Increased Muscle Size Research Articles

Resistance training induced changes in strength and specific force at the fiber and whole muscle level: a meta-analysis

Considerable debate exists as to whether increases in strength that occur with resistance exercise are the result of increases in muscle size. Most studies have attempted to answer this question using assessments of whole muscle size and voluntary muscle strength, but examining changes at the individual muscle fiber level may also provide some insight. The purpose of this meta-analysis was to compare adaptations at the whole muscle and individual fiber level. A meta-analysis was conducted in February, 2018 including all previously published papers and was analyzed using a random effects model. There were no differences (p = 0.88) when comparing hypertrophy at the whole muscle (4.6%) and individual fiber level (7.0%), but significantly larger (p < 0.001) strength gains were observed at the whole muscle level (43.3%) relative to the individual fiber (19.5%). Additionally, there was an increase in the specific tension of type 1 muscle fibers (p = 0.013), but not type 2 muscle fibers (p = 0.23) which was driven by similar increases in strength (type 1: 17.5%, type 2A: 17.7%), despite differences in muscle size (type 1: 6.7%, type 2A: 12.1%). These results support the hypothesis that the neural adaptations play a large role in increasing isotonic whole muscle strength, but also demonstrate that an improvement in specific tension of type 1 muscle fibers is present. These results would suggest that some mechanism intrinsic to the muscle fiber, and independent of muscle growth, may also be contributing to strength increases in response to resistance exercise providing an avenue for future research.

A12839 Angiotensin 1-7 functionally recovers aging-induced locomotive dysfunction, but is not associated with accelerated aging phenotypes in angiotensin-converting-enzyme 2 knockout mice

Objectives: The angiotensin-converting enzyme 2 (ACE2)-angitotensin 1-7 (A1-7)-A1-7 receptor (Mas) axis has been shown to have a protective role in the renin-angiotensin system (RAS). We recently found that ACE2 knockout (KO) mice exhibit earlier aging-associated muscle weakness, and A1-7 restores muscle weakness in aging mice. As ACE2 has a multifunctional role outside the RAS, we investigated the dependence on the A1-7-Mas pathway in the effect of ACE2 on physiological aging including locomotive dysfunction with muscle weakness and osteoporosis in mice. Methods: Wildtype (WT), ACE2KO, and MasKO mice were subjected to periodical grip strength measurement, followed by administration of A1–7 (100 ng/kg/min) or saline for 4 weeks with an osmotic pump in 24-month-old mice. Results: ACE2KO mice exhibited decreased grip strength compared with WT mice after 6 months of age, while MasKO mice had grip strength similar to WT mice during aging. A1-7 infusion at 24 months old improved grip strength with increased muscle size in WT and ACE2KO mice but not in MasKO mice. A1–7 significantly increased bone volume in WT and ACE2KO mice, but not in MasKO mice. Histological and gene expression analysis revealed that tissue aging including skin and adipose tissue was accelerated in aging ACE2KO mice, but not in MASKO mice, compared to WT mice. Conclusion: A1-7 improves muscle weakness and osteoporosis in aged mice via a Mas-dependent pathway. In contrast, the different aging phenotypes between ACEKO and MasKO mice suggest the A1-7-independent effect of ACE2 on senescence.

Hemodynamic Responses to Low-Load Blood Flow Restriction and Unrestricted High-Load Resistance Exercise in Older Women.

