Comparing Motor Unit Activation, Isometric Strength Before and After Warm-Up Exercise

Researchers tested several hypotheses related to changes in motor unit activation patterns, comparing strength before and after warm-up exercise.

Fifteen healthy young men participated in the experiment and the main task was to produce voluntary torque at the elbow joint via isometric flexion and extension at joint angles of 10° and 90°.

Participants were asked to increase the joint torque to the maximal level at a rate of 10% of the maximum voluntary torque.

Researcher used a warm-up protocol that followed the ACSM guidelines (American College of Sport Medicine), and with the exercise warm-up, an increase of body temperature of approximately 1.5°C was observed.

Researchers discovered that the magnitude of joint torque increased after the warm-up exercise for all the experimental conditions.

Also, the results of the motor unit analyses showed a positive and beneficial effect of the warm-up exercise, with an increase in both the mean firing rate and the recruitment threshold by about 56% and 33%, respectively, particularly in the agonist muscle.

Power spectral density in the gamma band, which is thought to be the dominant voluntary activity, was also increased by the warm-up exercise only in the high threshold motor units. Gamma-band activity (GBA) comprises an EEG frequency range, from 30 to 200 Hz, and is distributed widely throughout cerebral structures. GBA participates in various cerebral functions, such as perception, attention, memory, consciousness, synaptic plasticity, and motor control (muscular activity).

The research was conducted in South Korea, and published in April 2024..

See more on PubMed …
Lee J, Park D, Lee JY, Park J. Effect of Warm-Up Exercise on Functional Regulation of Motor Unit Activation during Isometric Torque Production. J Hum Kinet. 2024 Apr 25;92:29-41. doi: 10.5114/jhk/185157. PMID: 38736599; PMCID: PMC11079928.

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