Maximal Isometric Strength Tests Research Articles

Muscle Fiber Cross-Sectional Area Is Associated With Quadriceps Strength and Rate of Torque Development After ACL Injury.

Graham, MC, Thompson, KL, Hawk, GS, Fry, CS, and Noehren, B. Muscle fiber cross-sectional area is associated with quadriceps strength and rate of torque development after ACL injury. J Strength Cond Res 38(6): e273-e279, 2024-The purpose of this study was to investigate the relationship between muscle fiber type-specific properties of the vastus lateralis and quadriceps muscle performance in individuals after an anterior cruciate ligament (ACL) tear. 26 subjects (22.0 ± 5.4 years) were included in this cross-sectional study, and all data were collected before ACL reconstruction. Quadriceps peak torque (QPT) and early (0-100 ms) and late (100-200 ms) rate of torque development (RTD) were obtained from maximal voluntary isometric quadriceps strength testing. Muscle fiber cross-sectional area (fCSA) and percent fiber type distribution (FT%) were evaluated through immunohistochemical analysis of a muscle biopsy. Between-limb differences in fiber characteristics were assessed using paired t-tests (with α-level 0.05). Relationships between fiber-specific properties and quadriceps muscle performance were determined using separate multiple linear regression analyses for ACL-injured and noninjured limbs. There were significant differences in fCSA between ACL-injured and noninjured limbs across all fiber types, but no differences in FT%. Type 1 fCSA, type 2a fCSA, and their interaction effect were the explanatory variables with the strongest relationship to all performance outcomes for the ACL-injured limb. The explanatory variables in the ACL-injured limb had a significant relationship to QPT and late RTD, but not early RTD. These findings suggest that QPT and late RTD are more heavily influenced by fCSA than FT% in ACL-injured limbs. This work serves as a foundation for the development of more specific rehabilitation strategies aimed at improving quadriceps muscle function before ACL reconstruction or for individuals electing nonsurgical management.

Influence of menstrual cycle phase and oral contraceptive phase on exercise performance in endurance-trained females.

Limited data exists on the influence of menstrual cycle (MC) phase and oral contraceptive (OC) phase on physical performance in endurance-trained females due to poor control regarding MC verification and differentiation. We aimed to evaluate exercise performance and the respiratory response to exercise in three distinct phases of the MC and OC cycle in endurance-trained females. Using a prospective cohort study design, we recruited trained females (Vo<inf>2max</inf> 52±4 mL O<inf>2</inf>/min/kg) who were either not using oral contraceptives (NOC) or using monophasic OCs. NOC were tested in the early and late follicular phase (FP) and the mid-luteal phase (LP). OC-users were tested in the withdrawal phase (WP) and two times in the active OC phase (OCP). The test battery included DXA scans, blood sampling, a submaximal bike test, a maximal isometric knee-extensor strength test, 4 and 20-second bike sprints, and a 6 min time trial on a bike. MC phases were verified by the use of ovulation kits and circulating sex hormone levels. After the exclusion of four NOCs due to inadequate sex hormone levels, 11 NOC and 13 OC users were included in the final analysis. 6 min time trial performance, sprint performance, and most submaximal exercise intensity variables did not differ between MC phases and OC cycle phases. However, in NOC, ventilation (L/min) during exercise at 30% of aerobic peak power was 7.6% lower in the late FP compared to the LP (P<0.05). In OC users, muscle strength was 3.9% higher in the early OCP compared to WP (P<0.05), whereas body mass was higher in the late OCP compared to WP (P<0.05). Collectively, our study suggests that MC phase and OCP influence exercise performance to a limited extent in endurance-trained females.

Quadriceps torque complexity before and after anterior cruciate ligament reconstruction

ObjectivesThe purpose of this project was to longitudinally examine quadriceps torque complexity in a group of individuals who tore their ACL and underwent ACL reconstruction. DesignCohort analysis. MethodsThirty-four individuals completed maximal effort bilateral isometric strength testing after ACL injury but pre-surgery, five months' post-surgery (mid-point of rehabilitation), and when cleared to return to activity. Sample entropy, a nonlinear analysis of quadriceps torque control (complexity), was calculated from maximal isometric contractions. Two 3 × 2 repeated measures analysis of variance were used to examine changes over time and between limbs for quadriceps torque complexity and peak torque. ResultsQuadriceps peak torque was lower in the involved limb when compared to the uninvolved limb at every time point (p < 0.001). Peak torque of the involved limb was decreased at mid-point of rehabilitation compared to before surgery (p = 0.023) and at mid-point compared to return to activity (p = 0.041). Quadriceps sample entropy was higher in the involved limb compared to the uninvolved limb at the mid-point of rehabilitation (p < 0.001) and return to activity (p < 0.001), indicating greater complexity. The involved limb also demonstrated increased torque sample entropy from pre-surgery to mid-point of rehabilitation (p = 0.023), but not from pre-surgery to return to activity (p = 0.169) or from mid-point to return to activity (p = 0.541). ConclusionsNot only does quadriceps strength decline with ACL reconstruction, but quality of the quadriceps muscle contraction is also compromised. Increased torque complexity experienced in the ACL limb after reconstruction may contribute to impaired physical function in individuals following ACL reconstruction.

