Effects of combined treatment with blood flow restriction and low-current electrical stimulation on muscle hypertrophy in rats

Abstract

This study aimed to clarify the effects of a combined treatment comprising blood flow restriction and low-current electrical stimulation on skeletal muscle hypertrophy in rats. Male Wistar rats were divided into control (Cont), blood flow restriction (Bfr), electrical stimulation (Es), or Bfr with Es (Bfr + Es) groups. Pressure cuffs (80 mmHg) were placed around the thighs of Bfr and Bfr + Es rats. Low-current Es was applied to calf muscles in the Es and Bfr + Es rats. In experiment 1, a 1-day treatment regimen (5-min stimulation, followed by 5-min rest) was delivered four times to study the acute effects. In experiment 2, the same treatment regimen was delivered three times/wk for 8 wk. Body weight, muscle mass, changes in maximal isometric contraction, fiber cross-sectional area of the soleus muscle, expression of phosphorylated and total-ERK1/2, phosphorylated-rpS6 Ser235/236, phosphorylated and total Akt, and phosphorylated-rpS6 Ser240/244 were measured. Bfr and Es treatment alone failed to induce muscle hypertrophy and increase the expression of phosphorylated rpS6 Ser240/244. Combined Bfr + Es upregulated muscle mass, increased the fiber cross-sectional area, and increased phosphorylated rpS6 Ser240/244 expression and phosphorylated rpS6 Ser235/236 expression compared with controls. Combined treatment with Bfr and low-current Es can induce muscle hypertrophy via activation of two protein synthesis signaling pathways. This treatment should be introduced for older patients with sarcopenia and others with muscle weakness. NEW & NOTEWORTHY We investigated the acute and chronic effect of low-current electrical stimulation with blood flow restriction on skeletal muscle hypertrophy and the mechanisms controlling the hypertrophic response. Low-current electrical stimulation could not induce skeletal muscle hypertrophy, but a combination treatment did. Blood lactate and growth hormone levels were increased in the early response. Moreover, activation of ERK1/2 and mTOR pathways were observed in both the acute and chronic response, which contribute to muscle hypertrophy.

Enhancing Adaptations to Neuromuscular Electrical Stimulation Training Interventions

“…Regarding chronic interventions, NMES combined with BFR improved rat soleus muscle mass more than NMES alone (51), and this was associated with activation of ERK1/2 and mTOR pathways, a finding confirmed by Natsume et al (52) in rat gastrocnemius. In recreationally active humans, 6 wk of BFR + NMES training of the quadriceps (with four weekly sessions of 32 min) was more effective for increasing maximal knee extensor strength than BFR or NMES alone, although no significant changes in muscle mass were detected (53).…”

“…Regarding chronic interventions, NMES combined with BFR improved rat soleus muscle mass more than NMES alone ( 51 ), and this was associated with activation of ERK1/2 and mTOR pathways, a finding confirmed by Natsume et al . ( 52 ) in rat gastrocnemius.…”

Effects of lactate administration on hypertrophy and mTOR signaling activation in mouse skeletal muscle

“…Resistance exercise significantly decrease muscle glycogen content and increases glycolytic metabolites; however, glycolysis inhibition attenuates acute resistance exercise‐induced increases in mTOR signaling activity and muscle protein synthesis (Suginohara et al, 2021 ). Moreover, low‐load resistance exercise with blood flow restriction, which increases blood lactate levels, has been shown to be effective for increasing muscle mass, (Yoshikawa et al, 2019 ) suggesting that glycolytic metabolites might contribute to muscle hypertrophy. Lactate, a product of the glycolytic system, has been regarded as a mere waste product; in recent years, however, it has been recognized as a potential signaling molecule that induces beneficial adaptations in various tissues (Brooks, 2018 ; Ferguson et al, 2018 ).…”

A Comprehensive Model of Blood Flow Restriction in the Post-surgical Rat

“…squats), but they are less applicable to studies of BFR due to their inability to generate hindlimb-specific movement, thus potentially introducing compensation by the non-targeted limbs. Other studies that combine BFR and resistance training in rats use low-current neuromuscular electrostimulation in anesthetized rats, which allows for careful control of occlusion pressure but only stimulates contraction of a single muscle 45,47,52 . Further, prolonged exposure to systemic anesthesia can cause reductions in body temperature and impact blood flow through distal vasculature, affecting accurate measurement of blood flow occlusion 53 .…”