Effect of isolated hip abductor fatigue on single-leg landing mechanics and simulated ACL loading.

BACKGROUND: Altered movement biomechanics are a risk factor for ACL injury. While hip abductor weakness has been shown to negatively impact landing biomechanics, the role of this musculature and injury risk is not clear. The aim of this musculoskeletal simulation study was to determine the effect of hip abductor fatigue-induced weakness on ACL loading, force production of lower extremity muscles, and lower extremity biomechanics during single-leg landing. METHODS: Biomechanical data from ten healthy adults were collected before and after a fatigue protocol and used to derive subject-specific estimates of muscle forces and ACL loading using a 5-degree of freedom (DOF) model. RESULTS: There were no significant differences in knee joint angles and ACL loading between pre and post-fatigue. However, there were significant differences, due to fatigue, in lateral trunk flexion angle, total excursion of trunk, muscle forces, and joint moments. CONCLUSION: Altered landing mechanics, due to hip abductor fatigue-induced weakness, may be associated with increased risk of ACL injury during single-leg landings. Clinical assessment or screening of ACL injury risk will benefit from subject-specific musculoskeletal models during dynamic movements. Future study considering the type of the fatigue protocols, cognitive loads, and various tasks is needed to further identify the effect of hip abductor weakness on lower extremity landing biomechanics.

Sex and Limb Differences in Lower Extremity Alignment and Kinematics during Drop Vertical Jumps.

Sex and limb differences in lower extremity alignments (LEAs) and dynamic lower extremity kinematics (LEKs) during a drop vertical jump were investigated in participants of Korean ethnicity. One hundred healthy males and females participated in a drop vertical jump, and LEAs and LEKs were determined in dominant and non-dominant limbs. A 2-by-2 mixed model MANOVA was performed to compare LEAs and joint kinematics between sexes and limbs (dominant vs. non-dominant). Compared with males, females possessed a significantly greater pelvic tilt, femoral anteversion, Q-angle, and reduced tibial torsion. Females landed on the ground with significantly increased knee extension and ankle plantarflexion with reduced hip abduction and knee adduction, relatively decreased peak hip adduction, knee internal rotation, and increased knee abduction and ankle eversion. The non-dominant limb showed significantly increased hip flexion, abduction, and external rotation; knee flexion and internal rotation; and ankle inversion at initial contact. Further, the non-dominant limb showed increased peak hip and knee flexion, relatively reduced peak hip adduction, and increased knee abduction and internal rotation. It could be suggested that LEAs and LEKs observed in females and non-dominant limbs might contribute to a greater risk of anterior cruciate ligament injuries.

Small changes in ball position at address cause a chain effect in golf swing.

The purpose of this study was to investigate how the ball position along the mediolateral (M-L) direction of a golfer causes a chain effect in the ground reaction force, body segment and joint angles, and whole-body centre of mass during the golf swing. Twenty professional golfers were asked to complete five straight shots for each 5 different ball positions along M-L: 4.27 cm (ball diameter), 2.14 cm (ball radius), 0 cm (reference position at preferred ball position), - 2.14 cm, and - 4.27 cm, while their ground reaction force and body segment motions were captured. The dependant variables were calculated at 14 swing events from address to impact, and the differences between the ball positions were evaluated using Statistical Parametric Mapping. The left-sided ball positions at address showed a greater weight distribution on the left foot with a more open shoulder angle compared to the reference ball position, whereas the trend was reversed for the right-sided ball positions. These trends disappeared during the backswing and reappeared during the downswing. The whole-body centre of mass was also located towards the target for the left-sided ball positions throughout the golf swing compared to the reference ball position, whereas the trend was reversed for the right-sided ball positions. We have concluded that initial ball position at address can cause a series of chain effects throughout the golf swing.

Effects of a 4-Week Short-Foot Exercise Program on Gait Characteristics in Patients With Stage II Posterior Tibial Tendon Dysfunction.

