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Softball pitchers often pitch several games within a day and over consecutive days during a competitive season. High volumes of pitches thrown can decrease muscular strength, resulting in less proximal force generation and upper extremity compensation to maintain performance. Therefore, the purpose of this study was to assess upper and lower extremity muscular strength after pitching in a simulated game. Fourteen softball pitchers (17.9 ± 2.3 years, 166.4 ± 8.7 cm, 72.2 ± 12.6 kg) completed baseline isokinetic strength assessment for knee, hip, trunk and pitching elbow flexion and extension as well as trunk rotation. Seven days later, participants pitched a simulated game consisting of 105 fastballs prior to repeating all strength assessments. Changes in muscular strength were assessed using paired samples t-tests, with significance set a priori as p ≤ 0.05. Normalised (%BW) stride leg knee extension peak torque was significantly higher (p = 0.020) post-simulated game (75.1 ± 24.6%BW) as compared to baseline (64.0 ± 19.5%BW) and trunk flexion peak torque was significantly higher (p = 0.009) post-simulated game (84.8 ± 47.0%BW) as compared to baseline (63.5 ± 47.1%BW). This study showed an increase in knee extension and trunk flexion strength after an acute bout of pitching. The findings give insight into muscular changes following pitching which can assist in appropriate softball training and recovery.

Weaker hamstrings muscular forces and lower ratio of the hamstrings/quadriceps muscular forces in female athletes have been identified as modifiable risk factors for anterior cruciate ligament (ACL) injuries. However, sex differences in athletes' ability to react to visual cues (Choice Visual-Motor Reaction Time: VMRT) and to generate knee muscular forces (rate of force development: RFD) immediately following the visual cues were largely unknown. Therefore, the purpose of the study was to examine sex differences in Choice VMRT and RFD. A total of 50 high school basketball athletes (26F/24 M) participated in the study. Subjects sat in the knee dynamometer chair with their knee secured at 70° of knee flexion and performed knee extension or flexion maximum voluntary isometric contractions immediately after they saw the visual cue: "UP" or "DOWN" arrows, respectively. Choice VMRT was defined as the time between the visual cue and the initiation of muscular force development (>5Newtons). RFD was calculated by dividing the changes in forces over the changes in time at four time points (0-50/100/150/200 ms). Peak muscular forces and RFD were normalized to their body mass. Average of three trials in each direction (flexion and extension) in each leg was used for statistical analyses. Females had significantly slower Choice VMRT (p < 0.001-0.027) and lower knee extension RFD at 100 ms (p = 0.005). In addition, females had significantly higher knee flexion/extension ratio than males in late RFD (150 ms and 200 ms) (p < 0.004). The current study has provided additional sensorimotor characteristics of athletes and sexes in addition to their knee muscular characteristics., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Altered motor unit (MU) activity has been identified after anterior cruciate ligament (ACL) injury, but its effect on muscle tissue properties is unknown. The purpose of this study was to compare thigh musculature muscle stiffness between control and ACL-injured subjects., Methods: Thirty ACL-injured subjects and 25 control subjects were recruited. Subjects completed a randomized protocol of isometric contractions while electromyography (EMG) signals were recorded. Three maximum voluntary isometric contractions (MVIC) determined peak force for 10 and 25% MVIC trials. Shear wave elastography was captured during each 10 and 25% MVIC trials., Results: Differences in muscle stiffness were assessed between limbs and groups. 12 months post-surgery had higher stiffness for VM 0% MVIC, VL 0 and 10% MVIC, and ST 10 and 25% MVIC (all p ≤ 0.04)., Conclusion: Thigh musculature stiffness changed throughout rehabilitation and remained altered at 12 months after ACL reconstruction.