Introduction: Blood flow restriction (BFR) during low-load resistance exercise increases muscle size similarly to high-load training, and may be an alternative to lifting heavy weights for older people at risk of sarcopenia. However, few studies have addressed the safety of such exercise in older people, or whether this is impacted by the actual exercises performed during training. This study aimed to compare the acute hemodynamic and perceptual responses during low-load BFR exercise to unrestricted low-load and high-load exercise in older women, and to determine whether these responses depend on the type of exercise performed.Methods: Fifteen older women (63–75 year) were assessed for maximal strength (1RM) in the leg press and leg extension. Participants then completed three protocols using these exercises in a randomized order: (1) low-load exercise (LL); (2) low-load exercise with BFR (LLBFR), and; (3) high-load exercise (HL). Blood pressure was assessed at baseline and after each set, and impedance cardiography measured cardiovascular function during trials. Rating of perceived exertion (RPE) and muscle soreness scores were obtained throughout trials.Results: Baseline hemodynamic values were consistent between trials. Systolic, diastolic, and mean arterial pressures were higher in LLBFR compared with HL and LL (p ≤ 0.021). The LL condition resulted in lower heart rate (p ≤ 0.002) and rate-pressure product (p ≤ 0.011) responses compared with LLBFR and HL. The leg press generally conferred greater hemodynamic and perceptual demands than the leg extension for all conditions (p ≤ 0.002). RPE was lower during LL compared with LLBFR and HL (p ≤ 0.008), and there were no between-condition differences in perceived muscle soreness.Conclusion: The blood pressure data indicate that LLBFR causes greater stress on the vasculature than LL and HL exercise, and that the leg press was generally more demanding than the leg extension. While additional cardiovascular measures were similar between LLBFR and HL conditions, caution should be advised when prescribing BFR exercise for individuals with compromised cardiac or vascular function. Nevertheless, LLBFR and HL exercise were perceived similarly, indicating that BFR training may be viable for healthy older people.

Testosterone and Resistance Training Increased Muscle Size Compared to Testosterone Only after Spinal Cord Injury

Neuromuscular electrical stimulation (NMES)-resistance training (RT) and testosterone replacement therapy (TRT) have been used to increase lean mass after SCI. To investigate the combined effects of TRT+NMES-RT compared to TRT only on muscle size in men with SCI.

Functional Anaerobic and Strength Training in Young Adults with Cerebral Palsy.

This study aimed to investigate the efficacy of a 12-wk combined functional anaerobic and strength training program on neuromuscular properties and functional capacity in young adults with spastic-type cerebral palsy. A total of 17 young adults (21 ± 4 yr, 9 males, Gross Motor Function Classification System I = 11 and II = 6) were randomized to 12 wk, 3 sessions per week, of high-intensity functional anaerobic and progressive resistance training of the lower limbs (n = 8), or a waitlist control group (n = 9). Pre- and posttraining plantarflexor and tibialis anterior muscle volumes and composition, passive and active plantarflexor muscle properties, and functional capacity outcomes were assessed. The training group had higher values compared with the control group (adjusted mean difference) at 12 wk for the following: more- and less-impaired total plantarflexor and tibialis anterior muscle volumes, maximum isometric plantarflexion strength, muscle power sprint test peak power, agility shuttle time, composite functional strength score, and 6-min walk test distance. The change in total plantarflexor muscle volume was associated with the change in plantarflexor muscle strength. There were relationships between the change in plantarflexor muscle strength and the change in functional capacity outcomes (functional strength; 6-min walk test). Combined functional anaerobic and strength training increased muscle size, strength, and functional capacity in young adults with cerebral palsy. The addition of anaerobic training to progressive resistance training programs assists in the transfer to improved functional capacity.

Obturator externus was larger, while obturator internus size was similar in ballet dancers compared to nondancing athletes

ObjectivesTo compare the cross-sectional area (CSA) of hip external rotators, obturator externus (OE) and obturator internus (OI), in ballet dancers and nondancing athletes, and evaluate the relationship between obturator muscle size and hip pain. DesignCase-control study. SettingElite ballet and sport. Participants33 male and female professional ballet dancers and 33 age and sex-matched athletes. Main outcome measuresCSA's of OE and OI measured on magnetic resonance imaging (MRI) of one hip. Hip pain was scored with the Copenhagen Hip and Groin Outcome Score (HAGOS): HAGOS pain score of 100 was defined as no pain and a score less than 100 was defined as pain. Participants weight and height. ResultsEstimated marginal mean CSA of OE was 14% larger in dancers than athletes (p = 0.01, ηp2 = 0.1); the size of OI was similar (p > 0.05). Men and women in both groups had similar sized OI and OE. There was no interaction between the estimated marginal mean CSA of either obturator and hip pain. ConclusionsIt appears that ballet selectively increases muscle size of OE, but not OI. Obturator size was not related to mild hip pain, as OE and OI size was similar in dancers and athletes with and without pain.

