The purpose of this study was to examine the effectiveness of maximal and rapid isometric torque characteristics of the hip extensor muscles and postural balance performance to discriminate between female collegiate soccer athletes and non-athlete controls. Ten athletes (mean ± SE: age = 19·20 ± 0·36 year; mass = 62·23 ± 3·12 kg; height = 162·43 ± 1·70 cm) and 10 non-athletes (age = 20·30 ± 0·40 year; mass = 69·64 ± 3·20 kg; height = 163·22 ± 2·10 cm) performed two isometric maximal voluntary contractions (MVCs) of the hip extensor muscles. Peak torque (PT) and absolute and relative rate of torque development (RTD) at early (0-50 ms) and late (100-200 ms) phases of muscle contraction were examined during each MVC. Postural balance was assessed using a commercially designed balance testing device, which provides a measurement of static stability based on sway index (SI). Results indicated that absolute and relative RTD at 0-50 ms (RTD50 and RTD50norm) were greater (P = 0·007 and 0·026), and postural SI was lower (P = 0·022) in the athletes compared with the non-athletes. However, no differences (P = 0·375-0·709) were observed for PT nor absolute and relative RTD at 100-200 ms (RTD100-200 and RTD100-200norm). Significant relationships were also observed between RTD50 and RTD50norm and SI (r = -0·559 and -0·521; P = 0·010 and 0·019). These findings suggest that early rapid torque characteristics of the hip extensor muscles and postural balance performance may be sensitive and effective measures for discriminating between college-aged athletes and non-athletes. Coaches and practitioners may use these findings as performance evaluation tools to help in identifying athletes with both superior early rapid torque and balance performance abilities, which may possibly be an indicator of overall athletic potential.

Early rapid strength production of the hip extensor muscles may be a sensitive and effective measure for discriminating between elderly females of different fall histories. These findings may provide important insight regarding implications for the assessment of fall risk and in the development of proper training programs aimed at minimizing the occurrence of falls and other balance-related injuries in the elderly.

The benefits of intrinsic exercise motivation are well recognized, yet extrinsically focused group-fitness class names/descriptions dominate the fitness industry. To explore the impact of how fitness classes are marketed, women (N = 389) were asked to indicate their preference for either intrinsically or extrinsically focused fitness classes based on title/description. Participants who favored intrinsic class names/descriptions were more likely to report greater interest/enjoyment, perceived competence, and greater effort and report exercising for health/fitness-related reasons. Those favoring extrinsic class names/descriptions were more likely to experience tension/pressure when exercising and report exercising for appearance/weight-related reasons. The results demonstrate the importance of wording when marketing fitness classes.

The purpose of this study was to determine if passive muscle-tendon properties of the posterior muscles of the hip and thigh and lower-body muscle power could discriminate between athletic status in division I female soccer athletes and nonathlete controls. Ten athletes (mean ± SE, age = 18.70 ± 0.34 years; mass = 64.61 ± 2.16 kg; height = 165.99 ± 1.46 cm; thigh muscle cross-sectional area = 94.08 ± 2.58 cm) and 11 nonathletes (mean ± SE, age = 19.64 ± 0.51 years; mass = 62.81 ± 2.60 kg; height = 162.44 ± 2.20 cm; thigh muscle cross-sectional area = 86.33 ± 2.81 cm) performed 2 instrumented straight-leg raise (iSLR) assessments using an isokinetic dynamometer programmed in passive mode to move the foot toward the head at 5°·s. During each iSLR, passive stiffness was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve, and maximum range of motion (ROM) was determined as the point of discomfort but not pain, as indicated by the participant. Lower-body power characteristics were assessed through a countermovement vertical jump (CMJ) test. The results indicated that phase 1 and 2 slopes, CMJ height, and peak power (Pmax) were significantly higher (p = 0.004-0.036) for the athletes compared with the nonathletes; however, maximum ROM was not different (p = 0.601) between groups. Significant relationships were also observed between phase 1 and 2 slopes, and CMJ height and Pmax (r = 0.483-0.827; p ≤ 0.001-0.027). These findings suggest that in addition to traditional power characteristics, passive stiffness may also be a sensitive and effective measure for discriminating athletes from nonathletes. Coaches and practitioners may use these findings when designing training programs aimed at increasing musculotendinous stiffness of the posterior hip and thigh muscles and to help identify athletes with high overall athletic potential.

Highlights This study presented a new optimization methodology using a prismatic joint with high stiffness and damping. The virtual suspension model contained the main bodies, an optimization subsystem, and a free-floating cylinder. Under aggressive terrain, an optimized chassis platform resulted in a 19.5% increase in boom height stability. Abstract. Multibody dynamics (MBD) models are continuing to be valuable for engineering design and product development, especially regarding subsystem optimization. Most MBD optimization processes begin with a sensitivity analysis of treatment factors and levels to understand how uncertainty in model inputs can be attributed to different sources of uncertainty within model outputs; however, this study developed a new MBD methodology to automatically determine the optimized dynamic chassis suspension responses on each corner of the vehicle from a single simulation for a self-propelled sprayer model as the chosen application use-case. This technique leveraged a prismatic joint (with a high spring stiffness and damping coefficient) connected between the chassis mainframe and the simplified optimization tire to create a distance constraint that held the chassis body at a near-consistent height above the ground. Then the solver optimized the response of the chassis suspension system to maintain a stable chassis platform relative to the terrain beneath it as the vehicle traversed across dynamic terrain conditions. This optimization response was also accomplished by replacing the baseline chassis suspension components with a free-floating cylinder, which permitted the unrestricted, optimized motion needed to keep the chassis body at a near-level position with respect to the roll and pitch profiles of the terrain. For a simulation with an aggressive terrain configuration, the analysis showed that an optimized suspension system resulted in a 46% decrease in operator comfort and a 19.5% increase in overall boom height stability as the boom height control system better maintained a dynamic position closer to the specified target height. Keywords: Boom height, Chassis suspension, Multibody dynamics (MBD), Optimization, Prismatic joint, Simulation, Terrain.