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Leo Ng, Amity Campbell, Angus Burnett, and Peter O’Sullivan

The trunk and pelvis kinematics of 20 healthy male and female adolescent rowers were recorded during an ergometer trial using an electromagnetic tracking system (Fastrak). The kinematics of each drive phase were collected during the 1st and 20th minute, respectively. The mean and range of the kinematics, stroke rate and stroke length were compared between genders and over time. Male rowers postured their pelvis with more posterior tilt and their thoracic spine in more flexion than female rowers (P < .05). Both genders postured their pelvis in more posterior pelvic rotation and upper trunk in more flexion over time. Male rowers were found to have a significantly shorter drive phase than female rowers (P = .001). Differences in trunk and pelvic kinematics between adolescent male and female rowers suggest potentially various mechanisms for biomechanical stress. Assessment and training of rowers should take gender differences into consideration.

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Lara Mitchinson, Amity Campbell, Damian Oldmeadow, Will Gibson, and Diana Hopper

Volleyball players are at high risk of overuse shoulder injuries, with spike biomechanics a perceived risk factor. This study compared spike kinematics between elite male volleyball players with and without a history of shoulder injuries. Height, mass, maximum jump height, passive shoulder rotation range of motion (ROM), and active trunk ROM were collected on elite players with (13) and without (11) shoulder injury history and were compared using independent samples t tests (P < .05). The average of spike kinematics at impact and range 0.1 s before and after impact during down-the-line and cross-court spike types were compared using linear mixed models in SPSS (P < .01). No differences were detected between the injured and uninjured groups. Thoracic rotation and shoulder abduction at impact and range of shoulder rotation velocity differed between spike types. The ability to tolerate the differing demands of the spike types could be used as return-to-play criteria for injured athletes.

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Helen Crewe, Amity Campbell, Bruce Elliott, and Jacqueline Alderson

This study aimed to assess variability in lumbo-pelvic forces and moments during a dynamic high-impact activity (cricket fast bowling) when calculated using different body segment parameters (BSPs). The first three BSPs were estimated using methods where the trunk was divided into segments according to nonspinal anatomical landmarks. The final approach defined segment boundaries according to vertebral level. Three-dimensional motion analysis data from nine male cricketers’ bowling trials were processed using the four BSPs. A repeated-measures analysis of variance revealed no significant effect on peak lumbo-pelvic forces. However, the segmentation approach based on vertebral level resulted in significantly larger peak flexion and lateral flexion moments than the other BSP data sets. This has implications for comparisons between studies using different BSPs. Further, given that a method defined with reference to vertebral level more closely corresponds with relevant anatomical structures, this approach may more accurately reflect lumbar moments.

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M. M. Reid, Amity C. Campbell, and B. C. Elliott

Tennis stroke mechanics have attracted considerable biomechanical analysis, yet current filtering practice may lead to erroneous reporting of data near the impact of racket and ball. This research had three aims: (1) to identify the best method of estimating the displacement and velocity of the racket at impact during the tennis serve, (2) to demonstrate the effect of different methods on upper limb kinematics and kinetics and (3) to report the effect of increased noise on the most appropriate treatment method. The tennis serves of one tennis player, fit with upper limb and racket retro-reflective markers, were captured with a Vicon motion analysis system recording at 500 Hz. The raw racket tip marker displacement and velocity were used as criterion data to compare three different endpoint treatments and two different filters. The 2nd-order polynomial proved to be the least erroneous extrapolation technique and the quintic spline filter was the most appropriate filter. The previously performed “smoothing through impact” method, using a quintic spline filter, underestimated the racket velocity (9.1%) at the time of impact. The polynomial extrapolation method remained effective when noise was added to the marker trajectories.

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Leo Ng, Amity Campbell, Angus Burnett, Anne Smith, and Peter O’Sullivan

There is a high prevalence of low back pain (LBP) in adolescent male rowers. In this study, regional lumbar spinal kinematics and self-reported LBP intensity were compared between 10 adolescent rowers with moderate levels of LBP relating to rowing with 10 reporting no history of LBP during a 15-minute ergometer trial using an electromagnetic tracking system. Adolescent male rowers with LBP reported increasing pain intensity during ergometer rowing. No significant differences were detected in mean upper or lower lumbar angles between rowers with and without LBP. However, compared with rowers without pain, rowers with pain: (1) had relatively less excursion of the upper lumbar spine into extension over the drive phase, (2) had relatively less excursion of the lower lumbar spine into extension over time, (3) had greater variability in upper and lower lumbar angles over the 15-minute ergometer trial, (4) positioned their upper lumbar spine closer to end range flexion for a greater proportion of the drive phase, and (5) showed increased time in sustained flexion loading in the upper lumbar spine. Differences in regional lumbar kinematics exist between adolescent male rowers with and without LBP, which may have injury implication and intervention strategies.

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Yanxin Zhang, David G. Lloyd, Amity C. Campbell, and Jacqueline A. Alderson

The purpose of this study was to quantify the effect of soft tissue artifact during three-dimensional motion capture and assess the effectiveness of an optimization method to reduce this effect. Four subjects were captured performing upper-arm internal-external rotation with retro-reflective marker sets attached to their upper extremities. A mechanical arm, with the same marker set attached, replicated the tasks human subjects performed. Artificial sinusoidal noise was then added to the recorded mechanical arm data to simulate soft tissue artifact. All data were processed by an optimization model. The result from both human and mechanical arm kinematic data demonstrates that soft tissue artifact can be reduced by an optimization model, although this error cannot be successfully eliminated. The soft tissue artifact from human subjects and the simulated soft tissue artifact from artificial sinusoidal noise were demonstrated to be considerably different. It was therefore concluded that the kinematic noise caused by skin movement artifact during upper-arm internal-external rotation does not follow a sinusoidal pattern and cannot be effectively eliminated by an optimization model.