The Effects Of Cuff Width On Hemodynamics In The Legs During Blood Flow Restriction

Blood flow restriction allows individuals to exercise with low loads while producing similar increases in muscle size as high load resistance training. It has been suggested that the pressure should be made relative to the individual (as a percentage of their arterial occlusion pressure), but it remains unknown if a given pressure results in a similar reduction in blood flow, and further, whether this differs based on the width of the cuff being applied. PURPOSE: To examine hemodynamic responses to various relative pressures in the supine position using two commonly used cuffs (10 cm and 12 cm). METHODS: Participants (men=17, women=14) came to the laboratory for two visits. One cuff (10 cm or 12 cm) was randomly applied to the right proximal thigh for each visit and arterial occlusion pressure was measured. Ultrasound measures of blood flow, mean blood velocity, peak blood velocity, and artery diameter were taken from the posterior tibial artery at rest and during the application of 10% increments of the arterial occlusion pressure. A repeated measures ANOVA was used to examine differences across conditions. RESULTS: There was no significant interaction or overall difference between the 10 cm and 12 cm cuff relating to blood flow [-0.501 (7.9) ml•min-1, p = 0.728], mean blood velocity [-0.168 (1.7) cm•sec-1, p = 0.590], peak blood velocity [0.586 (11.7) cm•sec-1, p = 0.783], or artery diameter [0.003 (0.02) cm, p = 0.476]. There was a main effect of pressure for blood flow (p < 0.05), mean blood velocity (p < 0.05), peak blood velocity (p < 0.05), and artery diameter (p < 0.05), with each decreasing with increasing pressures. Peak blood velocity increased until 60% of arterial occlusion pressure before decreasing with increased pressure. The 80% and 90% arterial occlusion pressures reduced blood flow by 69.4% and 79.3% respectively when collapsed across the 10 cm and 12 cm cuffs. No other pressures differed significantly between the relative applied pressure and amount of blood flow restricted. CONCLUSIONS: Provided relative pressures are applied, cuff width appears to have little to no effect on the blood flow response at rest. Importantly, relative pressures may not indicate the magnitude of blood flow being reduced (e.g. 80% arterial occlusion may not reduce 80% of blood flow), particularly at higher arterial occlusion pressures.

Anabolic Steroid Effect on the Liver.

Anabolic steroids are synthetic derivatives of testosterone shown to increase muscle size and strength. Chemical substitutions on the testosterone molecule cause increased potency and duration of action. The 17-α-alkylation modification allows steroids to be taken orally, but the slower clearance in the liver makes them more hepatotoxic. The frequency and severity of side effects depends on several factors including the formulation of the drug, route of administration, dosage, duration of use, and individual sensitivity and response. Anabolic steroid users tend to take supraphysiologic doses or multiple steroids and other drugs simultaneously which increases risk of adverse effects. Hepatotoxicity can be seen as elevated liver transaminases, acute cholestatic syndrome, chronic vascular injury, hepatic tumors, and toxicant-associated fatty liver disease, as well as significant changes in lipoproteins. Many of these changes will stabilize or reverse with cessation of steroid use, but some can be life-threatening. Over-the-counter supplements can be contaminated with anabolic steroids, causing hepatotoxicity in unsuspecting consumers.

Resistance exercise and sports performance: The minority report

Resistance exercise is typically performed to increase both muscle size and strength and is regularly incorporated into training programs for sports performance. Presumably, the exercise would be expected to increase the force producing capabilities of skeletal muscle, which may have subsequent influence on various sports related abilities. Interestingly, few studies are designed to examine sports related benefits of resistance exercise while including a proper control group to account for adaptations to simply performing the sports related task. Much of our knowledge on resistance exercise for sport is based off cross-sectional work showing that stronger athletes tend to perform at the highest level, along with cross-sectional work demonstrating that higher levels of strength are associated with various performance related parameters. Although there is a large body of cross-sectional literature providing a rationale for resistance exercise for sport, its implementation is largely based on the following: 1) An increase in muscle size will produce an increase in strength and 2) a stronger muscle will increase sports performance. However, there is a lack of evidence to support these assumptions. The weight of evidence suggests that resistance exercise may indirectly impact sports performance through injury prevention, as opposed to directly improving sport related abilities.

