Affective, perceptual and physiologic responses to isokinetic contractions under blood flow restriction.

BACKGROUND: Blood flow restriction (BFR) has been shown to enhance the effectiveness of low load resistance exercise, but less research has examined its utility in conjunction with maximal isokinetic contractions, which may depend on the restrictive pressure and speed of contraction. METHODS: Individuals reported to the laboratory for three visits to complete three sets of 20 maximal elbow flexion exercises at 60°/s and 300°/s under 0%, 40% and 80% of their arterial occlusion pressure. Muscle thickness was measured before and after exercise, and ratings of discomfort, perceived activation, and exercise-induced feelings were obtained at the completion of each exercise. Fatigue was assessed as the decline in average peak torque across the three sets. RESULTS: A total of 27 individuals (11 females, 16 males) completed the study. There was a significant interaction for torque at both 60°/s and 300°/s (P<0.001), with each increasing pressure resulting in greater fatigue. Muscle swelling was present across all conditions but was lowest in the 40% BFR condition applied during the 300°/s speed. At both 60°/s and 300°/s speeds, the 80% BFR pressure was associated with lower enjoyment, greater discomfort, and greater perceived activation (all P<0.05). CONCLUSIONS: The combined effects of BFR to maximal isokinetic contractions increased fatigue with less of an impact on muscle swelling. These results indicate that BFR may enhance the effectiveness of long-term isokinetic training, but it is also important to consider the addition of BFR was associated with lower levels of enjoyment and greater discomfort which may decrease adherence.

The combined effectiveness of therapeutic ultrasound, electrical stimulations, and blood flow restriction to treat symptoms of muscle damage.

This study assessed whether symptoms of muscle damage could be reduced by a combination of therapeutic ultrasound and electrical stimulations, and whether this could be enhanced by blood flow restriction. Before and 48 h after performing eccentric elbow flexion exercises, individuals completed assessments of muscle damage. A 10-min therapeutic ultrasound and electrical stimulation treatment was then applied with and without blood flow restriction to assess short (5 min) and long-term (24 h) improvements. Twenty-three individuals completed the study (11 females). Data were analysed using Bayesian repeated measures ANOVAs. The damaging exercise increased discomfort (BF10 = 2.93e14) and relaxed joint angle (BF10 = 2425.90) while decreasing pain pressure threshold (BF10 = 289.71). Each of these variables was acutely improved with the combination treatment protocol (all BF10 ≥ 74) with no added effect of blood flow restriction. A combination of therapeutic ultrasound and interferential electrical stimulations appeared effective at acutely alleviating symptoms of muscle damage with no additive effect of blood flow restriction.

Assessing the effectiveness of Compare Assistant for improving intra-rater reliability of ultrasound-measured muscle thickness.

PURPOSE: Muscle thickness measured via ultrasound is commonly used to assess muscle size. The purpose of this study was to determine if the reliability of this measurement will improve if using the Compare Assistant tool, and whether this depends on technician experience and the muscle being assessed. METHODS: Individuals came to the laboratory for two visits each separated by 24 h. On day 1, two ultrasound images were taken on the individual's anterior upper arm (elbow flexors) and anterior lower leg (tibialis anterior) by two inexperienced and one experienced ultrasound technician. On day 2, three images were taken: (1) without looking at the previous images taken on day 1; (2) after re-examining the images taken on day 1, and (3) side-by-side with the images taken on day 1 via Compare Assistant. Bayes Factors (BF10) were used to provide evidence for the null (< 0.33) or alternative (> 3) hypotheses. RESULTS: There was no rater by measurement technique interaction (upper body: BF10 = 0.04, lower body: BF10 = 0.138), nor was there a main effect of measurement technique (upper body: BF10 = 0.052, lower body: BF10 = 0.331), indicating that reliability measures were not improved for either the upper body (CV%, no look: 2.92 vs. Compare Assistant: 2.87) or lower body (CV%, no look: 1.81 vs. Compare Assistant: 1.34) as a result of using Compare Assistant. CONCLUSION: The results of this study suggest that day-to-day reliability of muscle thickness measurement may be limited by random biological variability as opposed to technician error.

