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Ricky Watari, Blayne Hettinga, Sean Osis and Reed Ferber

The purpose of this study was to validate measures of vertical oscillation (VO) and ground contact time (GCT) derived from a commercially-available, torso-mounted accelerometer compared with single marker kinematics and kinetic ground reaction force (GRF) data. Twenty-two semi-elite runners ran on an instrumented treadmill while GRF data (1000 Hz) and three-dimensional kinematics (200 Hz) were collected for 60 s across 5 different running speeds ranging from 2.7 to 3.9 m/s. Measurement agreement was assessed by Bland-Altman plots with 95% limits of agreement and by concordance correlation coefficient (CCC). The accelerometer had excellent CCC agreement (> 0.97) with marker kinematics, but only moderate agreement, and overestimated measures between 16.27 mm to 17.56 mm compared with GRF VO measures. The GCT measures from the accelerometer had very good CCC agreement with GRF data, with less than 6 ms of mean bias at higher speeds. These results indicate a torsomounted accelerometer provides valid and accurate measures of torso-segment VO, but both a marker placed on the torso and the accelerometer yield systematic overestimations of center of mass VO. Measures of GCT from the accelerometer are valid when compared with GRF data, particularly at faster running speeds.

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Abigail S.L. Stickford, Daniel P. Wilhite and Robert F. Chapman

Investigations into ventilatory, metabolic, and hematological changes with altitude training have been completed; however, there is a lack of research exploring potential gait-kinematic changes after altitude training, despite a common complaint of athletes being a lack of leg "turnover" on return from altitude training.

Purpose:

To determine if select kinematic variables changed in a group of elite distance runners after 4 wk of altitude training.

Methods:

Six elite male distance runners completed a 28-d altitude-training intervention in Flagstaff, AZ (2150 m), following a modified “live high–train low” model, wherein higherintensity runs were performed at lower altitudes (945–1150 m) and low-intensity sessions were completed at higher altitudes (1950–2850 m). Gait parameters were measured 2–9 d before departure to altitude and 1 to 2 d after returning to sea level at running speeds of 300–360 m/min.

Results:

No differences were found in ground-contact time, swing time, or stride length or frequency after altitude training (P > .05).

Conclusions:

Running mechanics are not affected by chronic altitude training in elite distance runners. The data suggest that either chronic training at altitude truly has no effect on running mechanics or completing the live high–train low model of altitude training, where higher-velocity workouts are completed at lower elevations, mitigates any negative mechanical adaptations that may be associated with chronic training at slower speeds.

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Haley Bookbinder, Lindsay V. Slater, Austin Simpson, Jay Hertel and Joseph M. Hart

exercise for both the single-leg hop for distance as well as jump height and ground contact time during the 4-jump test. Methods Participants A total of 52 individuals volunteered for this study consisting of 27 patients with ACLR and 25 matched healthy, uninjured controls (Table  1 ). Based on an a priori

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Jessica G. Hunter, Alexander M.B. Smith, Lena M. Sciarratta, Stephen Suydam, Jae Kun Shim and Ross H. Miller

cushioning on spatiotemporal parameters. 18 Ground contact time (GCT) was similar between shoes with large differences in cushioning, 18 while increased shoe stiffness associated with mileage accumulation increased GCT. 19 The effects of shoes with different levels of cushioning and stiffness on VALR and

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Feng-Hua Tsai, I-Hua Chu, Chun-Hao Huang, Jing-Min Liang, Jia-Hroung Wu and Wen-Lan Wu

attack range and grant athletes a higher attack quality and efficiency; (2) taping influences the left foot-ground contact time. Shorter time means more efficient movement in the stretch-shortening cycle, which can shorten the attack time; (3) taping will change the ATF. Smaller force means a lower

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Mohsen Shafizadeh, Nicola Theis and Keith Davids

higher dominant frequency could be related to those parameters that affect active shock attenuation after foot–ground contact time, such as eccentric muscle contraction ( Gruber et al., 2014 ; Radin, 1972 ), muscle stiffness ( Boyer & Nigg, 2007 ), and joint kinematics ( Edwards et al., 2012 ). The

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Rahel Gilgen-Ammann, Thomas Wyss, Severin Troesch, Louis Heyer and Wolfgang Taube

-intrinsic sensory feedback. It has been previously demonstrated that ground-contact time (GCT) is a relevant performance variable in running, as it is the only period when large amounts of muscle force are generated and transmitted to the support surface. 6 – 10 A shorter GCT has been associated with faster

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Franziska Onasch, Anthony Killick and Walter Herzog

test with longer or shorter poles than those self-selected. For each subject, data of 5 different pole lengths were included in the analysis. The forces applied to the poles were measured continuously throughout all 5-minute trials. This information was used to calculate the ground contact time, the

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Christian A. Clermont, Lauren C. Benson, W. Brent Edwards, Blayne A. Hettinga and Reed Ferber

) bounce (vertical oscillation, in centimeters); (4) pelvic rotation (side-to-side movement of the pelvis, in degrees); (5) pelvic drop (side-to-side drop of the pelvis, in degrees); and (6) ground contact time (time foot is in contact with the ground at each step, in milliseconds). The Lumo Run® variables

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Jordan Santos-Concejero, Jesús Oliván, José L. Maté-Muñoz, Carlos Muniesa, Marta Montil, Ross Tucker and Alejandro Lucia

Purpose:

This study aimed to determine whether biomechanical characteristics such as ground-contact time, swing time, and stride length and frequency contribute to the exceptional running economy of East African runners.

Methods:

Seventeen elite long-distance runners (9 Eritrean, 8 European) performed an incremental maximal running test and 3 submaximal running bouts at 17, 19, and 21 km/h. During the tests, gas-exchange parameters were measured to determine maximal oxygen uptake (VO2max) and running economy (RE). In addition, ground-contact time, swing time, stride length, and stride frequency were measured.

Results:

The European runners had higher VO2max values than the Eritrean runners (77.2 ± 5.2 vs 73.5 ± 6.0 mL · kg−1 · min−1, P = .011, effect sizes [ES] = 0.65), although Eritrean runners were more economical at 19 km/h (191.4 ± 10.4 vs 205.9 ± 13.3 mL · kg−1 · min−1, P = .026, ES = 1.21). There were no differences between groups for ground-contact time, swing time, stride length, or stride frequency at any speed. Swing time was associated with running economy at 21 km/h in the Eritrean runners (r = .71, P = .033), but no other significant association was found between RE and biomechanical variables. Finally, best 10-km performance was significantly correlated with RE (r = –.57; P = .013).

Conclusions:

Eritrean runners have superior RE compared with elite European runners. This appears to offset their inferior VO2max. However, the current data suggest that their better RE does not have a biomechanical basis. Other factors, not measured in the current study, may contribute to this RE advantage.