Validity and reliability of upper extremity star excursion balance test in adolescent swimmers

Background/ObjectivesUpper limb balance is one of the important physical fitness parameters for all populations, especially overhead athletes like swimmers. Upper extremity star excursion balance test (UESEBT) is a comprehensive dynamic balance assessment, this study aims to explore the reliability and validity of UESEBT among adolescent swimmers. MethodsThis cross-sectional study recruited 70 adolescent swimmers. All participants were required to complete UESEBT, upper quarter Y-balance test (UQYBT), maximal isometric strength (MIS) tests in upper limb, closed kinetic chain upper extremity stability test (CKCUEST), trunk flexor endurance test (TFET) and lateral trunk endurance test (LTET). The intra- and inter-operator reliability and the correlation of UESEBT with other physical performances were conducted. ResultsFor reliability, the intra- and inter-operator reliability of all directions and composite score were high-to-excellent (ICC = 0.706−1.000) among all participants. For validity, the UESEBT has a moderate-to-strong correlation with UQYBT (r = 0.42−0.72, p < 0.001), and a weak-to moderate one with CKCUEST (r = 0.25−0.42, p < 0.05). Furthermore, the UESEBT performance showed weak-to-moderate correlations with MIS (r = 0.24−0.44, p < 0.05). UESEBT was correlated to LTET (r = 0.24−0.33, p < 0.05) whereas no relationship was found with TFET. ConclusionsUESEBT was a reliable and valid tool to screen upper extremity dynamic balance among adolescent swimmers. UESEBT provides more detailed information in eight directions to assess the upper limb sport performance. Further study should explore the prediction ability of UESEBT for injury.

Validity of a mobile device measuring isometric deadlift peak force

Introduction&#x0D; Muscular strength can be viewed as a product of force and velocity. Increases in both maximal force and velocity will ultimately result in an increase in power (Suchomel et al., 2016), thus contributing to performance in tasks such as athletic competition or police and military special operations.&#x0D; Testing isometric peak force is a reliable method to assess maximal strength (De Witt et al., 2018). Isometric mid-thigh pull tests and squat tests in various knee- and hip angles are well known. These tests, however, require force plates with computer and software, as well as a barbell that disallows displacement of the bar (usually a heavy equipment).&#x0D; Decentralized testing requires a reliable, lightweight and mobile measurement device comparable to standard isometric tests as described elsewhere (Maier et al., 2016). Therefore, a tension gauge (load cells) was attached to a board and a handle to perform isometric sumo stance deadlifts. The question is whether the mobile device produces comparable results to maximal isometric strength tests on force plates.&#x0D; Method&#x0D; Correlation analysis (Bayesian Pearson’s rho, Prior~Beta 1,1) and Equivalence Bayesian Paired Samples T-Tests (Lakens, 2017; Prior~Cauchy 0,0.707, a priori Limits of Agreement = +/-5%) of the measurements from the mobile test device and from force plates (CYCCESS) were performed using JASP Version 0.14.1. Healthy, trained subjects (n = 12) volunteered to perform maximal isometric deadlifts on each test device. Results were validated by additional 6 pairs of lifts on each device.&#x0D; Results&#x0D; Pearson’s rho was 0.969 (95% credible interval of the posterior distribution 0.824, 0.993). After adjusting the measures of the mobile device for the offset (mean of the differences of 416 N), Bayes factor favoring the hypothesis that the effect size lies inside the interval of +/-5% was 3.006. The additional measurements confirmed the substantial evidence for equivalence of the two measurements.&#x0D; Discussion&#x0D; Isometric tests are relatively simple, safe and time efficient to administer and possess high degrees of reliability (Grgic et al., 2022). The strong relationship between isometric peak force and deadlift 1RM (De Witt et al., 2018) makes them a valuable tool for exercise prescription. Our lightweight, mobile test device offers high precision (technical measurement error of the load cells = 0.5%) and safe testing procedure. Concurrent validity, as well as face validity, seems to be reasonably high: measurements with the mobile device do not differ from a isometric deadlift test on force plates, and lifting casualties and heavy loads could be well represented by force produced from the floor position (Bartolomei et al., 2022).&#x0D; References&#x0D; Bartolomei, S., Rovai, C., Lanzoni, I. M., &amp; di Michele, R. (2022). Relationships between muscle architecture, deadlift performance, and maximal isometric force produced at the midthigh and midshin pull in resistance-trained individuals. Journal of Strength and Conditioniung Research, 36(2), 299-303. https://doi.org/10.1519/jsc.0000000000003455&#x0D; De Witt, J. K., English, K. L., Crowell, J. B., Kalogera, K. L., Guilliams, M. E., Nieschwitz, B. E., Hanson, A. M., &amp; Ploutz-Snyder, L. L. (2018). Isometric midthigh pull reliability and relationship to deadlift one repetition maximum. The Journal of Strength and Conditioning Research, 32(2), 528-533. https://doi.org/10.1519/jsc.0000000000001605&#x0D; Grgic, J., Scapec, B., Mikulic, P., &amp; Pedisic, Z. (2022). Test-retest reliability of isometric mid-thigh pull maximum strength assessment: A systematic review. Biology of Sport, 39(2), 407-414. https://doi.org/10.5114/biolsport.2022.106149&#x0D; Lakens, D. (2017). Equivalence tests: A practical primer for t tests, correlations, and meta-analyses. Social Psychological and Personality Science, 8(4), 355-362. https://doi.org/10.1177/1948550617697177&#x0D; Maier, T., Gross, M., Trösch, S., Steiner, T., Müller, B., Bourban, P., Schärer, C., Hübner, K., Wehrlin, J., Tschopp, M., Wilhelm, M., Clenin, G. E., Züst, P., &amp; Seidel, R. (2016). Manual Leistungsdiagnostik [Performance diagnostics manual]. http://www.swissolympic.ch/Portaldata/41/Resources/03_sport/00_dokumente/Manual_Leistungsdiagnostik_(letzte_Aenderung_01.02.2016).pdf&#x0D; Suchomel, T. J., Nimphius, S., &amp; Stone, M. H. (2016). The importance of muscular strength in athletic performance. Sports Medicine, 46(10), 1419-1449. https://doi.org/10.1007/s40279-016-0486-0

