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Alex V. Rowlands, John M. Schuna Jr., Victoria H. Stiles and Catrine Tudor-Locke

Background:

Previous research has reported peak vertical acceleration and peak loading rate thresholds beneficial to bone mineral density (BMD). Such thresholds are difficult to translate into meaningful recommendations for physical activity. Cadence (steps/min) is a more readily interpretable measure of ambulatory activity.

Objective:

To examine relationships between cadence, peak vertical acceleration and peak loading rate during ambulation and identify the cadence associated with previously reported bone-beneficial thresholds for peak vertical acceleration (4.9 g) and peak loading rate (43 BW/s).

Methods:

Ten participants completed 8 trials each of: slow walking, brisk walking, slow running, and fast running. Acceleration data were captured using a GT3×+ accelerometer worn at the hip. Peak loading rate was collected via a force plate.

Results:

Strong relationships were identified between cadence and peak vertical acceleration (r = .96, P < .05) and peak loading rate (r = .98, P < .05). Regression analyses indicated cadences of 157 ± 12 steps/min (2.6 ± 0.2 steps/s) and 122 ± 10 steps/min (2.0 ± 0.2 steps/s) corresponded with the 4.9 g peak vertical acceleration and 43 BW/s peak loading rate thresholds, respectively.

Conclusions:

Cadences ≥ 2.0 to 2.6 steps/s equate to acceleration and loading rate thresholds related to bone health. Further research is needed to investigate whether the frequency of daily occurrences of this cadence is associated with BMD.

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J. Sinclair, J. Isherwood and P.J. Taylor

Chronic injuries are a common complaint in recreational runners. Foot orthoses have been shown to be effective for the treatment of running injuries but their mechanical effects are still not well understood. This study aims to examine the influence of orthotic intervention on multisegment foot kinematics and plantar fascia strain during running. Fifteen male participants ran at 4.0 m·s−1 with and without orthotics. Multisegment foot kinematics and plantar fascia strain were obtained during the stance phase and contrasted using paired t tests. Relative coronal plane range of motion of the midfoot relative to the rearfoot was significantly reduced with orthotics (1.0°) compared to without (2.2°). Similarly, relative transverse plane range of motion was significantly lower with orthotics (1.1°) compared to without (1.8°). Plantar fascia strain did not differ significantly between orthotic (7.1) and nonorthotic (7.1) conditions. This study shows that although orthotics did not serve to reduce plantar fascia strain, they are able to mediate reductions in coronal and transverse plane rotations of the midfoot.

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Mark Abel, James Hannon, David Mullineaux and Aaron Beighle

Background:

Current recommendations call for adults to be physically active at moderate and/or vigorous intensities. Given the popularity of walking and running, the use of step rates may provide a practical and inexpensive means to evaluate ambulatory intensity. Thus, the purpose of this study was to identify step rate thresholds that correspond to various intensity classifications.

Methods:

Oxygen consumption was measured at rest and during 10 minute treadmill walking and running trials at 6 standardized speeds (54, 80, 107, 134, 161, and 188 m·min-1) in 9 men and 10 women (28.8 ± 6.8 yrs). Two observers counted the participants’ steps at each treadmill speed. Linear and nonlinear regression analyses were used to develop prediction equations to ascertain step rate thresholds at various intensities.

Results:

Nonlinear regression analysis of the metabolic cost versus step rates across all treadmill speeds yielded the highest R 2 values for men (R 2 = .91) and women (R 2 = .79). For men, the nonlinear analysis yielded 94 and 125 step·min-1 for moderate and vigorous intensities, respectively. For women, 99 and 135 step·min-1 corresponded with moderate and vigorous intensities, respectively.

Conclusions:

Promoting a step rate of 100 step·min-1 may serve as a practical public health recommendation to exercise at moderate intensity.

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Jennifer Kappenstein, Jaime Fernández-Fernández, Florian Engel and Alexander Ferrauti

The aim of this study was to compare the effect of active (AR) and passive recovery (PR) after a high-intensive repeated sprint running protocol on physiological parameters in children and adults. Blood lactate (La) and blood pH were obtained during two sets of 5 × 5 s all-out sprints and several times during subsequent 30-min recovery in 16 children and 16 adults. End-exercise La was significantly lower and pH significantly higher in children (La: 5.21 ± 2.73 mmol·L1; pH: 7.37 ± 0.06) compared with adults (La: 10.35 ± 5.76 mmol·L−1; pH: 7.27 ± 0.10) (p > .01). La half-life during postexercise recovery was significantly shorter in children (AR: 436 ± 371 s, PR: 830 ± 349 s) than in adults (AR: 733 ± 371 s, PR: 1361 ± 372 s), as well as in active compared with passive recovery for both age groups (p > .01). The age x recovery interaction for La half-life only approached statistical significance (p = .06). The results suggest a faster lactate disappearance and an earlier return to resting pH after a repeated sprint running protocol in children compared with adults and a less pronounced advantage of active recovery in children.

