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

Abstract

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%, [Formula: see text] = 0.48, p = 0.02) and resting evoked twitch forces (29.4%, [Formula: see text] = 0.34, p = 0.03). The 30-s MVC induced significantly greater pre- to post-test decreases in potentiated twitch force ([Formula: see text] = 0.61, p = 0.0009) during inversion (↓75%) than upright (↓65.3%) conditions. Overall, BFR decreased MVC force 4.8% ([Formula: see text] = 0.37, p = 0.05). For upright position, BFR induced 21.0% reductions in M-wave amplitude ([Formula: see text] = 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.

Fig 1. Experimental design.

Fig 2. Representative 1) evoked resting twitch, 2) MVC force, 3) interpolated twitch technique (ITT), 4) biceps brachii EMG, 5) triceps brachii EMG and 6) potentiated twitch force (PTF) tracings presented under different conditions/posture.

Top channel represents elbow flexor MVC force, second channel illustrates biceps brachii EMG and third channel shows triceps brachii EMG.

Fig 3. Isometric maximal voluntary contraction force (MVC) interaction effects for seated position and time.

Star (*) symbol represents that significant MVC force decreases between initial and pre-fatigue tests, for upright and inverted seated positions. Means and standard deviations are illustrated. There was no statistically significant BFR interaction.

Fig 4. Voluntary muscle activation (VMA) interaction effects for BFR and time.

There was a non-significant effect for percentage of VMA (p = 0.07), with 7.9% and 16.4% decreases post-fatigue for without BFR and BFR conditions. Means and standard deviations are illustrated. There was no statistically significant interaction between seated positions (inverted versus upright).

Fig 5. Resting twitch force interaction effects for seated position and time.

Star (*) symbol represents significant decreases between initial and pre-fatigue tests, for upright and inverted seated positions. Means and standard deviations are illustrated. There was no statistically significant BFR interaction.

Fig 6. Biceps brachii M-wave interaction effects for seated position and BFR.

Star (*) symbol represents that significant decreases in amplitude of M-wave for Biceps Brachii, between without BFR and BFR, with 30.4% and 12.5% for upright and inverted seated positions, respectively. Means and standard deviations are illustrated.

Fig 7. Potentiation Twitch Force (PTF) interaction effects for seated position and time.

Star (*) symbol represents that significant Potentiation Twitch Force decreases between pre- and post-fatigue tests, for upright and inverted seated positions. The hashtag or number symbol (#) indicates that PTF tested with inversion post-fatigue was significantly lower than all other times and conditions. Means and standard deviations are illustrated. There was no statistically significant BFR interaction.