Validity and Reliability of an Isometric Row in Quantifying Maximal Force Production in Collegiate Rowers.

Pineda, D, Hudak, J, Bingham, GE, and Taber, CB. Validity and reliability of an isometric row in quantifying maximal force production in collegiate rowers. J Strength Cond Res 37(8): e462-e465, 2023-The objective of this study was to examine the relationship between a maximal isometric strength test with a maximal dynamic strength test. The main outcome was to evaluate the isometric test to determine if it was a valid and reliable measurement tool for testing and monitoring of rowing athletes. Collegiate Division 1 rowers were tested on measures of maximal dynamic and isometric strength on 2 occasions separated by 14 days. Thirty-two female athletes (age: 19.9 11.0 years; height: 168.2 ± 7.6 cm; body mass: 71.3 as13.2 kg) participated in this study. Although the isometric test had greater reliability, both tests displayed good-to-excellent reliability (intraclass correlation coefficient = 0.79-0.92). Strong correlations were present for the relationship between isometric and dynamic strength tests ( r = 0.76-0.82, p = <0.001). The data indicate that the isometric row test is valid and reliable compared with dynamic testing and may be used in conjunction with dynamic testing in the evaluation of collegiate rowers.

Abstract 13472: Physical Incapacity in Heart Failure Patients is Associated With Skeletal Muscle Mitochondrial Dysfunction

Introduction: The role of skeletal muscle mitochondrial dysfunction in exercise intolerance in heart failure patients is unknown. Therefore, this study aimed to identify the relationship between physical capacity and skeletal muscle mitochondrial function in patients with heart failure and reduced ejection fraction (HFrEF). Methods A total of 53 HFrEF patients and 20 age- and sex-matched controls underwent dual-energy X-ray absorptiometry to assess muscle mass by the appendicular lean mass index (ALMI), cardiopulmonary exercise testing (peakVO2), 6-minute walking test (6MWD) and maximal isometric knee-extensor strength test. In skeletal muscle biopsies from vastus lateralis, mitochondrial respiratory capacity was measured by high resolution respirometry. We performed Pearson correlations to examine the relationships between physical capacity tests and mitochondrial function. Results Mean age of the study cohort was 71.7 ±7.0 years. Compared with healthy controls, HFrEF patients had a lower peakVO2 (14.6 ±4.1 vs. 26.2 ±8.0 mL/kg/min, p &lt;0.001) and a shorter 6MWD (429 ±106 vs. 581 ±93 m, p &lt;0.001). HFrEF patients had a lower ALMI (0.74 ±0.15 vs. 0.86 ±0.16 kg/(kg/m 2 ), p = 0.005). Maximal coupled mitochondrial respiration was decreased in HFrEF patients compared with healthy controls (59.1 ±19.0 vs. 92.6 ±38.8 ρmol O 2 *s -1 mg -1 , p &lt;0.001) as well as the respiratory control ratio (7.2 ±2.5 vs. 9.7 ±3.1). Maximal coupled mitochondrial respiration was correlated to peakVO2 (r = 0.58, p &lt;0.001) and 6MWD (r = 0.44, p &lt;0.001), but not to muscle mass or maximal knee-extensor strength. Conclusions HFrEF patients had a lower peakVO2, shorter 6MWD and impaired skeletal muscle mitochondrial function as compared with controls. Maximal coupled mitochondrial respiration was correlated with physical capacity across the population of HFrEF patients and healthy controls establishing an association between skeletal muscle mitochondrial dysfunction and physical incapacity.