Daytime and nighttime casein supplements similarly increase muscle size and strength in response to resistance training earlier in the day: a preliminary investigation

BackgroundCasein protein consumed before sleep has been suggested to offer an overnight supply of exogenous amino acids for anabolic processes. The purpose of this study was to compare supplemental casein consumed earlier in the day (DayTime, DT) versus shortly before bed (NightTime, NT) on body composition, strength, and muscle hypertrophy in response to supervised resistance training.MethodsThirteen males participated in a 10-week exercise and dietary intervention while receiving 35 g casein daily. Isocaloric diets provided 1.8 g protein/kg body weight.ResultsBoth groups increased (p < 0.05) in lean soft tissue (DT Pre: 58.3 ± 10.3 kg; DT Post: 61.1 ± 11.1 kg; NT Pre: 58.3 ± 8.6 kg; NT Post: 60.3 ± 8.2 kg), cross-sectional area (CSA, DT Pre: 3.4 ± 1.5 cm2; DT Post: 4.1 ± 1.7 cm2; NT Pre: 3.3 ± 1.6 cm2; NT Post: 3.7 ± 1.6 cm2) and strength in the leg press (DT Pre: 341 ± 87.3 kg; DT Post: 421.1 ± 94.0 kg; NT Pre: 450.0 ± 180.3 kg; NT Post: 533.9 ± 155.4 kg) and bench press (DT Pre: 89.0 ± 27.0 kg; DT Post: 101.0 ± 24.0 kg; NT Pre 100.8 ± 32.4 kg; NT Post: 109.1 ± 30.4 kg) with no difference between groups in any variable (p > 0.05).ConclusionsBoth NT and DT protein consumption as part of a 24-h nutrition approach are effective for increasing strength and hypertrophy. The results support the strategy of achieving specific daily protein levels versus specific timing of protein ingestion for increasing muscle mass and performance.Trial registrationClinicalTrials.gov Identifier: NCT03352583.

INFLUENCE OF LOW, MEDIUM AND HIGH INTENSITY OF RESISTANCE TRAINING ON MUSCULAR HYPERTROPHY, AND SELECTED HEALTH RELATED FITNESS VARIABLES AMONG UNDERWEIGHT MALES

Introduction: Underweight (UW) individuals face lot of problems in increasing muscle size and also increasing body weight and fitness levels. Resistance training (RT) plays a very important role in increasing hypertrophy of the muscles one and all in general. (ACSM, 2009) stated that the resistance exercise for healthy adults provides program design recommendations for muscle hypertrophy [3]. The purpose of this study is to find out the influence of low, Medium and high intensity of (RT) on the muscular hypertrophy and selected health related fitness variables among the underweight males. Method: A group of (N=40) subjects was selected randomly to participate in this study. The age of the participants was in the range of 18-24 years, (RT) program was employed for 12 weeks, two days in a week, 45 minutes of training per session. The subjects were segregated into two groups namely Group-A (n=20, experimental group), Group –B (n=20 control group). The (RT) was employed on experimental group. Control group was not given any above mentioned special training program. The tests (pre and post) considered for this study was health related fitness variables are as follows; body composition, muscular strength, muscular endurance, Flexibility and cardio-vascular endurance. And test for muscular hypertrophy i.e. (neck, shoulders, chest, arms, waist, hips, thigh and calf; To compare the mean differences from pre to post test, mean, standard deviation, and t-test was computed by the help of statistica software. Results &amp; Discussion: 12 weeks of training protocol had revealed significant performance from pre to posttest among the subjects with regard to the selected fitness variables and presented by percentages i.e. BMI (4.45%), bench press (35.12%), sit-ups test (22.34%), sit &amp; reach test (26.83%), and 12 min run &amp; walk test (26.94%). Furthermore the muscular hypertrophy was enhance among the underweight students i.e. Neck (2.61%), shoulder (2.95%), chest (6.75%), arms (10.43%), waist (8.23%), thighs (11.15%), calves (4.08%) ; and lastly hip circumference by (3.33%) had shown reduction in size from pre to post test. Conclusion: It is concluded that the influence of training had shown significant performance among the (UW) students with regard to the selected fitness test i.e. (BMI), bench press, sit-ups test, sit &amp; reach test and 12 min run &amp; walk test. Furthermore the selected muscular hypertrophy of the (UW) students i.e. Neck, shoulder, chest, arms, waist, thighs, calves circumference had shown increased in the muscular size and hip circumference had shown reduction in size from pre to post test.

