Effects of low‐intensity bench press training with restricted arm muscle blood flow on chest muscle hypertrophy: a pilot study

Single‐joint resistance training with blood flow restriction (BFR) results in significant increases in arm or leg muscle size and single‐joint strength. However, the effect of multijoint BFR training on both blood flow restricted limb and non‐restricted trunk muscles remain poorly understood. To examine the impact of BFR bench press training on hypertrophic response to non‐restricted (chest) and restricted (upper‐arm) muscles and multi‐joint strength, 10 young men were randomly divided into either BFR training (BFR‐T) or non‐BFR training (CON‐T) groups. They performed 30% of one repetition maximal (1‐RM) bench press exercise (four sets, total 75 reps) twice daily, 6 days week^?1 for 2 weeks. During the exercise session, subjects in the BFR‐T group placed elastic cuffs proximally on both arms, with incremental increases in external compression starting at 100 mmHg and ending at 160 mmHg. Before and after the training, triceps brachii and pectoralis major muscle thickness (MTH), bench press 1‐RM and serum anabolic hormones were measured. Two weeks of training led to a significant increase (P<0.05) in 1‐RM bench press strength in BFR‐T (6%) but not in CON‐T (?2%). Triceps and pectoralis major MTH increased 8% and 16% (P<0.01), respectively, in BFR‐T, but not in CON‐T (?1% and 2%, respectively). There were no changes in baseline concentrations of anabolic hormones in either group. These results suggest that BFR bench press training leads to significant increases in muscle size for upper arm and chest muscles and 1‐RM strength.     

Effects of detraining on muscle strength and mass after high or moderate intensity of resistance training in older adults

This study examined the effects of a 12 weeks detraining period on muscle strength and mass in older adults who had previously participated in a 12 weeks resistance training programme of high [80% of one repetition maximum (1‐RM)] or moderate (60% of 1‐RM) intensity. Twenty older adults (60–74 years), separated into a high (HI; n = 10; age: 65 ± 5 years) and a moderate (MI; n = 10; age: 66 ± 4 years) intensity resistance training group, were measured in the 1‐RM knee extension and flexion strength, and the midthigh cross sectional areas (CSAs) of quadriceps, hamstrings and total thigh before and after a 12 weeks training period as well as after a 12 weeks detraining period. Maximum knee extension and flexion strength and the CSAs of all muscles decreased significantly (P<0·05) with detraining but remained higher (P<0·05) than pretraining levels for both groups. The HI group had a greater decrement (P<0·05) in maximum strength and the CSA of total thigh compared to the MI group but strength levels and the CSA following detraining were higher (P<0·05) for the HI group. The above data suggest that after a short detraining period of 12 weeks, muscle strength and hypertrophy levels of older adults decrease but remain greater than pretraining irrespective of training intensity. Greater declines in muscle strength are observed following HI training but still muscular strength and muscle mass are retained at a higher level than with MI probably due to the higher gains achieved during the training period.     

Relationship between limb and trunk muscle hypertrophy following high-intensity resistance training and blood flow-restricted low-intensity resistance training

We examined the relationship between training-induced limb and trunk muscle hypertrophy in high-intensity resistance training (HIT) or blood flow-restricted low-intensity resistance training (LI-BFR) programmes. Thirty young men were divided into three groups: HIT (n = 10), LI-BFR (n = 10) and non-training control (CON, n = 10). The HIT and LI-BFR groups performed 75% and 30%, respectively, of one-repetition maximal (1-RM) bench press exercise, 3 days per week for 6 weeks. During the training sessions, the LI-BFR group wore elastic cuffs around the most proximal region of both arms. Muscle cross-sectional area (CSA) and 1-RM bench press strength were measured before and 3 days after the final training session. Total training volumes (lifting weight × number of repetitions) for all of the sessions were similar between the two training groups. The training led to a significant increase (P < 0·05) in bench press 1-RM in the two training groups, but not in the CON group. Triceps brachii and pectoralis major muscle CSA increased 8·8% and 15·8% (P < 0·01), respectively, in the HIT group and 4·9% (P < 0·05) and 8·3% (P < 0·01), respectively, in the LI-BFR group, but not in the CON group (-1·1% and 0·0%, respectively). There was significant correlation (r = 0·70, P < 0·05) between increases in triceps brachii and pectoralis major muscle CSA in the HIT group; however, the correlation was lower and non-significant in the LI-BFR group (r = 0·54). Our results suggest that limb and trunk muscle hypertrophy occurs simultaneously during HIT but not during LI-BFR, possibly owing to individual differences in activation of the arm and chest muscles during the training sessions.     