How to identify patients with low muscle mass linked to physical capacity and physical activity in heart failure

Abstract Introduction Skeletal muscle wasting is frequent in heart failure (HF) patients, and low muscle mass (MM) is associated with increased morbidity and mortality. Current recommendations suggest the usage of dual-energy X-ray absorptiometry (DXA)-derived appendicular lean mass (ALM) adjusted for height squared to identify low MM. However, it has recently been suggested that ALM adjusted for body mass index (BMI) has a higher predictive value. The relationships between low MM, muscle strength, exercise capacity and daily physical activity (PA) are poorly understood in heart failure with reduced ejection fraction (HFrEF). Purpose This study examined the relationships between low MM defined by two different indices and muscle strength, physical capacity tests and accelerometer measurements. Methods A total of 104 HFrEF patients underwent DXA, maximal isometric knee-extensor strength test, cardiopulmonary exercise testing, 6-minute walking test and accelerometry. Two adjusted indices for low MM were assessed: ALM/m2 and ALM/BMI. We performed Pearson correlations to examine the relationships between low MM and muscle strength, exercise capacity and daily PA. Furthermore, we identified patients with low MM based on the two indices. For ALM/m2 we used guideline-recommended cut-offs and for ALM/BMI we used the mean value since no cut-offs has been validated. Results The ALM/m2-index showed no significant correlation to peak oxygen uptake (VO2peak), 6-minute walking distance (6MWD), average PA or daily time spent in moderate-to-vigorous physical activity (MVPA). A moderate correlation was found to maximal muscle strength was found (r=0.61, p&amp;lt;0.001). The ALM/BMI-index was moderately correlated to maximal muscle strength (r=0.65, p&amp;lt;0.001), VO2peak (r=0.40, p&amp;lt;0.001), 6MWD (r=0.41, p&amp;lt;0.001), average daily PA (r=0.27, p=0.012) and daily time spent in MVPA (r=0.29, p=0.007). Patients with low MM identified by ALM/m2 did not differ from patients with preserved MM with regards to VO2peak, 6MWD or accelerometer measurements. A difference in maximal muscle strength was found (95.7±35.6 Nm vs 116±44.8, p=0.02). Patients with low MM identified by ALM/BMI had lower maximal muscle strength (94.8±36.1 Nm vs 121.9±44.4 Nm, p=0.001), lower VO2peak (13.2±3.5 mL/kg/min vs 16.4±3.7 mL/kg/min, p&amp;lt;0.001), shorter 6MWD (370.5±99.4 m vs 467.3±93.9 m, p&amp;lt;0.001), average daily PA (15.1±4.4 ENMO* vs 17.3±5.3 ENMO*, p=0.04) and daily time spent in MVPA (14.2±16.7 min vs 24.7±21.6 min, p=0.01) compared to patients with preserved MM. Conclusion In HFrEF patients low MM identified by ALM/BMI seems to correlate better to well-established markers for physical capacity (VO2peak and 6MWD), muscle strength and daily PA compared to ALM/m2. No cut-offs have been established for ALM/BMI and there is a need for longitudinal studies to determine the association with mortality in HFrEF patients. *ENMO = Euclidean Norm Minus One, an acceleration metric. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): The Karen Elise Jensens Foundation

Muscle strength, aerobic capacity, and exercise tolerance are impaired in left ventricular assist devices recipients: A pilot study.

Background: Left ventricular assist devices (LVAD) are increasingly being used as a therapy for advanced heart failure, both as a bridge to heart transplant and, given the rapid advances in the LVAD’s functionality and safety, and constant lack in availability of donor organs, as long-term destination therapy. With the diffusion of such therapy, it is crucial to assess patients’ muscle strength, aerobic capacity and exercise tolerance, to improve their functional capacity. Methods: 38 LVAD recipients (33 men and five women) were included. Exercise testing including a maximal cardiopulmonary exercise test (CPET), handgrip, isometric and isokinetic strength testing of knee and ankle flexion/extension, and Romberg balance test in three conditions (eyes open, eyes closed, double task). Given the small and heterogeneous final sample size, a mostly descriptive statistical approach was chosen. Results: 12 participants were classified as “Obese” (BMI>29.9). The most common comorbidities were type II diabetes and chronic kidney disease. Only 12 participants were able to successfully complete all the assessments. CPET and isokinetic strength trials were the least tolerated tests, and the handgrip test the best tolerated. Mean VO2 peak was 12.38 ± 3.43 ml/kg/min, with 15 participants below 50% of predicted VO2 max, of which 6 below 30% VO2max. Mean handgrip strength was 30.05 ± 10.61 Kg; 25 participants were below the 25° percentile of their population’s normative reference values for handgrip strength, 10 of which were below the 5° percentile. Issues with the management of the external pack of the LVAD and its influence on the test limited the validity of the balance tests data, therefore, no solid conclusions could be drawn from them. VO2 peak did not correlate with handgrip strength or with any of the lower limb strength measures. Conclusion: LVAD recipients show greatly reduced functional capacity and tolerance to exercise and exercise testing, with low overall strength levels. As strength variables appear to be independent from VO2 peak, different lower limbs strength tests should be explored to find a tolerable alternative in this population, which is subjected to muscle wasting due to old age, reduced tissue perfusion, side effects from the pharmacological therapies, and prolonged periods of bedrest.

