Measures Of Muscular Performance Research Articles

Reliability and Utility of Load-Cell Derived Force–Time Variables Collected During a Constrained and Unconstrained Isometric Knee Extension Task on a Plinth

Rate of force development (RFD) and impulse (IMP) are important mechanical measures of muscular performance but are relatively unused within the rehabilitation and performance community. Due principally to access to low-cost testing devices and understanding the utility of these measures. The aim of this study therefore was to quantify the reliability of various force–time variables using load-cell technology collected via isometric knee extension whilst constrained in an isokinetic device (CON90) or unconstrained on a physiotherapy plinth at 60 and 90 degree angles (UNCON60 and UNCON90). Thirty-two volunteers had their peak force (PF), RFD, peak RFD (PRFD), and IMP assessed across three protocols. For all variables, UNCON60 had the largest variability across all measures. PF and PRFD were found to have small variability (ICC > 0.67 and CV < 10%). With regards to RFD 2080 all three protocols were found to have moderate variability all ICCs above 0.75, however, all CVs were greater than 10% ranging from ~ 11%–22%. Finally, IMP 2080 was found to have moderate variability for both CON90 and UNCON90, the absolute consistency once more greater than 10% (~ 11%–25%). Using the constrained and unconstrained protocols, PF and PRFD can be measured reliably between trials with 90 degree knee position.

Selected root plant supplementation reduces indices of exercise-induced muscle damage: A systematic review and meta-analysis.

This systematic review and meta-analysis examined the effects of selected root plants (curcumin, ginseng, ginger and garlic) on markers of muscle damage and muscular performance measures following muscle-damaging protocols. We included 25 studies (parallel and crossover design) with 353 participants and used the PEDro scale to appraise each study. Forest plots were generated to report on standardised mean differences (SMD) and p-values at 24 and 48 hours following the muscle-damaging protocols. The meta-analysis showed that the supplemental (SUPP) condition showed significantly lower levels of indirect muscle damage markers (creatine kinase, lactate dehydrogenase and myoglobin) and muscle soreness at 24 hours and 48 hours (p<0.01) than the placebo (PLA) condition. The inflammatory markers were significantly lower for the SUPP condition than the PLA condition at 24 hours (p=0.02), although no differences were identified at 48 hours (p=0.40). There were no significant differences in muscular performance measures between the SUPP and PLA conditions at 24 hours and 48 hours (p>0.05) post-exercise. According to our qualitative data, a number of studies reported a reduction in oxidative stress (e.g., malondialdehyde, superoxide dismutase) with a concomitant upregulation of anti-oxidant status, although other studies showed no effects. Accordingly, selected root plants minimised the level of several biomarkers of muscle damage, inflammation and muscle soreness during periods of exercise-induced muscle damage. However, the benefits of these supplements in ameliorating oxidative stress, increasing anti-oxidant status and accelerating recovery of muscular performance appears equivocal, warranting further research in these outcome measures.

Impact of Varying Dosages of Fish Oil on Recovery and Soreness Following Eccentric Exercise.

Fish oils (FOs) are rich in omega-3 long-chain polyunsaturated fatty acids, which have been purported to enhance recovery of muscular performance and reduce soreness post-exercise. However, the most effective FO dose for optimizing recovery remains unclear. The purpose of this investigation was to examine the effect of FO supplementation dosing on the recovery of measures of muscular performance, perceived soreness, and markers of muscle damage following a rigorous bout of eccentric exercise. Thirty-two college-aged resistance-trained males (~23.6 years, 71.6 kg, 172.1 cm) were supplemented with 2, 4, 6 g/day (G) FO or placebo (PL) for ~7.5 weeks. Following 7 weeks of supplementation, pre-exercise (PRE) performance assessments of vertical jump (VJ), knee extensor strength, 40-yard sprint, T-test agility, and perceived soreness were completed prior to a bout of muscle-damaging exercise and were repeated immediately post (IP), 1-, 2-, 4-, 24-, 48-, and 72-h (H) post-exercise. Repeated measures analysis of variance indicated a treatment × time interaction (p < 0.001) for VJ and perceived soreness, but no group differences were observed at any time point. VJ returned to PRE (54.8 ± 7.9 cm) by 1H (51.8 ± 6.5 cm, p = 0.112) for 6G, while no other groups returned to baseline until 48H. Lower soreness scores were observed in 6G compared to PL at 2H (mean difference [MD] = 2.74, p = 0.046), at 24H (MD: 3.45, p < 0.001), at 48H (MD = 4.45, p < 0.001), and at 72H (MD = 3.00, p = 0.003). Supplementation with 6G of FO optimized the recovery of jump performance and muscle soreness following a damaging bout of exercise.

