The purpose of this study was to investigate the relevance of hip joint angles to the production of the pelvic rotation torque in fast-pitch softball hitting and to examine the effect of ball height on this production. Thirteen advanced female softball players hit stationary balls at three different heights: high, middle, and low. The pelvic rotation torque, defined as the torque acting on the pelvis through the hip joints about the pelvic superior–inferior axis, was determined from the kinematic and force plate data using inverse dynamics. Irrespective of the ball heights, the rear hip extension, rear hip external rotation, front hip adduction, and front hip flexion torques contributed to the production of pelvic rotation torque. Although the contributions of the adduction and external rotation torques at each hip joint were significantly different among the ball heights, the contributions of the front and rear hip joint torques were similar among the three ball heights owing to cancelation of the two torque components. The timings of the peaks of the hip joint torque components were significantly different, suggesting that softball hitters may need to adjust the timings of the torque exertions fairly precisely to rotate the upper body effectively.
Yoichi Iino, Atsushi Fukushima and Takeji Kojima
Maureen I. Ogamba, Kari L. Loverro, Natalie M. Laudicina, Simone V. Gill and Cara L. Lewis
During pregnancy, the female body experiences structural changes, such as weight gain. As pregnancy advances, most of the additional mass is concentrated anteriorly on the lower trunk. The purpose of this study is to analyze kinematic and kinetic changes when load is added anteriorly to the trunk, simulating a physical change experienced during pregnancy. Twenty healthy females walked on a treadmill while wearing a custom made pseudo-pregnancy sac (1 kg) under 3 load conditions: sac-only condition, 10-lb condition (4.535 kg added anteriorly), and 20-lb condition (9.07 kg added anteriorly), used to simulate pregnancy in the second trimester and at full-term pregnancy, respectively. The increase in anterior mass resulted in kinematic changes at the knee, hip, pelvis, and trunk in the sagittal and frontal planes. In addition, ankle, knee, and hip joint moments normalized to baseline mass increased with increased load; however, these moments decreased when normalized to total mass. These kinematic and kinetic changes may suggest that women modify gait biomechanics to reduce the effect of added load. Furthermore, the increase in joint moments increases stress on the musculoskeletal system and may contribute to musculoskeletal pain.
Rose M. Angell, Stephen A. Butterfield, Shihfen Tu, E. Michael Loovis, Craig A. Mason and Christopher J. Nightingale
Object control skills (OCS) provide children the means to be physically active. However, gender equality in some OCS remains elusive. Particularly troublesome is the basic throwing pattern and, by extension, the striking pattern, both of which rely on forceful, rapid rotation of the pelvis, trunk, and shoulders. Some scholars argue that sex differences in throwing and striking are rooted in human evolution. The purpose of this study was to examine development of throwing and striking at the fundamental movement level. The design was multi-cohort sequential: 280 boys and girls grades K–8 (ages 4–15) were tested up to three times per year for 5 years on the Test of Gross Motor Development (TGMD-2). Hierarchical linear modeling (HLM) was applied to analyze individual growth curves. As anticipated, significant (p < .001) age-related gains were found for throwing and striking. In terms of sex (biology) or gender (sociocultural) differences, boys performed better longitudinally at throwing (p < .05) and striking (p < .05). These results reinforce theories that girls may be disadvantaged in achieving proficiency in throwing and striking. Interventions designed to enhance development of these skills should be in place long before grade 4, when most physical education curricula transitions to games and sports.
Jennifer E. Earl
Gluteus medius (GM) contraction during single-leg stance prevents the contralateral pelvis from “dropping,” providing stability for lower extremity motion.
To determine which combination of hip rotation and abduction exercise results in the greatest activity of the GM and whether the GM responds to increased loads in these exercises.
Design and Setting:
Repeated measures, laboratory.
20 healthy volunteers.
Resistance (2.26 and 4.53 kg) was provided to 3 variations of a single-leg-stance exercise: hip abduction only, abduction-internal rotation (ABD-IR), and abduction-external rotation.
Muscle activity was recorded from the anterior and middle portions of the GM using surface electromyography.
ABD-IR produced the most activity in the anterior and middle sections of the GM muscle. The 4.53-kg load produced significantly more activity than the 2.26-kg load (P < .05).
The GM is most active when performing abduction and internal rotation of the hip. This information could be used to develop GM-strengthening exercises.
