Relationship between fat-to-fat-free mass ratio and decrements in leg strength after downhill running.
The purpose of this study was to determine whether greater body fat mass (FM) relative to lean mass would result in more severe muscle damage and greater decrements in leg strength after downhill running. The relationship between the FM-to-fat-free mass ratio (FM/FFM) and the strength decline resulting from downhill running (-11% grade) was investigated in 24 male runners [age 23.4 +/- 0.7 (SE) yr]. The runners were divided into two groups on the basis of FM/FFM: low fat (FM/FFM = 0.100 +/- 0.008, body mass = 68.4 +/- 1.3 kg) and normal fat (FM/FFM = 0.233 +/- 0.020, body mass = 76.5 +/- 3.3 kg, P < 0.05). Leg strength was reduced less in the low-fat (-0.7 +/- 1.3%) than in the normal-fat individuals (-10.3 +/- 1.5%) 48 h after, compared with before, downhill running (P < 0.01). Multiple linear regression analysis revealed that the decline in strength could be predicted best by FM/FFM (r2 = 0.44, P < 0.05) and FM-to-thigh lean tissue cross-sectional area ratio (r2 = 0.53, P < 0.05), with no additional variables enhancing the prediction equation. There were no differences in muscle glycogen, creatine phosphate, ATP, or total creatine 48 h after, compared with before, downhill running; however, the change in muscle glycogen after downhill running was associated with a higher FM/FFM (r = -0.56, P < 0.05). These data suggest that FM/FFM is a major determinant of losses in muscle strength after downhill running.
Hickner
R C
RC
Human Performance Laboratory, Department of Exercise and Sports Science, East Carolina University, Greenville, North Carolina 27858, USA. Hicknerr@mail.ecu.edu
Mehta
P M
PM
Dyck
D
D
Devita
P
P
Houmard
J A
JA
Koves
T
T
Byrd
P
P
D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D001823:Body Composition / Q000502:physiology*; D003401:Creatine / Q000378:metabolism; D003402:Creatine Kinase / Q000097:blood; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D007866:Leg / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D009135:Muscular Diseases / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology; D010725:Phosphocreatine / Q000378:metabolism; D010809:Physical Fitness / Q000502:physiology*; D012044:Regression Analysis; D012420:Running / Q000502:physiology*
D010725:Phosphocreatine; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D006003:Glycogen; D003402:Creatine Kinase; D003401:Creatine