A systematic review examining if blood flow restriction can enhance the effectiveness of electrical stimulations.

INTRODUCTION: The use of blood flow restriction (BFR) has been shown to promote greater increases in muscle size and strength when applied during low intensity aerobic exercise and low load resistance exercise. Whether BFR can enhance the effectiveness of E-STIM has been less explored and is the purpose of this study. EVIDENCE ACQUISITION: The databases of Pubmed, Scopus, and Web of Science were searched using the following search: "blood flow restriction" OR "occlusion training" OR "KAATSU" AND "electrical stimulation" OR "E-STIM" OR "neuromuscular electrical stimulation" OR "NMES" OR "electromyostimulation." A three-level random effects restricted maximum likelihood model was computed. EVIDENCE SYNTHESIS: Four studies met the inclusion criteria. There was no additive effect of performing E-STIM under BFR when compared to E-STIM in the absence of BFR [ES: 0.88 (95% CI: -0.28, 2.05); P=0.13]. There was a greater increase in strength when E-STIM was performed under BFR as compared to the same protocol without BFR [ES: 0.88 (95% CI: 0.21, 1.54); P=0.01]. CONCLUSIONS: The lack of effectiveness for BFR to enhance muscle growth may be related to the non-orderly recruitment of motor units when performing E-STIM. The ability of BFR to augment increases in strength may also allow individuals to utilize lower amplitudes to reduce participant discomfort.

Does muscle growth mediate changes in a nonspecific strength task?

The purpose of this study was to determine if muscle growth mediates increases in a strength task which was not directly trained. One hundred fifty-one participants were randomized into control, one-repetition maximum training (1RM-TRAIN), or traditional training (TRAD-TRAIN). Training groups performed isotonic elbow flexion 3x/week for 6 weeks. Anterior muscle thickness at 50%, 60% and 70% upper arm length, and maximal isokinetic torque at 60°/sec were assessed pre- and post-training. Change-score mediation models (adjusted for sex, pre-muscle thickness, and pre-strength) were constructed for each muscle thickness site. The effects of each training group were evaluated relative to the control. Data is presented as coefficient (95% CI). There were no significant relative direct effects on nonspecific strength for either training group outside of the 60% model (1.7 [0.13, 3.27] Nm). The relative effect of 1RM-TRAIN on muscle thickness was greater in 60% (0.09 [0.01, 0.17] cm) and 70% (0.09 [0.00, 0.17] cm) models; while TRAD-TRAIN was greater in all three: (50% = 0.24 [0.15, 0.32]; 60% = 0.24 [0.16, 0.33]; 70% = 0.22 [0.14, 0.31] cm). The effect of muscle thickness on nonspecific strength was only significant for the 60% (-3.06 [-5.7, -0.35] Nm) model. The relative indirect effect on nonspecific strength was not significant for the 1RM-TRAIN or TRAD-TRAIN. Similar to previous findings on specific strength, we did not find evidence for a mediating effect of muscle growth on training induced increases in nonspecific strength. The importance of muscle growth for changes in nonspecifically trained strength may need to be reconsidered.

Sex segregation in strength sports: Do equal-sized muscles express the same levels of strength between sexes?

OBJECTIVES: Concerns have been raised against the current two-sex binary category in sports competitions. The thesis states that if males and females were separated based on muscle size, it would negate the strength advantage between the sexes. We tested the possible sex differences in various strength outcomes when pair-matched for muscle thickness. METHODS: A total of 16 different data sets (n = 963) were assessed to pair-match females with males who had a muscle thickness value within 2%. We further compared the competition performances of the smallest male weight class within the International Powerlifting Federation (IPF) to different weight classes in females. RESULTS: Overall, 76%-88% of the strength assessments were greater in males than females with pair-matched muscle thickness, regardless of contraction types (i.e., isotonic, isometric, isokinetic). Additionally, males in the lightest weight division in the IPF largely outperformed females in heavier weight divisions. CONCLUSIONS: Our results would suggest that segregation based on muscle mass or surrogates of muscle mass (e.g., lean body mass) might not be an appropriate classification to create fair competition within strength sports. This is not to refute the concept of the desegregation of the two-sex binary category but to present data that raises important concerns about the potential sex-based differences in strength performance.