Effect of very low‐intensity resistance training with slow movement on muscle size and strength in healthy older adults

We previously reported that low‐intensity [50% of one repetition maximum (1RM)] resistance training with slow movement and tonic force generation (LST) causes muscle hypertrophy and strength gain in older participants. The aim of this study was to determine whether resistance training with slow movement and much more reduced intensity (30%1RM) increases muscle size and strength in older adults. Eighteen participants (60–77 years) were randomly assigned to two groups. One group performed very low‐intensity (30% 1RM) knee extension exercise with continuous muscle contraction (LST: 3‐s eccentric, 3‐s concentric, and 1‐s isometric actions with no rest between each repetition) twice a week for 12 weeks. The other group underwent intermitted muscle contraction (CON: 1‐s concentric and 1‐s eccentric actions with 1‐s rest between each repetition) for the same time period. The 1RM, isometric and isokinetic strengths, and cross‐sectional image of the mid‐thigh obtained by magnetic resonance imaging were examined before and after the intervention. LST significantly increased the cross‐sectional area of the quadriceps muscle (5·0%, P<0·001) and isometric and isokinetic knee extension strengths (P<0·05). CON failed to increase muscle size (1·1%, P = 0·12), but significantly improved its strength (P<0·05). These results indicate that even if the intensity is as low as 30% 1RM, LST can increase muscle size and strength in healthy older adults. The large total contraction time may be related to muscle hypertrophy and strength gain. LST would be useful for preventing sarcopenia in older individuals.     

Effects of periodic and continued resistance training on muscle CSA and strength in previously untrained men

To determine muscle adaptations to retraining after short-term detraining, we examined the effects of continuous and interrupted resistance training on muscle size and strength in previously untrained men. Fifteen young men were divided into continuous training (CTr) or retraining (RTr) groups and performed high-intensity bench press training. The CTr group trained continuously for 15 weeks, while the RTr group trained for 6 weeks, stopped for a 3-week detraining period and resumed training at week 10. After the initial training phase, increases (P<0·01) in one repetition maximum (1-RM) and magnetic resonance imaging-measured triceps brachii and pectorals major muscle cross-sectional areas (CSAs) were similar in both groups. Muscle CSA and 1-RM increased (P<0·05) continuously for the CTr group, but the muscle adaptations were lower (P<0·05) after the last 6-week training period than after the initial phase. In the RTr group, there were no significant decreases in muscle CSA and 1-RM after the 3-week detraining period, and increases in muscle CSA after retraining were similar to those observed after initial training. Ultimately, improvements in 1-RM and muscle CSA in both groups were similar after the 15-week training period. Our results suggest that compared with continuous 15-week training, 3-week detraining does not inhibit muscle adaptations.     

Effects of low‐intensity resistance exercise with blood flow restriction on coagulation system in healthy subjects

