Sex-Based Differences in Lower Extremity Kinematics During Dynamic Jump Landing Tasks After Neuromuscular Fatigue of the Hip Extensors and Knee Flexors.

Background: Neuromuscular fatigue can increase the activation of antagonist muscles, thereby reducing the moment produced by the agonist. During the deceleration phase of landing, hip extensor and knee flexor muscles contract eccentrically to counteract the external hip flexion moment. Decreased hip flexion is associated with greater knee extensor moments and risk of injury. Purpose: To investigate sex-based differences in kinematics and muscle activity after neuromuscular fatigue of the hip extensors and knee flexors during dynamic single-leg tasks. Study Design: Controlled laboratory study. Methods: In this study, 9 female (age, 22.3 ± 3.4 years) and 7 male participants (age, 21.3 ± 2.6 years) completed the triple hop (THop) for distance and single-leg drop-jump (SJump) tasks before and after a fatigue protocol consisting of eccentric hip extension and knee flexion. Motion capture and electromyography were used to compare lower extremity kinematics and muscular activation between the sexes. Results: During the THop, neuromuscular fatigue resulted in significantly decreased maximum hip flexion angles (P = .01), maximum knee flexion angles (P = .039), and an effect of sex on all hip flexion angles, where both sexes saw decreased hip flexion postfatigue (P = .033). A significant interaction of fatigue and sex on hip flexion angular velocity was observed during the SJump, indicating that men experienced an increase while women experienced a decrease in hip flexion angular velocities due to fatigue (P = .03). Gluteus maximus activation was increased, and erector spinae activation was decreased postfatigue in women during the THop (P = .053 and P = .023, respectively). Conclusion: Results indicate that men and women compensated differently after fatigue of the hip extensors and knee flexors. Clinical Relevance: Women more commonly assumed an erect landing posture associated with increased injury risk after fatigue of the hip extensors and knee flexors.

Using principal component analysis to investigate pacing strategies in elite international canoe kayak sprint races.

The aim of this research was to use principal component analysis (PCA) to investigate the current pacing strategies of elite canoe kayak sprint athletes and to determine if there are differences in pacing patterns between medallists and non-medallists at major international competitions. Velocity data collected using global positioning systems (GPS) from all a-finals of major international competitions in 2016-2017 (including canoe and kayak, single and crew boat, and male and female) were downloaded from the International Canoe Federation's website. Data were normalised by the average velocity within each race and organised by race distance. In total 10, 14 and 16 races were analysed, and they followed all-out, positive, and 'seahorse-shaped' pacing strategies for the 200 m, 500 m, and 1000 m events, respectively. Normalised velocity PC1 (p = 0.039, ES = -0.44) and PC2 scores (p < 0.001, ES = -0.73) for 1000 m races were significantly different between medallists and non-medallists; however, significant differences between PCs were not found between groups in shorter race distances (i.e. 200 m and 500 m). Data collected using GPS provide information that can be used to better prepare athletes for canoe kayak sprint races lasting between 30 s and 240 s in duration.

Longitudinal evidence links joint level mechanics and muscle activation patterns to 3-year medial joint space narrowing.

BACKGROUND: It is currently not known if there are different mechanical factors involved in accelerated rates of knee osteoarthritis structural progression. Data regarding the role of the transverse plane moment along with the contributions to joint loading from muscle activity, a primary contributor to the joint loading environment, is not well represented in the current literature on knee OA radiographic progression. The objective of this study was to understand if a 3-year end point corroborates what has been shown for longer term radiographic progression or provides more insight into factors that may be implicated in more accelerated radiographic progression than those shown previously. METHODS: 52 participants visited the Dynamics of Human Motion laboratory at baseline for three-dimensional, self-selected speed over ground walking gait analysis. Differences in magnitude and patterns of 3D knee moments and electromyography waveforms between participants who progressed radiographically from those that did not were compared using t-tests (P < 0.05). FINDINGS: Features of the frontal and transverse plane knee moments along with muscle activation patterns for the lateral gastrocnemius and lateral hamstrings differentiated the progression group from the non-progression group at baseline. INTERPRETATION: In general, the walking gait biomechanics of the progression group in this 3-year radiographic study aligned well with previously reported characteristics of diagnosed or symptomatic osteoarthritis. The higher rotation moment range during stance found with the progression group is a novel finding that points to a need to better understand torsional joint loading and its implications for loading of the knee joint tissues.