Does performing resistance exercise to failure homogenize the training stimulus by accounting for differences in local muscular endurance?

The prescription of resistance exercise often involves administering a set number of repetitions to be completed at a given relative load. While this accounts for individual differences in strength, it neglects to account for differences in local muscle endurance and may result in varied responses across individuals. One way of potentially creating a more homogenous stimulus across individuals involves performing resistance exercise to volitional failure, but this has not been tested and was the purpose of the present study. Individuals completed 2 testing sessions to compare repetitions, ratings of perceived exertion (RPE), muscle swelling and fatigue responses to arbitrary repetition (SET) vs. failure (FAIL) protocols using either 60% or 30% one-repetition maximum. Statistical analyses assessed differences in the variability between protocols. Forty-six individuals (25 females and 21 males) completed the study. There was more variability in the number of repetitions completed during FAIL when compared to SET protocols. Performing the 60% 1RM condition to failure appeared to reduce the variability in muscle swelling (average variance: 60%-SET = .034, 60%-FAIL = .023) and RPE (average variance: 60%-SET = 4.0, 60%-FAIL = 2.5), but did not alter the variability in muscle fatigue. No differences in variability were present between the SET-30% and FAIL-30% protocols for any of the dependent variables. Performing resistance exercise to failure may result in a more homogenous stimulus across individuals, particularly when using moderate to high exercise loads. The prescription of resistance exercise should account for individual differences in local muscle endurance to ensure a similarly effective stimulus across individuals.Highlights There is a large variance in the number of repetitions individuals can complete even when exercising with the same relative load.Ratings of perceived exertion and muscle swelling responses become more homogenous when exercising to volitional failure as compared to using performing a set number of repetitions, particularly when moderate to higher loads are used.The prescription of exercise should take into consideration the individual's local muscle endurance as opposed to choosing an arbitrary number of repetitions to be completed at a given relative load.

Quantifying the Generality of Strength Adaptation: A Meta-Analysis.

BACKGROUND: Isotonic exercise is the most common mode of strength training. Isotonic strength is often measured in the movement that was exercised, but isometric and isokinetic movements are also commonly used to quantify changes in muscular strength. Previous research suggests that increasing strength in one movement may not lead to an increase in strength in a different movement. Quantifying the increase in strength in a movement not trained may be important for understanding strength training adaptations and making recommendations for resistance exercise and rehabilitation programs. OBJECTIVE: To quantify changes in non-specific strength relative to a control. DESIGN: A systematic review and random effects meta-analysis was conducted investigating the effects of isotonic strength training on isotonic and isokinetic/isometric strength. SEARCH AND INCLUSION: This systematic review was conducted in Google scholar, PubMed, Academic Search Premier, and MENDELEY. To be included in this review paper the article needed to meet the following criteria: (1) report sufficient data for our variables of interest (i.e., changes in isotonic strength and changes in isokinetic or isometric strength); (2) include a time-matched non-exercise control; (3) be written in English; (4) include healthy human participants over the age of 18 years; (5) the participants had to train and test isotonically; (6) the participants had to be tested isokinetically or isometrically on a device different from that they trained on; (7) the non-specific strength task had to test a muscle involved in the training (i.e., could not have trained chest press and test handgrip strength); and (8) the control group and the experimental group had to perform the same number of strength tests. RESULTS: We completed two separate searches. In the original search a total of 880 papers were screened and nine papers met the inclusion criteria. In the secondary search a total of 2594 papers were screened and three additional papers were added (total of 12 studies). The overall effect of resistance training on changes in strength within a movement that was not directly trained was 0.8 (Cohen's d) with a standard error of 0.286. This overall effect was significant (t = 2.821, p = 0.01) and the 95% confidence interval (CI) is 0.22-1.4. The overall effect of resistance training on strength changes within a movement that was directly trained was 1.84 (Cohen's d) with a standard error of 0.296. This overall effect was significant (t = 6.221, p < 0.001) and the 95% CI is 1.23-2.4. CONCLUSION: The results of our meta-analysis suggest that strength increases in both the specific and non-specific strength tests. However, the smaller effect size associated with non-specific strength suggests that it will be difficult for a single study to meaningfully investigate the transfer of strength training adaptions.

