Effects of remote limb ischemic conditioning on muscle strength in healthy young adults: A randomized controlled trial

Abstract

Remote limb ischemic conditioning (RLIC) is a clinically feasible method in which brief, sub-lethal bouts of ischemia protects remote organs or tissues from subsequent ischemic injury. A single session of RLIC can improve exercise performance and increase muscle activation. The purpose of this study, therefore, was to assess the effects of a brief, two-week protocol of repeated RLIC combined with strength training on strength gain and neural adaptation in healthy young adults. Participants age 18-40 years were randomized to receive either RLIC plus strength training (n = 15) or sham conditioning plus strength training (n = 15). Participants received RLIC or sham conditioning over 8 visits using a blood pressure cuff on the dominant arm with 5 cycles of 5 minutes each alternating inflation and deflation. Visits 3-8 paired conditioning with wrist extensors strength training on the non-dominant (non-conditioned) arm using standard guidelines. Changes in one repetition maximum (1 RM) and electromyography (EMG) amplitude were compared between groups. Both groups were trained at a similar workload. While both groups gained strength over time (P = 0.001), the RLIC group had greater strength gains (9.38 ± 1.01 lbs) than the sham group (6.3 ± 1.08 lbs, P = 0.035). There was not a significant group x time interaction in EMG amplitude (P = 0.231). The RLIC group had larger percent changes in 1 RM (43.8% vs. 26.1%, P = 0.003) and EMG amplitudes (31.0% vs. 8.6%, P = 0.023) compared to sham conditioning. RLIC holds promise for enhancing muscle strength in healthy young and older adults, as well as clinical populations that could benefit from strength training.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1. CONSORT flow diagram.

Fig 2. Order of experimental procedures.

Fig 3. Strength.

(A) Training load for each group during 2 weeks of strength training program. Training load was calculated as total number of repetitions by average load during each visit. Training visits 3–8 occurred on alternate weekdays. (B) 1 Repetition Maximum (1 RM) of the wrist extensor muscles on the non-dominant arm for each group. From pre- to post-test, mean change score in 1 RM in the RLIC group was 3.07 ± 0.75 lbs greater than the sham group. * indicates P

Fig 4. Electromyography (EMG).

(A) EMG activity in extensor carpi radialis longus muscle on the non-dominant arm. Average amplitude of the EMG signal from pre- to post-test was increased in the RLIC compared to the sham group. (B) Percent change in EMG amplitude between from pre- to post-test between groups. On average, the RLIC group demonstrated 22.36 ± 4.89% relative increase in EMG amplitude compared to the sham group. Values are means ± SE. * indicates P