Decreased isokinetic trunk muscle strength and performance in long-term survivors of childhood malignancies: Correlation with hormonal defects

Abstract

Objective: To evaluate trunk muscle strength and performance in long-term survivors of childhood malignancies relative to age and sex-matched controls, and to relate the muscle strength observations to the therapeutic agents used and possible hormonal disturbances. Design: Age and sex-matched cohort study. Setting: Referral center in the northern part of Finland. Patients: Forty-six long-term survivors of childhood cancer. Mean age at examination 19.1 years and median off-therapy time 9.4 years. Intervention: Isokinetic dynamometer testing. Main Outcome Measures: Measurements of trunk muscle peak torque (PT) and total work done (TWD) were performed at angle speeds of 50°/sec and 200°/sec. The results were normalized relative to body fat-free weight (FFW). Results: PT in the trunk muscles was lower in the patients at both angle speeds (mean normalized PT = 5.7Nm/kg FFW vs 7.6Nm/kg FFW for controls at 50°/sec), as also was TWD except for extension TWD at the higher angle speed (mean normalized TWD = 59.9J/kg FFW vs 84.6J/kg FFW for controls at 200°/sec). The normalized PT at 50°/sec and TWD at 200°/sec were lower in the males with testicular damage; also, low age at diagnosis correlated positively with muscle strength and performance. There were no differences in normalized PTs or TWDs between cranial radiation and non-radiation cases, or between growth-hormone-deficient and non-deficient cases, and the patients without cranial radiation or with normal growth hormone secretion still had lower normalized PTs and TWDs than the controls. Conclusions: Survivors of childhood malignancies have decreased maximal trunk muscle strength and performance. The etiology of this effect remains unclear, but young age at diagnosis, as well as serum testosterone levels in male survivors, evidently influence muscle strength and performance.