An upper arm model for simulated weightlessness

This investigation examined the effects of 4 weeks of non‐dominant arm unloading on the functional and structural characteristics of the triceps brachii muscle of six normo‐active college‐age males (age: 23 ± 1 years, height: 176 ± 4 cm, weight: 76 ± 6 kg). The primary intention of this study was to determine if arm unloading is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2–3 days preceding unloading in a standard arm sling and following removal of the sling. The sling was worn during waking hours to unload the arm. Subjects were allowed to remove the sling during sleep and bathing. Torque production (Nm) during maximal isometric extension at 90° significantly declined (P 0.05) in the force–velocity attributes of the triceps over the other measured velocities (1.05, 1.57, 2.09, 3.14, 4.19, 5.24 rad·s–1). Cross‐sectional muscle area (CSA) of the upper arm was smaller (44.3 ± 2.7 to 42.4 ± 2.5 cm2; 4%) following 4 weeks of unloading (P