Acute responses of strength-related gene expressions to maximum strength and force sense acuity

Although high muscle strength worsens the sense of force, it is unknown whether there is a relationship between this deterioration and the underlying molecular mechanisms. This study examined the relationship between decreased force sense (FS) acuity and strength-related gene expressions.

Maximal voluntary isometric contraction (MVIC) and FS (50% MVIC) tests were performed on the knee joints of twenty-two subjects. The expression analyses were evaluated by qRT-PCR in blood samples taken before, after MVIC, after 50% MVIC, and 15 min after the test.

MVIC and FS error values were significantly correlated with each other (r = .659, p = .001). The qRT-PCR analyses demonstrated that the expressed mRNAs of the interleukin 6 (IL-6), alpha-actinin 3 (ACTN3), angiotensin-converting enzyme (ACE), brain-derived neurotrophic factor (BDNF), and ciliary neurotrophic factor receptor (CNTFR) genes dramatically increased until 50% MVIC and subsequently decreased 15 min after the exercise (p < .05). The muscle-specific creatine kinase (CKMM), myosin light chain kinase (MLCK), and G-protein β3 subunit (GNB3) genes reached their peak expression levels 30 min after MVIC (p < .05). ACE and ACTN3 gene expression increased significantly in parallel with the increased FS error (p < .05). These gene expression fluctuations observed at 50% MVIC and after the rest could be related to changes in cellular metabolism leading to fatigue.

The time points of gene expression levels during exercise need to be considered. The force acuity of those whose maximal force develops too much may deteriorate.