Reliability and Validity of a Novel Trunk-Strength Assessment for High-Performance Sprint Flat-Water Kayakers.

PURPOSE: To determine the reliability and validity of a novel trunk maximal isometric force assessment involving 7 different tasks with 200-m times for elite sprint flat-water kayakers. METHODS: Ten elite sprint flat-water kayakers performed a series of maximal isometric voluntary contractions (MVCs) on 2 separate days to assess reliability. MVC force was assessed as the participants sat on a modified kayak ergometer and applied their maximal isometric force to a uniaxial load cell during 7 different tasks. The 7 tasks of interest were a seated trunk-forward flexion, bilateral (left and right) rotational pulls, bilateral rotational pushes, and a sport-specific bilateral kayak-stroke simulation. Twenty elite flat-water kayak athletes (10 male and 10 female) participated in the validity portion by completing the series of tasks in conjunction with a 200-m race. RESULTS: MVC force values ranged from 84 to 800 N across all participants and all tasks. The average coefficient of variation of the 7 tasks ranged from 2.4% to 7.7%. Regression analysis showed Pearson correlations ranging from -.84 to -.22 for both absolute and relative values with 200-m performance times. CONCLUSIONS: MVC force measured in each task was considered reliable as a small degree of variance between trials was found. The summation of the 7 trunk scores showed very strong correlations with on-water performance, indicating that this assessment is valid for elite sprint kayakers.

Effect of limb dominance and sex on neuromuscular activation patterns in athletes under 12 performing unanticipated side-cuts.

Non-contact ACL injuries are one of the most common injuries to the knee joint among adolescent/collegiate athletes, with sex and limb dominance being identified as risk factors. In children under 12years of age (U12), these injuries occur less often and there is no sex-bias present. This study set out to explore if sex and/or limb dominance differences exist in neuromuscular activations in U12 athletes. Thirty-four U12 males and females had six bilateral muscles analyzed during unanticipated side-cuts. Principal component analysis was performed, capturing differences in overall magnitudes and timing of peak magnitudes. Two-way mixed-model ANOVAs determined significant limb effects with both sexes displaying (i) greater magnitudes in the lateral gastrocnemius and both hamstrings in the dominant limb and (ii) earlier timing of peak magnitudes in both gastrocnemii, both hamstrings and vastus medialis in the non-dominant limb, while no sex differences were identified. This study demonstrated that limb dominance, not sex, affects neuromuscular activation strategies in U12 athletes during unanticipated side-cuts. When developing injury prevention programs for younger athletes, an increased focus on balancing neuromuscular activations in both limbs could be beneficial in reducing the likelihood of ACL injuries in these athletes as they mature through puberty.

Gender differences in lower extremity gait biomechanics during walking using an unstable shoe.

BACKGROUND: In recent years several unstable shoe designs that cause increased instability at the ankle joint have been developed with the aims of training static and dynamic posture and postural control. However, earlier research found significant gender differences in the generation of ankle torque and in the reaction times after a perturbation. Therefore it is possible that men and women are affected differently by the instability that unstable shoes create. The purpose of this study was to investigate if gender differences exist a) during bilateral quiet stance or b) in lower extremity gait kinematics and kinetics when using unstable shoes. METHODS: Seventeen females and seventeen males were included in this study. Masai Barefoot Technology shoes were used as test shoes. Center of pressure excursion was recorded during 30s bilateral quiet stance trials using a force plate. Joint angles, resultant joint moments and joint moment impulses during walking were determined using standard gait analysis methods. FINDINGS: In bipedal stance, female subjects had significantly greater anterior-posterior center of pressure excursion than male subjects. In the stance phase of the gait cycle gender differences were found in the ankle joint moments which had not been reported in earlier studies using barefoot or normal shoe conditions. INTERPRETATION: The results suggest that women and men use different strategies to control the ankle joint when standing or walking in unstable shoes. Gender effects should therefore be taken into consideration if functional or therapeutic effects of unstable shoes are assessed.

Standing in an unstable shoe increases postural sway and muscle activity of selected smaller extrinsic foot muscles.