Purpose: Quadriceps weakness is a common clinical sign following anterior cruciate ligament injury and reconstruction surgery (ACLR). The aim of this study was to compare strength deficits and the limb symmetry index (LSI) from three different types of functional tests: isokinetic dynamometry, hop test, and leg press., Methods: A total of 26 subjects with ACLR (average 8.3 months post-operation) participated in the study. The peak knee extension torque was tested with isokinetic dynamometry at 60/180/300 °/s (ISO60/180/300). Hop distance was tested during single hop (SH) and triple hop (TH). Unilateral peak leg power (POWER) was tested during a bilateral leg press test. LSI was calculated as the ratio of the involved limb over the uninvolved limb values. Pearson correlation coefficients and paired t-tests were used to establish relationships among ISO60/180/300, SH/TH, and POWER values and compare these values between the limbs, respectively. Within-subject one-way analysis of variance (ANOVA) with post hoc analyses was used to compare LSI values among different tests., Results: ISO60/180/300 values were significantly positively correlated with SH/TH and POWER (P < 0.05), while SH/TH and POWER values were not significantly correlated. Significant limb differences were found in all tests (P = 0.001-0.008). ANOVA revealed significant LSI differences among different tests. Specifically, post hoc analyses revealed that LSI during SH was significantly higher than LSI during ISO60. Similarly, LSI during TH was significantly higher than LSIs from ISO60, ISO180, and POWER tests., Conclusions: Peak knee extension torque values were positively associated with hop distance and leg power during the leg press test. However, LSI values should be interpreted with caution as hop tests provided significantly higher LSI values than isokinetic testing. Both isokinetic dynamometry and unilateral leg press machine could be used to isolate and strengthen the quadriceps in the involved limb. The current "gold standard" isokinetic testing at slow speed (ISO60) provided the lowest LSI value among all functional tests; therefore, the current study supported a continued use of isokinetic testing when examining individual's readiness and return-to-sport., Level of Evidence: III.

Musculoskeletal injuries have negatively impacted tactical readiness. The identification of prospective and modifiable risk factors of preventable musculoskeletal injuries can guide specific injury prevention strategies for Soldiers and health care providers., Objectives: To analyze physiological and neuromuscular characteristics as predictors of preventable musculoskeletal injuries., Design: Prospective-cohort study., Methods: A total of 491 Soldiers were enrolled and participated in the baseline laboratory testing, including body composition, aerobic capacity, anaerobic power/capacity, muscular strength, flexibility, static balance, and landing biomechanics. After reviewing their medical charts, 275 male Soldiers who met the criteria were divided into two groups: with injuries (INJ) and no injuries (NOI). Simple and multiple logistic regression analyses were used to calculate the odds ratio (OR) and significant predictors of musculoskeletal injuries (p<0.05)., Results: The final multiple logistic regression model included the static balance with eyes-closed and peak anaerobic power as predictors of future injuries (p<0.001)., Conclusions: The current results highlighted the importance of anaerobic power/capacity and static balance. High intensity training and balance exercise should be incorporated in their physical training as countermeasures., (Copyright © 2017 Sports Medicine Australia. All rights reserved.)

Despite many nonbattle injuries reported during deployment, few studies have been conducted to evaluate the effects of deployment on musculoskeletal and physiological characteristics and balance. A total of 35 active duty U.S. Army Soldiers participated in laboratory testing before and after deployment to Afghanistan. The following measures were obtained for each Soldier: shoulder, trunk, hip, knee, and ankle strength and range of motion (ROM), balance, body composition, aerobic capacity, and anaerobic power/capacity. Additionally, Soldiers were asked about their physical activity and load carriage. Paired t tests or Wilcoxon tests with an α = 0.05 set a priori were used for statistical analyses. Shoulder external rotation ROM, torso rotation ROM, ankle dorsiflexion ROM, torso rotation strength, and anaerobic power significantly increased following deployment (p < 0.05). Shoulder extension ROM, shoulder external rotation strength, and eyes-closed balance (p < 0.05) were significantly worse following deployment. The majority of Soldiers (85%) engaged in physical activity. In addition, 58% of Soldiers reported regularly carrying a load (22 kg average). The deployment-related changes in musculoskeletal and physiological characteristics and balance as well as physical activity and load carriage during deployment may assist with proper preparation with the intent to optimize tactical readiness and mitigate injury risk., (Reprint & Copyright © 2016 Association of Military Surgeons of the U.S.)

Context: Dynamic postural stability is important for injury prevention, but little is known about how lower-extremity musculoskeletal characteristics (range of motion [ROM] and strength) contribute to dynamic postural stability. Knowing which modifiable physical characteristics predict dynamic postural stability can help direct rehabilitation and injury-prevention programs., Objective: To determine if trunk, hip, knee, and ankle flexibility and strength variables are significant predictors of dynamic postural stability during single-leg jump landings., Design: Cross-sectional study., Setting: Laboratory., Participants: 94 male soldiers (age 28.2 ± 6.2 y, height 176.5 ± 2.6 cm, weight 83.7 ± 26.0 kg)., Intervention: None., Main Outcome Measures: Ankle-dorsiflexion and plantar-flexion ROM were assessed with a goniometer. Trunk, hip, knee, and ankle strength were assessed with an isokinetic dynamometer or handheld dynamometer. The Dynamic Postural Stability Index (DPSI) was used to quantify postural stability. Simple linear and backward stepwise-regression analyses were used to identify which physical characteristic variables were significant predictors of DPSI., Results: Simple linear-regression analysis revealed that individually, no variables were significant predictors of the DPSI. Stepwise backward-regression analysis revealed that ankle-dorsiflexion flexibility, ankle-inversion and -eversion strength, and knee-flexion and -extension strength were significant predictors of the DPSI (R2 = .19, P = .0016, adjusted R2 = .15)., Conclusion: Ankle-dorsiflexion ROM, ankle-inversion and -eversion strength, and knee-flexion and -extension strength were identified as significant predictors of dynamic postural stability, explaining a small amount of the variance in the DPSI.

