Author(s): ZACCARON, S., MARI, L., DALLEVA, M., STAFUZZA, J., PARPINEL, M., LAZZER, S., REJC, E., Institution: UNIVERSITA DEGLI STUDI DI UDINE, Country: ITALY, Abstract-ID: 602

INTRODUCTION:
Neuromuscular priming strategies can be implemented to enhance muscle strength and power generation (1), which are critical determinants for daily life activities and athletic performance. However, the effects of non-invasive spinal cord transcutaneous stimulation (scTS) on motor control and neuromuscular performance in healthy subjects are not known. Therefore, the aim of this study was to investigate the effects of an exercise-based priming protocol combined with scTS on the neuromuscular performance of lower limbs in young active males. We also evaluated how scTS alone influenced lower limb motor performance.
METHODS:
Twelve volunteers (age: 22.7±2.1 years) participated in this randomized crossover, sham-controlled study. Maximal voluntary contraction of the knee extensors (MVC) and maximal explosive power of the lower limbs were assessed at baseline, with scTS or sham stimulation, and after the priming protocol with scTS or sham across four experimental sessions. Further, characteristics of evoked potentials to scTS related to spinal circuitry excitability were assessed in supine position before and after the scTS priming protocol. The exercise component of the ~25-minute priming protocol was characterized by low-volume, low- and high-intensity lower limb motor tasks.
RESULTS:
We found trends toward enhanced mechanical outputs following the scTS priming protocol, whereas the sham priming protocol was associated with reduced neuromuscular performance. This resulted in a 9% difference between the scTS and sham priming protocols during MVC of knee extensors (p=0.002). Similarly, for maximal explosive power, the mean differences in peak force and rate of force development (RFD) were 3.1% and 21.1%, respectively (p = 0.019 and 0.002, respectively)). Conversely, no significant differences were observed between baseline and maximal efforts performed with scTS or sham for any of the investigated variables (p values between 0.850 and 0.465). Furthermore, assessment of evoked potentials to scTS in supine showed a trend of increased excitability after scTS priming protocol.
CONCLUSION:
scTS priming protocol enhanced the performance of lower limb maximal efforts when compared to the sham priming protocol. This is associated with trends of increased spinal excitability after the scTS priming protocol. Positive effects of scTS priming protocol on maximal neuromuscular performance might be related with spinal excitability modulation that brings neural networks closer to the activation threshold and amplifies descending neural drive during exercise. No effects of scTS alone might be related to the interference of stimulation with neural processes (2).

REFERENCES:
1) Harrison et al. 2019, Sports Med
2) Balbinot et al. 2024, J Physiol