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This study examined the impact of sport specificity on the time course of fatigue during maximal voluntary eccentric, concentric and isometric torque production following a submaximal isokinetic fatiguing exercise. Seven cyclists and seven triathletes performed a fatiguing exercise consisting of nine sets of 31 isokinetic concentric knee extensions at 1.05 rad·s-1. Fatigue was assessed pre-exercise, after three and six sets, and post-exercise. The maximal knee extension torque associated with electromyographic (EMG) activity was recorded during voluntary contractions and electrically induced contractions (single and paired twitches). The maximal voluntary eccentric torque production declined in cyclists (18 ± 3.5%, p <0.05) and was not significantly affected in triathletes (5 ± 2.5%, p >0.05). The decrease in cyclists was associated with an increase in the sum of the normalized EMG (nRMS) values of the three agonist muscles (p<0.01). Although no significant difference was observed between groups, the two-way repeated-measure analysis of variance revealed a time effect on maximal concentric and isometric torque, twitch contractile and electrophysiological response (Mmax) properties. No modification in the activation and coactivation levels was observed. In conclusion, these results indicate that the time course of fatigue, especially during eccentric contractions, is mediated by sport-specific adaptations likely due to the mode of muscle contraction used in the activity. [ABSTRACT FROM AUTHOR]

The article determines whether fatigue kinetics and fatigue origin (central vs. peripheral adaptations) of the knee extensor muscles are sport specific. The experiment involving fatiguing exercises for endurance-trained men (ENDU) and explosive power-trained men (EXPLO), subdivided into cyclists and triathletes is described. The results showed faster exhaustion in the EXPLO group as compared to the ENDU group. Following the fatiguing exercise used in this study, neuromuscular alterations mainly arose from peripheral mechanisms.

Abstract: The aim of this study was to determine whether patients with cystic fibrosis (CF), despite their ventilatory limitation, would develop neuromuscular fatigue of quadriceps muscles following a maximal cycling exercise. Eleven adults with CF (age=26.8±6.9years; forced expiratory volume in 1s=54.1±12.8% predicted) and 11 age-matched healthy subjects performed a maximal incremental cycle test with respiratory gas exchange measurements. Maximal voluntary contraction (MVC) and electromyographic (EMG) activity of the vastus medialis muscle were recorded before and after exercise. Neural and contractile properties of the quadriceps were also investigated using femoral nerve electrical stimulation. Patients had lower exercise capacity, peak oxygen uptake and MVC than controls. MVC fell significantly postexercise in both groups (CF: −20±10%, controls: −19±6%; p <0.01). EMG root mean square values, M-wave amplitude and duration were unchanged in both groups. Peak twitch (−46.9±13.8%), maximal rate of twitch torque development (−50.3±13.8%) and relaxation (−35.2±19.5%) were all reduced after exercise in CF patients. The control group followed the same pattern (−38.4±14.4%, −42.1±14.7% and −15±20.4%) but the statistical significance was not reached for the maximal rate of twitch torque relaxation. In conclusion, CF patients demonstrated lower limb fatigue following symptom-limited cycle exercise, which was comparable to that exhibited by healthy controls. This fatigue may be due to contractile impairments and not to transmission failure. Further studies should be conducted in a larger sample to confirm these preliminary results. [Copyright &y& Elsevier]