Abigail S. Laymon

Ground contact time as an indicator of metabolic cost in elite distance runners.

UNLABELLED Differences in running economy at common speeds have been demonstrated between male and female distance runners, as well as between middle-distance (MD) and long-distance (LD) specialists. Whether measures of foot ground contact time (tc), known to be proportional to the mass-specific cost of locomotion, follows the same running economy relationships in these groups is unknown. PURPOSE This study examined if differences in tc and selected gait kinematic variables exist between elite male and female distance runners, as well as between elite MD and LD specialists, as running speed increases. METHODS Twelve male and six female elite distance runners completed multiple 30-s trials on a treadmill at common competitive racing velocities. Wireless triaxial 10-g accelerometers, sampling at 1024 Hz, were securely attached to the laces of each shoe. Values of tc, swing time, stride length, and stride frequency were determined from accelerometric output corresponding to foot strike and toe-off events obtained from a minimum of 20 consecutive steps of each foot. A proportional estimate of metabolic cost was obtained by using 1/tc. RESULTS Women displayed shorter tc, swing time, and stride length with greater stride frequency compared with men at common speeds; however, these differences were largely negated by normalizing to standing height. At common speeds, women demonstrated smaller measures of tc compared with men, suggesting an increased metabolic cost, paralleling published oxygen uptake data. MD specialists displayed smaller increases in 1/tc as speed increased, compared with LD specialists. CONCLUSIONS Elite distance runners demonstrate ground contact measures that suggest that known differences in running economy between sexes and event specialties may be a result of differences in running gait.

Comments on Point: Counterpoint: Hypobaric hypoxia induces/does not induce different responses from normobaric hypoxia.

112:1788-1794, 2012. ; J Appl Physiol Joshua C. Weavil, Peter Bartsch and Charles F. Nelatury Samuel Verges, Patrick Levy, Eric M. Snyder, Bruce D. Johnson, Jonathon L. Stickford, Y. Millet, Benjamin D. Levine, James H. Wessel III, Bernard Wuyam, Renaud Tamisier, MacInnis, Michael S. Koehle, Thomas Rupp, Marc Jubeau, Stephane Perrey, Guillaume Laymon, Jack A. Loeppky, Matiram Pun, Kai Schommer, Mary C. Vagula, Martin J. S. Chapman, Johnny Conkin, Hugo Nespoulet, Darren P. Casey, Bryan J. Taylor, Abigail Olivier Girard, Michael S. Koehle, Jordan A. Guenette, Samuel Verges, Robert F. normobaric hypoxia induces/does not induce different responses from Comments on Point:Counterpoint: Hypobaric hypoxia

Timing of Arrival and Pre-acclimatization Strategies for the Endurance Athlete Competing at Moderate to High Altitudes

With the wide array of endurance sport competition offerings at moderate and high altitudes, clinicians are frequently asked about best practice recommendations regarding arrival times prior to the event and acclimatization guidelines. This brief review will offer data and current advice on when to arrive at altitude and various potential sea level-based pre-acclimatization strategies in an effort to maximize performance and minimize the risk of altitude sickness.