Background: Low back pain (LBP) is one of the most common musculoskeletal issues facing military helicopter pilots. It is clinically important to identify differences in musculoskeletal characteristics between pilots with and without a LBP history for formulating effective interventions., Objective: To compare lumbar spine and hip flexibility and trunk strength in pilots with and without a LBP history., Methods: A total of 30 pilots with a LBP history were matched with pilots without a LBP history. An isokinetic dynamometer and a digital inclinometer were used to evaluate trunk and hip strength and a range-of-motion (ROM), respectively. All tests were performed bilaterally, if applicable, and agonist/antagonist ratios and side-to-side (low/high) symmetries were calculated. Paired t-tests or Wilcoxon tests were used to assess group differences (p <  0.050)., Results: The LBP group demonstrated significantly lower trunk extension strength and trunk extension/flexion strength ratio (p <  0.008). The LBP group demonstrated significantly less lateral flexion ROM as well as greater lateral flexion and rotation side-to-side asymmetry (p <  0.009). The LBP group demonstrated significantly greater total hip rotation side-to-side asymmetry (p = 0.037)., Conclusions: Given the results, specific exercises that are targeted to improve trunk strength, ROM, and side-to-side symmetries could be developed to reduce LBP in helicopter pilots.

Context: The importance of the sensorimotor system in maintaining a stable knee joint has been recognized. As individual entities, knee-joint proprioception, landing kinematics, and knee muscles play important roles in functional joint stability. Preventing knee injuries during dynamic tasks requires accurate proprioceptive information and adequate muscular strength. Few investigators have evaluated the relationship between knee proprioception and strength and landing kinematics., Objective: To examine the relationship between knee proprioception and strength and landing kinematics., Design: Cross-sectional study., Setting: University research laboratory., Patients or Other Participants: Fifty physically active men (age = 26.4 ± 5.8 years, height = 176.5 ± 8.0 cm, mass = 79.8 ± 16.6 kg)., Intervention(s): Three tests were performed. Knee conscious proprioception was evaluated via threshold to detect passive motion (TTDPM). Knee strength was evaluated with a dynamometer. A 3-dimensional biomechanical analysis of a single-legged stop-jump task was used to calculate initial contact (IC) knee-flexion angle and knee-flexion excursion., Main Outcome Measure(s): The TTDPM toward knee flexion and extension, peak knee flexion and extension torque, and IC knee-flexion angle and knee flexion excursion. Linear correlation and stepwise multiple linear regression analyses were used to evaluate the relationships of both proprioception and strength against landing kinematics. The α level was set a priori at .05., Results: Enhanced TTDPM and greater knee strength were positively correlated with greater IC knee-flexion angle (r range = 0.281-0.479, P range = .001-.048). The regression analysis revealed that 27.4% of the variance in IC knee-flexion angle could be accounted for by knee-flexion peak torque and TTDPM toward flexion (P = .001)., Conclusions: The current research highlighted the relationship between knee proprioception and strength and landing kinematics. Individuals with enhanced proprioception and muscular strength had better control of IC knee-flexion angle during a dynamic task.

Joint trauma induces a presynaptic reflex inhibition termed arthrogenic muscle inhibition (AMI) that prevents complete activation of muscles. Reduced motor unit (MU) output is a hypothesised mechanism for persistent strength deficits. The objective of this study was to determine MU characteristics of thigh musculature and determine how they change with anterior cruciate ligament (ACL) injury compared to healthy controls. A randomised protocol of knee flexion/extension isometric contractions (10–50% maximal voluntary isometric contraction) was performed for each leg with surface EMG 5-pin array electrodes placed on the vastus medialis, vastus lateralis, semitendinosus and biceps femoris. Longitudinal assessments for average rate coding, recruitment thresholds and MU action potentials were acquired at 6-month intervals. With exception of the vastus medialis, all thigh musculature of ACL-injured demonstrated smaller MU action potential peak-to-peak amplitude. For average rate coding, ACL-injured demonstrated lower coding rates than Controls for the quadriceps (p <.05) and higher rates than Controls for the hamstrings (p <.05). These MU characteristics were different from Controls after ACL reconstruction up to 12 months post-surgery, yet maximal strength increased during this time frame. As thigh MU characteristics are known across phases of ACL rehabilitation, future studies can assess these patterns of motor control and their potential to determine risk of re-injury. Further, future rehabilitation can target specific intervention programmes to restore motor control. Highlights Motor unit strategies of arthrogenic muscle inhibition are characterised for the first time via decomposed EMG. Motor unit deficits of thigh musculature persist throughout all phases of ACL rehabilitation, even after return-to-sport. After ACL injury, motor unit sizes at similar recruitment thresholds were smaller than those of healthy controls. [ABSTRACT FROM AUTHOR]

