Deterioration of muscle function after 21-day forearm immobilization

Area of Science:

• Sports Medicine
• Human Physiology
• Rehabilitation Science

Background:

• Immobilization is known to cause muscle atrophy, primarily studied in lower limbs.
• Limited research exists on the effects of immobilization on forearm muscle morphology and function.

Purpose of the Study:

• To investigate the impact of forearm immobilization on muscle morphology and function.
• To establish a model for studying forearm muscle changes due to immobilization.

Main Methods:

• Six healthy males underwent 21-day immobilization of the non-dominant arm (CAST) with the dominant arm serving as control (CONT).
• Muscle morphology was assessed via forearm cross-sectional area (CSA) using MRI.
• Muscle function was evaluated through maximum grip strength, forearm muscle oxidative capacity (PCr-Tc via 31P MR spectroscopy), and dynamic grip endurance.

Main Results:

• No significant changes in CSA or circumference were observed in the immobilized forearm (CAST) compared to the control (CONT).
• Maximum grip strength decreased by 18% (P < 0.05) in the CAST group.
• Phosphocreatine recovery time constant (PCr-Tc) prolonged by 45% (P < 0.05), and grip endurance reduced by 19% (P < 0.05) in the CAST group.

Conclusions:

• Twenty-one days of forearm immobilization resulted in no significant changes in muscle morphology.
• Forearm muscle function demonstrated significant deterioration, with reductions in strength, oxidative capacity, and endurance.
• This study suggests that functional impairments can occur independently of morphological changes after immobilization.