Effects of vitamin E deficiency on fatigue and muscle contractile properties

Radical-mediated oxidative damage of skeletal muscle membranes has been implicated in the fatigue process. Vitamin E (VE) is a major chain breaking an-tioxidant that has been shown to reduce contraction-mediated oxidative damage. We hypothesized that VE de?ciency would adversely a?ect muscle contractile function, resulting in a more rapid development of muscular fatigue during exercise. To test this postulate, rats were fed either a VE-de?cient (EDEF) diet or a control (CON) diet containing VE. Following a 12-week feeding period, animals were anesthetized and mechan-ically ventilated. Muscle endurance (fatigue) and con-tractile properties were evaluated using an in situ preparationof the tibialis anterior (TA) muscle. Con-tractile properties of the TA muscle were determined before and after a fatigue protocol. The muscle fatigue protocol consisted of 60 min of repetitive contractions (250 ms trains at 15 Hz; duty cycle=11%) of the TA muscle. Prior to the fatigue protocol, no signi?cant di?erences existed in the force-frequency curves between EDEF and CON animals. At the completion of the fa-tigue protocol, muscular force productionwas signi?-cantly (P<0.05) lower inthe EDEF group (reduced by 69%) compared to CON group (reduced by 38%). Following the fatigue protocol, a right shift existed in the force-frequency curve at low stimulation frequencies ( £ 40 Hz) inthe EDEF animals compared to the CON animals (P<0.05). The stimulated and the contralateral TA muscle from the EDEF animals had signi?cantly higher markers of lipid peroxidationcompared to the same muscles inthe CON animals (P<0.05). These data support the hypothesis that VE de?ciency impairs muscular endurance and alters muscle contractile prop-erties following a prolonged series of contractions