Shane J. Gore, Brendan M. Marshall, Andrew D. Franklyn-Miller, Eanna C. Falvey and Kieran A. Moran
When reporting a subject’s mean movement pattern, it is important to ensure that reported values are representative of the subject’s typical movement. While previous studies have used the mean of 3 trials, scientific justification of this number is lacking. One approach is to determine statistically how many trials are required to achieve a representative mean. This study compared 4 methods of calculating the number of trials required in a hopping movement to achieve a representative mean. Fifteen males completed 15 trials of a lateral hurdle hop. Range of motion at the trunk, pelvis, hip, knee, and ankle, in addition to peak moments for the latter 3 joints were examined. The number of trials required was computed using a peak intraclass correlation coefficient method, sequential analysis with a bandwidth of acceptable variance in the mean, and a novel method based on the standard error of measurement (SEMind). The number of trials required across all variables ranged from 2 to 12 depending on method, joint, and anatomical plane. The authors advocate the SEMind method as it demonstrated fewer limitations than the other methods. Using the SEMind, the required number of trials for a representative mean during the lateral hurdle hop is 6.
Trent M. Guess, Swithin Razu, Amirhossein Jahandar, Marjorie Skubic and Zhiyu Huo
The Microsoft Kinect is becoming a widely used tool for inexpensive, portable measurement of human motion, with the potential to support clinical assessments of performance and function. In this study, the relative osteokinematic Cardan joint angles of the hip and knee were calculated using the Kinect 2.0 skeletal tracker. The pelvis segments of the default skeletal model were reoriented and 3-dimensional joint angles were compared with a marker-based system during a drop vertical jump and a hip abduction motion. Good agreement between the Kinect and marker-based system were found for knee (correlation coefficient = 0.96, cycle RMS error = 11°, peak flexion difference = 3°) and hip (correlation coefficient = 0.97, cycle RMS = 12°, peak flexion difference = 12°) flexion during the landing phase of the drop vertical jump and for hip abduction/adduction (correlation coefficient = 0.99, cycle RMS error = 7°, peak flexion difference = 8°) during isolated hip motion. Nonsagittal hip and knee angles did not correlate well for the drop vertical jump. When limited to activities in the optimal capture volume and with simple modifications to the skeletal model, the Kinect 2.0 skeletal tracker can provide limited 3-dimensional kinematic information of the lower limbs that may be useful for functional movement assessment.
J.-M. John Wilson, D. Gordon E. Robertson and J. Peter Stothart
In an effort to seek further understanding of lower limb muscle function in the rowing movement, an electromyographic analysis was undertaken of rowers rowing on a Gjessing ergometer. A strain gauged transducer was inserted in the ergometer linkage between handle and flywheel to detect pulling force. Electrodes were placed on the following lower limb muscles: gluteus maximus, biceps femoris, rectus femoris, vastus lateralis, gastrocnemius, and tibialis anterior. Linear envelope electromyograms from each muscle and the force signals were sampled synchronously at 50 Hz. The results indicated that all six muscles were active from catch to finish of the drive phase. Biceps femoris, gluteus maximus, gastrocnemius, and vastus lateralis all began their activity at or just prior to catch and reached maximal excitation near peak force of the stroke. Rectus femoris and tibialis anterior activity began prior to the catch and reached maximal excitation subsequent to peak force. The coactivation of the five leg muscles, of which four were biarticular, included potentially antagonistic actions that would cancel each other’s effects. Clearly, however, other explanations must be considered. Both gastrocnemius and biceps femoris have been shown to act as knee extensors and may do so in the case of the rowing action. Furthermore, rectus femoris may act with unchanging length as a knee extensor by functioning as a rigid link between the pelvis and tibia. In this manner, energy created by the hip extensors is transferred across the knee joint via the isometrically contracting rectus femoris muscle.
