Treadmill but not wheel running improves fatigue resistance of isolated extensor digitorum longus muscle in mice.
OBJECTIVE
The present study is the first to compare the physiological impact of either forced treadmill or voluntary wheel running exercise on hindlimb muscle in mice.


METHODS
Male C57BL/6 mice were subjected to either 6 weeks of forced treadmill or voluntary wheel running exercise. Mice in the treadmill running exercise group (TRE; n = 8) ran 1.9 km day(-1) at a speed of 16 m min(-1) against an uphill incline of 11 degrees. In the running wheel exercise group (RWE; n = 8) animals ran 8.8 +/- 0.2 km per day (average speed 42 +/- 2 m min(-1)). After the experimental period, animals were killed and mechanical performance and oxygen consumption of isolated extensor digitorum longus (EDL) muscle were determined during serial electrical stimulation at 0.5, 1 and 2 Hz.


RESULTS
Steady-state half-width time (HWT) of twitch contraction at 0.5 Hz was significantly shorter in TRE and RWE than controls (CON) (41.3 +/- 0.2, 41.3 +/- 0.1 and 44.3 +/- 0.1 s respectively; P < 0.05). The rate of fatigue development and HWT lengthening at 2 Hz was the same in RWE and CON but lower in TRE (1.2-fold and twofold respectively; P < 0.05). EDL oxygen consumption, mitochondrial content and myosin heavy chain (MyHC) composition were not different between the groups.


CONCLUSIONS
These results indicate that both exercise modalities have an effect on a hindlimb fast-twitch muscle in mice, with the greatest impact seen with forced treadmill running.
Jeneson
J A L
JA
Department of Pathobiology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
de Snoo
M W
MW
Verlinden
N A T
NA
Joosten
B J L J
BJ
Doornenbal
A
A
Schot
A
A
Everts
M E
ME
D000818:Animals; D001696:Biomechanical Phenomena; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D006614:Hindlimb; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000032:analysis; D010101:Oxygen Consumption / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000379:methods*; D005082:Physical Exertion / Q000502:physiology; D013997:Time Factors
D002950:Citrate (si)-Synthase; D018995:Myosin Heavy Chains