The impact of blood flow restricted electrical stimulations on recovery from muscle damage.

BACKGROUND: Both electrical stimulations (E-STIM) and blood flow restriction (BFR) have been shown to treat symptoms of exercise-induced muscle damage, but little is known about their combined effects which was the purpose of this study. METHODS: Individuals completed one set of eccentric elbow flexion exercises to induce muscle damage. Forty-eight hours later, E-STIM was applied using an interferential current administered to both arms for 20 min; however, only one arm completed the E-STIM protocol while also undergoing repeated bouts of BFR (full occlusion for 2 min separated by a 1-min rest intervals). Discomfort and isometric strength were assessed immediately before the damaging exercise, immediately before the treatments, and 0, 10, and 30 min posttreatment. RESULTS: A total of 22 individuals (11 females) completed the study. There were no interactions with respect to discomfort (BF10 = 0.008) or isometric strength (BF10 = 0.009) indicating that the addition of BFR did not alter the effectiveness of E-STIM. There was a main effect of time indicating that the damaging exercise was successful at depressing torque (pre: 284 N, post: 199 N; BF10 = 2.70e9) and inducing discomfort (pre: 0 au, post: 6.4 au; BF10 = 3.21e17). While isometric strength did not recover with the E-STIM treatments, discomfort was reduced at each the immediate post (5.3 au; BF10 = 56 294) 10-min post (5.0 au; BF10 = 46 163), and 30-min post (4.9 au; BF10 = 707 600) time points. CONCLUSION: E-STIM may be useful for treating discomfort, but does not appear capable of recovering strength associated with muscle damage. The efficacy of E-STIM would not appear to be enhanced if performed under BFR.

Blood Flow Restricted Electrical Stimulations to Prevent or Attenuate Symptoms of Muscle Damage.

The objective of this study was to determine if performing electrical stimulations (E-STIM) under blood flow restriction (BFR) would result in a greater protective effect against symptoms of muscle damage. 18 individuals (9 females) completed a damaging bout of exercise followed by a low frequency E-STIM treatment protocol on both arms, one of which was completed under BFR. The treatment protocol was then repeated 24-hours post-exercise. There were main effects of time for muscle thickness (pre: 3.5 cm; 48 h post: 3.8 cm; BF10 = 88.476), discomfort (pre: 0.0 au; 48 h post: 4.2 au; BF10 = 241.996), and isometric strength (pre: 278 N; 48 h post: 232 N; BF10 = 10,289.894) which all changed as a result of the damaging exercise protocol, but there were no differences between conditions [all Bayes Factors (BF10) < 0.28]. The effectiveness of low frequency E-STIM for preventing the onset of exercise-induced muscle damage would not appear to be enhanced if performed under BFR.

Injuries and Strength Training Practices in Collegiate Tennis.

Strength and conditioning practices may influence injury rates in the sport of tennis. Methods: Coaches reported the number injuries over the past year. Coaches were also surveyed on whether their training program included training related to upper-body or lower-body strength, power, muscle growth, and eccentric exercise. Separate regression analyses were run in the upper and lower body to examine the relationship between injuries and participation in training focused on strength, power, growth, and maximal eccentric exercise. A total of 111 coaches were surveyed. The most frequent injuries observed were ankle sprains (144 injures), followed by paraspinal muscle strains (126 injuries). When pooled, there were a total of 355 lower-body and 260 upper-body injuries. Strength and conditioning practices explained 9.9% of the variance of injury rates in the upper body (R2 = 0.099). The only significant predictor of upper-body injury was participation in upper-body muscle growth training (ß = 1.613, p = 0.013). In addition, training practices explained 11.1% of the variance of injury in the lower body (R2 = 0.111). Coaches value injury prevention exercise, sports-specific training and flexibility and mobility training the most, with muscle growth and maximal power ranked lowest. Additionally, the most frequent injuries observed in collegiate tennis players were ankle sprains (144 injures), followed by paraspinal muscle strains (126 injuries).