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James W. Navalta, Jeffrey Montes, Nathaniel G. Bodell, Charli D. Aguilar, Ana Lujan, Gabriela Guzman, Brandi K. Kam, Jacob W. Manning and Mark DeBeliso

population is utilizing wearable technology. Among the most common leisure activities is hiking, which has seen participation increase almost 200 fold in recent years, and is one of the top two outdoor activities performed ( Cordell et al., 2005 ; Manning et al., 2015 ). Additionally, trail running has seen

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Gareth N. Sandford, Sian V. Allen, Andrew E. Kilding, Angus Ross and Paul B. Laursen

Preparation for 800-m running represents a unique challenge to the middle-distance coach. With close interplay required between aerobic and anaerobic/neuromuscular physiology, athletes with distinctly different profiles have an opportunity for success in the event. Recently, a “changing of the

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Nicola Giovanelli, Filippo Vaccari, Mirco Floreani, Enrico Rejc, Jasmine Copetti, Marco Garra, Lea Biasutti and Stefano Lazzer

to the best of our knowledge the effects of SMFR on running performance have not been investigated yet. The energy cost of running (Cr) plays a relevant role in determining performance among middle- and long-distance runners along with the maximal oxygen uptake and the fraction of it that is

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Benno M. Nigg, Gerald K. Cole and Gert-Peter Brüggemann

Impact forces have been speculated to be associated with the development of musculoskeletal injuries. However, several findings indicate that the concepts of “impact forces” and the paradigms of their “cushioning” may not be well understood in relation to the etiology of running injuries and that complex mechanisms may be responsible for injury development during running. The purposes of this paper are (a) to review impact mechanics during locomotion, (b) to review injuries and changes of biological tissue due to impact loading, and (c) to synthesize the mechanical and biological findings. In addition, directions for future research are discussed. Future research should address the development of noninvasive techniques to assess changes in the morphology and biochemistry of bone, cartilage, tendon, and ligaments; researchers should also try to simulate impact loading during activities such as running, focusing on the interaction of the various loading parameters that determine the acceptable windows of loading for biological tissues.

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Martyn R. Shorten and Darcy S. Winslow

The purpose of this study was to determine the effects of increasing impact shock levels on the spectral characteristics of impact shock and impact shock wave attenuation in the body during treadmill running. Twelve male subjects ran at 2.0, 3.0, 4.0, and 5.0 m s−1 on a treadmill. Axial accelerations of the shank and head were measured using low-mass accelerometers. The typical shank acceleration power spectrum contained two major components which corresponded to the active (5–8 Hz) and impact (12–20 Hz) phases of the time-domain ground reaction force. Both the amplitude and frequency of leg shock transients increased with increasing running speed. Greatest attenuation of the shock transmitted to the head occurred in the 15–50 Hz range. Attenuation increased with increasing running speed. Thus transmission of the impact shock wave to the head was limited, despite large increases in impact shock at the lower extremity.

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Eric K. O’Neal, Brett A. Davis, Lauren K. Thigpen, Christina R. Caufield, Anthony D. Horton and Joyce R. McIntosh

The purpose of this study was to determine how accurately runners estimate their sweat losses. Male (n = 19) and female (n = 20) runners (41 ± 10 yr, VO2max 57 ± 9 ml · kg−1 · min−1) from the southeastern U.S. completed an ~1-hr run during late summer on a challenging outdoor road course (wet bulb globe temperature 24.1 ± 1.5 °C). Runs began at ~6:45 a.m. or p.m. Before and after running, participants filled race-aid-station paper cups with a volume of fluid they felt would be equivalent to their sweat losses. Total sweat losses and losses by percent body weight differed (p < .01) between men (1,797 ± 449 ml, 2.3% ± 0.6%) and women (1,155 ± 258 ml, 1.9% ± 0.4%). Postrun estimates (738 ± 470 ml) were lower (p < .001) than sweat losses (1,468 ± 484 ml), equaling underestimations of 50% ± 23%, with no differences in estimation accuracy by percentage between genders. Runners who reported measuring changes in pre- and postrun weight to assess sweat losses within the previous month (n = 9, –54% ± 18%) were no more accurate (p = .55) than runners who had not (n = 30, –48% ± 24%). These results suggest that inadequate fluid intake during runs or between runs may stem from underestimations of sweat losses and that runners who do assess sweat-loss changes may be making sweat-loss calculation errors or do not accurately translate changes in body weight to physical volumes of water.