Correlation between Isometric Maximum Strength and One Repetition Maximum in the Calf Muscle in Extended and Bended Knee Joint

Previous research points out high relevance of maximal strength measurement in the diagnostics of different populations. However, there is inconsistency in procedures of maximum strength measurements. Thus, it must be questioned whether the results from different studies are actually comparable. Due to the aforementioned problems in standardization, the aim of this study was to assess correlations between and reproducibility of isometric and dynamic strength testing. Since there are many studies investigating maximal strength in the calf muscles, this study will examine the plantar flexors. For this purpose, 87 active participants were recruited (m: 52, f: 35, age: 28.3 ± 5.5 years, range 18-38 years, height: 178.3 ± 6.6 cm, weight: 81.5 ± 7.4 kg) who performed maximal isometric strength testing and dynamic 1RM testing in plantar flexion both with extended and bended knee joint. Pearson correlation as well as concordance correlation coefficient (CCC) were determined. In literature, CCC is used to determine reproducibility between two different testing methods. There were correlation coefficients of r = 0.63 – 0.77 and &lt;i&gt;ρ&lt;sub&gt;c&lt;/sub&gt;&lt;/i&gt;=0.62 ‒ 0.77. Results are comparable with correlations between maximal isometric strength and 1-RM in previous studies in different movements. In consideration of CCC, isometric strength testing and 1RM seem to not measure the same parameter, therefore comparison of results measured with different procedures seems difficult. Our results exhibit a high influence of isometric maximal strength on 1RM performance. However, 1RM tests cannot be replaced by isometric strength testing. Care must be taken due to standardization of procedure when comparing results from different studies and, especially, if 1RM testing should be replaced with isometric strength measurement.

The effects of vertical trunk supportability improvement on one-leg rebound jump efficiency.

The purpose of this study was to examine the effects of vertical trunk supportability improvement on activities. The study participants were 36 people. Trunk function and physical performance were evaluated using the following tests: trunk righting test (TRT), maximal isometric knee extensor strength test, side hop test, triple hop distance test, stabilometry of one-leg standing, and one-leg rebound jump. The measurement was performed three times: pre-trunk training (pre), post-trunk training for 1 month (post), and 2 months after the second measurement (detraining). Details of trunk training: Two sets of 30-s maximal lateral reach exercises on each side, following the four sets of 15-s maximal raising trunk exercises on each side. The results with TRT in post-training were significantly larger than those in pre-and detraining. Similarly, the results with one-leg rebound jump efficiency in post-training were significantly larger than those in pre-and detraining. Our findings indicate that jump efficiency changes in proportion to the change in vertical trunk supportability.

Preliminary Research towards Acute Effects of Different Doses of Caffeine on Strength-Power Performance in Highly Trained Judo Athletes.

Although several previous studies examined the effect of pre-exercise caffeine ingestion on judo-specific performance, the optimal dose of caffeine to maximise the ergogenic effects for judoka is not clear. The main purpose of this study was to analyse the effects of oral administration of 3 and 6 mg/kg of caffeine on a battery of physical tests associated with judo performance. Ten highly trained national-level judoka (6 men and 4 women, age: 24.1 ± 4.7 years, body mass: 73.4 ± 12.9 kg, 15.1 ± 5.2 years of judo training experience, 2.6 mg/kg/day of habitual caffeine intake) participated in a randomized, crossover, placebo-controlled and double-blind experiment. Each judoka performed three identical experimental sessions after: (a) ingestion of 3 mg/kg of caffeine (CAF-3); (b) ingestion of 6 mg/kg of caffeine (CAF-6); (c) ingestion of a placebo (PLAC). After 60 min for substance absorption, participants performed the following tests: (a) bench press exercise with 50% of the load representing one-repetition maximum (1RM), including three sets of three repetitions; (b) bench pull exercise with 50% of 1RM including three sets of three repetitions; (c) countermovement jump; (d) maximal isometric handgrip strength test; (e) dynamic and isometric versions of the Judogi Grip Strength Test. In comparison with PLAC, the ingestion of CAF-3 and CAF-6 increased peak bar velocity in the bench press exercise (1.27 ± 0.11 vs. 1.34 ± 0.13 and 1.34 ± 0.15 m/s, respectively; p < 0.01) and mean bar velocity in the bench pull exercise (1.03 ± 0.15 vs. 1.13 ± 0.13 and 1.17 ± 0.15 m/s; p < 0.05). Only CAF-6 increased mean bar velocity in the bench press exercise when compared with PLAC (0.96 ± 0.09 vs. 1.02 ± 0.11 m/s; p < 0.05). Both CAF-3 and CAF-6 significantly increased the number of repetitions in the Judogi Grip Strength Test (17 ± 10 vs. 20 ± 10 and 20 ± 10 repetitions; p < 0.05). There were no differences between PLAC and caffeine doses in the remaining tests. The pre-exercise ingestion of 3 and 6 mg/kg of caffeine effectively obtained meaningful improvements in several aspects associated with judo performance. From a practical viewpoint, the selection between 3 or 6 mg/kg of caffeine may depend on previously tested individual responses during simulated competition.

