Abstract:
Objectives: High trunk muscle endurance, strength, and moderate flexibility
reportedly help maintain musculoskeletal health, but there is evidence for
tradeoffs among these variables as well as sex differences in trunk muscle
endurance and strength. To test if these observations extend similarly to both
men and women in nonindustrial and industrial environments, we investi-
gated intra-individual associations and group and sex differences in trunk mus-
cle endurance, strength, and flexibility among 74 (35 F, 39 M; age range: 18–
61 years) adults from the same Kalenjin-speaking population in western
Kenya. We specifically compared men and women from an urban community
with professions that do not involve manual labor with rural subsistence
farmers, including women who frequently carry heavy loads.
Methods: Trunk muscle endurance, strength, and flexibility were measured
with exercise tests and electromyography (EMG).
Results: We found a positive correlation between trunk extensor strength and
endurance (R = .271, p ≤ .05) and no associations between strength or endur-
ance and flexibility. Rural women had higher trunk extensor and flexor endur-
ance, EMG-determined longissimus lumborum endurance, and trunk extensor
strength than urban women (all p ≤ .05). Rural women had higher trunk
extensor and flexor endurance than rural men (both p ≤ .05). Urban women
had lower trunk flexor and extensor endurance than urban men (both p ≤ .01).
Conclusions: High levels of physical activity among nonindustrial subsistence
farmers, particularly head carrying among women, appear to be associated
with high trunk muscle endurance and strength, which may have important
benefits for helping maintain musculoskeletal health.
