Purpose: Bilateral deficit (BLD) occurs when the force (or power) generated by both limbs together is smaller than the sum of the forces (or powers) developed separately by the two limbs. The amount of BLD can be altered by neural adaptations brought about by the repetitive execution of specific motor tasks (training). Prolonged disuse also leads to relevant neural adaptations; however, its effects on BLD are still unknown. Thus, the aim of this study was to investigate the effects of a 35-day bed rest on the BLD of the lower limbs.
Methods: Ten young healthy volunteers performed maximal explosive efforts on a sledge ergometer with both lower limbs or with the right and the left limb separately. Electromyography (EMG) of vastus lateralis, rectus femoris, biceps femoris and gastrocnemius medialis was also measured.
Results: Before bed rest, maximal explosive power and peak force were significantly higher in monolateral than bilateral efforts (+18.7 and +31.0 %, respectively). Conversely, peak velocity was 11.9 % greater in bilateral than monolateral efforts. BLD attained a value of 18.1 % and was accompanied by lower EMG amplitude of knee extensors (-17.0 %) and gastrocnemius medialis (-11.7 %) during bilateral efforts. Bed rest led to a ~28.0 % loss in both bilateral and monolateral maximal explosive power. Neither BLD magnitude nor the difference in EMG amplitudes as well as in peak force and velocity between bilateral and monolateral efforts were affected by bed rest.
Conclusions: These results suggest that the neuromuscular factors underlying BLD are unaltered after prolonged disuse.