Brain oxygenation declines in elite Kenyan runners during a maximal interval training session

Sin financiación2.401 JCR (2017) Q2, 27/81 Sport sciences; Q3, 45/83 Physiology1.186 SJR (2017) Q1, 435/2878 Medicine (miscellaneous), 37/285 Orthopedics and Sports Medicine, 80/554 Public Health, Environmental and Occupational Health, 29/127 Sports Science; Q2, 36/107 Physiology (medical)No data IDR 2017UE

Maintained cerebral oxygenation during maximal self-paced exercise in elite Kenyan runners

The purpose of this study was to analyze the cerebral oxygenation response to maximal self-paced and incremental exercise in elite Kenyan runners from the Kalenjin tribe. On two separate occasions, 15 elite Kenyan distance runners completed a 5-km time trial (TT) and a peak treadmill speed test (PTS). Changes in cerebral oxygenation were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxyhemoglobin (Δ[O2Hb] and Δ[HHb]), tissue oxygenation index (TOI), and total hemoglobin index (nTHI). During the 5-km TT (15.2 ± 0.2 min), cerebral oxygenation increased over the first half (increased Δ[O2Hb] and Δ[HHb]) and, thereafter, Δ[O2Hb] remained constant (effect size, ES = 0.33, small effect), whereas Δ[HHb] increased until the end of the trial (P < 0.05, ES = 3.13, large effect). In contrast, during the PTS, from the speed corresponding to the second ventilatory threshold, Δ[O2Hb] decreased (P < 0.05, ES = 1.51, large effect), whereas Δ[HHb] continued to increase progressively until exhaustion (P < 0.05, ES = 1.22, large effect). Last, the TOI was higher during the PTS than during the 5-km TT (P < 0.001, ES = 3.08; very large effect), whereas nTHI values were lower (P < 0.001, ES = 2.36, large effect). This study shows that Kenyan runners from the Kalenjin tribe are able to maintain their cerebral oxygenation within a stable range during a self-paced maximal 5-km time trial, but not during an incremental maximal test. This may contribute to their long-distance running success.Sin financiación3.004 JCR (2015) Q1, 12/82 Sport Sciences; Q2, 27/83 PhysiologyUE

Are gait characteristics and ground reaction forces related to energy cost of running in elite Kenyan runners?

The aim of this study was to determine whether gait cycle characteristics are associated with running economy in elite Kenyan runners. Fifteen elite Kenyan male runners completed two constant-speed running sets on a treadmill (12 km ·h−1 and 20 km ·h−1). VO2 and respiratory exchange ratio values were measured to calculate steady-state oxygen and energy cost of running. Gait cycle characteristics and ground contact forces were measured at each speed. Oxygen cost of running at different velocities was 192.2 ± 14.7 ml· kg−1· km−1 at 12 km· h−1 and 184.8 ± 9.9 ml· kg−1· km−1 at 20 km· h−1, which corresponded to a caloric cost of running of 0.94 ± 0.07 kcal ·kg−1·km−1 and 0.93 ± 0.07 kcal· kg−1· km−1. We found no significant correlations between oxygen and energy cost of running and biomechanical variables and ground reaction forces at either 12 or 20 km· h−1. However, ground contact times were ~10.0% shorter (very large effect) than in previously published literature in elite runners at similar speeds, alongside an 8.9% lower oxygen cost (very large effect). These results provide evidence to hypothesise that the short ground contact times may contribute to the exceptional running economy of Kenyan runners.Sin financiación2.539 JCR (2016) Q2, 17/81 Sport Sciences1.280 SJR (2016) Q1, 31/280 Orthopedics and Sports Medicine, 18/195 Physical Therapy, Sports Therapy and Rehabilitation, 29/127 Sports ScienceNo data IDR 2016UE

Gait-cycle characteristics and running economy in elite Eritrean and European runners

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. 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.3.042 JCR (2015) Q1, 10/82 Sport sciences; Q2, 26/83 PhysiologyUE