Resistance exercise prevents plantar flexor deconditioning during bed rest

Area of Science:

• Neuromuscular Physiology
• Exercise Science
• Space Medicine

Background:

• Unloading and resistance exercise (REX) induce opposing neuromuscular adaptations.
• Bed rest unloading (BRU) leads to deconditioning, particularly in lower limb muscles.
• Understanding REX efficacy against unloading effects is crucial for maintaining muscle function.

Purpose of the Study:

• To test the efficacy of REX in preventing neuromuscular deconditioning caused by 14 days of bed rest unloading (BRU).
• To evaluate the impact of REX on plantar flexor muscle strength, torque-velocity, and power-velocity relationships during BRU.

Main Methods:

• Sixteen men were divided into no exercise (NOE) and REX groups.
• REX group performed constant resistance concentric/eccentric plantar flexion exercises every other day during 14 days of BRU.
• Measurements included 1-repetition maximum (1RM), angle-specific torque-velocity, power-velocity, and electromyography (EMG).

Main Results:

• 1RM strength decreased 9% in NOE but improved 11% in REX.
• Angle-specific torques and power decreased significantly in NOE across various velocities and muscle lengths.
• REX maintained or improved plantar flexor strength and performance at all tested conditions, with no change in maximal EMG.

Conclusions:

• Constant resistance concentric/eccentric REX completely prevented plantar flexor deconditioning induced by BRU.
• REX is effective in preserving muscle strength, torque, and power during prolonged unloading.
• These findings support REX interventions for astronauts in microgravity and patients during bed rest.