Measures Of Muscle Performance Research Articles

Factors contributing to lumbar region passive tissue characteristics in people with and people without low back pain

BackgroundPreviously, we demonstrated that people in the Rotation with Extension low back pain subgroup display greater asymmetry of passive tissue characteristics during trunk lateral bending than people without low back pain. The purpose of this secondary analysis is to examine factors that explain the group differences. MethodsTwenty-two people in the Rotation with Extension subgroup, and 19 people without low back pain were examined. Torque, lumbar region kinematics, and trunk muscle activity were measured during passive and isometric resisted trunk lateral bending. The dependent variables were lumbar region passive elastic energy to each side; the independent variables included group, gender, anthropometrics, trunk muscle characteristics, and an interaction factor of group and trunk muscle characteristics. Multiple linear regression was used for the analysis. FindingsAnthropometrics explained passive measures to the left (P=.03). Anthropometrics (P<.01), trunk muscle characteristics (P<.01), and the interaction of group and trunk muscle characteristics (P=.01) explained passive measures to the right. After accounting for gender and anthropometrics, 43.7% of the variance in passive measures to the right was uniquely accounted for by trunk muscle characteristics for the Rotation with Extension subgroup, compared to 0.5% for the group without low back pain. InterpretationAnthropometrics explained passive measures with trunk lateral bending to both sides, in both groups. For people in the Rotation with Extension subgroup, there was a direct relationship between trunk muscle performance and passive measures to the right. Muscle is an important contributing factor to asymmetry in this subgroup and should be considered in treatment.

Does Raising Morning Rectal Temperature to Evening Levels Offset the Diurnal Variation in Muscle Force Production?

Muscle force production and power output in active males, regardless of the site of measurement (hand, leg, or back), are higher in the evening than in the morning. This diurnal variation is attributed to motivational, peripheral and central factors, and higher core and, possibly, muscle temperatures in the evening. This study investigated whether increasing morning rectal temperatures to evening resting values, by active or passive warm-ups, leads to muscle force production and power output becoming equal to evening values in motivated subjects. Ten healthy active males (mean ± SD: age, 21.2 ± 1.9 yrs; body mass, 75.4 ± 8 kg; height, 1.76 ± .06 m) completed the study, which was approved by the University Ethics Committee. The subjects were familiarized with the techniques and protocol and then completed four sessions (separated by at least 48 h): control morning (07:30 h) and evening (17:30 h) sessions (with an active 5-min warm-up) and then two further sessions at 07:30 h but proceeded by an extended active or passive warm-up to raise rectal temperature to evening values. These last two sessions were counterbalanced in order of administration. During each trial, three measures of handgrip strength, isokinetic leg strength measurements (of knee flexion and extension at 1.05 and 4.19 rad.s−1 through a 90° range of motion), and four measures of maximal voluntary contraction (MVC) on an isometric ergometer (utilizing the twitch-interpolation technique) were performed. Rectal and intra-aural temperatures, ratings of perceived exertion (RPE) and thermal comfort (TC) were measured. Measurements were made after the subjects had reclined for 30 min and after the warm-ups and prior to the measurement of handgrip and isokinetic and isometric ergometry. Muscle temperature was taken after the warm-up and immediately before the isokinetic and MVC measurements. Warm-ups were either active (cycle ergometer at 150 W) or passive (resting in a room at 35°C, relative humidity 45%). Data were analyzed using analysis of variance models with repeated measures. Rectal and intra-aural temperatures were higher at rest in the evening (.56°C and .74°C; p < .05) than in the morning, but there were no differences after the active or passive warm-ups, the subjects' ratings of thermal comfort reflecting this. Muscle temperatures also displayed significant diurnal variation, with higher values in the evening (∼.31°C; p < .05). Grip strength, isokinetic knee flexion for peak torque and peak power at 1.05 rad.s−1, and knee extension for peak torque at 4.19 rad.s−1 all showed higher values in the evening. All other measures of strength or power showed a trend to be higher in the evening ( .10 > p > .05). There was no significant effect of active or passive warm-ups on any strength or power variable, and subjects reported maximal values for effort for each strength measure. In summary, effects of time of day were seen in some measures of muscle performance but, in this population of motivated subjects, there was no evidence that increasing morning rectal temperature to evening values by active or passive warm-up increased muscle strength to evening values. (Author correspondence: B.J.Edwards@ljmu.ac.uk)