The impact of postexercise blood flow restriction on local muscle endurance of a remote limb.

BACKGROUND: Studies have examined the influence of postexercise blood flow restriction as a mechanism to activate muscle afferents and assess nonlocal muscle fatigue. Although these studies have assessed fatigue during maximal contractions, less is known about how these afferents may impact submaximal local muscle endurance, which was the purpose of the present study. METHODS: Individuals completed two testing visits which involved completing a set of elbow flexion exercises to volitional failure on the nondominant followed by the dominant arm. During both trials, a pneumatic cuff was placed at the top of the nondominant arm before exercise. This cuff was inflated to either 0% (control) or 70% (experimental) of the individual's arterial occlusion pressure immediately after the set was completed. We then evaluated how this impacted local muscle endurance of the dominant arm using a Bayesian paired samples t-test with an uninformed prior width of 0.707 centred on 0. RESULTS: A total of 36 individuals completed the study (18 females). There was a greater discomfort present in the experimental trial when compared to the control trial (control: 4.5 standard deviation [SD]: 2.4); experimental: 5.8 [SD: 1.9]; BF10 = 61.46), but there were no differences in repetitions completed on the dominant arm (control: 43 [SD: 9], experimental: 43 [SD: 10]; BF10 = 0.179). CONCLUSION: Applying blood flow restriction postexercise induced sensations of discomfort but did not alter the local muscle endurance of the contralateral limb. These results suggest that increasing the activation of muscle afferents does not appear to alter the submaximal muscle endurance of a remote limb.

Isometric tests to evaluate upper and lower extremity functioning in people with multiple sclerosis: reliability and validity.

BACKGROUND: Both upper and lower extremity motor symptoms are common in people with multiple sclerosis (PwMS) and there is a need to develop objective, reliable, and valid outcome measures. The aim of this study was to evaluate the reliability and external validity of the standard and novel isometric tests in the assessment of neuromuscular functioning in both upper (grip force; GF) and lower (knee extensors; KE) extremities in PwMS. METHODS: Twenty-nine relapsing-remitting PwMS (Expanded Disability Status Scale (EDSS)<6) completed isometric and functional tests in upper (grip force) and lower (knee extension) extremity in two separate visits. Isometric testing included maximum force (maxF), maximum rate of force development (maxRFD), and our recently developed novel brief force pulse protocol (BFP). The dependent variables of BFP included rate of force development and relaxation scaling factors (RFD-SF and RFR-SF), which quantifies an individual's ability to scale the rates of force development and relaxation with the magnitude of force pulse produced. PwMS also completed functional tests of upper (9-hole peg (9HPT), finger tapping (FTT)) and lower extremity (25-ft walk test (T25WT), timed up and go (TUG), 5-time sit-to-stand (5StS), and Multiple Sclerosis Spasticity Scale (MSSS-88)). RESULTS: Most isometric outcome measures had high reliability (ICCs>0.87 and CVs<12%). In GF, both RFD-SF and RFR-SF had significant associations with 9HPT and FTT (r's between 0.49-0.55, p<0.05). In KE, while maxF, maxRFD, and RFD-SF were moderately correlated to some of the functional tests, the strongest correlations were observed for the RFR-SF (T25FW, r=0.71; TUG, r=0.60; 5StS, r=0.47; MSSS-88, r=0.60, and EDSS, r=0.71). Multiple linear regression analysis indicated that RFD-SF is the only predictor for 9HPT and RFR-SF is the only predictor of walking speed among the studied variables. CONCLUSIONS: BFP protocol provides highly reliable and relevant outcome measures to evaluate both upper and lower extremity functioning in PwMS. Specifically, the ability to relax muscle forces quickly after a quick force production highly contributes to walking speed in PwMS.

