Central and Peripheral Fatigue in Male Cyclists after 4-, 20-, and 40-km Time Trials

Abstract

DisclosuresThis project did not receive any funding and has no conflicts of interest to report. The results of the present study do not constitute endorsement by ACSM. AbstractPurpose: Few studies have assessed neuromuscular fatigue after self-paced locomotor exercise; moreover, none have assessed the degree of supraspinal fatigue. This study assessed central and peripheral fatigue after self-paced exercise of different durations. Methods:Thirteen well-trained male cyclists completed 4 km, 20 km and 40 km simulated time-trials (TTs). Pre-and immediately post-TT (< 2.5 min), twitch responses from the knee-extensors to electrical stimulation of the femoral nerve and transcranial magnetic stimulation of the motor cortex were recorded to assess neuromuscular and corticospinal function. Results: Time to complete 4 km, 20 km and 40 km was 6.0±0.2 min, 31.8±1.0 min and 65.8±2.2 min, at average exercise intensities of 96%, 92% and 87% of V O2max, respectively. Exercise resulted in significant reductions in maximum voluntary contraction, with no difference between TTs (-18%, -15% and -16% for 4, 20 and 40 km respectively). Greater peripheral fatigue was evident after the 4 km (40% reduction in potentiated twitch) compared to the 20 km (31%) and 40 km TTs (29%). In contrast, longer TTs were characterized by more central fatigue, with greater reductions in voluntary activation measured by motor nerve (-11% and -10% for 20 km and 40 km vs. -7% for 4 km) and cortical (-12% and -10% for 20 km and 40 km vs. -6% for 4 km) stimulation. Conclusions: These data demonstrate fatigue after self-paced exercise is taskdependent, with a greater degree of peripheral fatigue after shorter, higher intensity (~6 min) TTs and more central fatigue after longer, lower intensity TTs (>30 min). Words: 254

The assessment of neuromuscular fatigue during 120 min of simulated soccer exercise

“…In this regard, and in line with other investigations evaluating reliability of responses from the knee-extensors (Bachasson et al 2013;Rainoldi et al 2001), we used two approaches to evaluate measurement reliability, the CV and ICC, which provide an absolute and relative assessment, respectively. An excellent level of reliability was evident for measures of neuromuscular function pre-exercise (Table 2), which is in line with the previous work from our laboratory (Goodall et al 2015b;Thomas et al 2015), and importantly, enabled us to detect significant changes throughout the soccer-specific exercise. Similar reliability coefficients have been demonstrated in unfatigued states for both upper (Lee et al 2008;Madsen 1996;Taylor et al 1996) and lower limb (Amann et al 2013;Bachasson et al 2013;Place et al 2007;Todd et al 2004) muscle groups, but the reliability of the fatigue response following locomotor exercise is unknown.…”

“…2c). Over the 120 min simulated soccer match, central fatigue tended to be exacerbated, and this duration-dependent contribution of central processes to fatigue is broadly evident across a range of exercise modes (Lepers et al 2002;Place et al 2004;Thomas et al 2015). In this study, there was a pattern of a progressive decrease in voluntary activation across 120 min of the SMS (pre vs. HT; HT vs.…”

“…In line with the previous investigations from our laboratory (Goodall et al 2015a, b;Thomas et al 2015), the cathode was positioned over the nerve, high in the femoral triangle, whilst the anode was placed midway between the greater trochanter and the iliac crest. Single stimuli were delivered to the relaxed muscle beginning at 40 mA, the intensity was increased by 20 mA until a plateau occurred in twitch Fig.…”

Self-paced exercise in hot and cool conditions is associated with the maintenance of %V̇o2peak within a narrow range

“…Although these findings demonstrate the clear influence of heat stress on performance and V O 2 , it remains to be determined whether more severe (i.e., hot and/or humid) environmental conditions exacerbate the magnitude of decrease in these parameters and the relative exercise intensity sustained during prolonged self-paced efforts. Notwithstanding, data from the present study are within range of the relative exercise intensity (ϳ86%) maintained in other studies during a 40-km time trial in temperate conditions (27,44). Moreover, the percentage of peak heart rate maintained in all time trials, as well as the RPE responses (Fig.…”

Efeito agudo do exercício aeróbio com diferentes volumes no desempenho de força em indivíduos fisicamente ativos

“…No estudo de De Souza et al (2007) (GLADDEN et al, 1985;YEH et al, 1983 (LEPERS et al, 2002;MILLET et al, 2003;PETERSEN et al, 2007;PLACE et al, 2004;ROSS et al, 2010 (MILLET et al, 2003;LEPERS, 2004). Ao passo que, após a realização de volumes menores do exercício aeróbio a magnitude de redução na capacidade de ativação muscular observada é menor ou até mesmo inexistente (PLACE et al, 2004;ROSS et al, 2012;THOMAS et al, 2015). Assim, indicando que os mecanismos que limitam a função neuromuscular após o exercício aeróbio podem ser diferentes entre as atividades de maior e menor volume (LEPERS et al, 2002;LEPERS, 2004;VLECK;BENTLEY, 2009).…”