Validity and Reliability of Tools to Measure Muscle Mass, Strength, and Physical Performance in Community-Dwelling Older People: A Systematic Review

This study critically appraises the measurement properties of tools to measure muscle mass, strength, and physical performance in community-dwelling older people. This can support the selection of a valid and reliable set of tools that is feasible for future screening and identification of sarcopenia. The databases PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Cochrane were systematically searched (January 11, 2012). Studies were included if they investigated the measurement properties or feasibility, or both, of tools to measure muscle mass, strength, and physical performance in community-dwelling older people aged ≥60 years. The consensus-based standards for the selection of health status measurement instruments (COSMIN) checklist was used for quality appraisal of the studies. Sixty-two publications were deemed eligible, including tools for muscle mass (n= 16), muscle strength (n= 15), and physical performance (n= 31). Magnetic resonance imaging, computed tomography, and a 4-compartment model were used as gold standards for muscle mass assessment. Other frequently used measures of muscle mass are dual-energy x-ray and the bioelectrical impedance (BIA); however, reliability data of the BIA are lacking. Handheld dynamometry and gait speed or a short physical performance battery provide a valid and reliable measurement of muscle strength and physical performance, respectively. It can be concluded that several tools are available for valid and reliable measurements of muscle mass, strength, and performance in clinical settings. For a home-setting BIA, handheld dynamometry and gait speed or a short physical performance battery are the most valid, reliable, and feasible. The combination of selected instruments and its use for the screening and identification of sarcopenia in community-dwelling older people need further evaluation.

Validation of an adjustment equation for the burst superimposition technique in subjects post‐stroke

Deficits in voluntary force generation may be due to incomplete activation or decreased maximum force-generating ability (MFGA) of the targeted muscle. The validity of techniques used to measure MFGA in individuals post-stroke has not been assessed. The objective of this study was to determine the reliability of the MFGA predicted using an adjusted burst superimposition method within a post-stroke population. Differences in paretic-side plantar flexor muscle MFGA between 2 trials was calculated using the standard and adjusted burst superimposition technique for 17 individuals post-stroke (15 men, 58.7 ± 10 years of age, ≥6 months post-stroke) to assess reliability of the techniques. The adjusted measurement was shown to be more reliable (P = 0.03), especially when volitional effort differed by >40 N. Reliable measurement of the MFGA in individuals who have sustained a stroke is of clinical importance. These results suggest that the adjusted burst superimposition method may be useful when performing multiple measurements of muscle performance.

Effects of sleep disordered breathing on functional capacity and quality of life in chronic kidney disease Egyptian patients

We assessed the prevalence of sleep disordered breathing (SDB) and investigated its effects on the muscle functional capacity and quality of life (QoL) among chronic kidney disease (CKD) Egyptian patients, either maintained or not maintained on hemodialysis (HD). The study population comprised 100 CKD patients who were divided into patients maintained on HD (n = 60; M/F = 28:32) and patients not maintained on HD (n = 40; M/F = 24:16). Patients were observed overnight using the pulse-oximetry technique and further subdivided into patients with SDB and patients without SDB, according to their calculated oxygen desaturation index (cutoff 5). All patients were subjected also to estimation of Kt/V ratio (which is a measure for the efficiency of HD), body-composition analysis, biochemical analysis, muscle functional capacity, and QoL measurements using standard methods and questionnaires, respectively. Primary outcomes were intergroup differences regarding physical capacity and muscle performance, QoL, and body-composition measurements. CKD patients in general, either maintained on HD or not, suffer from SDB, and the levels of urea and creatinine may increase the incidence of SDB in CKD patients not maintained on HD. CKD patients maintained on HD with SDB had poorer functional capacity, physical performance, and muscle composition, in comparison with those without SDB. Overall, SDB appears to partly contribute to the total diminished functional capacity of HD patients. Thus, CKD patients maintained on HD with SDB had significantly lower sleep quality and QoL as compared to those not maintained on HD with or without SDB.