Recent studies have demonstrated that even a low‐intensity resistance exercise can effectively induce muscle hypertrophy and strength increase when combined with moderate blood flow restriction (BFR) into the exercising muscle. Although serious side effects of low‐intensity resistance exercise with BFR have not been reported, a concern of thrombosis has been suggested, because this type of exercise is performed with restricted venous blood flow and pooling of blood in extremities. Thus, the purpose of this study was to investigate the effects of low‐intensity resistance exercise with BFR on coagulation system in healthy subjects. Ten healthy men (25·1 ± 2·8 year) performed four sets of leg press exercises with and without BFR (150–160 mmHg) at an intensity of 30% of one‐repetition maximum (1RM). In each exercise session, one set with 30 repetitions was followed by three sets with 15 repetitions. Blood samples were taken before, and 10 min, 1, 4 and 24 h after the exercise. Prothrombin fragment 1 + 2 (PTF) and thrombin–antithrombin III complex (TAT) were measured as markers of thrombin generation, whereas D‐dimer and fibrin degradation product (FDP) were measured as markers of intravascular clot formation. Changes in plasma volume (PV) were calculated from haemoglobin and hematocrit values. PV reduction was significantly greater after the exercise with BFR than without (P<0·05). However, neither markers of thrombin generation nor intravascular clot formation increased after the exercises. These results suggest that low‐intensity resistance exercise with BFR does not activate coagulation system in healthy subjects.     

Low‐intensity resistance training with slow movement and tonic force generation increases basal limb blood flow

Metabolic syndrome is associated with reductions in basal limb blood flow. Resistance training increasing muscle mass and strength increases basal limb blood flow. Low‐intensity resistance exercise with slow movement and tonic force generation (LST) has been proposed as one of the effective methods of resistance training increasing muscle mass and strength. The hypothesis that LST training increases basal femoral blood flow as well as traditional high‐intensity resistance training at normal speed (HN) was examined. Thirty‐six healthy young men without a history of regular resistance training were randomly assigned to the LST [～55–60% one repetition maximum (1RM) load, 3 s lifting and 3 s lowering with no relaxation phase, n = 12], HN (～85–90% 1RM, 1 s lifting and 1 s lowering with 1 s relaxation, n = 12) or sedentary control (CON, n = 12) groups. Participants in the training groups underwent two whole‐body training sessions per week for 13 weeks. Basal femoral blood flow increased significantly by +18% in LST and +35% in HN (both P<0·05), while there was no such change in CON. There were no significant differences between these increases induced by LST and HN, although the increase in LST corresponded to about half that in HN. In conclusion, not only resistance training in HN but in LST as well, were effective for increasing basal limb blood flow, and that this effect was evident even in healthy young men.     

The influence of exercise load with and without different levels of blood flow restriction on acute changes in muscle thickness and lactate

The aim of this study was to compare exercise with and without different degrees of blood flow restriction (BFR) on acute changes in muscle thickness (MTH) and whole blood lactate (WBL). Forty participants were assigned to Experiment 1, 2 or 3. Each experiment completed protocols differing by pressure, load and/or volume. MTH and WBL were measured pre and postexercise. The acute changes in MTH appear be maximized at 30% one repetition maximum (1RM) with BFR, although the difference between 20% 1RM and 30% 1RM at the lateral site was small (0·1 versus 0·2 cm, P = 0·09). Increasing the exercise load from 20% to 30% 1RM with BFR produces clear changes in WBL (3·7 versus 5·5 mmol l^?1, P<0·001). The acute changes in MTH and WBL for 30% 1RM in combination with BFR were similar to that observed with 70% 1RM and 20 and 30% to failure, albeit at a lower exercise volume. These findings may have implications for designing future studies as it suggest that exercise load (to a point) may have a greater influence on acute changes in MTH and metabolic accumulation than the applied relative pressure.     

Impact of blood flow‐restricted bodyweight exercise on skeletal muscle adaptations

This study ascertains the ability of bodyweight blood flow‐restricted (BFR) exercise training to promote skeletal muscle adaptations of significance for muscle accretion and metabolism. Six healthy young individuals (three males and three females) performed six weeks of bodyweight BFR training. Each session consisted of five sets of sit‐to‐stand BFR exercise to volitional failure with 30‐second inter‐set recovery. Prior to, and at least 72 h after training, muscle biopsies were taken from m. vastus lateralis to assess changes in fibre type‐specific cross‐sectional area (CSA), satellite cell (SC) and myonuclei content and capillarization, as well as mitochondrial protein expression. Furthermore, magnetic resonance imaging was used to assess changes in whole thigh muscle CSA. Finally, isometric knee extensor muscle strength was evaluated. An increase in knee extensor whole muscle CSA was observed at middle and distal localizations after training (3·2% and 3·5%, respectively) (P<0·05), and a trend was observed towards an increase in type I fibre CSA, whereas muscle strength did not increase. Additionally, the number of SCs and myonuclei associated with type I fibres increased by 65·7% and 20%, respectively (P<0·05). No significant changes were observed in measures of muscle capillarization and mitochondrial proteins. In conclusion, six weeks of bodyweight‐based BFR exercise promoted myocellular adaptations related to muscle accretion, but not metabolic properties. Moreover, the study revealed that an appropriate total training volume needs further investigation before recommending bodyweight BFR to patient populations.     

