Rapid increase in plasma growth hormone after low-intensity resistance exercise with vascular occlusion

Abstract

Hormonal and inflammatory responses to low-intensity resistance exercise with vascular occlusion were studied. Subjects (n = 6) performed bilateral leg extension exercise in the seated position, with the proximal end of their thigh compressed at 214 +/- 7.7 (SE) mmHg throughout the session of exercise by means of a pressure tourniquet. Mean intensity and quantity of the exercise were 20% of 1 repetition maximum and 14 repetitions x 5 sets, respectively. In each set, the subjects repeated the movement until exhaustion. Plasma concentrations of growth hormone (GH), norepinephrine (NE), lacate (La), lipid peroxide (LP), interleukin-6 (IL-6), and activity of creatine phosphokinase (CPK) were measured before and after the exercise was finished and the tourniquet was released. Concentrations of GH, NE, and La consistently showed marked, transient increases after the exercise with occlusion, whereas they did not change a great deal after the exercise without occlusion (control) done at the same intensity and quantity. Notably, concentration of GH reached a level approximately 290 times as high as that of the resting level 15 min after the exercise. IL-6 concentration showed a much more gradual increase and was maintained at a slightly higher level than in the control even 24 h after exercise. Concentrations of LP and CPK showed no significant change. The results suggest that extremely light resistance exercise combined with occlusion greatly stimulates the secretion of GH through regional accumulation of metabolites without considerable tissue damage.

Exercise with Blood Flow Restriction: An Updated Evidence-Based Approach for Enhanced Muscular Development

“…Importantly, this accumulation of metabolites may increase muscle cell swelling [25], intramuscular anabolic/anti-catabolic signalling [9,26,27], and muscle fibre recruitment [4,28], which are all thought to be beneficial for muscular adaptation [23]. Furthermore, evidence suggests that the hypoxic environment created during BFR may increase the activation and proliferation of myogenic stem cells, enhancing the hypertrophic response [29].…”

“…Furthermore, evidence suggests that the hypoxic environment created during BFR may increase the activation and proliferation of myogenic stem cells, enhancing the hypertrophic response [29]. Significantly elevated endocrine responses have also been observed [4]. However, the role of acute endocrine responses in resistance training adaptation has been recently questioned, and may not have anabolic effects in healthy individuals as once thought [30].…”

“…While early research utilized restrictive pressures in excess of 200 mmHg [4], it is now accepted that BFR pressure should be high enough to occlude venous return from the muscles, yet low enough to maintain arterial inflow into the muscle [8]. Logic therefore dictates that BFR should not be universally applied at an absolute pressure, but should vary relative to each individual [43].…”

“…BFR training research typically employs training volumes ranging from 45 [13] to 75 [55] repetitions each exercise per session. Several investigations have utilized BFR combined with lowload resistance exercise to volitional fatigue [4,65,66]. However, exercise to failure is not submaximal by definition, and therefore may not be appropriate for many clinical populations who would otherwise benefit from BFR training [67].…”

“…This novel strategy involves the application of an inflatable cuff or tourniquet around a limb (proximal to the muscles being trained), which limits blood delivery to and from contracting muscles. Training with BFR can facilitate muscular changes in clinical populations [2,3] and athletes alike [4,5]. While the physiological mechanisms that underpin adaptive responses to BFR training are not yet fully understood, this form of training is becoming popular as a way to enhance muscular responses without the need for high mechanical loads.…”