Purpose: To examine strength, range of motion, anthropometric, and physiological contributions to novice surface-combat-swimming (sCS) performance and establish differences from freestyle-swimming (FS) performance to further understand the transition of FS to sCS performance. Methods: A total of 13 competitive swimmers (7 male and 6 female; 27.7 [2.3] y; 176.2 [2.6] cm; 75.4 [3.9] kg) completed 8 testing sessions consisting of the following: physiological land-based measurements for maximal anaerobic and aerobic capacity and upper- and lower-extremity strength and range of motion, an sCS anaerobic capacity swim test measuring peak and mean force and fatigue index, 2 aerobic capacity tests measuring maximal aerobic capacity for both FS and sCS, and four 500-m performance swims for time, 1 FS, and 3 sCS. Separate multiple linear-regression analysis was used to analyze predictors of both sCS and FS performance models. Results: FS performance was predicted by the final FS maximal oxygen uptake with an R2 of 42.03% (F1,10 = 7.25; P =.0226), whereas sCS performance was predicted by isometric hip-extension peak strength with an R2 of 41.46% (F1,11 = 7.79; P =.0176). Conclusions: Results demonstrate that different physiological characteristics predict performance, suggesting that an altered strategy is used for novice sCS than FS. It is suggested that this may be due to the added constraints as mandated by mission requirements including boots, weighted gear, and clandestine requirements with hips lowered beneath the surface. Further research should examine the kinematics of the sCS flutter kick to improve performance by developing training strategies specific for the task. [ABSTRACT FROM AUTHOR]

Context: In vivo scapular kinematics during humeral movements are commonly assessed with electromagnetic tracking devices despite few published data related to reliability and precision of these measurements. Objective: To determine the intrasession reliability and precision of assessing scapular kinematics using an electromagnetic tracking device. Design: Scapular position and orientation were measured with an electromagnetic tracking device during humeral elevation/depression in several planes. Intrasession reliability and precision were established by comparing 2 trials performed in succession. Setting: A human-movement research laboratory. Participants: 15 healthy individuals. Main Outcome Measures: Intrasession intraclass correlation coefficients and standard error of measurement of all scapular variables were established. Results: The mean intrasession reliability for all variables was ICC = .97 ± .03. The mean intrasession precision was .99° ± .36°. Conclusions: In vivo scapular kinematics can be measured with high reliability and precision during intrasession research designs. [ABSTRACT FROM AUTHOR]

Huang, H-C, Nagai, T, Lovalekar, M, Connaboy, C, and Nindl, BC. Physical fitness predictors of a warrior task simulation test. J Strength Cond Res 32(9): 2562–2568, 2018—The warrior task simulation test (WTST) has been developed in an attempt to better assess physical fitness required for soldiers to perform battlefield tasks and drills to determine whether laboratory-based measurements of physical fitness components could be used to predict the WTST. Forty-three healthy and physically active men participated in 2 sessions: the WTST and laboratory testing. The WTST comprised 282-m run, low hurdles, high crawl, casualty drag, balance beam, point-aim-move, 100-yard sprint, and agility sprint with participants wearing combat boots, uniform, helmet, and dummy rifle. The laboratory testing included assessments of participants' muscular strength and endurance, postural stability, aerobic capacity, anaerobic capacity, flexibility, body fat, fat-free mass, and agility. Correlation and simple and multiple linear regression analyses were used to analyze the relationship between the WTST and laboratory testing and predict the WTST, respectively (p < 0.05). The correlation and the simple linear regression analyses revealed that anaerobic capability, aerobic capacity, body fat, agility, and muscular endurance correlated with (r = 0.35–0.59) and accounted for 12–34% of the variance in (R 2 = 0.12–0.34) the WTST performance (p < 0.05). The final model included aerobic capacity, agility, fat-free mass, muscular endurance, and body fat (R 2 = 0.52, p < 0.001). The current results highlighted the importance of several components of physical fitness in simulated battlefield tasks and drills (assessed by the WTST). In particular, anaerobic capacity, aerobic capacity, and body fat had the highest correlational and predictive values of the WTST. Additionally, skill-related components of physical fitness, such as agility and muscular endurance, should not be ignored, and they should be assessed and tracked with the above-mentioned components. [ABSTRACT FROM AUTHOR]