The specific contributions of force and velocity to muscle power in older adults

The purpose of this study is to examine the relative importance of the force-based and velocity-based measures of muscle performance to explain inter-individual differences in power production capability and functional task performance. Participants included seventy-nine men and women: middle-aged healthy adults (MH: 40–55years), older healthy adults (OH: 70–85years), and older adults with mobility limitations (OML: 70–85years). Muscle power at 180°/s, isometric maximal torque, and maximal contraction velocity at 40% 1RM were measured during unilateral leg extension. The Short Physical Performance Battery (SPPB) was used to differentiate between healthy and mobility limited older adults. Functional task performance was assessed using multiple chair rise and stair climb tests. Leg extensor force (torque), but not maximal contraction velocity, was significantly associated with muscle power in MH. Both torque and velocity were significantly associated with muscle power in OH. Maximal velocity, but not torque, was associated with power in OML. Maximal velocity demonstrated an association with multiple chair rise time and stair climb time in OML, but not MH or OH. It is concluded that movement velocity is an increasingly important determinant of maximal power output with advancing age. Furthermore, movement velocity is also a critical component of functional task performance with aging and may contribute to functional deficits. These findings help to explain why the rate-dependent variable power has emerged as a critical component of both assessment and rehabilitation of muscular performance and physical function in older adults.

Chocolate Milk and Endurance Exercise Recovery

This study examined effects of fat-free chocolate milk (MILK) consumption on kinetic and cellular markers of protein turnover, muscle glycogen, and performance during recovery from endurance exercise. Male runners participated in two trials separated by 1 wk and consumed either MILK or a nonnitrogenous isocaloric carbohydrate (CHO) control beverage (CON) after a 45-min run at 65% of V˙O(2peak). Postexercise muscle protein fractional synthetic rate (FSR) and whole-body protein turnover were determined during 3 h of recovery using muscle biopsies and primed constant infusions of L-[ring-²H₅]phenylalanine and L-[1-¹³C]leucine, respectively. Phosphorylation of translational signaling proteins and activity of proteolytic molecules were determined using Western blotting and enzymatic activity assays. Muscle glycogen was quantified, and treadmill time to exhaustion was determined after the recovery period. Consuming MILK after exercise resulted in higher mixed muscle FSR with lower whole-body proteolysis and synthesis compared with CON (P ≤ 0.05). Phosphorylation of eIF4E-BP1 and FOXO3a was higher for MILK (P < 0.01), whereas Akt phosphorylation was lower during recovery regardless of dietary treatment (P < 0.05). Enzymatic activity assays indicated lower caspase-3 activity during recovery for MILK (P < 0.01) and higher 26S proteasome activity for CON (P < 0.01). Muscle glycogen was not affected by either dietary treatment; however, time to exhaustion was greater for MILK than for CON (P < 0.05). The effects of consumption of MILK after endurance exercise on FSR, signaling molecules of skeletal muscle protein turnover, leucine kinetics, and performance measures suggest unique benefits of milk compared with a CHO-only beverage.

Motor performance of young dystrophic mdx mice treated with long-circulating prednisolone liposomes

For Duchenne muscular dystrophy (DMD), a common myopathy that leads to severe disability, no causal therapy is available. Glucocorticosteroids improve patients' muscle strength, but their long-term use is limited by negative side effects. Thus, pharmacological modifications of glucocorticosteroids are required to increase the efficacy by drug targeting. Liposomal encapsulation augments systemic half-life and local tissue concentrations of glucocorticosteroids and, at the same time, reduces systemic side effects. In this study, the efficacy of novel, long-circulating, polyethylene-glycol-coated liposomes encapsulating prednisolone was compared with free prednisolone in the treatment of mdx mice, a well-established animal model for DMD. Using an objective and sensitive computerized 24-hr detection system of voluntary wheel-running in single cages, we demonstrate a significant impairment of the running performance in mdx compared with black/10 control mice aged 3-6 weeks. Treatment with liposomal or free prednisolone did not improve running performance compared with saline control or empty liposomes. Histopathological parameters, including the rate of internalized nuclei and fiber size variation, and mRNA and protein expression levels of transforming growth factor (TGF)-β and monocytes chemotactic protein (MCP)-1 also remained unchanged. Bioactivity in skeletal muscle of liposomal and free prednisolone was demonstrated by elevated mRNA expression of muscle ring finger protein 1 (MuRF1), a mediator of muscle atrophy, and its forkhead box transcription factors (Foxo1/3). Our data support the assessment of voluntary running to be a robust and reproducible outcome measure of skeletal muscle performance during the early disease course of mdx mice and suggest that liposomal encapsulation is not superior in treatment efficacy compared with conventional prednisolone. Our study helps to improve the future design of experimental treatment in animal models of neuromuscular diseases.