The increase in fiber size in male rat gastrocnemius after chronic central leptin infusion is related to activation of insulin signaling.

Insulin potentiates leptin effects on muscle accrual and glucose homeostasis. However, the relationship between leptin's central effects on peripheral insulin sensitivity and the associated structural changes remain unclear. We hypothesized that central leptin infusion modifies muscle size through activation of insulin signaling. Muscle insulin signaling, enzymes of fatty acid metabolism, mitochondrial respiratory chain complexes, proliferating cell nuclear antigen (PCNA) and fiber area were analyzed in the gastrocnemius of chronic central infused (L), pair-fed (PF) and control rats. PCNA-positive nuclei, fiber area, GLUT4 and glycogen levels and activation of Akt and mechanistic target of rapamycin were increased in L, with no changes in PF. Acetyl-CoA carboxylase-β mRNA levels and non-esterified fatty acid and triglyceride content were reduced and carnitine palmitoyltransferase-1b expression and mitochondrial complexes augmented in L. These results suggest that leptin promotes an increase in muscle size associated with improved insulin signaling favored by lipid profile.

The effects of supramaximal versus submaximal intensity eccentric training when performed until volitional fatigue.

Our purpose was to compare supramaximal versus submaximal intensity eccentric training performed until volitional fatigue. Thirty-two young adults (19 males) were randomized into one of three groups: (1) ECC110 performed eccentric (ECC) only contractions at 110% of concentric (CON) 1-repetition maximum (1RM); (2) ECC80 performed ECC only contractions at 80% of CON 1RM; (3) a control group. Training progressed from 3 to 6 sets of unilateral ECC training of the elbow flexors over 8weeks, with each set performed until volitional fatigue. Elbow flexors muscle thickness (via ultrasound) and 1RM were assessed pre- and post-training. Rating of perceived exertion (RPE) and muscle soreness was self-reported. Both ECC110 (+0.25cm) and ECC80 (+0.21cm) showed a greater post-training increase in muscle thickness compared to control (-0.01cm) (p<0.05), with no differences between ECC110 and ECC80. ECC80 (+1.23kg) showed a greater post-training increase in strength compared to control (p<0.05), while ECC110 (+0.76kg) had no significant difference post-training vs. control (-0.01kg). ECC80 had significantly lower average RPE scores than ECC110 (p<0.05). Both supramaximal intensity eccentric training and submaximal intensity eccentric training are effective for increasing muscle size, but submaximal eccentric training is perceived to require less exertion than supramaximal training. These findings suggest that submaximal eccentric training may be an ideal strategy to increase muscle size and strength in individuals whose needs warrant training at a lower level of exertion.

Correlations Do Not Show Cause and Effect: Not Even for Changes in Muscle Size and Strength.

It is well known that resistance exercise results in increased muscle strength, but the cause of the improvement is not well understood. It is generally thought that initial increases in strength are caused by neurological factors, before being predominantly driven by increases in muscle size. Despite this hypothesis, there is currently no direct evidence that training-induced increases in muscle size contribute to training-induced increases in muscle strength. The evidence used to support this hypothesis is exclusively correlational analyses and these are often an afterthought using data collected to answer a different question of interest. Not only do these studies not infer causality, but they have inherent limitations associated with measurement error and limited inter-individual variability. To answer the question as to whether training-induced increases in muscle size lead to training-induced increases in strength requires a study designed to produce differential effects on muscle size based on group membership (i.e., one group increases muscle size and one does not) and observe how this impacts muscle strength. We have performed studies in our laboratory in which muscle strength increases similarly independent of whether muscle growth is or is not present, illustrating that the increases in muscle strength are not likely driven by increases in muscle size. The hypothesis that training-induced increases in muscle size contribute to training-induced increases in muscle strength requires more appropriately designed studies, and until such studies are completed, this statement should not be made as there are no data to support this hypothesis.

