Vol. 90, Issue 4, 1334-1341, April 2001
Relationship between fat-to-fat-free mass ratio and decrements
in leg strength after downhill running
R. C.
Hickner,
P. M.
Mehta,
D.
Dyck,
P.
Devita,
J. A.
Houmard,
T.
Koves, and
P.
Byrd
Human Performance Laboratory, Department of Exercise and Sports
Science, East Carolina University, Greenville, North Carolina 27858
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.
adiposity; eccentric contractions; exercise; isokinetic
strength; muscle soreness
