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Are the lungs built for rowing?

For a biological tissue, including the brain, to develop and to remain alert, it requires challenges, and, sadly, early retirement reduces cerebral blood flow. InWestern style societies, the brain may be stimulated adequately, but the physical activity needed to maintain the locomotor and cardiovascular systems depends on leisure time activity. Interest in sports allows for the evaluation of health benefits – beginning with the finding of a 2-year prolonged life of former English rowers already in 1873 and now explained by the excellent physiological profile of elderly oarsman in several papers by Yoshiga and Higuchi (e.g. Yoshiga et al., 2002). Sport activities demand specific skills, and with excellence requiring years of training, adaptations can be evaluated in detail. As stated by A. V. Hill, ‘‘the most accurate data are found not in textbooks on physiology, not even in textbooks on medicine, but in the World records (of runners)’’. Oarsmen are familiar with ergometer rowing including competitions over ‘‘2000m’’, and the physiology of maximal exercise is studied in the laboratory. This issue addresses the O2 transport system. Yoshiga and Higuchi (2003a) establish a relationship between maximal O2 uptake (VO2max) and body size among a large number of rowers to explain the difference in the work performed by females and males. Although the majority of the variation in power is explained by body dimensions, a 5% difference remains when sexes are compared at similar lean body mass. They (Yoshiga & Higuchi, 2003b) also evaluate the heart rate (HR) response to rowing and running. Surprisingly, the relationship between HR and VO2 does not always prevail when different types of exercise are compared. Despite a larger VO2max during rowing than during running, the HR response is attenuated. The authors argue that the central blood volume is reduced during (upright) running compared with (seated) rowing. Hereby they address a variable that has been overlooked in the cardiovascular adaptation to exercise, and its integration could provide insight not only to the regulation of HR but also to the regulation of flow and, in turn, metabolism. Yoshiga and Higuchi (2003b) pose the idea that the larger ventilation during rowing than during running indicates that it does not limit VO2max, but the situation may be more complicated than that. Skeletal muscles extract almost all the O2 provided by blood, and whole-body exercise in particular challenges the O2 transport system. The traditional view is that the circulation limits VO2max; however, the lungs may fail to secure oxygenation of arterial blood. A reduction in the arterial O2 tension (PaO2) is reported for some intensively trained runners and cyclists, but for all oarsmen during (ergometer) rowing (Hanel et al., 1994). At the same time, pH decreases to an impressive 6.74 reflecting blood lactate levels of 30mM (Nielsen, 2003). The Bohr effect on the oxyhaemoglobin dissociation curve is considered to promote O2 delivery to the tissue, but with the combined lowering of PaO2 and pH the arterial saturation (SaO2) is affected. During rowing, SaO2 decreases to B90% corresponding to what is manifest at an altitude of more than 3000m above sea level. In support, an increase in the inspired O2 fraction, or the administration of bicarbonate, restores SaO2, and the percent increase in VO2max corresponds to the enhanced SaO2 (Nielsen, 2003). It may be questioned as to when it pays off to perform work provided for by anaerobic metabolism in situations where PaO2 is low. Clearly there is a delicate balance between ATP production by anaerobic metabolism and the lowering of aerobic metabolism caused by a reduced SaO2. Some patients and also normal subjects exposed to high altitude tend to produce very little lactate (‘‘the lactate paradox’’) (Lundby et al., 2000). The implication of the findings by Nielsen (2003) is that for endurance-type exercise, people and patients are wise not to lower their arterial pH so as to preserve SaO2, and thereby VO2, when PaO2 is low. Conversely, hyperventilation secures an increase in alveolar O2 tension to overcome the diffusion limitation of the lungs. Could it be that oarsmen cannot increase their alveolar O2 tension to the same extent as the often smaller runners and cyclists?