CONTEXT: Clinically, it has been suggested that increased activation of intrinsic foot muscles may alter the demand of extrinsic muscle activity surrounding the ankle joint in patients with stage II posterior tibial tendon dysfunction. However, there is limited empirical evidence supporting this notion. OBJECTIVE: The purpose of this study was to investigate the effects of a 4-week short-foot exercise (SFE) on biomechanical factors in patients with stage II posterior tibial tendon dysfunction. DESIGN: Single-group pretest-posttest. SETTING: University laboratory. PARTICIPANTS: Fifteen subjects (8 males and 7 females) with stage II posterior tibial tendon dysfunction who had pain in posterior tibial tendon, pronated foot deformity (foot posture index ≥+6), and flexible foot deformity (navicular drop ≥10 mm) were voluntarily recruited. INTERVENTION: All subjects completed a 4-week SFE program (15 repetitions × 5 sets/d and 3 d/wk) of 4 stages (standing with feedback, sitting, double-leg, and one-leg standing position). MAIN OUTCOME MEASURES: Ankle joint kinematics and kinetics and tibialis anterior and fibularis longus muscle activation (% maximum voluntary isometric contraction) during gait were measured before and after SFE program. Cohen d effect size (ES [95% confidence intervals]) was calculated. RESULTS: During the first rocker, tibialis anterior activation decreased at peak plantarflexion (ES = 0.75 [0.01 to 1.49]) and inversion (ES = 0.77 [0.03 to 1.51]) angle. During the second rocker, peak dorsiflexion angle (ES = 0.77 [0.03 to 1.51]) and tibialis anterior activation at peak eversion (ES = 1.57 [0.76 to 2.39]) reduced. During the third rocker, the peak abduction angle (ES = 0.80 [0.06 to 1.54]) and tibialis anterior and fibularis longus activation at peak plantarflexion (ES = 1.34 [0.54 to 2.13]; ES = 1.99 [1.11 to 2.86]) and abduction (ES = 1.29 [0.50 to 2.08]; ES = 1.67 [0.84 to 2.50]) decreased. CONCLUSIONS: Our 4-week SFE program may have positive effects on changing muscle activation patterns for tibialis anterior and fibularis longus muscles, although it could not influence their structural deformity and ankle joint moment. It could produce a potential benefit of decreased tibialis posterior activation.

Safety Evaluation of Protective Equipment for the Forearm, Shin, Hand and Foot in Taekwondo.

The objective of the study was to evaluate and compare different brands of forearm, shin, hand and foot protective equipment used in Taekwondo. The most popular brands of large forearm, shin, hand and foot protectors (D®, A®, K ®), approved by the World Taekwondo and Korean Taekwondo Association, were examined. A drop test was used to test the protective equipment using impact levels of 3J, 9J, 12J and 15J for the forearm and shin guards, and 3J and 9J for the hand and foot protectors. The protective equipment was hit ten times from each of the designated drop heights. The drop test is described in the European standards manual of protective equipment for martial arts (SRPS EN 13277-2). The maximum force (MF) and impulse were lowest for brand K® (2610.3 ± 1474.1 N), and brand A® (9.6 ± 3.1 Ns), respectively, for the forearm guards; for brand A® (2053.4 ± 1267.1 N) and brand K® (9.8 ± 3.5 Ns), respectively, for the shin guards; for brand K® (4486.5 ± 1718.4 N), and brand A® (6.3 ± 1.1 Ns), respectively for the hand protectors; and for brand A® (3733.7 ± 2465.3 N), and brand D® (6.8 ± 0.6 Ns), respectively, for the foot protectors. For the forearm guard brand and impact level, there was a significant interaction effect for the MF (F=42.44, η2=.677, p <0.001) and impulse (F = 33.97, η2 = 0.626, p <0.001). Based on the MF, brand K® performed the best for the forearm guards and hand protectors, and brand A®, for the shin guards and foot protectors. The best results for the impulse were for brand A® (forearm guards and hand protectors), brand K® (shin guards) and brand D® (foot protectors).

Proprioceptive Training and Outcomes of Patients With Knee Osteoarthritis: A Meta-Analysis of Randomized Controlled Trials.