Blood flow in humans following low-load exercise with and without blood flow restriction

Blood flow restriction (BFR) in combination with exercise has been used to increase muscle size and strength using relatively low loads (20%-30% 1-repetition maximum (1RM)). In research, the range of applied pressures based on a percentage of arterial occlusion pressure (AOP), is wide. The purpose of the study is to measure the blood flow response before exercise, following each set of exercise, and postexercise to low-load elbow flexion combined with no restriction (NOBFR), 40% of AOP (40BFR), and 80% of AOP (80BFR). One hundred and fifty-two participants volunteered; 140 completed the protocol (women = 75, men = 65). Participants were counter-balanced into 1 of 3 conditions. Following AOP and 1RM measurement, ultrasound was used to measure standing blood flow at rest in the right brachial artery. Participants performed 4 sets of elbow flexion at 30% 1RM. Blood flow was measured between sets and at 1 and 5 min postexercise. Blood flow decreased following inflation, with no difference between conditions (p < 0.001). Men had greater blood flow than women in all conditions at all time points (p < 0.001). Resting hyperemia decreased with pressure (NOBFR > 40BFR > 80BFR, p < 0.001). Blood flow increased from rest to after set 1 regardless of condition. Following cuff deflation, blood flow increased in both the 80BFR and 40BFR conditions. The reduction in hyperemia during BFR is pressure-dependent. Contrary to previous investigations, blood flow was increased above baseline following exercise.

Skeletal Muscle Remodeling in Response to Eccentric vs. Concentric Loading: Morphological, Molecular, and Metabolic Adaptations.

Skeletal muscle contracts either by shortening or lengthening (concentrically or eccentrically, respectively); however, the two contractions substantially differ from one another in terms of mechanisms of force generation, maximum force production and energy cost. It is generally known that eccentric actions generate greater force than isometric and concentric contractions and at a lower metabolic cost. Hence, by virtue of the greater mechanical loading involved in active lengthening, eccentric resistance training (ECC RT) is assumed to produce greater hypertrophy than concentric resistance training (CON RT). Nonetheless, prevalence of either ECC RT or CON RT in inducing gains in muscle mass is still an open issue, with some studies reporting greater hypertrophy with eccentric, some with concentric and some with similar hypertrophy within both training modes. Recent observations suggest that such hypertrophic responses to lengthening vs. shortening contractions are achieved by different adaptations in muscle architecture. Whilst the changes in muscle protein synthesis in response to acute and chronic concentric and eccentric exercise bouts seem very similar, the molecular mechanisms regulating the myogenic adaptations to the two distinct loading stimuli are still incompletely understood.Thus, the present review aims to, (a) critically discuss the literature on the contribution of eccentric vs. concentric loading to muscular hypertrophy and structural remodeling, and, (b) clarify the molecular mechanisms that may regulate such adaptations.We conclude that, when matched for either maximum load or work, similar increase in muscle size is found between ECC and CON RT. However, such hypertrophic changes appear to be achieved through distinct structural adaptations, which may be regulated by different myogenic and molecular responses observed between lengthening and shortening contractions.

Soluble activin receptor type IIB decoy receptor differentially impacts murine osteogenesis imperfecta muscle function.

Osteogenesis imperfecta (OI) is characterized by skeletal fragility and muscle weakness. In this study we investigated the effects of soluble activin type IIB receptor (sActRIIB-mFc) on muscle mass and function in 2 distinct mouse models of OI: osteogenesis imperfecta murine (oim) and +/G610C. Wild-type (WT), +/G610C, and oim/oim mice were treated from 2 to 4 months of age with Tris-buffered saline (vehicle) or sActRIIB-mFc and their hindlimb muscles evaluated for mass, morphology, and contractile function. sActRIIB-mFc-treated WT, +/G610C, and oim/oim mice had increased hindlimb muscle weights and myofiber cross-sectional area compared with vehicle-treated counterparts. sActRIIB-mFc-treated oim/oim mice also exhibited increased contractile function relative to vehicle-treated counterparts. Blocking endogenous ActRIIB was effective at increasing muscle size in mouse models of OI, and increasing contractile function in oim/oim mice. ActRIIB inhibitors may provide a potential mutation-specific therapeutic option for compromised muscle function in OI. Muscle Nerve 57: 294-304, 2018.

