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Nicholas D. Gilson, Caitlin Hall, Angela Renton, Norman Ng and William von Hippel

completing computer tasks for prolonged periods of time. 6 Consequently, activity-promoting desks have been proposed as a potential strategy for reducing and interrupting occupational sitting, based on the rationale that they allow desk work to occur while standing (sit–stand desk) or walking (treadmill

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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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Monika Lohkamp, Simon Craven, Colin Walker-Johnson and Matt Greig

Context:

Postural stability diminishes with longer activity, which may increase the risk of injury. Tape can increase stability, but this effect diminishes after exercise.

Objective:

To investigate the influence of ankle taping on postural stability during soccer-specific activity.

Participants:

10 male, injury-free, semiprofessional soccer players.

Intervention:

A 45-min treadmill protocol replicating the activity profile of soccer match play—with and without ankle tape. Postural stability was assessed every 7.5 min, requiring response to sudden ankle plantar flexion and inversion during single-leg stance.

Main Outcome Measure:

Reaction time to perturbation and center- of-gravity (CoG) displacement.

Results:

Reaction time was significantly longer (P < .05) with longer exercise for both movements and conditions. No significant effect was evident in CoG displacement. For both outcome measures a nonsignificant benefit of taping was observed during the first 22.5 min of activity.

Conclusion:

Prolonged exposure to soccer-specific activity negates any beneficial effect of taping in improving postural stability.

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Rebecca J. Bedard, Kyung-Min Kim, Terry L. Grindstaff and Joseph M. Hart

Objective:

To compare active hamstring stiffness in female subjects with and without a history of low back pain (LBP) after a standardized 20-min aerobic-exercise session.

Design:

Case control.

Setting:

Laboratory.

Participants:

12 women with a history of recurrent episodes of LBP (age = 22.4 ± 2.1 y, mass = 67.1 ± 11.8 kg, height = 167.9 ± 8 cm) and 12 matched healthy women (age = 21.7 ± 1.7 y, mass = 61.4 ± 8.8 kg, height = 165.6 ± 7.3 cm). LBP subjects reported an average 6.5 ± 4.7 on the Oswestry Disability Index.

Interventions:

Participants walked at a self-selected speed (minimum 3.0 miles/h) for 20 min. The treadmill incline was raised 1% grade per minute for the first 15 min. During the last 5 min, participants adjusted the incline of the treadmill so they would maintain a moderate level of perceived exertion through the end of the exercise protocol.

Main Outcome Measures:

During session 1, active hamstring stiffness, hamstring and quadriceps isometric strength, and concurrently collected electromyographic activity were recorded before and immediately after the exercise protocol. For session 2, subjects returned 48–72 h after exercise for repeat measure of active hamstring stiffness.

Results:

Hamstring active stiffness (Nm/rad) taken immediately postexercise was not significantly different between groups. However, individuals with a history of recurrent LBP episodes presented significantly increased hamstring stiffness 48–72 h postexercise compared with controls. For other outcomes, there was no group difference.

Conclusions:

Women with a history of recurrent LBP episodes presented greater active hamstring stiffness 48–72 h after aerobic exercise.

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Ian Rollo and Clyde Williams

The aim of this study was to investigate the influence of ingesting a carbohydrate-electrolyte solution (CHO-E) on performance during a 1-hr treadmill run. Eight male endurance-trained runners (age 31 ± 8 yr, M ± SD) completed three 1-hr performance runs separated by 1 wk. The study used a double-blind placebo (PLA) controlled design. On 2 occasions (P1, P2) runners consumed a placebo solution, 8 ml/kg body mass (BM), 30 min before and 2 ml/kg BM at 15-min intervals throughout the 1-hr run. On a separate occasion they consumed the same quantity of a 6.4% CHO-E solution (C). Total distances covered for P1, P2, and C trials were 13,685 ± 1,116 m, 13,715 ± 1,143 m, and 14,046 ± 1,104 m, respectively. Although there was no difference between the 2 PLA trials (p > .05), the distance covered during the C trial was significantly greater than in either PLA trial (p < .05). CHO ingestion resulted in a higher blood glucose concentration only at the onset of exercise (p < .05) compared with the PLA trials. Blood lactate, respiratory-exchange ratio, and CHO oxidation were similar in all 3 trials. In conclusion, ingestion of a 6.4% CHO-E solution before and during exercise was associated with improved running performance in runners compared with the ingestion of a color- and taste-matched placebo.

