Time course of functional recovery during the first 3 mo after surgical transection and repair of nerves to the feline soleus and lateral gastrocnemius muscles.

Locomotion outcomes after peripheral nerve injury and repair in cats have been described in the literature for the period immediately following the injury (muscle denervation period) and then again for an ensuing period of long-term recovery (at 3 mo and longer) resulting in muscle self-reinnervation. Little is known about the changes in muscle activity and walking mechanics during midrecovery, i.e., the early reinnervation period that takes place between 5 and 10 wk of recovery. Here, we investigated hindlimb mechanics and electromyogram (EMG) activity of ankle extensors in six cats during level and slope walking before and every 2 wk thereafter in a 14-wk period of recovery after the soleus (SO) and lateral gastrocnemius (LG) muscle nerves in one hindlimb were surgically transected and repaired. We found that the continued increase in SO and LG EMG magnitudes and corresponding changes in hindlimb mechanics coincided with the formation of neuromuscular synapses revealed in muscle biopsies. Throughout the recovery period, EMG magnitude of SO and LG during the stance phase and the duration of the stance-related activity were load dependent, similar to those in the intact synergistic medial gastrocnemius and plantaris. These results and the fact that EMG activity of ankle extensors and locomotor mechanics during level and upslope walking recovered 14 wk after nerve transection and repair suggest that loss of the stretch reflex in self-reinnervated muscles may be compensated by the recovered force-dependent feedback in self-reinnervated muscles, by increased central drive, and by increased gain in intermuscular motion-dependent pathways from intact ankle extensors. NEW & NOTEWORTHY This study provides new evidence that the timeline for functional recovery of gait after peripheral nerve injury and repair is consistent with the time required for neuromuscular junctions to form and muscles to reach preoperative tensions. Our findings suggest that a permanent loss of autogenic stretch reflex in self-reinnervated muscles may be compensated by recovered intermuscular force-dependent and oligosynaptic length-dependent feedback and central drive to regain adequate locomotor output capabilities during level and upslope walking.

Temporal and spatial features of gait in older adults transitioning to frailty.

Examining gait characteristics in older adults who are transitioning to frailty enhances our understanding of movement control in this fall-prone population and helps to better target preventive interventions. This work presents data on temporal and spatial gait parameters of a group of older adults who have been operationally defined as "transitionally frail". Gait speed, cadence, stride length, stance, swing, double-support, and horizontal heel velocity at heel contact were measured in 50 transitionally frail older adults while walking at a self-selected pace. These data suggest that the temporal and spatial gait features of these older adults differ substantially from published results from other older adults.

The influence of Tai Chi training on the center of pressure trajectory during gait initiation in older adults.

OBJECTIVE: To determine if a program of intense Tai Chi exercise that has been shown to reduce the risk of falling in older adults improves postural control by altering the center of pressure (COP) trajectory during gait initiation. DESIGN: Before-after trial. SETTING: Biomechanics research laboratory. PARTICIPANTS: Twenty-eight older adults transitioning to frailty who participated in either a 48-week intervention of intense Tai Chi training or a wellness education (WE) program. INTERVENTIONS: Eight Tai Chi forms emphasizing trunk rotation, weight shifting, coordination, and narrowing of lower-extremity stance were taught twice weekly. WE program participants met once a week and received lectures focused on health. Main outcome measures The COP was recorded during gait initiation both before and after the 48-week intervention by using a forceplate sampling at 300 Hz. The COP trajectory was divided into 3 periods (S1, S2, S3) by identifying 2 landmark events. Displacement and average velocity of the COP trace in the anteroposterior (x) and mediolateral (y) directions, as well as smoothness, were calculated. RESULTS: Tai Chi training increased the posterior displacement of the COP during S1 and improved the smoothness of the COP during S2. CONCLUSIONS: Tai Chi improved the mechanism by which forward momentum is generated and improved coordination during gait initiation, suggesting improvements in postural control.