Quantitative gait analysis after total hip arthroplasty through a minimally invasive direct anterior approach: A case control study

IntroductionTotal Hip Arthroplasty (THA) leads to excellent clinical and functional results. The Minimally Invasive Anterior Approach (MIAA) theoretically allows rapid recovery and a reduction in the need for rehabilitation, but alterations in muscle and static balance have previously been demonstrated. Kinetic, kinematic and muscular alterations have been shown to persist up to 1year postoperatively but data beyond 1year postoperatively is lacking. Thus, the objective of this study was to compare the data from Quantitative Gait Analysis (QGA) coupled with electromyography (EMG), of patients one year postoperatively with THA through MIAA, compared to an asymptomatic control group. HypothesisWe hypothesized that QGA and EMG parameters would not normalize beyond one year postoperatively. Patients and MethodsTwenty-seven patients were recruited, including 15 subjects (64.6±6.6years) operated on by MIAA, who at 15.9±3.1months postoperatively, along with 12 asymptomatic control subjects (68.9±9.7years), who underwent QGA and maximal isometric muscle strength tests, coupled with EMG on the gluteus medius and maximus, Tensor Fascia Lata (TFL) and Sartorius muscles. The spatiotemporal parameters of walking (step length, walking speed, cadence, single leg support time), kinetics (vertical ground reaction forces, hip moments in the 3 planes) and kinematics (coxofemoral and pelvic amplitudes) were analyzed. ResultsThe walking speed was lower on the non-operated side of the experimental subjects (0.96ms−1 compared to 1.13ms−1 for asymptomatic [p=0.018]), as was the step length on the operated side (0.53m compared to 0.60m for asymptomatic [p=0.042]). Maximal isometric muscle strength was lower in subjects operated on for the gluteus maximus and medius (p=0.004), compared to asymptomatic subjects. Moments were lower in the subjects operated on in extension (0.72Nm on the operated side, 0.75Nm on the non-operated side compared to 1.06Nm for asymptomatic [p=0.007 and p=0.024]) and lateral rotation (0.09Nm on the operated side, 0.05Nm on the non-operated side compared to 0.16Nm for asymptomatic subjects [p=0.009 and p=0.0005]). Hip adduction amplitudes were lower on the operated side compared to asymptomatic subjects (3.93° versus 9.14° for asymptomatic [p=0.005]). Pelvic amplitudes in the frontal plane were lower amongst operated subjects (0.44° against 1.97° for asymptomatic [p=0.041]). Pelvic amplitudes in the sagittal plane were higher in the operated subjects (15.74° on the operated side, 15.43° on the non-operated side compared to 9.65° for asymptomatic [p=0.041 and p=0.032]). DiscussionOur initial hypothesis was validated, since walking deficits persisted beyond one year postoperatively after THA through MIAA. A decrease in maximal isometric muscle strength of the gluteus medius and gluteus maximus was observed, as well as an alteration of kinetic and kinematic parameters in the sagittal and frontal planes. The results were in agreement with the literature and reflected the establishment of compensatory mechanisms to overcome alterations in joint strength and range more than one year postoperatively. These results would allow rehabilitation programs to be more specific and would justify a study on the other approaches for THA. Level of evidenceIII; non-randomized control trial.

Grip Strength-Endurance in Ambitious and Recreational Climbers: Does the Strength Decrement Index Serve as a Feasible Measure?

The present study investigated the time course of repetitive maximal isometric grip strength, depending on the arm position, laterality (dominant vs. non-dominant side), and climbing level. The intervention aimed to provide a feasible indicator of maximal strength-endurance in climbing. Seventeen recreational (climbing level (CL): 6.8 (SD 0.5) on the Union Internationale des Associations d’Alpinisme (UIAA) metric scale) and eleven ambitious (CL: 8.7 (SD 0.6) UIAA metric scale) climbers (age: 27 (8) years; BMI: 21.6 (1.9) kg/m2; ape index (arm span divided by body height): 1.05 (0.18); training volume: 2.2 (1.0) h/week). Participants completed maximal isometric handgrip strength (Fmax) tests in four positions (left and right hand beside the trunk as well as left and right hand above the shoulder) plus twelve repetitive work-relief cycles, lasting 4 and 1 s where isometric strength, heart rate, and perceived exertion were recorded. Fmax differed between groups in nearly all positions. A large side × position × time × group interaction was observed for repetitive isometric grip strength (p = 0.009, ηp2 = 0.71). However, subsequent post-hoc tests did not reveal a significant difference between groups during each testing position. Additional correlation analysis between asymmetry and CL showed an inverse relationship for ambitious climbers (r = −0.71). In conclusion, the degree of grip strength decline did not relevantly differentiate between ambitious and recreational climbers. Thus, the time course of handgrip strength seems to mainly rely on maximal grip strength during the first contraction.