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Adam C. Clansey, Mark J. Lake, Eric S. Wallace, Tom Feehally and Michael Hanlon

The purpose of this study was to investigate the effects of prolonged high-intensity running on impact accelerations in trained runners. Thirteen male distance runners completed two 20-minute treadmill runs at speeds corresponding to 95% of onset of blood lactate accumulation. Leg and head accelerations were collected for 20 s every fourth minute. Rating of perceived exertion (RPE) scores were recorded during the third and last minute of each run. RPE responses increased (P < .001) from the start (11.8 ± 0.9, moderate intensity) of the first run to the end (17.7 ± 1.5, very hard) of the second run. Runners maintained their leg impact acceleration, impact attenuation, stride length, and stride frequency characteristics with prolonged run duration. However, a small (0.11–0.14g) but significant increase (P < .001) in head impact accelerations were observed at the end of both first and second runs. It was concluded that trained runners are able to control leg impact accelerations during sustained high-intensity running. Alongside the substantial increases in perceived exertion levels, running mechanics and frequency domain impact attenuation levels remained constant. This suggests that the present trained runners are able to cope from a mechanical perspective despite an increased physiological demand.

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Daniel Arvidsson, Mark Fitch, Mark L. Hudes, Catrine Tudor-Locke and Sharon E. Fleming

Background:

Different movement efficiency in overweight children may affect accelerometer output data. The purpose was to investigate the ability of accelerometers to assess physical activity intensity and number of steps in normal-weight compared with overweight children.

Methods:

Eleven normal-weight and 14 overweight African American children walked at 2, 4, 5, and 6 km/h on a treadmill wearing Lifecorder, ActiGraph, RT3, and Biotrainer. Oxygen uptake was measured and steps manually counted. Fat free mass (FFM) was assessed from bioelectrical impedance analysis. Accelerometer counts and the individual linear regression lines of accelerometer counts versus VO2/FFM were evaluated, together with steps recorded by Lifecorder and Actigraph.

Results:

Correlations between accelerometer counts and VO2/FFM for all monitors were r ≥ .95 (P < .01). The accelerometer counts and their relationship to VO2/FFM did not generally differ significantly by body weight status. Lifecorder and Actigraph underestimated steps at 4, 5, and 6 km/h by less than 9%, but the error was up to −95% at 2 km/h.

Conclusions:

All 4 accelerometers show high ability to assess physical activity intensity, and can be used to compare physical activity between normal-weight and overweight children. The Lifecorder and the ActiGraph showed high accuracy in assessing steps, providing speed of movement exceeded 2 km/h.

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Ben J. Lee and Charles Douglas Thake

). 6 , 8 – 10 For example, walking with 75% BWS reduced energy expenditure by 45% compared with a nonsupported walk. 8 However, the metabolic cost of running at increasing levels of BWS can be offset by increasing treadmill speed. 6 , 8 , 10 Indeed, both submaximal and maximal V ˙ O 2 achieved

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Daniel E. Lidstone, Justin A. Stewart, Reed Gurchiek, Alan R. Needle, Herman van Werkhoven and Jeffrey M. McBride

standard Bruce protocol was used to test V ˙ O 2   max in our participants. Subjects performed the protocol to volitional fatigue on a motor driven treadmill (Full Vision Inc. Trackmaster TMX425C, Newton, KS, USA). The first stage of the test is 2.7 km·h –1 at a 10% gradient for 3 minutes. At 3-minute

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James S. Hogg, James G. Hopker and Alexis R. Mauger

Purpose:

The novel self-paced maximal-oxygen-uptake (VO2max) test (SPV) may be a more suitable alternative to traditional maximal tests for elite athletes due to the ability to self-regulate pace. This study aimed to examine whether the SPV can be administered on a motorized treadmill.

Methods:

Fourteen highly trained male distance runners performed a standard graded exercise test (GXT), an incline-based SPV (SPVincline), and a speed-based SPV (SPVspeed). The GXT included a plateau-verification stage. Both SPV protocols included 5 × 2-min stages (and a plateau-verification stage) and allowed for self-pacing based on fixed increments of rating of perceived exertion: 11, 13, 15, 17, and 20. The participants varied their speed and incline on the treadmill by moving between different marked zones in which the tester would then adjust the intensity.

Results:

There was no significant difference (P = .319, ES = 0.21) in the VO2max achieved in the SPVspeed (67.6 ± 3.6 mL · kg−1 · min−1, 95%CI = 65.6–69.7 mL · kg−1 · min−1) compared with that achieved in the GXT (68.6 ± 6.0 mL · kg−1 · min−1, 95%CI = 65.1–72.1 mL · kg−1 · min−1). Participants achieved a significantly higher VO2max in the SPVincline (70.6 ± 4.3 mL · kg−1 · min−1, 95%CI = 68.1–73.0 mL · kg−1 · min−1) than in either the GXT (P = .027, ES = 0.39) or SPVspeed (P = .001, ES = 0.76).

Conclusions:

The SPVspeed protocol produces VO2max values similar to those obtained in the GXT and may represent a more appropriate and athlete-friendly test that is more oriented toward the variable speed found in competitive sport.