Four Weeks of Time-Restricted Feeding Combined with Resistance Training Does Not Differentially Influence Measures of Body Composition, Muscle Performance, Resting Energy Expenditure, and Blood Biomarkers.

Recently, interest in time-restricted feeding (TRF) has increased from reports highlighting improvements in body composition and muscular performance measures. Twenty-six recreationally active males were randomly assigned to either TRF (n = 13; ~22.9 years; 82.0 kg; 178.1 cm; 8 h eating window, 25% caloric deficit, 1.8 g/kg/day protein) or normal diet (ND; n = 13; ~22.5 years; 83.3 kg; 177.5 cm; normal meal pattern; 25% caloric deficit, 1.8 g/kg/day protein) groups. Participants underwent 4-weeks of supervised full body resistance training. Changes in body composition (fat mass (FM), fat free mass (FFM), and body fat percentage (BF%)), skeletal muscle cross sectional area (CSA) and muscle thickness (MT) of the vastus lateralis (VL), rectus femoris, (RF), and biceps brachii (BB) muscles, resting energy expenditure (REE), muscular performance, blood biomarkers, and psychometric parameters were assessed. Significant (p < 0.05) decreases were noted in BM, FM, BF%, testosterone, adiponectin, and REE, along with significant increases in BP1RM, LP1RM, VJHT, VJPP, VLCSA, BBCSA, and BBMT in both groups. Plasma cortisol levels were significantly elevated at post (p = 0.018) only in ND. Additionally, FFM was maintained equally between groups. Thus, a TRF style of eating does not enhance reductions in FM over caloric restriction alone during a 4-week hypocaloric diet.

Relationships Between Circulating MicroRNA and Muscular Performance Responses to a 30 Day Bed Rest Protocol

Microgravity is known to have detrimental effects on muscle tissue, leading to atrophy and a decline in performance. Although underlying mechanisms are not clear, microRNAs (miRNA) may play a role as they have regulatory effects on skeletal muscle gene expression. PURPOSE: To determine the effects of a 30 day six-degree head-down bed rest protocol at an ambient 0.5% CO2 on lower body muscular performance. Relationships between circulating miRNAs and changes in muscle variables were also examined. METHODS: 11 healthy subjects, 5 males and 6 females, were recruited for this study. The intervention involved a 30 day, six-degree head-down bed rest platform to simulate International Space Station flight. Maximal muscular performance was assessed for isokinetic knee extension (IsokKE), isokinetic knee flexion (IsokKF), isometric knee extension (IsomKE), isometric knee flexion (IsomKF), jump velocity (JV), absolute jump power (AbJP), and relative jump power (RelJP) 5 days before and 2 days after bed rest. Serum miRNAs (miR-21-5p, -100-5p, -125b-5p, -126-3p) were assessed by qPCR and fold changes (FC) were correlated with muscle performance variables. RESULTS: All muscular performance measures decreased (p<0.05) after bed rest (absolute changes: IsokKE -36±27N, IsokKF -16±17N, IsomKE -28±22N, IsomKF -12±14N, JV -0.21±0.08m/s, AbsJP -0.45±0.19kW, RelJP Power -5.23±1.88W/kg). Pre bed rest miR-100-5p relative expression was positively correlated with Pre strength measures and jump power (r=0.603 to 0.727, p<0.05). MiR-126-3p FC was negatively related to absolute change in relative power (r=-0.705, p<0.05), and miR-125b-5p FC was positively correlated (p<0.05) with absolute changes in IsomKE (r=0.627), IsomKF (r=0.817), and JV (r=0.700). MiR-100-5p FC was positively correlated (p<0.05) with absolute changes in IsomKE (r=0.652) and IsomKF (r=0.759). CONCLUSION: As expected, muscle performance significantly declined after 30 days of bed rest. Significant relationships were found between miRNAs and muscle variables at baseline (miR-100-5p), and miRNA fold changes (miR-100-5p, -125b-5p, -126-3p) were correlated with absolute changes in muscle strength and power. These miRNAs require further investigation to explore their possible mechanistic roles in muscle performance declines after bed rest.