Inactivity or the under-utilization of lower limb muscles can lead to strength and functional deficits and potential injury. Traditional shoes with stability and support features can overprotect the foot and potentially contribute to the deterioration of the smaller extrinsic foot muscles. Healthy subjects (n=28) stood in an unstable MBT (Masai Barefoot Technology) shoe during their work day for a 6-week accommodation period. A two-way repeated measures ANOVA was used to determine (i) if unstable shoe wear increased electromyographic (EMG) activity of selected extrinsic foot muscles and increased postural sway compared to standing barefoot and in a stable control shoe and (ii) if postural sway and muscle activity across footwear conditions differed between a pre- and post-accommodation testing visit. Using an EMG circumferential linear array, it was shown that standing in the unstable shoe increased activity of the flexor digitorum longus, peroneal (PR) and anterior compartment (AC) muscles of the lower leg. No activity differences for the larger soleus (SOL) were identified between the stable and unstable shoe conditions. Postural sway was greater while standing in the unstable shoe compared to barefoot and the stable control shoe. These findings suggest that standing in the unstable MBT shoe effectively activates selected extrinsic foot muscles and could have implications for strengthening and conditioning these muscles. Postural sway while standing in the unstable MBT shoe also decreased over the 6-week accommodation period.

Gender differences exist in neuromuscular control patterns during the pre-contact and early stance phase of an unanticipated side-cut and cross-cut maneuver in 15-18 years old adolescent soccer players.

Non-contact ACL injuries generally occur as the foot contacts the ground during cutting or landing maneuvers and the non-contact ACL injury rate is 2-8 times greater in females compared to males. To provide insight into the gender bias of this injury, this study set out to identify gender differences in the neuromuscular response of the quadriceps, hamstrings and gastrocnemii muscles in elite adolescent soccer players during the pre-contact and early stance phases of an unanticipated side-cut and cross-cut. For the early stance phase of the two maneuvers, females demonstrated greater rectus femoris activity compared to males. Throughout the pre-contact phase of the maneuvers, a rectus femoris activation difference was identified with females having an earlier and more rapid rise in muscle activity as initial ground contact approached. Females demonstrated greater lateral and medial gastrocnemii activity for the pre-contact and early stance phases of the side-cut and greater lateral gastrocnemii activity during early stance of the cross-cut. Timing of hamstring activity also differed between genders prior to foot contact. The differences suggest that the activation patterns observed in females might not be providing adequate joint protection and stability, thereby possibly having a contributing role towards increased non-contact ACL injuries in females.

Neuromuscular and lower limb biomechanical differences exist between male and female elite adolescent soccer players during an unanticipated side-cut maneuver.

BACKGROUND: Female athletes are 2 to 8 times more likely than male athletes to injure the anterior cruciate ligament during a non-contact athletic maneuver. Identifying anterior cruciate ligament injury risk factors in female athletes may help with the development of preventive training programs aimed at reducing injury rates. HYPOTHESIS: Differences between genders in lower limb kinematics, kinetics, and neuromuscular patterns will be identified in an adolescent soccer population during an unanticipated side-cut maneuver. STUDY DESIGN: Controlled laboratory study. METHODS: Forty-two elite adolescent soccer players (21 male and 21 female) performed an unanticipated side-cut maneuver, with the 3-dimensional kinematic, kinetic, and electromyographic lower limb data being analyzed using principal component analysis. RESULTS: The female athletes had higher gastrocnemius activity, normalized to maximal voluntary isometric contractions, and a mediolateral gastrocnemius activation imbalance that was not present in the male athletes during early stance to midstance of the side-cut. Female athletes demonstrated greater rectus femoris muscle activity throughout stance, and the only hamstring difference identified was a mediolateral activation imbalance in male athletes only. Female athletes performed the side-cut with less hip flexion and more hip external rotation and also generated a smaller hip flexion moment compared with the male athletes. CONCLUSION: This is the first study to identify gender-related differences in gastrocnemius muscle activity during an unanticipated cutting maneuver. CLINICAL RELEVANCE: The increased and imbalanced gastrocnemius muscle activity, combined with increased rectus femoris muscle activity and reduced hip flexion angles and moments in female subjects, may all have important contributing roles in the higher noncontact ACL injury rates observed in female athletes.

Neuromuscular and lower limb biomechanical differences exist between male and female elite adolescent soccer players during an unanticipated run and crosscut maneuver.