Leanne Sawle, Jennifer Freeman and Jonathan Marsden
Context: Athletic pelvic/groin pain is a common yet often challenging problem to both diagnose and manage. A new tool has been developed based on the clinical effects of applied force on the pelvis. Early findings indicate that this customized compression orthosis may have a positive effect on pelvic/groin pain and performance measures. Objectives: To inform the design and test the practicality of procedures for a future definitively powered randomized controlled trial and to provide an estimate of the effect size of this orthosis on selected clinical and performance measures. Design: Pilot randomized controlled trial with participants randomly allocated to an intervention or waiting-list control group. Setting: The training location of each athlete. Participants: 24 athletes with subacute and chronic pelvic conditions were proposed to be recruited. Intervention: A customized compression orthosis, delivering targeted compression to the pelvic girdle. Outcome Measures: Measures were the active straight leg raise (ASLR) test, squeeze test, broad jump, and the multiple single-leg hop-stabilization test. Results: A total of 16 athletes completed the study. The invention group demonstrated moderate to large estimated effect sizes on the squeeze test and active straight leg raise tests (d = 0.6–1.1) while wearing the orthosis. Small effect sizes (d = 0.2) were seen on jump distance and the dominant leg balance score. Compared with the control group, the intervention group also showed moderate to large estimated effect sizes on the active straight leg raise measures (d = 0.5–0.9) when wearing sports shorts. Conclusions: The protocol was feasible. Effect sizes and recruitment/attrition rates suggest that the intervention holds promise and that a future definitively powered randomized controlled trial appears feasible and is indicated.
Yuta Koshino, Tomoya Ishida, Masanori Yamanaka, Mina Samukawa, Takumi Kobayashi and Harukazu Tohyama
Identifying the foot positions that are vulnerable to lateral ankle sprains is important for injury prevention. The effects of foot position in the transverse plane on ankle biomechanics during landing are unknown.
To examine the effects of toe-in or toe-out positioning on ankle inversion motion and moment during single-leg landing.
Motion analysis laboratory.
18 healthy participants (9 men and 9 women).
Participants performed single-leg landing trials from a 30-cm high box under 3 conditions: natural landing, foot internally rotated (toe-in), and foot externally rotated (toe-out).
Main Outcome Measures:
4 toe-in or toe-out angles were calculated against 4 reference coordinates (laboratory, pelvis, thigh, and shank) in the transverse plane. Ankle inversion angle, angular velocity, and external moment in the 200 ms after initial foot-to-ground contact were compared between the 3 landing conditions.
All toe-in or toe-out angles other than those calculated against the shank were significantly different between each of the 3 landing conditions (P < .001). Ankle inversion angle, angular velocity, and moment were highest during toe-in landings (P < .01), while eversion angle and moment were highest during toe-out landings (P < .001). The effect sizes of these differences were large. Vertical ground reaction forces were not different between the 3 landing conditions (P = .290).
Toe-in or toe-out positioning during single-leg landings impacts on ankle inversion and eversion motion and moment. Athletes could train not to land with the toe-in positioning to prevent lateral ankle sprains.
Ram Haddas, Steven F. Sawyer, Phillip S. Sizer, Toby Brooks, Ming-Chien Chyu and C. Roger James
Recurrent lower back pain (rLBP) and neuromuscular fatigue are independently thought to increase the risk of lower extremity (LE) injury. Volitional preemptive abdominal contraction (VPAC) is thought to improve lumbar spine and pelvis control in individuals with rLBP. The effects of VPAC on fatigued landing performance in individuals with rLBP are unknown.
To determine the effects of VPAC and LE fatigue on landing performance in a rLBP population.
Cross-sectional pretest-posttest cohort control design.
A clinical biomechanics laboratory.
32 rLBP (age 21.2 ± 2.7 y) but without current symptoms and 33 healthy (age 20.9 ± 2.3 y) subjects.
(i) Volitional preemptive abdominal contraction using abdominal bracing and (ii) fatigue using submaximal free-weight squat protocol with 15% body weight until task failure was achieved.
Main Outcome Measure(s):
Knee and ankle angles, moments, electromyographic measurements from semitendinosus and vastus medialis muscles, and ground reaction force (GRF) were collected during 0.30 m drop-jump landings.
The VPAC resulted in significantly earlier muscle onsets across all muscles with and without fatigue in both groups (mean ± SD, 0.063 ± 0.016 s earlier; P ≤ .001). Fatigue significantly delayed semitendinosus muscle onsets (0.033 ± 0.024 s later; P ≤ .001), decreased GRF (P ≤ .001), and altered landing kinematics in a variety of ways. The rLBP group exhibited delayed semitendinosus and vastus medialis muscle onsets (0.031 ± 0.028 s later; P ≤ .001) and 1.8° less knee flexion at initial contact (P ≤ .008).
The VPAC decreases some of the detrimental effects of fatigue on landing biomechanics and thus may reduce LE injury risk in a rLBP population.