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Nick Ball and Joanna Scurr

Electromyograms used to assess neuromuscular demand during high-velocity tasks require normalization to aid interpretation. This paper posits that, to date, methodological approaches to normalization have been ineffective and have limited the application of electromyography (EMG). There is minimal investigation seeking alternative normalization methods, which must be corrected to improve EMG application in sports. It is recognized that differing normalization methods will prevent cross-study comparisons. Users of EMG should aim to identify normalization methods that provide good reliability and a representative measure of muscle activation. The shortcomings of current normalization methods in high-velocity muscle actions assessment are evident. Advances in assessing alternate normalization methods have been done in cycling and sprinting. It is advised that when normalizing high-intensity muscle actions, isometric methods are used with caution and a dynamic alternative, where the muscle action is similar to that of the task is preferred. It is recognized that optimal normalization methods may be muscle and task dependent.

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Emma Burnett, Jenny White and Joanna Scurr

Background:

The importance of physical activity is well known.1 However, previous research suggests that breast movement during exercise can be painful, embarrassing, and anecdotally deter exercise participation.2,3 Therefore, this research investigates whether the breast influences physical activity participation.

Methods:

Female respondents (n = 249) completed a breast health and physical activity survey assessing bras and bra fit, physical activity, breast pain, comments and improvements, breast history, and demographics.

Results:

Results found that the breast was a barrier to physical activity participation for 17% of women. “I can’t find the right sports bra” and “I am embarrassed by excessive breast movement” were the most influential breast related barriers to activity. Breast pain increased with vigorous activity and poor breast support. Breast health knowledge increased the use of a sports bra and levels of physical activity.

Conclusions:

The breast was the fourth greatest barrier to physical activity, behind energy/motivation (first), time constraints (second), and health (third), despite its omission from previous physical activity literature. As 33% of women were not meeting physical activity guidelines, increasing breast health knowledge may reduce barriers to physical activity.

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Alexandra Milligan, Chris Mills and Joanna Scurr

More and more studies are emerging reporting breast kinematics. These studies rarely present effect sizes, power, and variance in the data. Important inferences are drawn from these data, including applications to product design, breast pain assessment, sports performance effects, and more. The aim of the study was to explore the within-participant variance in breast kinematic data during a 5 km run. Multiplanar breast kinematics and within-participant variance, defined by the coefficient of variation, for 10 female participants wearing a low and high level breast support were calculated during a 5 km run. Greater within-participant variance was reported in the high level (mean = 15%) breast support compared with the low level (mean = 12%). Within-participant variance in breast kinematics did not change over the 5 km run. Differences in the magnitude of within-participant variance in breast kinematics were reported between directions of breast movement, with greater levels in the anteroposterior direction compared with mediolateral and vertical. It is important for the progression of this research area that the presence and sources of within-participant variance in breast kinematics are quantified and acknowledged, ensuring that the margin for meaningful differences can be reported.

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Jennifer White, Joanna Scurr and Wendy Hedger

Comparisons of breast support requirements during overground and treadmill running have yet to be explored. The purpose of this study was to investigate 3D breast displacement and breast comfort during overground and treadmill running. Six female D cup participants had retro-reflective markers placed on the nipples, anterior superior iliac spines and clavicles. Five ProReflex infrared cameras (100 Hz) measured 3D marker displacement in four breast support conditions. For overground running, participants completed 5 running trials (3.1 m/s ± 0.1 m/s) over a 10 m indoor runway; for treadmill running, speed was steadily increased to 3.1 m/s and 5 gait cycles were analyzed. Subjective feedback on breast discomfort was collected using a visual analog scale. Running modality had no significant effect on breast displacement (p > .05). Moderate correlations (r = .45 to .68, p < .05) were found between breast discomfort and displacement. Stride length (m) and frequency (Hz) did not differ (p < .05) between breast support conditions or running modalities. Findings suggest that breast motion studies that examine treadmill running are applicable to overground running.

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Joanna Scurr, Jennifer White and Wendy Hedger

This study aimed to assess the trajectory of breast displacement in 3 dimensions during walking and running gait, as this may improve bra design and has yet to be reported. Fifteen D-cup participants had reflective markers attached to their nipples and trunk to monitor absolute and relative breast displacement during treadmill walking (5 kph) and running (10 kph). During the gait cycle, the breast followed a figure-of-eight pattern with four movement phases. Despite a time lag in resultant breast displacement compared with the trunk, similar values of breast displacement were identified across each of the four phases. Fifty-six percent of overall breast movement was vertical, suggesting that 3-D assessment and the elimination of trunk movement in 6 degrees of freedom are essential to accurately report breast displacement during the gait cycle.

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Tim Blackmore, David Jessop, Stewart Bruce-Low and Joanna Scurr

Despite manufacturer claims that athletic socks attenuate force during exercise, no device exists to assess this. Therefore, this study outlines the development of a custom-built impact-testing device for assessing the cushioning properties of socks. The device used a gravity-driven impact striker (8.5 kg), released from 0.05 m, which impacted a no-sock, sock or a basic shoe/sock condition in the vertical axis. A load cell (10,000 Hz) assessed peak impact force, time to peak impact force and loading rate. Reliability was investigated between day, between trial and within trial. Excellent reliability (coefficient of variation < 5% adjusted for 95% confidence limits) was reported for peak impact force in all conditions, with no evidence of systematic bias. Good reliability (coefficient of variation < 10% adjusted for 68% confidence limits) was reported for time to peak impact force and loading rate with some evidence of systematic bias. It was concluded that the custom-built impact-testing device was reliable and sensitive for the measurement of peak impact force on socks.

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Claire Bridgman, Joanna Scurr, Jennifer White, Wendy Hedger and Heather Galbraith

Anecdotal reports suggest two-step star jumps cause excessive breast movement and discomfort, leading to recommendations for this activity as a diagnostic tool to determine effective breast support in a retail environment. The aim was to investigate multiplanar bare-breast kinematics during the two-step star jump and to establish the relationship between breast kinematics, discomfort and cup size. Thirty-nine females completed five two-step star jumps with no breast support after which breast discomfort was rated. To establish relative breast kinematics infrared cameras tracked the 3D co-ordinates of breast and body markers. Maximum resultant breast displacement, velocity and acceleration during jumping reached 18.7 cm, 93.1 cm·s−1 and 3.6 g, respectively. Significantly more vertical breast displacement (p < 0.01) and velocity (p < 0.01) occurred compared with mediolateral and anteroposterior kinematics. Breast discomfort increased as cup size increased (r = .61). Two-step star jumping stimulated multiplanar breast kinematics and high levels of breast discomfort. Therefore, this activity may be useful in a retail outlet to determine the function and comfort of a sports bra.