Effects of an inverted seated position on single and sustained isometric contractions and cardiovascular parameters of trained individuals

Effect of an inverted seated position with upper arm blood flow restriction on measures of elbow flexors neuromuscular performance

Purpose

The objective of the investigation was to determine the concomitant effects of upper arm blood flow restriction (BFR) and inversion on elbow flexors neuromuscular responses.

Methods

Randomly allocated, 13 volunteers performed four conditions in a within-subject design: rest (control, 1-min upright position without BFR), control (1-min upright with BFR), 1-min inverted (without BFR), and 1-min inverted with BFR. Evoked and voluntary contractile properties, before, during and after a 30-s maximum voluntary contraction (MVC) exercise intervention were examined as well as pain scale.

Results

Inversion induced significant pre-exercise intervention decreases in elbow flexors MVC (21.1%, ηp2 = 0.48, p = 0.02) and resting evoked twitch forces (29.4%, ηp2 = 0.34, p = 0.03). The 30-s MVC induced significantly greater pre- to post-test decreases in potentiated twitch force (ηp2 = 0.61, p = 0.0009) during inversion (↓75%) than upright (↓65.3%) conditions. Overall, BFR decreased MVC force 4.8% (ηp2 = 0.37, p = 0.05). For upright position, BFR induced 21.0% reductions in M-wave amplitude (ηp2 = 0.44, p = 0.04). There were no significant differences for electromyographic activity or voluntary activation as measured with the interpolated twitch technique. For all conditions, there was a significant increase in pain scale between the 40–60 s intervals and post-30-s MVC (upright<inversion, and without BFR<BFR).

Conclusion

The concomitant application of inversion with elbow flexors BFR only amplified neuromuscular performance impairments to a small degree. Individuals who execute forceful contractions when inverted or with BFR should be cognizant that force output may be impaired.