal oxygen uptake assessment from a step cycling incremental test and verification tests on the same or different day

2020 ◽  
Vol 45 (4) ◽  
pp. 357-361 ◽  
Author(s):  
Leonardo Trevisol Possamai ◽  
Fernando de Souza Campos ◽  
Paulo Cesar do Nascimento Salvador ◽  
Rafael Alves de Aguiar ◽  
Luiz Guilherme Antonacci Guglielmo ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Power Output ◽  
Maximal Oxygen Uptake ◽  
Peak Power ◽  
Individual Variability ◽  
Peak Power Output ◽  
Time To Exhaustion ◽  
Incremental Test ◽  
Incremental Protocol

The present study aimed to compare maximal oxygen uptake of a step incremental test with time to exhaustion verification tests (TLIM) performed on the same or different day. Nineteen recreationally trained cyclists (age: 23 ± 2.7 years; maximal oxygen uptake: 48.0 ± 5.8 mL·kg−1·min−1) performed 3 maximal tests as follows: (i) same day: an incremental test with 3-min stages followed by a TLIM at 100% of peak power output of the incremental test (TLIM-SAME) interspaced by 15 min; and (ii) different day: a TLIM at 100% of peak power output of the incremental test (TLIM-DIFF). The maximal oxygen uptake was determined for the 3 tests. The maximal oxygen uptake was not different among the tests (incremental: 3.83 ± 0.41; TLIM-SAME: 3.72 ± 0.42; TLIM-DIFF: 3.75 ± 0.41 L·min−1; P = 0.951). Seven subjects presented a variability greater than ±3% in both verification tests compared with the incremental test. The same-day verification test decreased the exercise tolerance (240 ± 38 vs. 310 ± 36 s) compared with TLIM-DIFF (P < 0.05). In conclusion, the incremental protocol is capable of measuring maximal oxygen uptake because similar values were observed in comparison with verification tests. Although the need for the verification phase is questionable, the additional tests are useful to evaluate individual variability. Novelty Step incremental test is capable of measuring maximal oxygen uptake with similar values during TLIM on the same or different day. Although the necessity of the verification phase is questionable, it can allow the determination of variability in maximal oxygen uptake.

How to test maximal oxygen uptake: a study on timing and testing procedure of a supramaximal verification test

2011 ◽  
Vol 36 (1) ◽  
pp. 153-160 ◽  
Author(s):  
Friederike Scharhag-Rosenberger ◽  
Anja Carlsohn ◽  
Michael Cassel ◽  
Frank Mayer ◽  
Jürgen Scharhag
Keyword(s):  
Oxygen Uptake ◽  
Maximal Oxygen Uptake ◽  
Testing Procedure ◽  
Peak Oxygen Uptake ◽  
Time To Exhaustion ◽  
Maximal Velocity ◽  
Testing Session ◽  
Incremental Test ◽  
Testing Procedures ◽  
Verification Test

Verification tests are becoming increasingly common for confirming maximal oxygen uptake (VO2 max) attainment. Yet, timing and testing procedures vary between working groups. The aims of this study were to investigate whether verification tests can be performed after an incremental test or should be performed on a separate day, and whether VO2 max can still be determined within the first testing session in subjects not satisfying the verification criterion. Forty subjects (age, 24 ± 4 years; VO2 max, 50 ± 7 mL·min–1·kg–1) performed a maximal incremental treadmill test and, 10 min afterwards, a verification test (VerifDay1) at 110% of maximal velocity (vmax). The verification criterion was a VerifDay1 peak oxygen uptake (VO2 peak) ≤5.5% higher than the incremental test value. Subjects not achieving the verification criterion performed another verification test at 115% vmax (VerifDay1′) 10 min later, trying to confirm VerifDay1 VO2 peak as VO2 max. All other subjects exclusively repeated VerifDay1 on a separate day (VerifDay2). Of the 40 subjects, 6 did not satisfy the verification criterion. In 4 of them, attainment of VO2 max was confirmed by VerifDay1′. VO2 peak was equivalent between VerifDay1 and VerifDay2 (3722 ± 991 mL·min–1 vs. 3752 ± 995 mL·min–1, p = 0.56), whereas time to exhaustion was significantly longer in VerifDay2 (2:06 ± 0:22 min:s vs. 2:42 ± 0:38 min:s, p < 0.001, n = 34). The verification test VO2 peak does not seem to be affected by a preceding maximal incremental test. Incremental and verification tests can therefore be performed within the same testing session. In individuals not achieving the verification criterion, VO2 max can be determined by means of a subsequent, more intense verification test in most but not all cases.

scholarly journals Functional Threshold Power in Cyclists: Validity of the Concept and Physiological Responses