A comparison of variability between absolute and relative blood flow restriction pressures.

INTRODUCTION: Recommendations are that blood flow restriction (BFR) be applied relative to arterial occlusion pressure (AOP) to provide a similar stimulus. PURPOSE: Compare variability of the change in blood flow, shear rate and discomfort between recommended relative pressures and an absolute pressure. METHODS: During one visit, brachial arterial blood flow was measured in 91 participants using pulse-wave Doppler ultrasonography. After 5-min seated rest, AOP was measured. Following another 5-min rest, blood flow and discomfort were assessed twice before cuff inflation as controls (C1 and C2), then again with a cuff inflated to each BFR pressure (all measures separated by 1-min). Change scores from C1 to all subsequent measures were calculated (i.e., C2-C1; 40% AOP-C1; 80% AOP-C1; 100 mmHg-C1). Variability of the changes were compared via pairwise modified Pitman-Morgan tests (α = 0.008). RESULTS: Variance (95% CI) of the change for blood flow (ml/min), shear rate (1/s), and discomfort (AU) had similar trends. C2-C1 differed from all conditions (all p < 0.001), 40% AOP-C1 differed from 80% AOP-C1 and 100 mmHg-C1 (all p < 0.001), which did not differ (both p ≥ 0.117). Blood flow: C2-C1 = 469.79 (357.90, 644.07), 40% AOP-C1 = 1263.18 (962.34, 1731.80), 80% AOP-C1 = 1752.90 (1335.42, 2403.18), 100 mmHg-C1 = 1603.18 (1221.36, 2197.92); shear rate: C2-C1 = 6248.24 (4760.10, 8566.15), 40% AOP-C1 = 14 625.30 (11 142.06, 20 050.95), 80% AOP-C1 = 22 064.02 (16 809.13, 30 249.27), 100 mmHg-C1 = 20 778.76 (15 829.98, 28 487.21); discomfort: C2-C1 = 0.07 (0.05, 0.08), 40% AOP-C1 = 2.03 (1.55, 2.78), 80% AOP-C1 = 4.26 (3.25, 5.84), 100 mmHg-C1 = 4.50 (3.43, 6.17). CONCLUSION: Contrary to previous suggestions, applying relative pressures does not necessarily guarantee a similar stimulus. It seems that higher pressures produce more variable changes even if the external pressure applied is made relative to each individual.

Muscle growth adaptations to high-load training and low-load training with blood flow restriction in calf muscles.

PURPOSE: To compare muscle growth adaptations between traditional high-load training and low-load training with blood flow restriction (BFR) in the calf muscles over 6 weeks. METHODS: 27 trained individuals performed calf exercise in both legs for 6 weeks. Each leg was randomly assigned to one of the two conditions: (1) Traditional (70% of 1RM) training (TRAD); and (2) Low-load (30% of 1RM) training with BFR. In addition, subjects performed standing calf raises with or without BFR. Measures were taken pre- and post-intervention. RESULTS: For the posterior muscle site, there was no condition (BFR vs. TRAD) × time (pre vs. post) interaction (p = 0.15). In addition, there was no main effect for condition (p = 0.83) or time (p = 0.20). For the lateral muscle site, there was no condition × time interaction (p = 0.47). In addition, there was no main effect for condition (p = 0.10) or time (p = 0.57). For the medial muscle site, there was no condition × time interaction (p = 0.60). In addition, there was no main effect for condition (p = 0.44) or time (p = 0.72). For RPE, there was no condition × time interaction. However, there was a main effect for condition (p < 0.05) with BFR having higher RPE. For discomfort, there was no condition × time interaction. However, there was a main effect for condition (p < 0.001) with the BFR condition displaying higher discomfort. CONCLUSION: No muscle growth was detected in the calf musculature. BFR was not more effective at eliciting muscle hypertrophy compared to traditional training. However, it was accompanied with higher exertion and discomfort.