The effects of muscle action, repetition duration, and loading strategies of a whole-body, progressive resistance training programme on muscular performance and body composition in trained males and females.

Research has produced equivocal results with regard to eccentric (ECC) only compared with traditional concentric/eccentric resistance training (RT). When considered in relation to load- and repetition duration-accentuated (ECC) training as well as the use of isokinetic and isoinertial training methods, there is a relative dearth of literature considering multi-joint, multi-exercise RT interventions. The present study considered 59 male and female participants randomly divided in to 3 sex counterbalanced groups; ECC only (ECC, n = 20), repetition duration-accentuated ECC (ECC-A, n = 20), and traditional (CON, n = 19) performing full-body, effort matched RT programmes for 2 days·week-1 for 10 weeks. Outcomes were muscular performance, including absolute muscular endurance and predicted 1-repetition maximum, in addition to body composition. No significant between-groups differences were identified for change in muscular performance measures for leg press or chest press exercises, or for body composition changes. Analyses revealed a significantly greater improvement for CON compared with ECC groups (p < 0.05) for change in absolute muscular endurance for the pull-down exercise. Effect sizes for muscular performance changes were moderate to large for all groups and exercises (0.75-2.00). The present study supports previous research that ECC-only training produces similar improvements in muscular performance to traditional training where intensity of effort is controlled. Data herein further supports the use of uncomplicated, low-volume RT to momentary failure as an efficacious method of improving muscular performance in trained persons.

PLASMA LEVELS OF INTERLEUKIN-6 AND SOLUBLE TUMOR NECROSIS FACTOR RECEPTOR ARE ASSOCIATED WITH MUSCLE PERFORMANCE IN PRE-FRAIL COMMUNITY-DWELLING OLDER WOMEN?

Aim: Increased plasma levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α have been associated with frailty syndrome and reduced muscle strength in older. Sarcopenia influenced loss of mobility and functional independence, and contributed to frailty syndrome. Furthermore, sarcopenia mainly entails a decrease in type II muscle fibers, with consequent loss of muscle power; this could occur as a result of a lack of physical activity. Objective: To examine the correlation of muscular performance and the plasma levels of IL-6 and soluble TNF receptor (sTNFr) in pre-frail community-dwelling women. Methods: The study included 32 pre-frail women (≥ 65ys). The measurements were plasma concentrations of IL-6 and sTNFr1 (ELISA); muscle strength (isokinetics Biodex System). The muscle resistance program constituted 75% of maximum load (3 times/week, 10 weeks). Statistical analysis were made through Pearson and Spearman correlation (α = 5%). Results: There was a significant inverse correlation between sTNFr1 and muscle strength, pre- (r = −0.36, P = .04) and post-training (r = −0.37, P = .04) and, a significant positive correlation between IL-6 and muscle strength (r = 0.45, P = .01). Conclusion: The correlations found between the inflammatory mediators and the measures of muscular performance evaluated before and after training suggest that, as the muscles increase their ability to generate power, sTNFr concentrations decrease, and the levels of IL-6 increase. Muscle resistance exercises should be encouraged in pre-frail older women to induce the release of cytokines.

