Differences in the coordination of agonist and antagonist muscle groups in below-knee amputee and able-bodied children during dynamic exercise.

A lack of co-contraction may predispose to knee instability or laxity, resulting in additional shear stress on the internal structures of the knee, especially in below-knee amputee (BKA) subjects. The purposes of this study were: (1) to provide information on how BKA children regulate agonist and antagonist muscle coordination, and (2) to quantify the level of knee co-contraction in able-bodied (AB) and BKA children during the stepping-in-place (SIP) task. Fourteen children (7 BKA vs. 7 AB), paired for age, weight and height, participated in this study. One-way ANOVA with Newman-Keuls post hoc tests (p<0.05) were used to compare peak power, the co-contraction index, and the resultant agonist and antagonist moments during different phases of SIP. Statistical analysis revealed that BKA children perform the task with similar kinematics than AB children while they generated less co-contraction in both their non-amputated limb and amputated limb, notably because the two groups of children used different agonist and antagonist muscles during the same periods of the SIP. This lack of co-contraction may reduce knee stability and may stress the internal structures of the knee in both the NAL and AL, and may lead to the development of premature knee osteoarthritis.

Muscle adaptation patterns of children with a trans-tibial amputation during walking.

BACKGROUND: Many studies have shown that trans-tibial amputation involves modifications of resultant muscle patterns during gait. However, these experiments did not estimate the contribution of simultaneous agonist and antagonist muscle action (co-contraction) during gait tasks. Diminution of co-contraction could create joint instability and, thus, change joint integrity, which is particularly important in the etiology of degenerative diseases, such as osteoarthritis, present at the knees of amputated limbs, and particularly in non-amputated limbs. The purpose of this study was to determine if there is any difference in the production of co-contraction about the knee between able-bodied children and children with a trans-tibial amputation during gait. METHODS: Six children with a trans-tibial amputation vs. six able-bodied children paired for gender, age, weight and height participated in this study. Four one-way ANOVAs (P<0.05) were used to observe differences in resultant, agonist and antagonist moments, power, and co-contraction index during different phases of gait between able-bodied children limbs, the amputated and the non-amputated limbs of children with trans-tibial amputation. FINDINGS: Children with a trans-tibial amputation modified muscle patterns at their amputated limb and produced smaller co-contraction (P<0.05) during single limb support, for both the non-amputated and amputated limbs when compared to able-bodied children. INTERPRETATION: These results suggest that children with a trans-tibial amputation altered their muscle patterns to perform locomotion. These changes produced a diminution of co-contraction during single limb support for both the amputated and non-amputated limbs and, thus, could create joint instability.

Postural control following a self-initiated reaching task in type 2 diabetic patients and age-matched controls.

Although the postural stability of diabetic patients is affected in the presence of polyneuropathy, it has been suggested that diabetes per se has no effect on balance control during quiet standing. However, recent studies have reported muscular mechanical deficits in patients with type 2 diabetes (T2D) that may be highlighted during a more destabilizing task than quiet standing. Therefore, the objective of this study was to compare non-diabetic and T2D subjects during a modified version of the functional reach (FR) test in order to discriminate differences in postural control associated with diabetes per se. Thirty subjects (15 non-diabetic and 15 T2D) were requested to stand on a force platform and to perform the FR test. Center of pressure velocity (V(COP)), root-mean-square (RMS) amplitude and range of the COP were calculated in the anterior-posterior direction during three specific periods of the FR performance: namely "before", "on-going" and "after". No significant difference between the non-diabetic subjects and the T2D subjects was found for the FR performance. However, T2D subjects had significantly higher V(COP), RMS and range of COP displacements for the "after" period compared to the non-diabetic group (p<0.05). These results suggest that T2D subjects without peripheral neuropathy may have difficulties regaining their stability after a self-initiated reaching task. Therefore, diabetes mellitus per se, could have a direct effect on postural control during standing after a self-induced forward reaching movement.