Muscular Fitness Improves during the First Year of Academy Studies among Fighter Pilot Cadets.

Background: An adequate level of muscular fitness is related to occupational performance in military personnel, including pilots flying high performance aircraft. The aim of this study was to describe the baseline level and the change in muscular fitness between the first and the second years of the Air Force Academy among fighter pilot cadets. Methods: The muscular strength and endurance test results of 182 male fighter pilot cadets were analyzed during their first year in the Air Force Academy and one year after. Maximal isometric strength tests included trunk flexion, trunk extension and bilateral leg extension tests, whereas muscle endurance was measured with modified a sit-up test and seated alternative dumbbell press. Results: The maximal isometric bilateral strength of the leg extensor muscles increased from 220 ± 42 to 232 ± 42 kg. The maximal isometric trunk extension strength increased from 117 ± 21 to 120 ± 19 kg and trunk flexion from 82 ± 16 to 86 ± 17 kg. Muscle endurance increased from 68 ± 13 to 75 ± 15 repetitions/min in seated dumbbell press and from 47 ± 12 to 51 ± 13 repetitions/min in sit-up test. Conclusions: Both maximal strength and muscular endurance improved among fighter pilot cadets, which indicates that occupational performance is well maintained or improved from the perspective of physical fitness during the early phase of academy studies. Education in the Air Force Academy, including physical education, seems beneficial in improving muscular fitness among military pilots.

Electromyographic amplitude versus torque relationships are different in young versus postmenopausal females and are related to muscle mass after controlling for bodyweight.

To examine differences in the electromyographic vs torque (EMG-T) relationship, as well as muscle strength and indicators of muscle mass and quality between young versus postmenopausal females, and explore whether the potential differences in the EMG-T relationships could be explained by differences in muscle mass. Thirty young (age = 20.7 ± 2.8 y) and 30 postmenopausal (age = 56.3 ± 4.7 y) females completed maximal isometric strength testing (MVIT) and isometric ramp contractions at 40% and 70% MVIT, during which electromyographic signals were collected to quantify the slopes (Slope40; Slope70) and intercepts (Intercept40; Intercept70) of the EMG-T relationships. Muscle mass and quality measurements were also completed. Postmenopausal females exhibited lower skeletal muscle mass (-2.3 ± 1.5kg), fat-free mass index (-1.1 ± 0.7kg·m-2), MVIT (-17.1 ± 16.3 Nm), phase angle (-0.5 ± 0.0°), muscle cross-sectional area (-5.5 ± 1.1cm2), muscle quality (-0.1 ± 0.0 a.u), Slope40 (-0.0003 ± 0.0002mV·%MVIT-1), Slope70 (-0.0003 ± 0.0002mV·%MVIT-1), and had a higher echo intensity (+ 9.8 ± 2.8 a.u), Intercept40 (+ 0.001 ± 0.001mV), and Intercept70 (+ 0.004 ± 0.003mV) (p ≤ 0.001-0.04) than the young females. The EMG-T relationship variables were correlated with both muscle mass and quality after controlling for bodyweight. When controlling for muscle mass and bodyweight, group differences in the slopes of the EMG-T relationship and muscle strength were eliminated. Muscle mass and quality are primary contributors to the decrements in neuromuscular function observed in postmenopausal versus young females, and the preservation of muscle mass should be prioritized in the years leading up to, during, and immediately after menopause.

Association Between Lower Extremity Muscular Strength And Functional Performance In Community-Dwelling Elderly

The combination of aging with reduced muscle mass and muscle strength results in a higher risk of falls, hospitalizations, dependence, poorer quality of life, and all-cause mortality. Our hypothesis, in the present study, is that the elderly who present higher values in gait speed, as well as lower values in the Time Up and Go test, will have higher values of lower limb muscle strength. PURPOSE: To correlate functional capacity of walking and time up and go tests with the maximal isometric lower limb strength test in community-dwelling elderly. METHODS: Thirty-two elderly (2 men; age: 72 ± 9,2 yrs; body mass: 66 ± 10,6 kg; height: 152,27 ± 7,79 cm) who attended the Centro de Convivência do Idoso located in Paranoá, Brasília, DF participated. The tests were performed in an integrated and dynamic circuit format, where each station had a single evaluator. The maximal isometric muscle strength of lower limbs used the mid tight pull position where a traction dynamometer (E-lastic) was fixed to the ground by a metal chain and at its other end a hand strap. The elderly were instructed to perform their maximal concentric movement strength with semi-flexed knees and extended arms for 3-5 seconds with verbal encouragement. The muscle strength was measured in kilograms (kg). In the Walking Test (TC), the elderly should walk through the distance of 10m as fast as possible. Gait speed (m/s) was calculated. In the Time Up and Go (TUG) test, the elderly should get up from a chair without the aid of their arms and walk at a comfortable pace at a distance of three meters, get around an obstacle, return and sit again while time to end the task was measured. A Pearson correlation coefficient was determined between the maximum isometric strength test and the walking and time up and go tests. The statistical package adopted was SPSS (IBM, version 23). RESULTS: The findings revealed a significant and moderate correlation for gait speed and lower limb muscle strength (r = 0.391; p = 0.033) as well as the functional test and lower limb muscle strength level (r = -0.376; p = 0.041). CONCLUSION: Elderly who had higher lower limb strength values obtained the shortest times in the time up and go test and the highest gait speed in the walking test.

