Accuracy of physical working capacity 170 to estimate aerobic fitness in prepubertal diabetic boys and in 2 insulin dose conditions.

Author(s): Heyman E, Briard D, Dekerdanet M, Gratas-Delamarche A, Delamarche P

Affiliation(s): Department of Pediatric Endocrinology, University Hospital of Rennes, Rennes, France. elsaheyman@yahoo.com

Publication date & source: 2006-06, J Sports Med Phys Fitness., 46(2):315-21.

Publication type: Comparative Study; Randomized Controlled Trial

AIM: Exercise tests evaluate the effects of physical activity, which is one of the four recommendations for diabetes treatment. An adjusted and accurate measure of aerobic capacity in diabetic patients is thus needed. This study compared two estimates of aerobic fitness (maximal oxygen uptake vs physical working activity PWC170, i.e., the workload at a pulse of 170) and the usual versus a reduced insulin dose in preadolescent boys with type 1 diabetes mellitus. METHODS: Sixteen prepubertal type 1 diabetic boys performed a submaximal test, the PWC(170). Gas exchange values and capillary blood glucose levels were monitored and, when possible, the test was extended to exhaustion. In 7 boys, the test was performed twice on separate days. On one day they received their usual insulin dose and on the other, their short-acting insulin was reduced by 1/3; the two tests were held in random order. The 9 other children were tested only once after receiving their usual insulin dose. RESULTS: For the 16 boys who performed the test with the usual insulin dose, PWC(170) (W) and peak oxygen uptake (peak VO(2)) (L.min(-1)) correlated closely (r=0.81, P=0.002). Aerobic fitness did not change with insulin dose, but some hypoglycemic episodes occurred when insulin dose was not reduced. CONCLUSIONS: Since maximal effort does not add more information, routine use of the submaximal peak VO(2)-correlated test, the PWC(170), seems sufficient, possibly in association with a planned insulin dose reduction. This dose change does not interfere with performance, but could reduce the risk of hypoglycemia.