The Effect of Blood Flow Restriction Therapy on Recovery After Experimentally Induced Muscle Weakness and Pain.

ABSTRACT: Wong, V, Dankel, SJ, Spitz, RW, Bell, ZW, Viana, RB, Chatakondi, RN, Abe, T, and Loenneke, JP. The effect of blood flow restriction therapy on recovery after experimentally induced muscle weakness and pain. J Strength Cond Res 36(4): 1147-1152, 2022-The purpose was to determine if blood flow restriction with no external load could be used as a means of active therapy after experimentally induced fatigue and soreness. Twelve women and 7 men (aged 18-35 years) participated in a randomized controlled trial using a within-subject design. The study intervention was 3 consecutive visits. Visit 1 included the fatiguing/soreness-inducing protocol for the elbow flexors, which was performed only once during the study. Torque was measured before/after to confirm individuals began in a weakened state. Subjects then completed blood flow restriction therapy on one arm and the sham therapy on the other. Subjects performed elbow flexion/contraction with no external load on both arms. Torque was measured once more 10 minutes after the fatiguing/soreness-inducing protocol. Twenty-four hours later, soreness and torque were assessed in each arm, followed by another bout of therapy. Forty-eight hours after the initial visit, soreness and torque were measured again. There were no differences (median difference [95% credible interval]) in the recovery of torque between the blood flow restriction and sham therapy conditions at 10 minutes (0.5 [-2.7, 3.8] N·m), 24 hours (-2.34 [-6, 1.14] N·m), or 48 hours (-1.94 [-5.45, 1.33] N·m). There were also no differences in ratings of soreness at 24 hours (-2.48 [-10.05, 5.05]) or 48 hours (2.58 [-4.96, 10.09]). Our results indicate that this specific model of blood flow restriction therapy did not enhance the recovery of the muscle compared with a sham condition without the application of pressure.

Machines and free weight exercises: a systematic review and meta-analysis comparing changes in muscle size, strength, and power.

INTRODUCTION: The aim of this study was to compare changes in muscle size, strength, and power between free-weight and machine-based exercises. EVIDENCE ACQUISITION: The online databases of Pubmed, Scopus, and Web of Science were each searched using the following terms: "free weights" OR barbells OR dumbbells AND machines" up until September 15, 2020. A three-level random effects meta-analytic model was used to compute effect sizes. EVIDENCE SYNTHESIS: When strength was tested using a free-weight exercise, individuals training with free-weights gained more strength than those training with machines (ES: 0.655; [95% CI: 0.269, 1.041]). When strength was tested a machine-based exercise incorporated as part of the machine-based training program, individuals training with machines gained more strength than those training with free-weights (ES: -0.784 [95% CI: -1.223, -0.344]). When strength was tested using a neutral device, machines and free-weight exercises resulted in similar strength gains (ES: 0.128 [95% CI: -0303, 0.559]). There were no differences in the change in power (ES: -0.049 [95% CI: -0.557, 0.460]) or muscle hypertrophy (ES: -0.01 [95% CI: -0.525, 0.545]) between exercise modes. CONCLUSIONS: Individuals looking to increase strength and power should consider the specificity of exercise, and how their strength and power will be tested and applied. Individuals looking to increase general strength and muscle mass to maintain health may choose whichever activity they prefer and are more likely to adhere to.

The Effect of Increasing Blood Flow Restriction Pressure When the Contractions Are Already Occlusive.