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Amity Campbell, Leon Straker, David Whiteside, Peter O’Sullivan, Bruce Elliott, and Machar Reid

Adolescent tennis players are at risk for low back pain (LBP). Recent research has demonstrated a potential mechanical etiology during serves; however, groundstrokes have also been suggested to load this region. Therefore, this study compared lumbar mechanics between players with and without a history of LBP during open and square stance tennis forehands and backhands. Nineteen elite, adolescent, male tennis players participated, 7 with a history of recurrent disabling LBP and 12 without. Differences in three-dimensional lumbar kinetics and kinematics were compared between pain/no pain groups and groundstrokes using linear mixed models (P < .01). There were no significant differences between pain/no pain groups. Relative to a right-handed player, groundstroke comparisons revealed that forehands had greater racquet velocity, greater lumbar right lateral flexion force, as well as upper lumbar extension/rightward rotation and lower lumbar right rotation/lateral flexion movements that were closer to or further beyond end of range than backhands. Backhands required upper lumbar leftward rotation that was beyond end range, while forehands did not. Given that players typically rotated near to their end of range during the backswing of both forehands and backhands, independent of pain, groundstrokes may contribute to the cumulative strain linked to LBP in tennis players.

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Melanie Wade, Amity Campbell, Anne Smith, Joanne Norcott, and Peter O’Sullivan

The link between static and dynamic landing lumbar postures, when gymnasts are exposed to large ground reaction forces, has not been established. This investigation aimed to (a) determine if a relationship exists between sagittal static and dynamic landing lumbar spine angles at peak ground reaction force (GRF) and (b) quantify how close to end-range postures the gymnasts were at landing peak GRF. Twenty-one female gymnasts’ upper and lower lumbar spine angles were recorded: statically in sitting and standing, during landing of three gymnastic skills, and during active end-range lumbar flexion. Pearson’s correlations were used to investigate relationships between the angles in different postures. Significant correlations (r = .77–.89, p < .01) were found between all the static/dynamic postures in the lower lumbar spine angle, while fewer and less significant upper lumbar spine correlations were reported. Thirty percent of gymnasts landed a backsault with their lower lumbar spine flexed beyond their active end-range while experiencing GRF 6.8–13.3 times their body weight. These results inform low back pain prevention and management strategies in this population and highlight areas for future research.

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James R. Debenham, William I. Gibson, Mervyn J. Travers, Amity C. Campbell, and Garry T. Allison

Context:

Eccentric exercises are increasingly being used to treat lower-limb musculoskeletal conditions such as Achilles tendinopathy. Despite widespread clinical application and documented efficacy, mechanisms underpinning clinical benefit remain unclear. Positive adaptations in motor performance are a potential mechanism.

Objective:

To investigate how an eccentric loading intervention influences measures of stretch-shortening-cycle (SSC) behavior during a hopping task.

Design:

Within-subjects repeated-measures observational study.

Setting:

University motion-analysis laboratory.

Participants:

Healthy adults.

Interventions:

A single intervention of 5 sets of 10 eccentric plantar-flexion contractions at 6 repetitions maximum using a commercial seated calf-raise machine.

Main Outcome Measures:

Lower-limb stiffness, sagittal-plane ankle kinematics, and temporal muscle activity of the agonist (soleus) and antagonist (tibialis anterior) muscles, measured during submaximal hopping on a custom-built sledge-jump system.

Results:

Eccentric loading altered ankle kinematics during submaximal hopping; peak angle shifted to a less dorsiflexed position by 2.9° and ankle angle precontact shifted by 4.4° (P < .001). Lower-limb stiffness increased from 5.9 to 6.8 N/m (P < .001), while surface EMG measures of soleus occurred 14–44% earlier (P < .001) after the loading intervention.

Conclusions:

These findings suggest that eccentric loading alters SSC behavior in a manner reflective of improved motor performance. Decreased ankle excursion, increased lower-limb stiffness, and alterations in motor control may represent a positive adaptive response to eccentric loading. These findings support the theory that mechanisms underpinning eccentric loading for tendinopathy may in part be due to improved “buffering” of the tendon by the neuromuscular system.

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Leon Straker, Amity Campbell, Svend Erik Mathiassen, Rebecca Anne Abbott, Sharon Parry, and Paul Davey

Background:

Capturing the complex time pattern of physical activity (PA) and sedentary behavior (SB) using accelerometry remains a challenge. Research from occupational health suggests exposure variation analysis (EVA) could provide a meaningful tool. This paper (1) explains the application of EVA to accelerometer data, (2) demonstrates how EVA thresholds and derivatives could be chosen and used to examine adherence to PA and SB guidelines, and (3) explores the validity of EVA outputs.

Methods:

EVA outputs are compared with accelerometer data from 4 individuals (Study 1a and1b) and 3 occupational groups (Study 2): seated workstation office workers (n = 8), standing workstation office workers (n = 8), and teachers (n = 8).

Results:

Line graphs and related EVA graphs highlight the use of EVA derivatives for examining compliance with guidelines. EVA derivatives of occupational groups confirm no difference in bouts of activity but clear differences as expected in extended bouts of SB and brief bursts of activity, thus providing evidence of construct validity.

Conclusions:

EVA offers a unique and comprehensive generic method that is able, for the first time, to capture the time pattern (both frequency and intensity) of PA and SB, which can be tailored for both occupational and public health research.