Change in intramuscular inorganic phosphate during multiple sets of blood flow-restricted low-intensity exercise

Muscular blood flow reduction (BFR) during multiple sets of low-intensity exercise training has been shown to elicit muscle hypertrophy and strength gain. Several hypotheses have been proposed to explain the hypertrophic adaptations to low-intensity BFR exercise, which include muscle fatigue with metabolic stress. However, the change in intramuscular inorganic phosphate (Pi, an index of muscle fatigue) during multiple sets of low-intensity exercise with BFR is poorly understood. Eight men performed four sets of unilateral plantar flexion exercise (20% 1-RM) on a (31)P-magnetic resonance spectroscopy. Each subject wore a cuff (5-cm wide) on the most proximal portion of the thigh; the cuff was inflated during the exercise session at three different pressures [0 mmHg as the control ± (CON), 180 mmHg as moderate restriction (BFR-M) and 230 mmHg as high restriction (BFR-H)]. During the first and second exercise sets, the increase in Pi was higher (P<0·05) with BFR-H than with BFR-M and CON. On the other hand, the decrease in Pi was lower with BFR-H than with CON during the second and third rest periods between sets. As a result, the Pi concentration increased progressively (P<0·05) with BFR-H, while the Pi was relatively constant with BFR-M and CON during the exercise session. Our results suggest that intramuscular Pi accumulation during multiple sets of low-intensity exercise can be produced only by a high level of BFR, but not by moderate reduction. The Pi accumulation was associated both with exercise and with the rest period between sets.     

Effect of strength training with blood flow restriction on muscle power and submaximal strength in eumenorrheic women

Blood flow restriction (BFR) training stimulates muscle size and strength by increasing muscle activation, accumulation of metabolites and muscle swelling. This method has been used in different populations, but no studies have evaluated the effects of training on muscle power and submaximal strength (SS) in accounted for the menstrual cycle. The aim of this study was to analyse the effect of strength training (ST) with BFR on the muscle power and SS of upper and lower limbs in eumenorrheic women. Forty untrained women (18–40 years) were divided randomly and proportionally into four groups: (i) high-intensity ST at 80% of 1RM (HI), (ii) low-intensity ST at 20% of 1RM combined with partial blood flow restriction (LI + BFR), (iii) low-intensity ST at 20% of 1RM (LI) and d) control group (CG). Each training group performed eight training sessions. Tests with a medicine ball (MB), horizontal jump (HJ), vertical jump (VJ), biceps curls (BC) and knee extension (KE) were performed during the 1st day follicular phase (FP), 14th day (ovulatory phase) and 26–28th days (luteal phase) of the menstrual cycle. There was no significant difference among groups in terms of the MB, HJ, VJ or BC results at any time point (P>0·05). SS in the KE exercise was significantly greater in the LI + BFR group compared to the CG group (P = 0·014) during the LP. Therefore, ST with BFR does not appear to improve the power of upper and lower limbs and may be an alternative to improve the SS of lower limbs of eumenorrheic women.     