BACKGROUND: Cumulative effects of high-impact vertical forces, like those experienced on an open-ocean mission, could be an injury concern for the cervical spine. OBJECTIVE: Compare cervical range of motion (ROM) and strength measures between students and NSW Crewmen and secondarily to compare these measures between students and Crewmen separated into three groups based on years of service. METHODS: A volunteer sample of 186 students (age: 22.8±3.1 years) and 167 Operators (age: 26.9±5.1 years) completed cervical isometric strength (% BW) and ROM (°) measurements using a handheld dynamometer and CROM-3 device, respectively. Independent samples t-tests were done to evaluate differences between students and Crewmen. Analysis of Variance and appropriate post-hoc tests were calculated to compare students to Crewmen separated into three groups based on years of service. Data is reported as mean±SD and (student mean vs. Operator mean). RESULTS: Students demonstrated higher flexion strength (21.7±4.9 vs. 19.1±5.0) and greater ROM: flexion (54.3±10.6 vs. 51.2±9.2), and extension (77.0±14.4 vs. 71.3±11.4) than Crewmen. Students demonstrated greater flexion strength than Crewmen with ≤2 (19.4±5.1), 3–6 (19.4±5.3), and ≥7 (18.6±4.7) years of service. CONCLUSIONS: Students demonstrated greater cervical strength and ROM. A trend of decreasing ROM/strength in Crewmen with greater years of service was also observed. [ABSTRACT FROM AUTHOR]

Low back pain is a common cause of disability in the US with increasing financial burden on healthcare. A variety of treatment options exist to combat LBP. Home-based therapy is a low-cost option, but there is a lack of data on how it compares to therapy in clinical settings. It was hypothesized that when using artificial intelligence-guided therapy, supervised in-clinic interventions would have a greater influence on patient-reported outcomes and strength than unsupervised, home interventions. This is a non-randomized controlled trial of 51 patients (28 female, 23 male). The investigation compared an 8-week, core-focused exercise intervention in a Clinic (supervised) versus Home (unsupervised) setting. Outcome variables included measures of strength, performance, and patient-reported outcomes related to function. Generalized linear regression (p < 0. 05) was used to evaluate outcomes were evaluated with respect to sex, intervention setting, and time. Male subjects exhibited greater strength (p ≤ 0.02) but not greater patient-reported outcomes (p ≥ 0.30) than females. The Clinic group exhibited slightly greater lateral pull-down strength (p = 0.002), greater eccentric phase range of motion during overhead press (p < 0.01), and shorter concentric phase duration during bench press (p < 0.01) than the Home group. Significance between groups was not observed in any other strength, performance, or patient-reported outcome (p ≥ 0.11). A lack of consistent significance indicated that the hypothesis was not supported. AI-guided, telehealth exercise produced comparable outcomes in both home and clinical settings. Telehealth options may offer a lower-cost alternative to clinic-based exercise therapy for patients with nonspecific lower back pain. • A paucity of data compares home-based therapy to supervised clinic-based therapy. • We compared clinic and home-based therapy interventions for lower back pain. • Patient reported pain, physical function, and kinesiophobia were assessed. • Both home- and clinic-based therapy provide comparable patient reported outcomes. [ABSTRACT FROM AUTHOR]

Soldiers must maintain tactical performance capabilities over the course of their career. Loss in physical readiness may be a function of age and the operational demands associated with increasing years of service. The purpose of this study was to assess strength and physiological characteristics in different cohorts of U.S. Army Soldiers based on years of service and age. A total of 253 Soldiers (age: 28.1 ± 6.8 years; height: 1.76 ± 0.11 m; mass: 84.1 ± 12.2 kg) participated. Individual subject cohorts were created based on years of service (1-5 years, 6-10 years, 11-15 years) and age (20-24 years, 25-29 years, 30-34 years, 35-39 years, 40-44 years). Testing included shoulder, knee, ankle, and torso strength, aerobic capacity/lactate threshold, anaerobic power/capacity, and body composition/total mass. Those with 11 to 15 years of service and between ages 30 and 34 had a higher percentage of body fat, and lower aerobic capacity and lactate threshold than younger Soldiers with fewer years of service. Physical training interventions should focus on maintenance of physiological characteristics to offset the loss of readiness at the similar time point of 11 to 15 years of service and 30 to 34 years of age. [ABSTRACT FROM AUTHOR]