Our meta analysis of a homogeneous set of studies is the first to provide valuable LLNs for fiber CSA according to fiber type and gender .
Skeletal muscle atrophy is a major systemic impairment in chronic diseases .
Yet its determinants have been hard to identify because a clear research definition has not been agreed upon .
The reduction in muscle fiber cross-sectional area ( CSA ) is a widely acknowledged marker of muscle atrophy , but no reference values for the muscle fiber CSA at the age of the onset of chronic disease have ever been published .
African runners exhibit greater fatigue resistance, lower lactate accumulation, and higher oxidative enzyme activity.
Nine African and eight Caucasian 10-km runners resident at sea level volunteered . Maximal O2 consumption and peak treadmill velocity ( PTV ) were measured by using a progressive test , and fatigue resistance [ time to fatigue ( TTF ) ] was measured by using a newly developed high-intensity running test : 5 min at 72 , 80 , and 88 % of individual PTV followed by 92 % PTV to exhaustion . Skeletal muscle enzyme activities were determined in 12 runners and 12 sedentary control subjects . In a comparison of African and Caucasian runners , mean 10-km race time , maximal O2 consumption , and PTV were similar . In African runners , TTF was 21 % longer ( P < 0.01 ) , plasma lactate accumulation after 5 min at 88 % PTV was 38 % lower ( P < 0.05 ) , and citrate synthase activity was 50 % higher ( 27.9 + /- 7.5 vs. 18.6 + /- 2.1 micromol . g wet wt-1 . min-1 , P = 0.02 ) . Africans accumulated lactate at a slower rate with increasing exercise intensity ( P < 0.05 ) . Among the entire group of runners , a higher citrate synthase activity was associated with a longer TTF ( r = 0.70 , P < 0.05 ) , a lower plasma lactate accumulation ( r = -0.73 , P = 0.01 ) , and a lower respiratory exchange ratio ( r = -0.63 , P < 0.05 ) . We conclude that the African and Caucasian runners in the present study differed with respect to oxidative enzyme activity , rate of lactate accumulation , and their ability to sustain high-intensity endurance exercise
Our meta analysis of a homogeneous set of studies is the first to provide valuable LLNs for fiber CSA according to fiber type and gender .
Skeletal muscle atrophy is a major systemic impairment in chronic diseases .
Yet its determinants have been hard to identify because a clear research definition has not been agreed upon .
The reduction in muscle fiber cross-sectional area ( CSA ) is a widely acknowledged marker of muscle atrophy , but no reference values for the muscle fiber CSA at the age of the onset of chronic disease have ever been published .