CONTEXT: Blood flow restricted exercise involves the use of external pressure to enhance fatigue and augment exercise adaptations. The mechanisms by which blood flow restricted exercise limits muscular endurance are not well understood. OBJECTIVE: To determine how increasing blood flow restriction pressure impacts local muscular endurance, discomfort, and force steadiness when the contractions are already occlusive. DESIGN: Within-participant, repeated-measures crossover design. SETTING: University laboratory. PATIENTS: A total of 22 individuals (13 males and 9 females). INTERVENTION: Individuals performed a contraction at 30% of maximal isometric elbow flexion force for as long as possible. One arm completed the contraction with 100% of arterial occlusion pressure applied, while the other arm had 150% of arterial occlusion pressure applied. At the end of the protocol, individuals were asked to rate their perceived discomfort. MAIN OUTCOME MEASURES: Time to task failure, discomfort, and force steadiness. RESULTS: Individuals had a longer time to task failure when performing the 100% arterial occlusion condition compared with the 150% arterial occlusion pressure condition (time to task failure = 82.4 vs 70.8 s; Bayes factors = 5.77). There were no differences in discomfort between the 100% and 150% conditions (median discomfort = 5.5 vs 6; Bayes factors = 0.375) nor were there differences in force steadiness (SD of force output 3.16 vs 3.31 N; Bayes factors = 0.282). CONCLUSION: The results of the present study suggest that, even when contractions are already occlusive, increasing the restriction pressure reduces local muscle endurance but does not impact discomfort or force steadiness. This provides an indication that mechanisms other than the direct alteration of blood flow are contributing to the increased fatigue with added restrictive pressure. Future studies are needed to examine neural mechanisms that may explain this finding.

Examination of Changes in Echo Intensity Following Resistance Exercise among Various Regions of Interest.

AIM: Within the resistance exercise literature, echo intensity (EI) is often quantified using different regions of interest (ROI). PURPOSE: To compare changes in the EI of images of the biceps muscle using different ROI immediately following exercise as well as 24 and 48 h following exercise. METHODS: Twenty seven non-resistance trained individuals visited the laboratory 4 times. One arm was assigned to the experimental condition, and the other was a non-exercise control. During visit 1, paperwork and strength were measured. During visit, 2 participant's muscles were imaged before performing biceps curls. Additional muscle images were taken immediately after exercise, as well as 24 and 48 h post. EI was measured using three different ROI: 1) Trace around the entire muscle; 2) Small box placed in the middle of the muscle (2 × 2cm); and 3) Maximal rectangular box. Results are displayed as means (95%CI). RESULTS: There was no condition (experimental vs. control) x time (pre, post, 24h and 48h) x box size (small, large, full trace) interaction (p = 0·592). However, there was a main effect for box size (p < 0·001). EI values were higher with the small box [28·2 (23·3, 33·1) AU] compared to the large box [26·8 (22·3, 31·2) AU, p = 0·016] and compared to the full trace [24·2 (20·3, 28·0) AU p < 0·001)]. In addition, EI values were higher with the large box compared to the full trace technique (p = 0·001). CONCLUSION: Similar changes in EI are detected when using different commonly used ROI for analysing EI. However, when larger ROI are examined, EI values appear to be lower.

Is there Evidence for the Suggestion that Fatigue Accumulates Following Resistance Exercise?

It has been suggested that improper post-exercise recovery or improper sequence of training may result in an 'accumulation' of fatigue. Despite this suggestion, there is a lack of clarity regarding which physiological mechanisms may be proposed to contribute to fatigue accumulation. The present paper explores the time course of the changes in various fatigue-related measures in order to understand how they may accumulate or lessen over time following an exercise bout or in the context of an exercise program. Regarding peripheral fatigue, the depletion of energy substrates and accumulation of metabolic byproducts has been demonstrated to occur following an acute bout of resistance training; however, peripheral accumulation and depletion appear unlikely candidates to accumulate over time. A number of mechanisms may contribute to the development of central fatigue, postulating the need for prolonged periods of recovery; however, a time course is difficult to determine and is dependent on which measurement is examined. In addition, it has not been demonstrated that central fatigue measures accumulate over time. A potential candidate that may be interpreted as accumulated fatigue is muscle damage, which shares similar characteristics (i.e., prolonged strength loss). Due to the delayed appearance of muscle damage, it may be interpreted as accumulated fatigue. Overall, evidence for the presence of fatigue accumulation with resistance training is equivocal, making it difficult to draw the conclusion that fatigue accumulates. Considerable work remains as to whether fatigue can accumulate over time. Future studies are warranted to elucidate potential mechanisms underlying the concept of fatigue accumulation.