The role of rotational mobility and power on throwing velocity.

Sound rotational power and mobility are an integral component in functional performances, such as throwing and striking. The purpose of this study was to examine the role of rotational power and mobility on cricket ball-throwing velocity. Eleven professional cricketers and 10 under-19 club-level cricketers performed the chop and lift, seated and standing cricket ball throw, seated and standing side medicine ball throw, and seated active thoracic rotation range of motion (ROM) and hip rotation ROM on one occasion. Participants were divided into 2 groups (fast and slow) based on their standing cricket ball-throwing velocity. The seated and standing cricket ball throw on the dominant side was significantly different (p < 0.00) between fast and slow throwers (11.03 and 10.7 km·h(-1), respectively). Muscular performance measures, such as bilateral thoracic rotation ROM, hip external rotation ROM on the dominant side, and force and work required in the chop, were significantly different (p ≤ 0.05) between fast and slow throwers. Faster throwers in this study displayed greater force (18.4%) and work (31.2%) outputs in the chop compared with the slower throwers; however, slower throwers showed significantly greater ROM in the thoracic (13.4-16.8%) and hip regions (11.8%). It was concluded that greater ROM at proximal segments, such as hips and thoracic, may not increase throwing velocity in cricket as reduced ROM at proximal segments can be useful in transferring the momentum from the lower extremity in an explosive task such as throwing.

Effects of TRX versus Traditional Resistance Training Programs on Measures of Muscular Performance in Adults

Effects of TRX versus Traditional Resistance Training Programs on Measures of Muscular Performance in Adults

Indirect measures of substrate utilisation following exercise-induced muscle damage

This study investigated whether exercise-induced muscle damage (EIMD) resulted in changes to whole-body substrate utilisation during exercise performed during the subsequent 48 hours. Eight males (31±6 years) performed 30 minutes of bench-stepping exercise. One leg performed eccentric contractions (Ecc) by lowering the body whilst the control leg performed concentric contractions (Con) by raising the body. On the two days following bench-stepping exercise participants performed measures of muscle function on an isokinetic dynamometer and undertook a bout of one leg cycling exercise, at two differing workloads, with the first workload (WL1) at 1.5±0.25 W/kg and the second workload (WL2) at 1.8±0.25 W/kg with each leg. Expired respiratory gases were collected during cycling to estimate whole body substrate utilisation. There were significant decrements in measures of muscular performance (isometric force, concentric and eccentric torque) and increased perception of soreness in Ecc compared with Con (P < 0.05). The effect of the Ecc treatment on substrate utilisation during one-legged cycling revealed a significant trial×time interaction with higher rates of CHO oxidation in the Ecc condition compared with Con that were further increased 48 hours later (P = 0.02). A significant treatment×time×effort interaction (P < 0.01) indicated the effect of the treatment altered as workload increased with higher rates of CHO oxidation occurring in WL2. This is consistent with greater reliance upon muscle glycogen. Suggesting that in EIMD, reductions in strength and increased feelings of soreness can be associated with greater reliance upon intramuscular CHO oxidation, than lipid, during subsequent concentric work.

Relationships between measures of muscular performance, proprioceptive acuity, and aging in elderly women with knee osteoarthritis

