Balance training and ballistic strength training are associated with task‐specific corticospinal adaptations

Abstract

The aim of this study was to investigate the role of presumably direct corticospinal pathways in long-term training of the lower limb in humans. It was hypothesized that corticospinal projections are affected in a training-specific manner. To assess specificity, balance training was compared to training of explosive strength of the shank muscles and to a nontraining group. Both trainings comprised 16 1-h sessions within 4 weeks. Before and after training, the maximum rate of force development was monitored to display changes in motor performance. Neurophysiological assessment was performed during rest and two active tasks, each of which was similar to one type of training. Hence, both training groups were tested in a trained and a nontrained task. H-reflexes in soleus (SOL) muscle were tested in order to detect changes at the spinal level. Corticospinal adaptations were assessed by colliding subthreshold transcranial magnetic stimulation to condition the SOL H-reflex. The short-latency facilitation of the conditioned H-reflex was diminished in the trained task and enhanced in the nontrained task. This was observable in the active state only. On a functional level, training increased the rate of force development suggesting that corticospinal projections play a role in adaptation of leg motor control. In conclusion, long-term training of shank muscles affected fast corticospinal projections. The significant interaction of task and training indicates context specificity of training effects. The findings suggest reduced motor cortical influence during the trained task but involvement of direct corticospinal control for new leg motor tasks in humans.

Exercise of mechanisms of dynamic stability improves the stability state after an unexpected gait perturbation in elderly

“…This finding is in accordance with our earlier results during simulated forward falls , indicating that exercising the mechanisms of dynamic stability may lead to upgraded neuromuscular coordination and may be sufficient to convey successful strategies for regaining balance after perturbations. Improved capacity of maximal and explosive force production, as well as better neuronal activation, was already found in earlier sensorimotor training studies (Granacher et al 2007;Schubert et al 2008) and was explained by increased intermuscular coordination. Further, the repeated application of the mechanisms of dynamic stability seems to facilitate the adequate use of those mechanisms even in unfamiliar situations in order to regain balance.…”

Balance Training for Neuromuscular Control and Performance Enhancement: A Systematic Review

“…No SMDs were calculated for the neuromuscular control group differences because data were insufficient. Both improvements in the balance training group 15,16 and no group differences 25 were reported for plantar-flexion RFD and H-reflex modulation. With regard to electromyographic (EMG) activity, balance training effects were reported for soleus and gastrocnemius medialis muscle EMG median frequency and reactive rectus femoris root mean square (RMS).…”

“…With regard to electromyographic (EMG) activity, balance training effects were reported for soleus and gastrocnemius medialis muscle EMG median frequency and reactive rectus femoris root mean square (RMS). 15,19 No effects were shown for EMG mean amplitude voltage or RMS of the soleus, gastrocnemius medialis, or tibialis anterior 15,25 or for prelanding and postlanding biceps femoris and soleus EMG activity. 19 Balance Training Versus Strength Training.…”

“…Although the control groups in most trials had no intervention, some authors compared balance training with strength training 13,[15][16][17]20,25,27 or plyometric training. 22 Treatment length varied between 4 and 12 weeks.…”

Effects of single vs. multiple-set short-term strength training in elderly women

“…The inability of surface electromyography to detect longitudinal changes, at least in part, is due to changes in skin (fat layer) and muscle tissue (muscle fiber pennation) (Aagaard 2003), which may explain the current results. Moreover, ST results in neural adaptations, which may not be perceptible by surface electromyography, such as changes in the organization of the synaptic circuitry in the spinal cord, as well as an increase in cortical excitability (Carroll et al 2002;Schubert et al 2008), Muscle hypertrophy is related to several variables, such as muscle damage (Hill and Goldspink 2003), hormone secretion (Crewther et al 2006), and activation myogenic pathways (Schoenfeld 2010), and it is believed that multiple sets may be related to greater responses in these variables. However, in the present study, both groups demonstrated similar increases.…”