BACKGROUND: Noncontact anterior cruciate ligament injuries often occur during sports such as soccer and basketball in which cutting or landing maneuvers are frequently performed. These injuries are more common in female athletes, and identifying biomechanical or neuromuscular risk factors related to gender may help with the development of preventive training programs aimed at reducing anterior cruciate ligament injury. HYPOTHESIS: Lower limb biomechanical and/or neuromuscular differences between male and female soccer players will be identified during unanticipated running and cutting maneuvers. STUDY DESIGN: Descriptive laboratory study. METHODS: A complete 3-dimensional kinematic, kinetic, and electromyographic analysis of the lower limb for an unanticipated straight-run and crosscut maneuver was performed on 42 (male, 21; female, 21) elite adolescent soccer players. RESULTS: For both maneuvers, female players had greater lateral gastrocnemius activity, normalized to maximal voluntary isometric contractions, and demonstrated a mediolateral gastrocnemii imbalance that was not present in male players. Rectus femoris activity for both maneuvers and vastus medialis and lateralis activity for the straight run only were also greater in female than in male athletes. Other notable differences captured for the maneuvers included female players having reduced hamstring activity, a reduced hip flexion moment, a reduced hip flexion angle, and an increased ankle eversion angle throughout stance compared with male players. CONCLUSION: This is one of the first studies to identify gastrocnemii differences between genders as a possible anterior cruciate ligament injury risk factor. Additional biomechanical and neuromuscular differences were also identified as potential risk factors. CLINICAL RELEVANCE: These findings provide insight into the noncontact anterior cruciate ligament injury gender bias and may help improve preventive training programs.

Gender differences exist in osteoarthritic gait.

BACKGROUND: Knee osteoarthritis is 2-3 times more prevalent in females than males. Biomechanical differences in gait may play a role in this gender predisposition. The purpose of this study was to determine if there are gender-based biomechanical differences in the gait patterns of people with knee osteoarthritis. METHODS: Three-dimensional gait analysis was performed on healthy (18 males and 24 females) subjects and patients with moderate knee osteoarthritis (24 males and 15 females). Kinematics and kinetics at the hip, knee and ankle were calculated. Variables including anthropometrics, stride characteristics, strength, pain, stiffness, function and radiographic disease severity were also quantified. Multivariate statistical techniques and analysis of variance were used to test for main disease effects, main gender effects and disease vs. gender interactions. FINDINGS: A significant interaction effect between gender and disease was found in the knee flexion angle and the knee moments in the sagittal, frontal and transverse planes. In each of these measures the females exhibited different biomechanics with osteoarthritis, while the osteoarthritic males maintained the same biomechanics as healthy males. This interaction between gender and osteoarthritis was not associated with differences in anthropometrics, stride characteristics, strength, pain, stiffness, function or radiographic disease severity between the populations. INTERPRETATION: This study has found gait pattern differences between the genders in the osteoarthritic patients that were not apparent in the healthy subjects. This suggests that the biomechanics associated with knee osteoarthritis are gender dependent. Therefore, gender specific design of biomechanical interventions to slow the progression of osteoarthritis should be explored.

Knee biomechanics of moderate OA patients measured during gait at a self-selected and fast walking speed.

Osteoarthritis (OA) is a chronic disorder resulting in degenerative changes to the knee joint. Three-dimensional gait analysis provides a unique method of measuring knee dynamics during activities of daily living such as walking. The purpose of this study was to identify biomechanical features characterizing the gait of patients with mild-to-moderate knee OA and to determine if the biomechanical differences become more pronounced as the locomotor system is stressed by walking faster. Principal component analysis was used to compare the gait patterns of a moderate knee OA group (n=41) and a control group (n=43). The subjects walked at their self-selected speed as well as at 150% of that speed. The two subject groups did not differ in knee joint angles, stride length, and stride time or walking speed. Differences in the magnitude and shape of the knee joint moment waveforms were found between the two groups. The OA group had larger adduction moment magnitudes during stance and this higher magnitude was sustained for a longer portion of the gait cycle. The OA group also had a reduced flexion moment and a reduced external rotation moment during early stance. Increasing speed was associated with an increase in the magnitude of all joint moments. The fast walks did not, however, increase or bring out any biomechanical differences between the OA and control groups that did not exist at the self-selected walks.