OBJECTIVE: To describe the effects of proprioceptive training on pain, stiffness, function, and functional test outcomes among patients with knee osteoarthritis (OA). DATA SOURCES: All studies completed from 1946 to 2017 were obtained from 4 databases (PubMed, MEDLINE, CINAHL, and SPORTDiscus). STUDY SELECTION: Three reviewers independently identified appropriate studies and extracted data. DATA EXTRACTION: Methodologic quality and level of evidence were assessed using the Physiotherapy Evidence Database scale and Oxford Centre for Evidence-Based Medicine guidelines. The standardized mean differences (SMDs) and 95% confidence intervals (CIs) were calculated for pain, stiffness, function, and functional test outcomes. DATA SYNTHESIS: Seven randomized controlled trials involving 558 patients with knee OA met the inclusion criteria. The selected studies had Physiotherapy Evidence Database scores of 6 to 8. All randomized controlled trials had an Oxford Centre for Evidence-Based Medicine level of evidence of 2. Meta-analysis of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale (SMD = -0.56; 95% CI = -1.06, -0.07; P = .026), function subscale (SMD = -0.40; 95% CI = -0.59, -0.21; P < .001), and non-WOMAC walking speed test (SMD = -1.07; 95% CI = -2.12, -0.01; P = .048) revealed that proprioceptive training had significant treatment effects. Proprioceptive training was not associated with reductions in WOMAC stiffness subscale scores and did not improve non-WOMAC get-up-and-go scores. CONCLUSIONS: Proprioceptive training effectively promoted pain relief and completion of functional daily activity among patients with knee OA and should be included in rehabilitation programs. Stiffness and other mobility measures were unchanged after proprioceptive training. Modified proprioceptive training programs are needed to target stiffness and improve additional physical function domains.

Biomechanical Effects of Ball Position on Address Position Variables of Elite Golfers.

The purpose of this study was to investigate address position variables in response to changes in ball position in golfers. Eleven male professional golfers were instructed to perform their golf swing. A three-dimensional motion analysis system, with eight infrared cameras and two force platforms, was used to capture the address positions. A golf ball has a diameter of 4.27 cm, and a radius of 2.14 cm. Even small movements of ball position in the mediolateral (M-L) and anteroposterior (A-P) directions significantly changed the address position. When the ball was moved to the left, the shoulder rotation and club-face aim rotated toward the left of the target, and the left vertical ground reaction force increased. When the ball was moved to the right, the opposite findings were observed. When the ball was moved closer, the trunk, hip, knee, ankle, and absolute arm angle extended; the lie angle of the golf club increased; and the center of pressure moved toward the posterior direction. These changes were reversed when the ball was moved further away. The M-L ball position critically changed the address positions of the upper extremities in the horizontal plane, and the A-P ball position critically changed the angles of whole body parts in the sagittal plane. Furthermore, club-head kinematics at impact such as club-face aim, club path, and angle of attack were significantly changed in the M-L ball position; and club-head speed and angle of attack were significantly changed in the A-P ball position. This in-depth understanding of the address position in association with the ball position could provide valuable data for swing coaches when finding a golfer's optimal address position.

Rearfoot eversion has indirect effects on plantar fascia tension by changing the amount of arch collapse.

BACKGROUND: Rearfoot eversion motion and arch height are believed to contribute to increased tension on the plantar fascia and arch collapse during gait but the specifics of these relationships are not clear. OBJECTIVE: To examine the relationships among static arch height, rearfoot eversion, dynamic arch height, and plantar fascia tension. METHODS: 28 healthy males participated. After static arch height was measured, the subjects were asked to run at 4.5m/s while frontal plane rearfoot motion, dynamic arch height, and ground reaction forces were collected. The relationships among variables were examined with bivariate correlations and path analysis. RESULTS: The results indicated a high correlation between dynamic arch height and static arch height (r=0.642), plantar fascia tension (r=-0.797), and maximum rearfoot eversion motion during gait (r=-0.518). The path analysis model without the direct rearfoot eversion effect explained 81.2% of the variance in plantar fascia tension, while the model with the direct rearfoot eversion effect explained 82.1% of the variance in plantar fascia tension. DISCUSSION: Including the indirect effect of maximum rearfoot eversion motion on plantar fascia tension through control of dynamic arch height is the model that best explains the interrelationships of these foot characteristics. CONCLUSION: The amount of maximum rearfoot eversion motion itself is not a good predictor of plantar fascia tension, however, together with the arch height, maximum rearfoot eversion motion is a good predictor because it has a pronounced indirect effect on plantar fascia tension.