Peters et al1 report the results of the novel use of a number of datasets from the UK. By pooling data from five UK studies between 1980 and 2008, the authors used an overall sample of 22 843 white European children who had resting pulse rate assessed at around 10 years of age. Although the sample at each time-point varied (from n=12 164 in the 1980 study to as little as n=774 in 1984/1985 study) and each time-point typically represented a cross-section of a different geographic area, similar methodologies to measure resting pulse rate were used in each study at each time-point. The authors reported that the mean resting pulse rate in assumed prepubertal children (mean age 10.3 years) had increased by 2 beats/min in boys and 1 beat/min in girls over the 28 years. These increases would seem to be independent of concurrent secular changes in height and, interestingly, body mass index (BMI). The authors postulated that persistence of these increases into adulthood could elevate later cardiovascular disease risk, especially in men. If resting pulse rate is regarded as an adequate marker of physical fitness in children, the results align with other cross-sectional results from the Chelmsford Fitness and …