Morpho‐functional response of the elbow extensor muscles to twelve‐week self‐perceived maximal resistance training

The aim of this study was to determine morphological and functional changes of the elbow extensor muscles in response to a 12‐week self‐perceived maximal resistance training (MRT). Twenty‐one healthy sedentary young men were engaged in elbow extensor training using isoacceleration dynamometry for 12 weeks with a frequency of five sessions per week (five sets of ten maximal voluntarily contractions, 1‐min rest period between each set). Prior to, at 6 weeks and after the training, a series of cross‐sectional magnetic resonance images of the upper arm were obtained and muscle volumes were calculated. Maximal and endurance strength increased (P<0·01) by 15% and 45% at 6 weeks, and by 29% and 70% after 12 weeks compared with baseline values, while fatigue rate of the elbow extensors decreased by 67%. The volume of triceps brachii increased in both arms (P<0·01) by 4% at 6 weeks, and by 8% after 12 weeks compared with baseline values (right arm – from 487·4 ± 72·8 cm³ to 505·8 ± 72·3 cm³ after 6 weeks and 525·3 ± 73·7 cm³ after 12 weeks; left arm – from 475·3 ± 79·1 cm³ to 493·2 ± 72·7 cm³ after 6 weeks and 511·3 ± 77·0 cm³ after 12 weeks). A high correlation was found between maximal muscle strength and muscle volume prior (r² = 0·62) and after (r² = 0·69) the training (P≤0·05). A self‐perceived MRT resulted in an increase in maximal and endurance strength. Morphological adaptation changes of triceps brachii as a result of 12‐week specific strength training can explain only up to 26% of strength gain.     

Acute response of peripheral CCr5 chemoreceptor and NK cells in individuals submitted to a single session of low‐intensity strength exercise with blood flow restriction

The purpose of this study was to compare the peripheral expression of natural killers and CCR5 in a session of low‐intensity strength training with vascular occlusion and in high‐intensity training. Young males were randomized into session groups of a high‐intensity strength training (HI) and a session group of low‐intensity strength training with vascular occlusion (LI‐BFR). The exercise session consisted in knee extension and bicep curl in 80% 1RM (HI) and 30% 1RM (LI‐BFR) with equalized volumes. Blood collection was made before, immediately after and 24 h after each training session. Immunophenotyping was carried out through CD195+ (CCR5) e CD3‐CD16+CD56+ (NK) in peripheral blood and analysed by flow cytometry and presented in frequency (%). Peripheral frequency of NK cells showed no significant difference in LI‐BFR group in time effect, while a gradual reduction of NK cells was identified in HI group in before‐24 h postexercise and after‐24 h postexercise comparison. However, significant differences have been found in relative change of NK cells immediately after exercise between sessions. In addition, HI and LI‐BFR groups showed a significant reduction in the cells expressed CCR5 during 24 h postsession compared to the postsession, but CCR5 also differed when comparing before‐24 h after session in the HI group. No differences were observed amongst the groups. LIO induced CCR5 response similar to the HI session, while the NK cells remained in similar frequency during the studied moments in LI‐BFR, but not in HI group, suggesting that local hypoxia created by the blood flow restriction was able to prevent a change in the frequency of peripheral cells and a possible immunosuppression.     

Hamstrings‐to‐quadriceps strength and size ratios of male professional soccer players with muscle imbalance

The aim of this study was to determine the correlation between the concentric hamstrings/quadriceps muscle strength (H_con:Q_con) and cross‐sectional area ratios (H_csa:Q_csa) in professional soccer players with H_con:Q_con imbalance. Nine male professional soccer players (25·3 ± 4·1 years) performed five maximal concentric contractions of the knee extensors (KE) and flexors (KF) at 60 s^?1 to assess H_con:Q_con. The test was performed using the dominant (preferred kicking), and non‐dominant limb with a 5‐min recovery period was allowed between them. Only players with H_con:Q_con < 0·60 (range: 0·45–0·59) in both limbs were included in this study. The muscle cross‐sectional area (CSA) of KE and KF was determined by magnetic resonance imaging. The correlations between H_con:Q_con and H_csa:Q_csa in the dominant leg (r = ?0·33), non‐dominant leg (r = 0·19) and in the both legs combined (r = 0·28) were not statistically significant (P>0·05). Thus, the H_con:Q_con seems not to be determined by H_csa:Q_csa in professional soccer players with H_con:Q_con imbalance.     