Introduction: OA is a multifactorial condition, which predisposes elderly individuals to disabilities. Therefore, aging, especially in women, is considered to be a risk factor for the development and progression of this disease. The aging process and the presence of degenerative diseases lead to losses of strength and proprioceptive acuity. However, studies have reported conflicting results regarding the relationships between these variables. Moreover, it is unclear whether age remains an aggravating factor of these variables in individuals with knee OA. Objectives: To analyze the relationships between measures of muscular performance, proprioceptive acuity, and age in community-dwelling elderly women with knee OA. Methods: This cross-sectional study involved 35 elderly women aged 65 years and over, who had a clinical diagnosis of unilateral or bilateral knee OA and were able to walk independently. The volunteers were tested for proprioceptive acuity (joint position sense and kinesthesia) and isokinetic muscular performance of the quadriceps and hamstrings on the isokinetic dynamometer Biodex System 3 Pro®. Descriptive statistics were carried out for all outcome variables and correlation coefficients were calculated with a significance level of α < 0.05. Results: No significant correlations were found between the measures of muscular performance and proprioceptive acuity. Furthermore, no significant correlations were found between age and measures of strength and proprioception. Conclusions: The results suggested no significant relationships between measures of proprioceptive acuity and muscular performance of the quadriceps and hamstring muscles and, especially, no influences of age on these variables in elderly women with knee OA.

A low dose of alcohol does not impact skeletal muscle performance after exercise-induced muscle damage

Moderate, acute alcohol consumption after eccentric exercise has been shown to magnify the muscular weakness that is typically associated with exercise-induced muscle damage (EIMD). As it is not known whether this effect is dose-dependent, the aim of this study was to investigate the effect of a low dose of alcohol on EIMD-related losses in muscular performance. Ten healthy males performed 300 maximal eccentric contractions of the quadriceps muscles of one leg on an isokinetic dynamometer. They then consumed either a beverage containing 0.5 g of alcohol per kg bodyweight (as vodka and orange juice) or an isocaloric, isovolumetric non-alcoholic beverage. At least 2 weeks later, they performed an equivalent bout of eccentric exercise on the contralateral leg after which they consumed the other beverage. Measurement of peak and average peak isokinetic (concentric and eccentric) and isometric torque produced by the quadriceps was made before and 36 and 60 h post-exercise. Significant decreases in all measures of muscular performance were observed over time under both conditions (all P < 0.05); however, no difference between treatments was evident at any of the measured time points (all P > 0.05). Therefore, consumption of a low dose of alcohol after damaging exercise appears to have no effect on the loss of force associated with strenuous eccentric exercise.

Pre-Exercise Hypohydration Effects On Jumping Ability And Muscle Strength, Endurance And Anaerobic Capacity: A Meta-Analysis

A recent systematic review reported that pre-exercise hypohydration (PEH) impairs skeletal muscle performance. The extent to which PEH influences muscular performance-related outcomes remains to be quantified using standard meta-analytic procedures. PURPOSE: To determine the magnitude of the effects of PEH on leg and arm muscle strength, leg muscle endurance and anaerobic capacity, and jumping ability using a meta-analytic approach. METHODS: Studies were located via database searches and cross-referencing. Inclusion criteria: standard measures of muscular performance; hydration level in the euhydrated control group < 0.5% ≥ -1% bodyweight (BW); hypohydration level in the experimental group > 1% BW and > 0.5% than control BW. Exclusion criteria: diuretics- and caloric restriction-induced BW loss. Results were analyzed using a random-effect model for mean weighted summary effects and a random-effect analog to the ANOVA for subgroup analyses. RESULTS: Thirty-five research articles were retrieved, among which 11, 4, 7 and 4 met the inclusion criteria for muscle strength, muscle endurance, anaerobic capacity and jumping ability, respectively, providing 27, 7, 11 and 11 effect estimates. Mean BW decrease in experimental groups was 3.0 ± 1.4%, 3.2 ± 0.5%, 3.2 ± 1.2% and 2.5 ± 1.3% for muscle strength, muscle endurance, anaerobic capacity and jumping ability, respectively (range: 1.3 to 5.7%). Mean muscle strength fell by 4.6% (95% CI: 2.9 to 6.3%) with PEH relative to control, with leg (3.8%, 95% CI: 0.4 to 7.2%) and arm (4.8%, 95% CI: 2.9 to 6.8%) strength declining similarly. PEH resulted in a mean decrease in muscle endurance of 11.7% (95% CI: 0.002 to 23.4%) and a decline in anaerobic capacity by 5.7% (95% CI: 1.5 to 9.9%). When pooled together, results of studies indicated that the decline in muscular performance is not significantly different between studies with BW losses ≤ or > 3%. PEH did not alter jumping ability compared with control. CONCLUSIONS: PEH of 1.5 to 5.5% BW does not affect jumping ability, but decreases leg (-4%) and arm (-5%) muscle strength, as well as leg muscle endurance (-12%) and anaerobic capacity (-6%) in a significant and practical manner. The opinions or assertions contained herein should not to be construed as official or reflecting the views of the Army or the DoD.