Postoperative muscle training improves tidal volume and vital capacity in the postoperative period of CABG surgery

To evaluate lung function and respiratory muscle strength in the postoperative period and investigate the effect of inspiratory muscle training on measures of respiratory muscle performance in patients undergoing coronary artery bypass grafting.A randomized study with 47 patients undergoing coronary artery bypass grafting with cardiopulmonary bypass. They were divided into study group (SG) 23 patients and control group (CG) 24 patients, mean age 61.83 ± 8.61 and 66.33 ± 10.20 years, EuroSCORE SG 0.71 ± 0.0018 and CG 0.76 ± 0.0029, respectively. The study group underwent physical therapy and inspiratory muscle training with threshold IMT® and CG underwent conventional physiotherapy. We compared the maximal respiratory pressures (MIP and MEP), tidal volume (TV), vital capacity (VC) and peak expiratory flow (peak flow) preoperatively (Pre-OP), 1st (PO1) and 3rd (PO3) postoperative day.There was a significant reduction in all variables measured on PO1 compared to preoperative values in both groups, MIP (P <0.0001), MEP (P <0.0001), TV SG (P <0.0004) and CG (P <0.0001) and VC SG (P <0.0001) and CG (P <0.0001) and peak flow (P <0.0001). At PO3, SG presented higher value of VC, GE 1230.4 ± 477.86 ml vs. GC 919.17 ± 394.47 ml (P=0.0222) and TV SG 608.09 ± 178.24 ml vs. CG 506.96 ± 168.31 ml (P= 0.0490).Patients undergoing cardiac surgery experience reduced ventilatory capacity and respiratory muscle strength after surgery. Muscle training was performed to retrieve TV and VC in the PO3, in the trained group.

Effect of high‐speed power training on muscle performance, function, and pain in older adults with knee osteoarthritis: A pilot investigation

To examine the effect of high-speed power training (HSPT) on muscle performance, mobility-based function, and pain in older adults with knee osteoarthritis. Thirty-three participants (mean ± SD age 67.6 ± 6.8 years) were randomized to HSPT (n = 12), slow-speed strength training (SSST; n = 10), or control (CON; n = 11) for a 12-week intervention. HSPT performed 3 sets of 12-14 repetitions at 40% of the 1-repetition maximum (1RM) "as fast as possible," SSST performed 3 sets of 8-10 repetitions at 80% of the 1RM slowly, and CON performed stretching and warm-up exercises. Outcome measures included leg press (LP) 1RM and LP peak power (PP) from 40-90% of the 1RM and the corresponding PP velocity (PPV) and PP force; 400-meter walk, Berg Balance Scale, and timed chair rise; and self-reported function and pain using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Analysis of variance models were used to compare changes from baseline to 12 weeks. Statistical significance was accepted at P < 0.05. LP PP improved in both HSPT and SSST compared to CON (P = 0.04). LP PPV improved only in HSPT (P = 0.01). There were also improvements in timed chair rise (P = 0.002), WOMAC function (P = 0.004), and WOMAC pain (P = 0.02) across all of the groups. HSPT was effective at improving function and pain, but no more so than either SSST or CON. Because HSPT improved multiple muscle performance measures (strength, power, and speed), it is a more effective resistance training protocol than SSST and may increase safety in this population, especially when high-speed movements are required during daily tasks.

Effects on muscle performance of NSAID treatment with Piroxicam versus placebo in geriatric patients with acute infection-induced inflammation. a double blind randomized controlled trial

