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Purpose: The purpose of this study was to characterise the cerebral oxygenation (Cox) response during a high-intensity interval training session in Kenyan runners, and to examine any relationship with running performance.Methods: 15 Kenyan runners completed a 5-km time trial (TT) and a Fatigue Training Test on a treadmill (repeated running bouts of 1-km at a pace 5% faster than their mean 5-km TT pace with a 30-s recovery until exhaustion). Changes in Cox were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxy-haemoglobin (Δ[O2Hb] and Δ[HHb]), tissue oxygenation index (TOI), and total hemoglobin index (nTHI).Results: The number of 1-km repetitions achieved by the participants was 5.5 ± 1.2 repetitions at a mean pace of 20.5 ± 0.7 km h-1. Δ[O2Hb] measured at the end of each running repetition declined progressively over the course of the trial (p = 0.01, ES = 4.59). Δ[HHb] increased during each running bout until the end of the Fatigue Training Test (p < 0.001; ES = 6.0). TOI decreased significantly from the beginning of the test (p = 0.013, ES = 1.83), whereas nTHI remained stable (ES = 0.08). The Cox decline in the Fatigue Training Test was negatively correlated with the speed at which the test was completed (p = 0.017; r = -0.61), suggesting that the best performers were able to defend their Cox better than those of lower running ability.Conclusions: In conclusion, this study suggests that elite Kenyan runners cannot defend cerebral oxygenation when forced to exercise to their physiological limits. This emphasises the critical importance of pacing in their racing success. [ABSTRACT FROM AUTHOR]

To investigate the response to endurance training on physiological characteristics, 10 Nandi town boys and 14 Nandi village boys 16.5 and 16.6 years of age, respectively, from western Kenya performed 12 weeks of running training. The study was performed at altitude (∼2000 m.a.s.l.∼595 mm Hg). Training heart rate and speed were registered during every training session throughout the entire training period. While town and village boys trained at similar heart rates (172.1 vs. 172.5 beats min−1), the training speed of the town boys was 9% lower compared with the village boys (12.4 vs. 13.6 km h−1,P<0.001). Significant increases in VO2max were observed in the town boys (from 50.3 to 55.6 mL kg−1 min−1,P<0.001) and in village boys (from 56.0 to 59.1 mL kg−1 min−1,P<0.002). Significant decreases in submaximal heart rate (from 172.4 to 160.3 beats min−1 (P<0.005)), blood lactate (from 2.7 to 1.4 mmol L−1 (P<0.005)) and ammonia concentration (from 102.0 to 71.4 μmol L−1 (P<0.01)) at 9.9 km h−1 were observed in the town boys, while similar decreases in heart rate (from 170.2 to 159.2 beats min−1 (P<0.001)), blood lactate (from 2.4 to 1.4 mmol L−1 (P<0.001)) and ammonia concentration (from 102.5 to 72.7 lmol L−1 (P<0.001)) at 10.9 km h−1 were observed in the village boys. The oxygen cost of running was decreased from 221.5 to 211.5 mL kg−1 km−1 (P<0.03) in the town boys and from 220.1 to 207.2 mL kg−1 km−1 (P<0.01) in the village boys. The 5000 m performance time of the town boys was significantly greater than that of the village boys (20.25 vs. 18.42 min (P=0.01)). It is concluded that no difference was observed in trainability with respect to VO2max, running economy, submaximal heart rate, and submaximal blood lactate and ammonia concentration between Kenyan Nandi town and village boys. The higher performance level of the village boys was likely due to a higher VO2max of these boys. [ABSTRACT FROM AUTHOR]