Strength and Power Determinants of Grinding Performance in America's Cup Sailors

The purpose grinding is a physically demanding component of America's Cup sailing that is important to overall team performance, but little research is available on the determinants of grinding performance. We examined the relationship between various measures of muscular performance and the performance of upper-body grinding. Eleven elite male America's Cup sailors (33.9 +/- 5.5 yr, 97.8 +/- 12.5 kg, 186.0 +/- 7.1 cm) who performed grinding as part of their on-board role with extensive strength training experience participated in this study. Muscular performance testing examined the force, velocity, and power capabilities of the upper-body musculature, with upper-body push (bench press) and pull (bench pull) movements performed across loads of 10-100% of 1 repetition maximum (1RM). Functional grinding performance was examined for both forward and backward grinding and at 2 different resistances (moderate = 48 N x m, heavy = 68 N x m) using a land-based ergometer. Bench press 1RM and maximum force capability were the measures demonstrating the strongest correlation with forward grinding performance (r = 0.88-0.99 and 0.87-0.99, respectively), with the relationship increasing with grinding load. For backward grinding, there was a very strong relationship with bench pull maximum power (r = 0.85-0.98) in addition to 1RM (r = 0.90-0.95) and maximum force (r = 0.87-0.95). It appears that although maximal strength is a crucial muscular performance characteristic for grinding performance in all conditions, for backward grinding, there is the additional need to focus on the development of speed strength/power to maximize performance gains. This information was used by the Emirates Team New Zealand physical conditioner to develop a conditioning intervention to help improve grinding performance.

Gains in Flexibility Related to Measures of Muscular Performance: Impact of Flexibility on Muscular Performance

Studies that investigated possible correlations between flexibility and muscular performance are scarce in the literature. Therefore, the purpose of this study was to investigate the impact of a program of static stretching on the flexibility of the hamstrings and on muscular performance of the knee flexors and extensors. Pre-post experimental design. University laboratory. Thirty subjects aged 22.8 +/- 4.9 years with bilaterally shortened hamstrings. Using a protocol that has been previously described, the intervention consisted of 30 sessions of static stretching, performed bilaterally five times a week for 6 weeks. Measures of knee range of motion and isokinetic muscular performance (peak torque, angle of peak torque, and work) of knee flexors and extensors at speeds of 60 and 300 degrees/s. After intervention, significant gains in measures of flexibility (P < 0.0001) were observed, with an average gain of the knee-extension angle of 12.6 degrees, ranging from -1.2 to 30.7 degrees. In addition, we found significant increases in the following parameters of muscular performance: angle of peak torque of hamstrings at 60 and 300 degrees/s (P < 0.0001 and 0.018) and for work at 60 and 300 degrees/s for knee flexors (P = 0.012 and 0.005) and for knee extensors (P < 0.0001). The intervention resulted in gains in measures of flexibility, and these gains had a positive impact on some parameters of muscular performance.