BackgroundInflammation is the main cause of disease-associated muscle wasting. In a previous single blind study we have demonstrated improved recovery of muscle endurance following celecoxib treatment in hospitalized geriatric patients with acute infection. Here we further evaluate NSAID treatment with piroxicam in a double blind RCT and investigate the role of cytokines and heat shock proteins (Hsp) with respect to muscle performance. We hypothesized that NSAID treatment would preserve muscle performance better than antibiotic treatment alone, by reducing infection-associated inflammation and by increasing expression of cytoprotective Hsp.MethodsConsecutive admissions to the geriatric ward were screened. 30 Caucasian patients, median age 84.5 years, with acute infection-induced inflammation and serum levels of CRP > 10 mg/L were included and randomized to active treatment with 10 mg piroxicam daily or placebo. Assessment comprised general clinical and biochemical parameters, 25 cytokines in serum, intra-and extracellular Hsp27 and Hsp70, Elderly Mobility Scale (EMS) scores, grip strength (GS), fatigue resistance (FR) and lean body mass (LBM). Patients were evaluated until discharge with a maximum of 3 weeks after treatment allocation.ResultsEMS scores, FR and grip work (GW), a measure taking into account GS and FR, significantly improved with piroxicam, but not with placebo. Early decreases in IL-6 serum levels with piroxicam correlated with better muscle performance at week 2. Basal expression of Hsp27 in monocytes without heat challenge (WHC) was positively correlated with FR at baseline and significantly increased by treatment with piroxicam compared to placebo. Profound modifications in the relationships between cytokines or Hsp and changes in muscle parameters were observed in the piroxicam group.ConclusionsPiroxicam improves clinically relevant measures of muscle performance and mobility in geriatric patients hospitalized with acute infection-induced inflammation. Underlying mechanisms may include modifications in the cytokine network and increases in monocytic expression of cytoprotective Hsp27.Trial registration numberISRCTN: ISRCTN96340690

Secondary Mediation and Regression Analyses of the PTClinResNet Database: Determining Causal Relationships Among the International Classification of Functioning, Disability and Health Levels for Four Physical Therapy Intervention Trials

Each of the 4 randomized clinical trials (RCTs) hosted by the Physical Therapy Clinical Research Network (PTClinResNet) targeted a different disability group (low back disorder in the Muscle-Specific Strength Training Effectiveness After Lumbar Microdiskectomy [MUSSEL] trial, chronic spinal cord injury in the Strengthening and Optimal Movements for Painful Shoulders in Chronic Spinal Cord Injury [STOMPS] trial, adult stroke in the Strength Training Effectiveness Post-Stroke [STEPS] trial, and pediatric cerebral palsy in the Pediatric Endurance and Limb Strengthening [PEDALS] trial for children with spastic diplegic cerebral palsy) and tested the effectiveness of a muscle-specific or functional activity-based intervention on primary outcomes that captured pain (STOMPS, MUSSEL) or locomotor function (STEPS, PEDALS). The focus of these secondary analyses was to determine causal relationships among outcomes across levels of the International Classification of Functioning, Disability and Health (ICF) framework for the 4 RCTs. With the database from PTClinResNet, we used 2 separate secondary statistical approaches-mediation analysis for the MUSSEL and STOMPS trials and regression analysis for the STEPS and PEDALS trials-to test relationships among muscle performance, primary outcomes (pain related and locomotor related), activity and participation measures, and overall quality of life. Predictive models were stronger for the 2 studies with pain-related primary outcomes. Change in muscle performance mediated or predicted reductions in pain for the MUSSEL and STOMPS trials and, to some extent, walking speed for the STEPS trial. Changes in primary outcome variables were significantly related to changes in activity and participation variables for all 4 trials. Improvement in activity and participation outcomes mediated or predicted increases in overall quality of life for the 3 trials with adult populations. Variables included in the statistical models were limited to those measured in the 4 RCTs. It is possible that other variables also mediated or predicted the changes in outcomes. The relatively small sample size in the PEDALS trial limited statistical power for those analyses. Evaluating the mediators or predictors of change between each ICF level and for 2 fundamentally different outcome variables (pain versus walking) provided insights into the complexities inherent across 4 prevalent disability groups.

