CJ. Aerobic exercise capacity at sea level and at altitude in Kenyan boys, junior and senior runners compared with Scandinavian runners.

The aim of this study was to characterize untrained Nandi boys (mean age 16.6 years) from a town (n = 11) and from a rural area (n = 19) in western Kenya (altitude approximately 2000 m.a.s.l.) in regard to their body dimensions, oxygen uptake and physical activity level. The town boys had a mean maximal oxygen uptake (VO(2 max)) of 50 (range: 45-60) mL kg(-1) min(-1), whereas the village boys reached a value of 55 (37-63) mL kg(-1) min(-1) ( p<0.01) in VO(2 max). The running economy, determined as the oxygen cost at a given running speed, was 221 mL kg(-1) km(-1) (597 mL kg(-0.75) km(-1)) for town as well as for village boys. The body mass index (BMI) was very low for town as well as for village boys (18.6 vs 18.4 kg m(-2)). The daily mean time spent working in the field during secondary school and doing sports were significantly higher in village boys compared to town boys (working in the field: 44.2 (0-128) vs 1.3 (0-11) min, p<0.01; sports: 32.0 (11-72) vs 12.8 (0-35) min, p<0.01, respectively). A positive correlation between the daily time spent doing sports and VO(2 max) was found when pooling the data from the town and the village boys (R = 0.55, p<0.01). It is concluded that the body dimensions of adolescent Nandi town and village boys corresponds well with findings in Kenyan elite runners. They are very slender with relatively long legs. In addition, the VO(2 max) of the village boys was higher than that of the town boys, which is probably due to a higher physical activity level of the village boys during secondary school.

The study comprises data on 12 Scandinavian runners who had either trained for two weeks in Kenya (n= 6; ∼2000 meters above sea level (m.a.s.l.)) or in Portugal (n= 6; sea level (s.l.)) and on 13 Kenyan runners (9 junior and 4 senior) living and training at ∼2000 m.a.s.l. Muscle biopsies were taken before and after the training camps in the Scandinavian runners and once on the Kenyan runners from the vastus lateralis (v.l.) and the gastrocnemius muscles. Muscle fiber size and composition were similar in the various groups (4.6–5.1 × 103μm2; ST ∼60–70%; FTa 30–40%; FTb < 6.0%) with a tendency for some more (∼5%) FTa fibers in the gastrocnemius muscle. Mean number of capillaries in v.l. varies between 405–493 cap · (mm2)−1, 2.0–2.7 cap · fiber−1, and 4.4–6.2 cap around the various fiber types, with the Kenyan seniors having the highest and the Kenyan juniors the lowest values. All runners had 10–20% more capillaries in their gastrocnemius muscle. Similar levels for citrate synthase (CS) activity were found in the v.l. of the Kenyan seniors and Scandinavian runners, whereas the Kenyan juniors were 10–15% lower. The 3‐hydroxyacyl‐CoA‐dehydrogenase (HAD) activity was 20% higher in the Kenyan than in the Scandinavian runners. In the gastrocnemius muscle, both enzyme activities were 20–50% higher in Scandinavian and Kenyan runners. The ratio for lactate dehydrogenase (LDH) isoform1–2 and isoform4–5 was increased when training at altitude due to a lowering of LDH4–5 and became close to what was observed in the Kenyan runners. Also muscle buffer capacity became increased in the altitude training groups. It is concluded that muscle morphology is quite similar in Scandinavian and Kenyan runners with no effect of training at altitude. Mitochondrial enzyme activities are also unaltered at altitude, but the Kenyan runners have markedly higher HAD activity. Muscle buffer capacity is elevated in the Scandinavian runners training at altitude, and it appears to be an effect of altitude, as no change was observed in the Scandinavian runners training at s.l., which was also the case for the LDH1–2: LDH4–5 ratio as a result of a lowering of LDH4–5 activity.

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