Triceps Brachii Strength and Regional Body Composition Changes After Detraining Quantified by MRI

Purpose: To determine the triceps brachii functional adaptation and regional body composition changes after 12 months of detraining. Materials and Methods: Seventeen healthy young men (22.2 +/- 1.0 y, body mass index 24.9 +/- 3.1 kg/m(2)) were put in the detraining regimen for 12 months after completing a 12-week exercise protocol on isoacceleration dynamometer (5 times a week, 5 daily series with 10 maximal elbow extensions, 1 min rest between sets). Triceps brachii muscle strength was measured by isoacceleration dynamometry, using identical protocol as during the training. Muscle volumes, subcutaneous adipose tissue (SCAT), and intermuscular adipose tissue (IMAT) at mid-humerus were assessed by using MRI. Results: Long-term detraining resulted in the significant decrease of 17% and 19% in endurance strength and fatigue rate, respectively Maximal muscle strength slightly changed, and its 4% decrease was not significant. Triceps brachii volumes of both arms returned to their pretraining values (475.7 +/- 54.91 cm(3) for right arm, and 483.9 +/- 77.5 cm(3) for left arm). IMAT depots in upper arm significantly increased by 14% after 12 months of detraining, when compared with baseline values (P < 0.05). Conclusion: Long-term detraining leads to triceps brachii adaptation with endurance strength decrease, volume return to its baseline values, and significant IMAT accumulation. IMAT values after 12 months of detraining exceed baseline, pretraining values, which is significant accumulation as a result of physiologically decreased muscle activity.