Purpose:
To study the effects of a physical activity program on exercise capacity, muscle force, and subjective fatigue levels in children with mild to moderate forms of osteogenesis imperfecta (OI).

Participants:
Thirty-four children from 8 to 18 years of age were randomly assigned to either 12 weeks of graded exercise intervention or usual care.

Method:
Supervised exercise occurred 2 times per week for 45 minutes, with an additional home-based session beginning at 6 weeks. Exercise intervention included a 10-minute warm-up, 10 minutes of aerobic training at 60%-80% peak heart rate, 15 minutes of free play, 10 minutes of aerobic training, and a 10-minute cool-down, as well as strength training with light weights.

Outcomes were measured at baseline, 3 months, 6 months, and 9 months, and included the following:

• Exercise capacity (VO2peak) using the Godfrey cycle ergometer protocol;
• Maximal working capacity (Wmax) during the Godfrey cycle ergometer protocol;
• Muscle force of 4 muscle groups using a dynamometer;
• Subjective fatigue using the Checklist Individual Strength-20 (CIS-20);
• Perceived competence using the Self-perception Profile for Children (CBSK);
• Health-related quality of life (HRQoL) using the Child Health Questionnaire Parent-Form 50 (CHQ).

Results:
VO2peak, relative VO2peak, Wmax, and muscle force were significantly improved by 17%, 18%, 10%, and 12%, respectively, compared to the control group. Subjective fatigue decreased significantly. At 6 months follow-up, there was still a significant decrease in VO2peak, but relative VO2peak and maximal working capacity as well as subjective fatigue showed no significant difference. At 9 months, there was a further decrease in the previously gained improvements.

Discussion:
A supervised exercise-training program can safely and effectively improve aerobic capacity and muscle force as well as decrease levels of subjective fatigue in children with OI.