Strength and Proprioceptive Training Increases Muscle Size in Patients with Chronic Ankle Instability

Chronic ankle instability (CAI) is related to strength deficits in ankle and hip musculature. Rehabilitation training improves muscular strength, but it is unclear whether strength gain results from an increase in muscle size or neuromuscular efficiency. PURPOSE: To examine the effect of a 6-week ankle and hip strength and proprioceptive program on peroneus longus (PL) and gluteus medius (GM) muscle size in patient with CAI. METHODS: 15 CAI subjects in a rehab group (23±2 yrs, 178±8 cm, 76±9 kg, 83±7% FAAM ADL, 56±10% FAAM Sports, 4.7±2 ankle sprains) completed a series of 10 ankle and hip strength and proprioceptive exercises (theraband, wobble board, ankle disk, etc.) 3 times/week for 6 weeks under supervision. 14 CAI subjects participated in a control group (22±2 yrs, 177±9 cm, 75±12 kg, 81±9% FAAM ADL, 56±12% FAAM Sports, 5.9±3.3 sprains). A Siemens Trio MRI scanner with a large flex coil was used to acquire images using a 3D multi-slice spiral gradient echo sequence with TE: 7.48 ms, TR: 17 ms, slice thickness: 5 mm. Images were acquired at pre- and post-intervention. Axial cross-sectional area (CSA) from each muscle was segmented using Analyze 12.0 software. PL muscle belly was consistently defined at 15th/96 slices (7.5 cm) from the superior head of the fibula. GM muscle belly was defined at 15th/64 slices (7.5 cm) from the superior greater trochanter of the femur. ANCOVA analyses (covariate: pre-intervention value) were used to detect group x time differences. RESULTS: ANCOVA analyses confirmed between-group differences in PL (F 1,26=39.087; p < .05) and GM CSA (F 1,26=22.965; p < .05) over time. The rehabilitation intervention resulted in a 3.9% increase in PL (pre= 5.9±1.5 cm2, post= 6.1±1.5 cm2; p < .05) and a 5.1% increase in GM CSA (pre=42.0±7.1 cm2, post=44.2±7.3 cm2; p < .05). No significant changes were detected in PL (0.7% reduction; pre= 6.96±1.7 cm2, post= 6.91±1.6 cm2; p > .05) and GM CSA (0.6% increase; pre=47.5±7.9 cm2, post=47.7±7.8 cm2; p > .05) in the control group. CONCLUSIONS: Relative to the control group, a 6-week strength and proprioceptive program is effective in increasing muscle size of ankle and hip musculature. As muscle size is proportional to muscular strength, increased muscle size might have a positive impact on dynamic functions at the ankle and hip.

Are Higher Blood Flow Restriction Pressures More Beneficial When Lower Loads Are Used?

