Mercier, J., Vago, P., Ramonatxo, M., Bauer, C., & Prefaut, C. (1987). Effect of aerobic training quantity on the VO2max of circumpubertal swimmers. International Journal of Sports Medicine, 8, 26-30.

The effects of extensive training on developing swimmers has been considered for some time with mixed opinions and research results. Often limited research methods and designs have confused the understanding of this topic.

This investigation tracked boys swimming either 7 or 14 hours per week in a predominantly aerobic training program for a period of two years. Ages ranged from 10 to 14 years and so it was possible to assess long-term training effects when the boys went through the adolescent growth spurt (the time just after puberty). The two groups were quite similar in physical structure and aerobic capacity at the commencement of the study.

Aerobic capacity changes were evaluated using a non-swimming test. Such a lack of specificity would dampen any changes or differences if they were to occur.

The quantity-aerobic training group exhibited a greater amount of growth in the growth spurt stage. Two measures of aerobic function changed significantly after the age of 12 years: (a) VO2max (ml/kg/min), and (b) maximum oxygen pulse per kg body weight (VO2max / HRmax ml/kg/bts). The differences at both ages were approximately 16 percent. The major variable that changed to produce this improvement was the stroke volume of the heart, that is, the heart pumped more blood per beat. No differences in maximum heart rates were found between the groups.

A comparison of previous literature findings that agree and disagree with these findings was included in the article. It is this reviewer's assessment that studies conducted over a long period of time (e.g., a number of years) agree with this observed phenomenon.

The aerobic values obtained for both groups exceeded the more standard measures for boys of the same age by values between 48 and 53 percent.

Implications. The results of this study suggest several principles for consideration. Until further research becomes available, a coach should assume that the growth-training phenomenon would also occur in girls but at an earlier age.

1. It is important to concentrate training programs on aerobic/distance work up to, during, and for several years after puberty. The developmental stage coincides with the adolescent growth spurt. It seems that quantity-aerobic training stimulates growth in the aerobic capacity (particularly how well the heart pumps blood) at the same time as the body goes through this accelerated developmental stage. If a swimmer was not to train with sufficient aerobic stimulation, this enhancement opportunity might be missed.
2. Since most training programs are driven/motivated to accommodate the type of competitive program that is offered, it would seem to be in the best interests of individuals and national programs to provide competitive opportunities to perform in dominantly aerobic events for swimmers in this age-range. That would require a radical shift from the present "sprint/short-distance" orientation of age-group programs.
3. If programming changes were possible, a complicating factor would be that they should occur earlier for girls than for boys because of the earlier developmental patterns of girls.
4. One further coaching complication would also be the restraining of swimmers to emphasize aerobic volume until their developmental ages were appropriate for changing the emphasis. If progress was determined by chronological age, then some swimmers would be taken out of potentially beneficial aerobic work because they were late-maturers.
5. The major programming implication for coaches is that it is the quantity of aerobic work that produces aerobic development in swimmers prior to, at, and after the onset of puberty.
6. If a coach was to over-emphasize an aspect of programming for swimmers around pubertal ages, it would be best to concentrate on aerobic work rather than sprint work because aerobic function is dominant in all swimming events longer than 100 m.

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