EXERCISE-INDUCED HYPOHYDRATION AND ISOKINETIC MUSCULAR STRENGTH AND ENDURANCE

There has long been an interest in the deleterious effects of hypohydration on exercise. The majority of the research pertaining to hypohydration and muscular performance has focused on isometric and isotonic strength and endurance and the results are inconclusive. Furthermore, little has been done using isokinetic measures. PURPOSE: This investigation was done in an attempt to examine the extent to which exercise-induced hypohydration affects isokinetic muscular strength and endurance. METHODS: Nine moderately fit males performed a Thorstensson Fatigue Test using the quadriceps muscle group of the dominant leg 3-h after completing an exercise-induced dehydration (DT) and rehydration (RT) protocol. DT consisted of 100 min of low intensity exercise in a vinyl sweatsuit combined with fluid restriction during exercise and recovery. RT was identical to DT except participants were encouraged to rehydrate using water during both exercise and recovery. Peak torque values were used as the measure of muscular strength (MS), while muscular endurance was quantified using a fatigue index (FI). Hydration status was assessed using practical measures that included body weight change and urine specific gravity. RESULTS: Mean weight loss during DT and RT, was 3.46% and 1.29% lean body mass (LBM), respectively. MS, FI, and blood lactate concentration were not different (P > .05) between trials. Mean (± SE) MS for DT and RT was, 125.2 ± 6.9 and 127.9 ± 7.0ft-lbs, respectively. Mean (± SE) FI for DT and RT was, 66 ± 6.6 and 65.5 ± 7.7%, respectively. CONCLUSIONS: A 3.46% reduction in LBM following DT did not significantly affect MS or FI when compared to RT. While there was evidence of learning across the trials, these results suggest that moderate hypohydration did not affect isokinetic muscular strength and endurance, and support others who have suggested similar results for other measures of muscular performance.

Studies on maximal voluntary muscle contraction in patients with fibromyalgia.

In view of clinical experience of a low-force output in testing situations in patients with fibromyalgia syndrome (FS), this study evaluated the possibility of reaching a higher muscular performance by use of superimposed electrical stimulation: the tests mainly involved knee-extension in a Kin Com dynamometer. Twenty-five patients fulfilling the criteria of FS were compared with 22 healthy subjects. The patients showed a markedly reduced maximal voluntary contraction, but superimposed electrical stimulation revealed submaximal values. The electromyographic activity during stool climbing exceeded that recorded during maximum voluntary contraction during the dynamometric test. The cause of the reduced voluntary maximal performance is discussed. An impaired control mechanism at a supraspinal level is suggested. This has to be considered when measuring muscle strength in FS patients. Tests related to functional activities are recommended as measures of muscular performance in this patient group.

The Reliability of Selected Measures of Muscular Performance in Knee Flexion and Extension Using the Hydra-Fitness Omni Tron Total Power Unit: A Pilot Study

This research was supported in part by an equipment grant from Hydra-Fitness Industries. Inc., Belton, TX. Thirty-one subjects were included in this investigation (19 female and 12 male). The subjects ranged in age from 19-38 years with a mean age of 25 years. The subjects performed a maximal strength test of knee flexion and extension using the Omni Tron Total Power Unit employing one resistance setting. Values were obtained for eight muscular performance indicators. An identical strength test was repeated the following day. Reliability coefficients were calculated using the two sets of data. Pearson product coefficients for the eight performance indicators ranged from 0.85 to 0.97. Values from test 1 were also compared to test 2 values for significant difference using the student t-test. No significant difference was found (p < 0.05). The authors concluded that, based on the data obtained in this pilot study, the Omni Tron Total Power Unit holds the potential to produce reliable data relating to muscular performance. J Orthop Sports Phys Ther 1989;10(10):418-422.

The Definition and Assessment of Muscular Power

Considerable confusion still exists in the sports medicine literature concerning the measurement of muscular power and what it represents. Measures of muscular performance cannot be conveniently categorized as "strength " or ''power" on the basis of the contractile velocity employed in the performance task. Given the proper physical definitions and formulations involved in muscular power measurement, it is concluded that although strength (force output) and power (work/time) are quantitatively related, they remain separate physical parameters that can be measured in all dynamic muscular contractions, whether fast or slow. J Orthop Sports Phys Ther 1983;5(1):7-9.