Interactive Processes Link the Multiple Symptoms of Fatigue in Sport Competition

Muscle physiologists often describe fatigue simply as a decline of muscle force and infer this causes an athlete to slow down. In contrast, exercise scientists describe fatigue during sport competition more holistically as an exercise-induced impairment of performance. The aim of this review is to reconcile the different views by evaluating the many performance symptoms/measures and mechanisms of fatigue. We describe how fatigue is assessed with muscle, exercise or competition performance measures. Muscle performance (single muscle test measures) declines due to peripheral fatigue (reduced muscle cell force) and/or central fatigue (reduced motor drive from the CNS). Peak muscle force seldom falls by >30% during sport but is often exacerbated during electrical stimulation and laboratory exercise tasks. Exercise performance (whole-body exercise test measures) reveals impaired physical/technical abilities and subjective fatigue sensations. Exercise intensity is initially sustained by recruitment of new motor units and help from synergistic muscles before it declines. Technique/motor skill execution deviates as exercise proceeds to maintain outcomes before they deteriorate, e.g. reduced accuracy or velocity. The sensation of fatigue incorporates an elevated rating of perceived exertion (RPE) during submaximal tasks, due to a combination of peripheral and higher CNS inputs. Competition performance (sport symptoms) is affected more by decision-making and psychological aspects, since there are opponents and a greater importance on the result. Laboratory based decision making is generally faster or unimpaired. Motivation, self-efficacy and anxiety can change during exercise to modify RPE and, hence, alter physical performance. Symptoms of fatigue during racing, team-game or racquet sports are largely anecdotal, but sometimes assessed with time-motion analysis. Fatigue during brief all-out racing is described biomechanically as a decline of peak velocity, along with altered kinematic components. Longer sport events involve pacing strategies, central and peripheral fatigue contributions and elevated RPE. During match play, the work rate can decline late in a match (or tournament) and/or transiently after intense exercise bursts. Repeated sprint ability, agility and leg strength become slightly impaired. Technique outcomes, such as velocity and accuracy for throwing, passing, hitting and kicking, can deteriorate. Physical and subjective changes are both less severe in real rather than simulated sport activities. Little objective evidence exists to support exercise-induced mental lapses during sport. A model depicting mind-body interactions during sport competition shows that the RPE centre-motor cortex-working muscle sequence drives overall performance levels and, hence, fatigue symptoms. The sporting outputs from this sequence can be modulated by interactions with muscle afferent and circulatory feedback, psychological and decision-making inputs. Importantly, compensatory processes exist at many levels to protect against performance decrements. Small changes of putative fatigue factors can also be protective. We show that individual fatigue factors including diminished carbohydrate availability, elevated serotonin, hypoxia, acidosis, hyperkalaemia, hyperthermia, dehydration and reactive oxygen species, each contribute to several fatigue symptoms. Thus, multiple symptoms of fatigue can occur simultaneously and the underlying mechanisms overlap and interact. Based on this understanding, we reinforce the proposal that fatigue is best described globally as an exercise-induced decline of performance as this is inclusive of all viewpoints.

The Effect of a Multi-Ingredient High Caffeine Pre-Exercise Supplement on Strength Power and Body Composision in 8 Weeks of Resistance Training

Pre-workout supplements are broadly marketed to athletes and recreational exercisers with claims of improved performance or exercise effectiveness. Many such supplements contain a variable blend of known ergogenic aids and often include caffeine. PURPOSE: The purpose of this study was to examine the effects of a multi-component high caffeine pre-workout supplement on lean body mass (LBM) and measures of muscle performance during an eight week strength training exercise program. METHODS: Thirty physically active, resistance trained, college age (19.5 ± 0.269 yr) males were recruited for this double blind taste placebo control investigation. Subjects were randomly assigned into 2 groups: 1) Experimental (EXP) (n = 15) and 2) Control (CON) (n = 15). Subjects in the EXP drank the supplement containing a variety of common ergogenic aids including 450mg caffeine 15 minutes before each training session. Subjects in the CON drank a non-caloric placebo mixture at the same times. Both groups completed an eight week exercise program consisting of three days of strength training per week and all subjects completed the same training protocol. The following tests were performed prior to the training protocol and after 8 weeks of training: Body Weight, Body Composition via dual-energy X-ray absorptiometry (DEXA); maximal strength was determined using 1 RM tests for 8 different exercises; squat and bench press power was determined using an external dynamometer; and vertical jump. Twenty-five subjects completed the training protocol (EXP n = 14 and CON n = 11). Separate repeated measures ANOVAs were performed to test for differences between EXP and CON groups for strength, power, and body composition. The criteria for statistically significant differences were identified as an p value ≤ 0.05. RESULTS: A main effect for time was identified for each of the 1RM strength measures tested (p<0.05) except biceps curls (p = 0.34). A significant group x time interaction was found for the bench press exercise (F1/22 = 4.843, p = 0.039). Significant main effects were found for lean body mass (F1/22 = 20.32, p<0.001), but there were no significant group × time interactions for changes in LBM (F1/22 = 0.142 p = 0.710). Squat power measurements also showed a significant group x time interaction (F1/22 = 4.857, p = 0.038). Vertical Jump and bench press power did not differ between groups. CONCLUSIONS: Significant improvements in strength and lean body mass were observed in both the EXP and CON groups as would be expected with a resistance exercise training program. The primary purpose of this study was to examine the effectiveness of the supplement as an ergogenic aid. Two measures of muscle performance, bench press 1RM and squat power, increased more in the EXP group, but LBM changes did not differ. PRACTICAL APPLICATIONS: 8 weeks of pre-workout supplementation may provide some muscle performance benefit when combined with resistance exercise training. Significant improvements in LBM over the placebo drink were not observed however. ACKNOWLEDGEMENT: This study was funded by LaBrada Nutrition Inc, Houston, TX. *Denotes Equal Author Contribution