2018 ◽  
Vol 39 (10) ◽  
pp. 737-742 ◽  
Author(s):  
Fernando Borszcz ◽  
Artur Tramontin ◽  
Arthur Bossi ◽  
Lorival Carminatti ◽  
Vitor Costa
Keyword(s):  
Power Output ◽  
Time Trial ◽  
Threshold Power ◽  
Time To Exhaustion ◽  
Mean Power ◽  
Incremental Test ◽  
Individual Anaerobic Threshold ◽  
The Mean ◽  
The Individual ◽  
Mean Power Output

AbstractFunctional threshold power is defined as the highest power output a cyclist can maintain in a quasi-steady state for approximately 60 min (FTP60). In order to improve practicality for regular evaluations, FTP60 could theoretically be determined as 95% of the mean power output in a 20-min time trial (FTP20). This study tested this assumption and the validity of FTP20 and FTP60 against the individual anaerobic threshold (IAT). Twenty-three trained male cyclists performed an incremental test to exhaustion, 20- and 60-min time trials, and a time to exhaustion at FTP20. Power output, heart rate and oxygen uptake representing FTP20, FTP60 and IAT were not different (p>0.05), and large to very large correlations were found (r=0.61 to 0.88). Bland-Altman plots between FTP20, FTP60 and IAT showed small bias (–1 to –5 W), but large limits of agreement ([–40 to 32 W] to [–62 to 60 W]). Time to exhaustion at FTP20 was 50.9±15.7 min. In conclusion, FTP20 and FTP60 should not be used interchangeably on an individual basis and their validity against IAT should be interpreted with caution.

Exercise slightly above the maximal lactate steady state reduces self-efficacy and increases negative affect

2019 ◽  
Author(s):  
James Graeme Wrightson ◽  
Louis Passfield
Keyword(s):  
Steady State ◽  
Negative Affect ◽  
Power Output ◽  
Self Efficacy ◽  
Repeated Measures ◽  
Physiological State ◽  
Constant Load ◽  
Peak Power Output ◽  
Time To Exhaustion ◽  
Maximal Lactate Steady State

Objectives: To examine the effect of exercise at and slightly above the maximal lactate steady state (MLSS) on self-efficacy, affect and effort, and their associations with exercise tolerance.Design: Counterbalanced, repeated measures designMethod: Participants performed two 30‐minute constant‐load cycling exercise at a power output equal to that at MLSS and 10 W above MLSS, immediately followed by a time‐to‐exhaustion test at 80% of their peak power output. Self-efficacy, affect and effort were measured before and after 30 minutes of cycling at and above MLSS.Results: Negative affect and effort higher, and self-efficacy and time to exhaustion were reduced, following cycling at MLSS + 10 W compared to cycling at the MLSS. Following exercise at the MLSS self-efficacy, affect and effort were all associated with subsequent time-to exhaustion. However, following exercise at MLSS + 10 W, only affect was associated with time-to exhaustion. Conclusions: Self efficacy, affect and effort are profoundly affected by physiological state, highlighting the influence of somatic states on perceptions and emotions during exercise. The affective response to exercise appears to be associated with exercise tolerance, indicating that the emotional, as well as physiological, responses should be considered when prescribing exercise training.

Tissue tolerance mechanisms conferring salinity tolerance in a halophytic perennial species Nitraria sibirica Pall.

2020 ◽  
Author(s):  
Xiaoqian Tang ◽  
Huilong Zhang ◽  
Sergey Shabala ◽  
Huanyong Li ◽  
Xiuyan Yang ◽  
...  
Keyword(s):  
Plant Root ◽  
Transcriptional Level ◽  
Distribution Analysis ◽  
Specific Level ◽  
Saline Environment ◽  
Nitraria Sibirica ◽  
Mechanistic Basis ◽  
Plant Salt Tolerance ◽  
Cellular Compartments ◽  
Growth Of Seedlings

Abstract Plant salt tolerance relies on a coordinated functioning of different tissues and organs. Salinity tissue tolerance is one of the key traits that confers plant adaptation to saline environment. This trait implies maintenance low cytosolic Na+/K+ ratio in metabolically active cellular compartments. In this study, we used Nitraria sibirica Pall., a perennial woody halophytes species, to understand the mechanistic basis of its salinity tissue tolerance. The results showed that the growth of seedlings was stimulated by 100-200 mM NaCl treatment. The ions distribution analysis showed that the leaves acted as Na+ sink while plant root possess superior K+ retention. The excessive Na+ absorbed from soil was mainly transported to the shoot and eventually sequestrated into mesophyll vacuoles in the leaves. As a result, N. sibirica could keep optimal balance of K+/Na+ at a tissue- and cell-specific level under saline condition. To enable this, N. sibirica increased both vacuolar H+-ATPase and H+-PPase enzymes activities and up-regulated expressions of NsVHA, NsVP1 and NsNHX1 genes. Vacuolar Na+ sequestration in the leaf mesophyll mediated by NsVHA, NsVP1 and NsNHX1 reduced the Na+ concentration in cytosol and inhibited further K+ loss. Meanwhile, N.sibirica enhanced the TPK expression at the transcriptional level to promote K+ efflux from vacuole into cytoplasm, assisting in maintaining cytosolic K+ homeostasis. It is concluded that the tissue tolerance traits such as vacuolar Na+ sequestration and intracellular K+ homeostasis is critical to confer adaptation of N. sibirica to soil salinity.

