Fatiguing handgrip exercise alters maximal force-generating capacity of plantar-flexors

• Published in: European journal of applied physiology 2013-03, Vol.113 (3), p.559-566
• Main Authors: Kennedy, Ashleigh, Hug, François, Sveistrup, Heidi, Guével, Arnaud
• Format: Article
• Language: English
• Subjects: Adult; Adult Ankle Joint / physiology Exercise / physiology Female Foot / physiology Hand Strength / physiology Humans Isometric Contraction / physiology Male Muscle Fatigue / physiology Muscle Strength / physiology Muscle, Skeletal / physiology Physical Exertion / physiology Torque Young Adult; Ankle; Ankle Joint - physiology; Biomedical and Life Sciences; Biomedicine; Exercise - physiology; Female; Foot - physiology; Hand Strength - physiology; Health sciences; Human Physiology; Humans; Isometric Contraction - physiology; Life Sciences; Male; Muscle Fatigue - physiology; Muscle Strength - physiology; Muscle, Skeletal - physiology; Nervous system; Occupational Medicine/Industrial Medicine; Original Article; Physical Exertion - physiology; Production capacity; Sports Medicine; Torque; Young Adult
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-012-2462-1

Exercise-induced fatigue causes changes within the central nervous system that decrease force production capacity in fatigued muscles. The impact on unrelated, non-exercised muscle performance is still unclear. The primary aim of this study was to examine the impact of a bilateral forearm muscle contraction on the motor function of the distal and unrelated ankle plantar-flexor muscles. The secondary aim was to compare the impact of maximal and submaximal forearm contractions on the non-fatigued ankle plantar-flexor muscles. Maximal voluntary contractions (MVC) of the forearm and ankle plantar-flexor muscles as well as voluntary activation (VA) and twitch torque of the ankle plantar-flexor muscles were assessed pre-fatigue and throughout a 10-min recovery period. Maximal (100 % MVC) and submaximal (30 % MVC) sustained isometric handgrip contractions caused a decreased handgrip MVC (to 49.3 ± 15.4 and 45.4 ± 11.4 % of the initial MVC for maximal and submaximal contraction, respectively) that remained throughout the 10-min recovery period. The fatigue protocols also caused a decreased ankle plantar-flexor MVC (to 77 ± 8.3 and 92.4 ± 6.2 % of pre-fatigue MVC for maximal and submaximal contraction, respectively) and VA (to 84.3 ± 15.7 and 97.7 ± 16.1 % of pre-fatigue VA for maximal and submaximal contraction, respectively). These results suggest central fatigue created by the fatiguing handgrip contraction translated to the performance of the non-exercised ankle muscles. Our results also show that the maximal fatigue protocol affected ankle plantar-flexor MVC and VA more severely than the submaximal protocol, highlighting the task-specificity of neuromuscular fatigue.