Muscle Performance and Electrically Evoked Ca 2+ Release are Compromised in Calsequestrin-1 Null Mice

In skeletal muscle the sarcoplasmic reticulum (SR) Ca2+ release channels (i.e., ryanodine receptor; RyR1) are critical determinants of contractile filament activation. Recent evidence suggests that several SR proteins may modulate RyR dependent SR Ca2+ release and thus could alter overall function. Recent attention has been focused on the SR luminal protein calsequestrin (Casq) as a SR Ca2+ buffer as well as its potential role in modulating the RyR1, the DHPR and other sarcolemmal channels. In our current work, we tested the hypothesis that mice null for Casq1 will have functional impairments reflecting the role of Casq1 in fast type skeletal muscle. Here we examined functional measures of overall muscle performance in vivo and of fast muscle in vitro, and identified significant deficits in functional performance that indicate an inability to sustain repetitive contractile activation. We then used measures of voltage dependent SR Ca2+ release and SR Ca2+ release flux in single fast type skeletal muscle fibers. Here we demonstrate a decrease in voltage dependent RyR Ca2+ release with single action potentials and a collapse of the Ca2+ release with repetitive trains of pulses. Finally in single voltage clamped muscle fibers we show that SR Ca2+ release flux as well as total SR Ca2+ release is markedly reduced in the Casq1 null myofibers. The voltage dependence of the Ca2+ release flux was not shifted but showed about 50% decrease in the maximum peak Ca2+ release flux in the Casq1 null fibers when compared to the WT counterpart. Taken together we have revealed that the genetic depletion of Casq1 results in significant deficits in contractile activation consistent with alterations in SR Ca2+ release. Supported by RC2 NR011968, R01-AR055099, and T32- AR007592.

A Comparison of High-Speed Power Training and Traditional Slow-Speed Resistance Training in Older Men and Women

Muscle power, the product of force × velocity, is a critical determinant of function in older adults. Resistance training (RT) at high speed has been shown to improve peak muscle power in this population; however, different functional tasks may benefit from the improvement of power at values other than "peak" values, for example, tasks that require a greater velocity component or a greater force component. This study compared the effect of high-speed RT on muscle performance (peak power [PP] and its components [PP force and PP velocity] and overall peak velocity [VEL]) across a broad range of external resistances. Thirty-eight older men and women were randomized to high-speed power training at 40% of the 1-repetition maximum (1RM) (n = 13 [74.1 ± 6.4 years]); traditional RT at 80% 1RM (n = 13 [70.1 ± 7.0 years]); or control (n = 12 [72.8 ± 4.1 years]). Measures of muscle performance were obtained at baseline and after the 12-week training intervention. Muscle power and 1RM strength improved similarly with both high-speed and traditional slow-speed RT. However, speed-related muscle performance characteristics, PP velocity and overall VEL, were most positively impacted by high-speed power training, especially at lower external resistances. Because gains in speed-related measures with high-speed training compared to traditional RT do not come at the expense of other muscle performance outcomes, we recommend using an RT protocol in older adults that emphasizes high-speed movements at low external resistances.

Muscle contractile characteristics: relationship to high-intensity exercise

We investigated the relationship between muscle contractile characteristics, collected using percutaneous electrical stimulation, and high-intensity exercise performance. Seventeen participants performed a muscle performance test for the calculation of rate of torque development (RTD), rate of relaxation (RR(1/2)), rate of fatigue and fatigue resistance. On a second visit the participants completed a Wingate cycle ergometer test with peak power, mean power, fatigue index and fatigue rate calculated. The muscle fatigue index related significantly to the WAnT fatigue index and fatigue rate (p < 0.01). The change in rate of torque development (%DeltaRTD) was also related significantly to the fatigue rate (W/s) during the WAnT. Subjects displaying the greatest reduction in RTD had the greatest fatigue rate during the WAnT and greater fatigue during the electrical stimulation protocol. There were no significant relationships between peak (r 0.36; p > 0.01) or mean power (r -0.11, p > 0.01) with any of the muscle performance measures. These findings demonstrate that muscle contractile characteristics, elicited during standardised in vivo electrical stimulation, relate to performance during a Wingate anaerobic test. They suggest that muscle contraction characteristics play an important role in high-intensity exercise performance and indicate that electrical stimulation protocols can be a useful additional tool to explore muscle contraction characteristics in relation to exercise performance and trainability.