Reproducibility of blood oxygen level‐dependent signal changes with end‐tidal carbon dioxide alterations

Hypercapnia has been utilized as a stimulus to elicit changes in cerebral blood flow (CBF). However, in many instances it has been delivered in a non‐controlled method that is often difficult to reproduce. The purpose of this study was to examine the within‐ and between‐visit reproducibility of blood oxygen level‐dependent (BOLD) signal changes to an iso‐oxic square wave alteration in end‐tidal carbon dioxide partial pressure (P_etCO₂). Two 3‐Tesla (3T) MRI scans were performed on the same visit, with two square wave alterations administered per scan. The protocol was repeated on a separate visit with minimum of 3 days between scanning sessions. P_etCO₂ was altered to stimulate changes in cerebral vascular reactivity (CVR), while P_etO₂ was held constant. Eleven subjects (six females; mean age 26·5 ± 5·7 years) completed the full testing protocol. Excellent within‐visit square wave reproducibility (ICC > 0·75) was observed. Similarly, square waves were reproducible between scanning sessions (ICC > 0·7). This study demonstrates BOLD signal changes in response to alterations in P_etCO₂ are reproducible both within‐ and between‐visit MRI scans.     

Effects of blood flow restriction duration on muscle activation and microvascular oxygenation during low‐volume isometric exercise

The purpose of the investigation was to observe how varying occlusion durations affected neuromuscular activation and microvascular oxygenation during low‐volume isometric knee extension exercise. Healthy, recreationally active males performed isometric knee extension at a variety of submaximal intensities under different blood flow restriction (BFR) occlusion durations. The occlusion pressure (130% SBP) was applied either 5 min prior to exercise (PO), immediately prior to exercise (IO) or not during exercise (CON). Surface electromyography (sEMG) and near‐infrared spectroscopy (NIRS) was used to record the neuromuscular activation and microvascular oxygenation of the knee extensors during exercise. No difference in sEMG was observed in the vastus lateralis or vastus medialis during any exercise condition or any submaximal intensity. PO elicited greater microvascular deoxygenation (deoxy‐[Hb + Mb]) compared to CON (P≤0·05) at all submaximal intensities and also compared to IO at 20% maximal voluntary contraction (MVC). IO resulted in a greater deoxy‐[Hb + Mb] response during low‐intensity exercise (20% and 40% MVC) compared to CON (P≤0·05). These findings suggest that applying BFR 5 min before exercise can enhance the exercise‐induced metabolic stress (i.e. deoxy‐[Hb + Mb]), measured via NIRS, during low‐intensity exercise (20% MVC) compared to applying BFR immediately prior to exercise. Furthermore, the increased metabolic stress observed during IO is attenuated during high‐intensity (60% MVC, 80% MVC) exercise when compared to CON conditions. Knowledge of the changes in exercise‐induced metabolic stress between the various occlusion durations may assist in developing efficient BFR exercise programmes.     

Effects of resistance training with blood flow restriction on haemodynamics: a systematic review

This study systematically reviewed the available scientific evidence on the changes promoted by low‐intensity (LI) resistance training (RT) combined with blood flow restriction (BFR) on blood pressure (BP), heart rate (HR) and rate‐pressure product (RPP). Searches were performed in databases (PubMed, Web of Science^?, Scopus and Google Scholar), for the period from January 1990 to May 2015. The study analysis was conducted through a critical review of contents. Of the 1 112 articles identified, 1 091 were excluded and 21 met the selection criteria, including 16 articles evaluating BP, 19 articles evaluating HR and four articles evaluating RPP. Divergent results were found when comparing the LI protocols with BFR versus LI versus high intensity (HI) on BP, HR and RPP. The evidence shows that the protocols using continuous BFR following a LIRT session apparently raise HR, BP and RPP compared with LI protocols without BFR, although increases significantly in BP seem to exist between the HI protocols when compared to LI protocols. Haemodynamic changes (HR, SBP, DBP, MBP, RPP) promoted by LIRT with BFR do not seem to differ between ages and body segments (upper or lower), although they are apparently affected by the width of the cuff and are higher with continuous BFR. However, these changes are within the normal range, rendering this method safe and feasible for special populations.