scholarly journals Locomotor exercise induces long-lasting impairments in the capacity of the human motor cortex to voluntarily activate knee extensor muscles

2009 ◽  
Vol 106 (2) ◽  
pp. 556-565 ◽  
Author(s):  
Simranjit K. Sidhu ◽  
David J. Bentley ◽  
Timothy J. Carroll
Keyword(s):  
Motor Cortex ◽  
Motor Nerve ◽  
Maximum Voluntary Contraction ◽  
Voluntary Activation ◽  
Exercise Session ◽  
Knee Extensors ◽  
Central Component ◽  
Control Session ◽  
Cycling Exercise ◽  
Human Motor Cortex

Muscle fatigue is a reduction in the capacity to exert force and may involve a “central” component originating in the brain and/or spinal cord. Here we examined whether supraspinal factors contribute to impaired central drive after locomotor endurance exercise. On 2 separate days, 10 moderately active individuals completed a locomotor cycling exercise session or a control session. Brief (2 s) and sustained (30 s) isometric knee extension contractions were completed before and after locomotor exercise consisting of eight, 5-min bouts of cycling at 80% of maximum workload. In the control session, subjects completed the isometric contractions in a rested state. Twitch responses to supramaximal motor nerve stimulation and transcranial magnetic stimulation were obtained to assess peripheral force-generating capacity and voluntary activation. Maximum voluntary contraction (MVC) force during brief contractions decreased by 23 ± 6.3% after cycling exercise and remained 12 ± 2.8% below baseline 45 min later ( F1,9 > 15.5; P < 0.01). Resting twitch amplitudes declined by ∼45% ( F1,9 = 28.3; P < 0.001). Cortical voluntary activation declined from 90.6 ± 1.6% at baseline to 80.6 ± 2.1% after exercise ( F1,9 = 28.0; P < 0.001) and remained significantly reduced relative to control 30–45 min later (80.6 ± 3.4%; F1,9 = 10.7; P < 0.01). Thus locomotor exercise caused a long-lasting impairment in the capacity of the motor cortex to drive the knee extensors. Force was reduced more during sustained MVC after locomotor exercise than in the control session. Peripheral mechanisms contributed relatively more to this force reduction in the control session, whereas supraspinal fatigue played a greater role in sustained MVC reduction after locomotor exercise.

Unilateral isometric muscle fatigue decreases force production and activation of contralateral knee extensors but not elbow flexors

2014 ◽  
Vol 39 (12) ◽  
pp. 1338-1344 ◽  
Author(s):  
Israel Halperin ◽  
David Copithorne ◽  
David G. Behm
Keyword(s):  
Muscle Fatigue ◽  
Force Production ◽  
Voluntary Activation ◽  
Knee Extensors ◽  
Elbow Flexors ◽  
Post Intervention ◽  
Nonlocal Effects ◽  
And Performance ◽  
Voluntary Contractions ◽  
Isometric Muscle

Nonlocal muscle fatigue occurs when fatiguing 1 muscle alters performance of another rested muscle. The purpose of the study was to investigate if fatiguing 2 separate muscles would affect the same rested muscle, and if fatiguing the same muscle would affect 2 separate muscles. Twenty-one trained males participated in 2 studies (n = 11; n = 10). Subjects performed 2 pre-test maximum voluntary contractions (MVCs) with the nondominant knee extensors. Thereafter they performed two 100-s MVCs with their dominant knee extensors, elbow flexors, or rested. Between and after the sets, a single MVC with the nondominant rested knee extensors was performed. Subsequently, 12 nondominant knee extensors repeated MVCs were completed. Force, quadriceps voluntary activation (VA), and electromyography (EMG) were measured. The same protocol was employed in study 2 except the nondominant elbow-flexors were tested. Study 1: Compared with control conditions, a significant decrease in nondominant knee extensors force, EMG, and VA was found under both fatiguing conditions (P ≤ 0.05; effect size (ES) = 0.91–1.15; 2%–8%). Additionally, decrements in all variables were found from the first post-intervention MVC to the last (P ≤ 0.05; ES = 0.82–2.40; 9%–20%). Study 2: No differences were found between conditions for all variables (P ≥ 0.33; ES ≤ 0.2; ≤3.0%). However, all variables decreased from the first post-intervention MVC to the last (P ≤ 0.05; ES = 0.4–3.0; 7.2%–19.7%). Whereas the rested knee extensors demonstrated nonlocal effects regardless of the muscle being fatigued, the elbow-flexors remained unaffected. This suggests that nonlocal effects are muscle specific, which may hold functional implications for training and performance.

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