Motor unit activation strategy during a sustained isometric contraction of finger flexor muscles in elite climbers

Abstract

The aim of the study was to evaluate, by an electromyographic (EMG) and mechanomyographic (MMG) combined approach, whether years of specific climbing activity induced neuromuscular changes towards performances related to a functional prevalence of fast resistant or fast fatigable motor units. For this purpose, after the maximum voluntary contraction (MVC) assessment, 11 elite climbers and 10 controls performed an exhaustive handgrip isometric effort at 80% MVC. Force, EMG and MMG signals were recorded from the finger flexor muscles during contraction. Time and frequency domain analysis of EMG and MMG signals was performed. In climbers: (i) MVC was higher (762 ± 34 vs 512 ± 57 N; effect size: 1.64; confidence interval: 0.65–2.63; P < 0.05); (ii) endurance time at 80% MVC was 43% longer (34.2 ± 3.7 vs 22.3 ± 1.5 s; effect size: 1.21; confidence interval: 0.28–2.14; P < 0.05); (iii) force accuracy and stability were greater during contraction (P < 0.05); (iv) EMG and MMG parameters were higher throughout the entire isometric effort (P < 0.05). Collectively, force, EMG and MMG combined analysis revealed that several years of specific climbing activity addressed the motor control system to adopt muscle activation strategies based on the functional prevalence of fast resistant motor units.

Keywords:

• sport climbing
• electromyogram
• mechanomyogram
• handgrip

Acknowledgement

The authors wish to thank all the people involved in this study, for their committed participation and efforts.

ORCID

Eloisa Limonta http://orcid.org/0000-0001-7246-2819

Emiliano Cè http://orcid.org/0000-0003-0691-3153

Arsenio Veicsteinas http://orcid.org/0000-0002-4019-6824

Claudio Orizio http://orcid.org/0000-0003-2534-2296

Fabio Esposito http://orcid.org/0000-0002-4420-2611