Reliability and Validity of a Method for the Assessment of Sport Rock Climbers' Isometric Finger Strength.

Torr, O, Randall, T, Knowles, R, Giles, D, and Atkins, S. The reliability and validity of a method for the assessment of sport rock climbers' isometric finger strength. J Strength Cond Res 36(8): 2277-2282, 2022-Isometric strength of the finger flexors is considered to be one of the main physical determinants of sport rock climbing performance. We set out to determine the test-retest reliability and criterion validity of a low resource maximal isometric finger strength (MIFS) testing protocol that uses a pulley system to add or remove weight to/from a climber's body. To determine test-retest reliability, 15 subjects' MIFS was assessed on 2 occasions, separated by a minimum of 48 hours. Body mass and maximum load were recorded on both occasions. Intra-class correlation coefficients (ICCs) between visits for all variables were very good (ICC > 0.91), with small bias and effect sizes-particularly when expressed as a percentage of body mass (ICC = 0.98, 95% confidence interval 0.93-0.99). To determine the criterion validity of MIFS and climbing ability, data of 229 intermediate to higher elite climbers were compared. Pearson's product moment correlations demonstrated good agreement, again particularly between total load when expressed as a percentage of body mass and climbing performance ( r = 0.421-0.503). The results illustrate the sensitivity of a simple test for the determination of MIFS in intermediate to height elite climbers from an ecologically valid, climbing specific test that only requires equipment found at most climbing walls. This low resource test protocol for the assessment of isometric finger strength has wide-reaching utility, for instance when assessing strength before and after a training intervention or when prescribing load intensities for exercises aimed at improving maximal finger strength.

Strength-training effectively alleviates skeletal muscle impairments in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a multisystemic disease characterized by progressive muscle weakness. The aim of this project is to evaluate the effects of a 12-week lower limb strength training program in 11 men with DM1. Maximal isometric muscle strength, 30-second sit-to-stand, comfortable and maximal 10-m walk test (10 mwt) were evaluated at baseline, 6 and 12 weeks, and at 6 and 9 months. The one-repetition maximum strength evaluation method of the training exercises was completed at baseline, 6 and 12 weeks. Muscle biopsies were taken in the vastus lateralis at baseline and 12 weeks to evaluate muscle fiber typing and size (including atrophy/hypertrophy factors). Performance in strength and functional tests all significantly improved by week 12. Maximal isometric muscle strength of the knee extensors decreased by month 9, while improved walking speed and 30 second sit-to-stand performance were maintained. On average, there were no significant changes in fiber typing or size after training. Further analysis showed that individual abnormal hypertrophy factor at baseline could explain the different changes in muscle size among participants. Strength training induces maximal isometric muscle strength and lasting functional gains in DM1. Abnormal hypertrophy factor could be a key component to identify high and low responders to hypertrophy in DM1.

The Minimum Number of Attempts for a Reliable Isometric Strength Test Score

The maximal isometric strength test is widely used in general, athletic, and clinical populations. However, this test has often been used without considering how many trials are needed or appropriate to obtain reliable test scores. Thus, the aim of this study was to examine the maximal isometric strength test in upper and lower body for the purpose of determining the reliability of best isometric strength score and the ideal number of trials for a reliable test score. One hundred and twelve healthy adults were assigned to four different groups (elbow flexion with the vertical and horizontal forearm positions, knee flexion, and knee extension). After familiarization, all participants performed three maximal isometric voluntary contractions with the designated muscle group. The reliability of best isometric strength test score was calculated using the intraclass correlation coefficients (ICC) from a one-way ANOVA model. The Spearman–Brown prophecy formula was used to identify the minimum number of trials needed. The reliability of the best maximal isometric strength test scores out of three trials were high (ICC = 0.92 to 0.98). At least two trials of maximal isometric strength test for knee flexion and one trial for elbow flexion and knee extension would be necessary to achieve an acceptable reliability coefficient of 0.80. In addition, one trial of elbow flexion would be enough for women, but men would need two trials. Our results suggest that overall, at least two trials would be necessary to test isometric strength in upper and lower body muscles in both sexes.