Ultrasonographic Measurement of Tendon Displacement Caused by Active Force Generation in the Psoas Major Muscle

Six Weeks of Hip Joint Training Using a Novel Multihip Joint Board Improves Sprint Performance in Competitive Collegiate Male Sprinters

ABSTRACT

Nakata, H, Nakanishi, Y, Otsuki, S, Mizuno, M, Connor, J, and Doma, K. Six weeks of hip joint training using a novel multihip joint board improves sprint performance in competitive collegiate male sprinters. J Strength Cond Res XX(X): 000-000, 2021-In a previous study, we identified the possibility that hip joint training using a multihip joint board (MHJB) may increase the cross-sectional area (CSA) of the psoas major (PM) muscle and improve sprint performance. However, the preliminary study reported descriptive findings because of a limited sample size. Therefore, we aimed to investigate and statistically infer the effects of the MHJB training protocol with a larger sample of male collegiate sprinters. The sprinters were randomly assigned to either the MHJB group (n = 7) or the control group (n = 7). The MHJB protocol consisted of 7 separate exercises targeting the development of the hip musculature, all using the MHJB device. The MHJB group undertook the MHJB protocol 3 times per week for 6 weeks, after their normal daily workout, whereas the control group completed their normal daily workout without the MHJB protocol. Sprint performance was recorded from official 100-m competitions before, and after, the 6-week training period. At the end of the training period, significantly greater improvement in PM CSA and 100-m sprint was noted in the MHJB group compared with the control group. These findings confirm the efficacy of MHJB training for increasing PM CSA and improve sprint performance in competitive male sprinters.

In Vivo Flattening of the Central Aponeurosis of the Rectus Femoris Due to Knee Extension Torque in Healthy Young and Elderly Individuals With Knee Osteoarthritis

ABSTRACT

We aimed to elucidate the relationship between active force production and the curvature of the central aponeurosis (CA) of the rectus femoris in young healthy participants as fundamental data and compare the muscle CA curvature before and after straight leg raising (SLR) training in participants with knee osteoarthritis (OA). Central aponeurosis curvature was determined during submaximal and maximal voluntary contractions (MVCs) using ultrasonography. Twenty-five young healthy female volunteers underwent ultrasonographic measurements under conditions of isometric MVC. They were divided into a flat shaped CA group (flat) and an incompletely flat shaped CA group (remnant). Central aponeurosis curvature was calculated as the ratio of CA height and length in the axial view. Central aponeurosis shape and muscular strength before and after muscle training were measured in 11 participants with knee OA. In the young healthy individuals, maximal voluntary torque and changes in CA curvature were significantly higher in the flat group than in the remnant group (2.15 Nm/kg and - 17.7% vs 1.75 Nm/kg and -9.8%, respectively; P = 0.005). The rate of change of the CA curvature during contraction was significantly correlated with maximal voluntary torque corrected for body mass (r = 0.512). The CA curvature progressively decreased as %MVC increased. In the OA group, CA curvature during MVC after SLR training was significantly lower than that before SLR training (3.2% vs 7.2%; P = 0.031). Central aponeurosis curvature was associated with muscle strength, and the results supported our hypothesis that geometric observation of CA changes during contractions may reflect muscle fiber function. We aim to develop a new ultrasonographic skeletal muscle evaluation method based on our present findings.

Efficacy of a newly designed trunk orthosis with joints providing resistive force in adults with post-stroke hemiparesis

BACKGROUND

Few studies have examined the efficacy of trunk orthoses that support the upper trunk and a paretic limb in stroke patients. To improve stability and alignment of the trunk and pelvis in hemiparetic patients, we developed a newly designed trunk orthosis that provides resistive force through spring joints.

OBJECTIVES

This study aimed to determine the newly designed trunk orthosis's biomechanical effects during level walking.

STUDY DESIGN

Before-after trials must be better.

METHODS

Measurements were taken for nine chronic-phase (>2 years post-onset) stroke patients using a three-dimensional motion capture system and force plates under three experimental conditions: self-selected gait speed without the newly designed trunk orthosis, with the newly designed trunk orthosis, and after newly designed trunk orthosis removal. We analyzed and compared spatiotemporal and kinetic parameters of the paretic and non-paretic limbs and kinematic parameters of the trunk and bilateral limbs.

RESULTS

Several pre-swing gait parameters (e.g. hip joint flexion moment and ankle joint plantar flexion angle) after newly designed trunk orthosis removal were significantly increased compared to those without newly designed trunk orthosis. Step length of the paretic limb tended to increase after newly designed trunk orthosis removal.

CONCLUSION

The newly designed trunk orthosis effectively modified trunk alignment, but larger improvements in kinetic and kinematic parameters were observed in the bilateral limbs after newly designed trunk orthosis removal than with the newly designed trunk orthosis.

CLINICAL RELEVANCE

Stroke patients improved only trunk malalignment while wearing the newly designed trunk orthosis. Gait after newly designed trunk orthosis removal was better than with the newly designed trunk orthosis. Positive changes after removal were mostly observed in pre-swing of the hemiparetic limb. The newly designed trunk orthosis might be effective for gait training in stroke patients.

The minimum required muscle force for a sit-to-stand task

The purpose of this study was to reveal the minimum required muscle force for a sit-to-stand task. Combining experimental procedures and computational processing, movements of various sit-to-stand patterns were obtained. Muscle forces and activations during a movement were calculated with an inverse dynamics method and a static numerical optimization method. The required muscle force for each movement was calculated with peak muscle activation, muscle physiological cross sectional area and specific tension. The robustness of the results was quantitatively evaluated with sensitivity analyses. From the results, a distinct threshold was found for the total required muscle force of the hip and knee extensors. Specifically, two findings were revealed: (1) the total force of hip and knee extensors is appropriate as the index of minimum required muscle force for a sit-to-stand task and (2) the minimum required total force is within the range of 35.3-49.2 N/kg. A muscle is not mechanically independent from other muscles, since each muscle has some synergetic or antagonistic muscles. This means that the mechanical threshold of one muscle varies with the force exertion abilities of other muscles and cannot be evaluated independently. At the same time, some kinds of mechanical threshold necessarily exist in the sit-to-stand task, since a muscle force is an only force to drive the body and people cannot stand up from a chair without muscles. These indicate that the existence of the distinct threshold in the result of the total required muscle force is reasonable.