Comparison of bilateral and unilateral contractions between swimmers and nonathletes during leg press and hand grip exercises

Abstract

The bilateral limb deficit (BLD) is defined as the reduction in force production during bilateral compared with summed unilateral contractions of homologous muscles. The underlying mechanism for the BLD has been elusive to determine. The purpose of this study was to examine the presence of the BLD during maximal isometric leg press and handgrip exercises in female swimmers (n = 9, mean age = 20.1 ± 1.3 years) and nonathletes (n = 9, mean age = 21.7 ± 1.3 years) to gain further insight into this phenomenon. Force and electromyography (EMG) measures were collected from participants under bilateral and unilateral conditions for handgrip and leg press exercises. Bilateral limb ratios (BLR) were calculated for swimmers (BLRS) and nonathletes (BLRNA). A deficit was found for swimmers and nonathletes in leg force (BLRS = 79.84% ± 13.09% and BLRNA = 81.44% ± 19.23%) and leg EMG (BLRS = 88.45% ± 15.41% and BLRNA = 94.66% ± 13.62%); however, no BLD was seen in hand force (BLRS = 98.30% ± 11.21% and BLRNA = 95.91% ± 11.04%) and hand EMG (BLRS = 102.42% ± 11.20% and BLRNA = 103.30% ± 16.50%). Furthermore, no significant differences were found between groups for leg force, leg EMG, hand force, and hand EMG. In conclusion, a BLD was detected for both groups during bilateral isometric leg press. This suggests that while the BLD may be affected by neural influences, there may other factors involved such as postural stability requirements to perform the exercise.

The bilateral limb deficit (BLD) phenomenon during leg press: a preliminary investigation into central and peripheral factors

“…This pilot study presents BLD leg press similar to other studies [ 11 , 21 , 22 ], but with varying results. The mean BLR detected in the present study was 94.8 ± 22.0%, with the mean BLR of individuals that incurred a deficit being ~ 81%.…”

“…Evidence suggests that lower forces are produced with bilateral limb contraction when compared to the summed force produced when the same homologous muscles are contracted unilaterally [ 21 , 32 ]. This phenomenon, termed as bilateral limb deficit (BLD), has been exhibited in both upper and lower limbs, however the magnitude of the deficit is typically larger in lower limbs [ 22 ].…”

“…Two primary theories for the cause of the BLD have been suggested, the postural stability theory and the neural inhibition theory [ 21 ]. The postural stability theory postulates that postural stability requirements of the exercise studied may be the cause of the deficit [ 7 , 22 ].…”

Comparación del déficit bilateral en la potencia muscular de futbolistas y estudiantes

“…Por definición, DBL es una condición que se produce cuando la fuerza total ejercida por las dos extremidades es menor a la suma de las fuerzas que producen la extremidad derecha más la izquierda por separado (MacDonald, et al, 2014), la cual puede variar según el tipo de movimiento y según la persona (Beurskens, et al, 2015). En contraposición al concepto de déficit bilateral se encuentra el concepto de facilitación bilateral (FBL) (Botton, et al, 2016) El DBL ha sido estudiado en las acciones deportivas, especialmente en aquellas que tienen relación con el salto y la potencia de los miembros inferiores.…”

Bilateral Strength Deficit Is Not Neural in Origin; Rather Due to Dynamometer Mechanical Configuration

“…This theory was initially proposed through the study of simultaneous non-homonymous muscle activity [ 18 ] and reviewed across studies [ 3 ]. Recently, the postural theory was further explored by comparing upper body hand exercise with lower body leg extension [ 9 , 21 ]. However, this compelling argument for postural contributions is lessened because spinal connections are disparate between the upper and lower body [ 22 ], postural adjustments vary between sitting and standing [ 23 , 24 ], and the magnitude of force production is greater in leg extension compared with hand grip.…”