Acute and Chronic Bone Marker and Endocrine Responses to Resistance Exercise With and Without Blood Flow Restriction in Young Men

Abstract

In this study, we compared acute and chronic bone marker and hormone responses to 6 weeks of low intensity (20% 1RM) blood flow restriction (BFR20) resistance training to high intensity (70% 1RM) traditional resistance training (TR70) and moderate intensity (45% 1RM) traditional resistance training (TR45) in young men (18–35 years). Participants were randomized to one of the training groups or to a control group (CON). The following training programs were performed 3 days per week for 6 weeks for knee extension and knee flexion exercises: BFR20, 20%1RM, 4 sets (30, 15, 15, 15 reps) wearing blood flow restriction cuffs around the proximal thighs; TR70, 70% 1RM 3 sets 10 reps; and TR45, 45% 1RM 3 sets 15 reps. Muscle strength and thigh cross-sectional area were assessed at baseline, between week 3 and 6 of training. Acute bone marker (Bone ALP, CTX-I) and hormone (testosterone, IGF-1, IGFBP-3, cortisol) responses were assessed at weeks 1 and 6, with blood collection done in the morning after an overnight fast. The main findings were that the acute bone formation marker (Bone ALP) showed significant changes for TR70 and BFR20 but there was no difference between weeks 1 and 6. TR70 had acute increases in testosterone, IGF-1, and IGFBP-3 (weeks 1 and 6). BFR20 had significant acute increases in testosterone (weeks 1 and 6) and in IGF-1 at week 6, while TR45 had significant acute increases in testosterone (week 1), IGF-1 (week 6), and IGFBP-3 (week 6). Strength and muscle size gains were similar for the training groups. In conclusion, low intensity BFR resistance training was effective for stimulating acute bone formation marker and hormone responses, although TR70 showed the more consistent hormone responses than the other training groups.

Hormonal, immune, and oxidative stress responses to blood flow‐restricted exercise

“…A total of seven studies evaluated acute IGF-1 secretion at initial (n = 6), intermediate (n = 3), and late (n = 3) timepoints post-exercise. 35,45,46,70,75,77,79 There was no significant difference in IGF-1 plasma levels at the initial (SMD = 0.61 [95% CI −0.43, 1.65]) and intermediate (SMD = 0.34 [95% CI −0.41, 1.09]) post-exercise phases when comparing LL-BFRRE to overall FFRE. When performing subgroup analysis based on loading intensities, there was a borderline significant increase in IGF-1 plasma levels at the initial (SMD = 1.14 [95% CI −0.15, 2.42]) and intermediate (SMD = 0.88 [95% CI −0.14, 1.91]) post-exercise timepoints in LL-BFRRE compared to LL-FFRE.…”

“…Nine studies measured acute testosterone responses following LL-BFRRE compared to FFRE in the initial (n = 7), intermediate (n = 6), and late (n = 4) post-exercise time intervals. 35,[44][45][46]70,71,74,76,78 No differences in testosterone plasma levels were observed in the initial (SMD = 0.35 [95% CI −0.34, 1.05]) and intermediate (SMD = 0.55 [95% CI −0.26, 1.36]) post-exercise phase when comparing LL-BFRRE to overall FFRE. Subgroup analysis on load intensity did not demonstrate any difference at the initial and intermediate post-exercise time intervals between LL-BFRRE and LL-FFRE or HL-FFRE, respectively.…”

“…A total of seven studies compared the initial (n = 6), intermediate (n = 4), and late (n = 1) responses in postexercise plasma cortisol levels between LL-BFRRE and overall FFRE. 35,44,46,[70][71][72][73] Production in cortisol plasma levels did not differ between LL-BFRRE and FFRE at the initial (SMD = 0.65 [95% CI −0.00, 1.31]) and intermediate (SMD = 0.60 [95% CI −0.47, 1.68]) post-exercise phases. Pertaining to the single study at the late post-exercise timepoints, an increase in plasma cortisol levels was detected for LL-BFRRE compared to LL-FFRE.…”

“…Also, similar changes in structural and mechanical tendon properties have been observed following LL-BFRRE compared to HL-FFRE. 30,31 The adaptive mechanisms of LL-BFRRE have been proposed to involve a hypoxic cellular milieu leading to high levels of metabolic stress, 32,33 increased fiber type recruitment, [34][35][36][37] proliferation of myogenic satellite cells leading to increased numbers of myonuclei, [38][39][40] angiogenesis, 37,41,42 along with elevated acute hormonal, [43][44][45][46] immune, [47][48][49] and oxidative stress responses. [50][51][52] While the mechanisms of hypertrophy and strength gains related to training-induced elevations in endogenous hormone secretion remain a matter of controversy, [53][54][55] it has been speculated that certain circulating and paracrine hormones, for example, testosterone and IGF-1, may play a critical role in activating intracellular signaling pathways (Akt-mTOR-P70 S6k ) and regulating myofibrillar protein synthesis.…”

Effects of blood flow restriction training on anthropometric and blood lipids in overweight/obese adults: Meta-analysis

“…As well, blood flow restriction combined with endurance training has also been shown to improve cardiopulmonary health ( Conceição and Ugrinowitsch, 2019 ). Furthermore, BFRT can effectively improve muscle mass and strength in different populations ( Davids et al, 2021 ; Korkmaz et al, 2022 ), improve muscle fitness ( Hill et al, 2021 ), increase aerobic capacity ( Billaut et al, 2022 ), promote knee rehabilitation ( Centner et al, 2019 ), stimulate acute bone formation markers and hormonal responses ( Bemben et al, 2022 ), and improve athletic performance thereby maintaining overall good health ( Wortman et al, 2021 ). However, in the field of BFRT intervention for overweight/obesity, studies on anthropometric indicators and blood lipids have shown different results ( Da Silva et al, 2020 ; Kim and LeeDongminWon, 2021 ; Mohammadiyan et al, 2021 ; Yong et al, 2021 ).…”