Usefulness of the Trendelenburg test for identification of patients with hip joint osteoarthritis

This study examined validity indices of the Trendelenburg test as a measure of hip abductor muscle performance (adduction of pelvis-on-femur [P-O-F]) when identifying subjects with and without hip joint osteoarthritis (OA). Muscle performance of the hip abductor muscles was obtained in standing by using the P-O-F position measured with a goniometer and in supine using a handheld dynamometer (HHD) and a manual muscle test (MMT). We studied 20 healthy adults (10 men and 10 women) and 20 adults (10 men and 10 women) with radiographically documented hip joint OA. Indices including sensitivity, specificity, and positive likelihood ratios examined values obtained from the P-O-F position and the MMT when used to identify subjects with and without hip joint OA. Sensitivity of the P-O-F position for identifying subjects with hip joint OA was 0.55, and specificity was 0.70, yielding a positive likelihood ratio of 1.83. Sensitivity of normalized hip abductor MMT strength for identifying subjects with hip joint OA was 0.35 and specificity was 0.90, yielding a positive likelihood ratio of 3.5. Based on validity information from the present study, the Trendelenburg test (P-O-F angle) is not useful in identifying subjects in the early stages of hip joint OA.

Mouth and Nasal Inspiratory Pressure: Learning Effect and Reproducibility in Healthy Adults

Background: Inspiratory muscle strength measurements have become a cornerstone in monitoring neuromuscular disorders. Usually, sniff nasal inspiratory pressure (SNIP) and maximal inspiratory pressure (MIP) are performed. To our knowledge the session-to-session learning effect has rarely been evaluated for MIP performance and has never been done for SNIP performance. Objectives: We hypothesized that the sniff manoeuvre was natural and did not need to be learned, whereas the Muller manoeuvre, used for MIP measurement, was an isometric contraction which needed to be learned because it is rarely performed in real life conditions. This hypothesis suggests that from the first session and continuing through a subsequent one, the maximal SNIP value and the number of sniff trials necessary to attain it are more reproducible than the maximal MIP value and the number of Muller manoeuvre trials necessary to attain it. Methods: Seventy-one healthy subjects were included. SNIP and MIP manoeuvres were repeated 12 and 6 times, respectively, per week during 2 sessions a week apart. Results: We observed a session effect on MIP but not on SNIP. Maximal value for MIP was higher during the second session, whereas SNIP maximal value did not increase during the second session. The number of trials needed to obtain the maximal value for MIP was lower during the second session whereas it was not different for SNIP. Conclusions: SNIP is less sensitive to a learning effect than is MIP. It requires only a routine warm-up. We suggest that SNIP is preferable to MIP for repeated measurement of inspiratory muscle performance.

Muscle performance, work ability and physical functioning in middle-aged men

Limited data exist on the associations between muscle performance and work ability measures in working age adults. To evaluate how the results of simple muscle performance tests correlate with self-reported work ability and physical functioning in middle-aged men. Muscle performance was measured with handgrip, sit-up, arch-up, squatting and lifting tests. The Physical Functioning scale and the Role Limitations due to Physical Health Problems scale of the RAND-36 health questionnaire were used to assess functioning and the Work Ability Index (WAI) questionnaire to assess perceived work ability in a subgroup of 51 subjects. A total of 104 men aged 45-55 years employed in physically active work participated. Muscle performance was weakly associated with WAI and functioning measures, accounting for 10% of the variance at most. Dynamic lifting test results for both arms correlated with WAI scores (right: r = 0.31, left: r = 0.34). Scores of the dynamic lifting test for both arms correlated with the Physical Functioning scores (right: r = 0.23, left: r = 0.28) and with the Role Limitations due to Physical Health Problems scores (right: r = 0.25, left: r = 0.28). Results of the squatting test were associated with the Physical Functioning scores (r = 0.24). The study failed to provide support for the use of muscle performance tests in work-related fitness evaluations in middle-aged men employed in physical jobs.