Age, muscle fatigue, and walking endurance in pre-menopausal women.
Aging is associated with loss of endurance; however, aging is also associated with decreased fatigue during maximal isometric contractions. The aims of this study were to examine the relationship between age and walking endurance (WE) and maximal isometric fatigue (MIF) and to determine which metabolic/fitness components explain the expected age effects on WE and MIF. Subjects were 96 pre-menopausal women. Oxygen uptake (walking economy) was assessed during a 3-mph walk; aerobic capacity and WE by progressive treadmill test; knee extension strength by isometric contractions, MIF during a 90-s isometric plantar flexion (muscle metabolism measured by (31)P MRS). Age was related to increased walking economy (low VO(2), r = -0.19, P < 0.03) and muscle metabolic economy (force/ATP, 0.34, P = 0.01), and reduced MIF (-0.26, P < 0.03). However, age was associated with reduced WE (-0.28, P < 0.01). Multiple regression showed that muscle metabolic economy explained the age-related decrease in MIF (partial r for MIF and age -0.13, P = 0.35) whereas walking economy did not explain the age-related decrease in WE (partial r for WE and age -0.25, P < 0.02). Inclusion of VO(2max) and knee endurance strength accounted for the age-related decreased WE (partial r for WE and age = 0.03, P > 0.80). In premenopausal women, age is related to WE and MIF. In addition, these results support the hypothesis that age-related increases in metabolic economy may decrease MIF. However, decreased muscle strength and oxidative capacity are related to WE.
Hunter
Gary R
GR
Department of Human Studies, University of Alabama at Birmingham, 901 South 13th Street, Birmingham, AL 35294-1250, USA. ghunter@uab.edu
Bickel
C Scott
CS
Del Corral
Pedro
P
Byrne
Nuala M
NM
Hills
Andrew P
AP
Larson-Meyer
D Enette
DE
Bamman
Marcas M
MM
Newcomer
Bradley R
BR
D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D001706:Biopsy; D005080:Exercise Test; D005260:Female; D006801:Humans; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000473:pathology / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D017697:Premenopause / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D016138:Walking / Q000502:physiology*; D055815:Young Adult