Low load (~20% one repetition maximum (1RM)) exercise in combination with blood flow restriction (BFR) produces robust increases in muscle size and strength. However, little is known about relative loads less than 20% 1RM. PURPOSE: To determine the effect of BFR in combination with very low loads on acute changes in electromyography (EMG) amplitude, muscle thickness (Mth), and torque; all variables associated with long term muscle growth. METHODS: Fourteen participants completed four visits. The 1RM was determined during visit 1. Visits 2-4 involved the same procedures but differed based on the load (10%, 15%, or 20% of their 1RM) lifted and level of restriction (40% or 80% of arterial occlusion). Each condition (i.e. load (%1RM)/pressure (% arterial occlusion)) began with a measure of arterial occlusion. Measurements of Mth and torque were taken before and after exercise. EMG amplitude of the last 3 reps was analyzed and expressed relative to the value obtained during a maximal isometric contraction (%MVC). Both arms were exercised each visit. A repeated measures ANOVA was used to identify differences in the dependent variables. Data represented as means (95% CI) and mean (SD) for EMG. RESULTS: There was an interaction with torque and Mth (p<0.001). There were no differences across Pre (p=0.312) but there were for Post (p<0.001) with torque. Increasing load [e.g. 10/40: -5.2 (-7.2, -3.2) Nm vs. 20/40: -24.4 (-32.9, -15.8) Nm] and pressure [e.g. 15/40: -15.1 (-22.3, -7.9) Nm vs. 15/80: -20.7 (-29.2, -12.2) Nm] resulted in a gradient pre-post decrease in torque (p<0.001). Increasing load [e.g. 10/40: 0.18 (0.1, 0.25) cm vs. 20/40: 0.38 (0.29. 0.47) cm] and pressure [e.g. 15/40: 0.31 (0.23, 0.4) cm vs. 15/80: 0.43 (0.37, 0.48) cm] resulted in a gradient pre-post increase in Mth (p<0.001). For EMG amplitude there was a condition (p=0.002) and time (p=0.019) effect. EMG amplitude increased across time [e.g. 1st set: 40 (12.6) %MVC vs. 4th set: 45 (14.4) %MVC, p=0.033] and was augmented by increasing the load to 20% 1RM [15/80: 40 (9) %MVC vs. 20/40: 55 (15) %MVC, p=0.003] with no effect of pressure [20/80: 54 (20) %MVC]. CONCLUSIONS: These acute findings provide important information for implementing BFR with very low loads. We wish to suggest that higher pressures may be useful when implementing BFR with loads less than 20% 1RM.

Cardiovascular And Perceptual Responses To Various Blood Flow Restriction Pressures And Exercise Loads

Blood flow restriction (BFR) allows individuals to exercise with lower loads while producing similar increases in muscle size as high load training. Most studies implement moderate to high pressures with loads corresponding to 20-30% of their one-repetition maximum (1RM). No study has examined perceptual or cardiovascular responses using loads lower than 20% 1RM, which may provide a more widely inclusive and palatable stimulus. PURPOSE: To determine the cardiovascular and perceptual response to very low load BFR exercise using both moderate (40%) and high (80%) relative arterial occlusion pressures (AOP). METHODS: 14 participants came to the lab on four separate days to complete six exercise protocols (2 per visit on visits 2-4) consisting of 4 sets (1 set of 30 followed by 3 sets of 15) of BFR elbow flexion exercise with either a 10%, 15% or 20% 1RM load, each of which was performed with a moderate (40% AOP) and high (80% AOP) relative pressure. A repeated measures ANOVA was used to determine differences in AOP pre and post exercise and a Friedman test was used to determine differences in discomfort and ratings of perceived exertion (RPE) following each set. AOP is expressed as [mean (95% confidence interval)] with RPE and discomfort expressed as [median (25th, 75th percentile)]. RESULTS: There was an interaction for AOP (p=0.002) with higher pressures and loads producing a gradient increase. The pre to post changes ranged from 21 (95% CI: 10-32) mmHg in the 10% 1RM/40% AOP condition to 62 (95% CI: 45-78) mmHg in the 20% 1RM/80% AOP condition. Ratings of discomfort were primarily dependent on the level of restriction pressure applied, with higher pressures resulting in greater discomfort (p<0.001) ranging from 2.5 (1, 5) in the 15% 1RM/40% AOP condition to 6.5 (5.5, 7.25) in the 15% 1RM/80% AOP condition. Additionally, a gradient increase in RPE accompanied higher pressures and loads which ranged from 8.5 (7,12) at the conclusion of the 10%1RM/40% AOP condition to 15.5 (12.75, 17.25) at the conclusion of the 20% 1RM/80% AOP condition. CONCLUSIONS: Increases in load and restrictive pressure resulted in elevated AOP and RPE, but higher pressures were primarily responsible for increased discomfort. Individuals experiencing discomfort during low load BFR exercise may wish to decrease the applied pressure and increase the exercise load.