Effects of power versus endurance training on bone metabolism markers, serum hormone concentrations and physical performance in young athletes

Abstract

Bone remodelling is a balance between bone formation (anabolic) and bone resorption (catabolic), and it is affected by natural growth and training. High force impact plyometric training and heavy strength training have been shown to associate with increased bone strength. Children and adolescents, who have participated in these kinds of activities, have usually had higher bone mass and long-lasting benefits on bone health in later life. Bone turnover can be evaluated with bone metabolism markers - bone formation and bone resorption markers. Purpose. The purpose of this study was to compare power and endurance training effects of young post pubertal track and field athletes, especially, on their bone metabolism markers, but also on hormone concentrations and physical performance. Material and methods. The experimental group consisted of young Finnish track and field athletes (boys n = 18, age = 16.9 ± 1.5 yr; girls n = 18, age = 16.6 ± 0.8 yr). The control group consisted of 12 high school students (boys n = 6, age = 17.5 ± 1.0 yr; girls n = 6, age = 17.8 ± 0.8 yr). The experimental group was divided into power group and endurance group according to their track and field event. During a 6-month study period the subjects trained with their own training plans and took part in three different training camps, where testing took place (pre-, mid-, and post-tests). The control group did not train and was tested twice (pre- and post-tests). Measurements in the tests included anthropometric tests (height, weight, and body fat percentage with skinfolds), blood tests (osteocalcine, and serum enzyme band tartrate-resistant acid phosphatase = TRAP5b, testosterone, and cortisol) and physical performance tests (20 m sprint running with a flying start, standing 5-jump, maximal isometric leg strength, and 12 minutes maximal running test). Results. During the 6-month training period there were significant increases in osteocalcine concentration in boys (15.3 ± 6.4 ng/mL vs 23.2 ± 8.4 ng/mL; p < 0.01) and in girls (8.1 ± 3.7 ng/mL vs 11.5 ± 5.3 ng/mL; p < 0.01), in osteocalcine/TRAP5b -ratio in boys (2.7 ± 1.5 vs 4.2 ± 2.1; p < 0.01) and in girls (2.2 ± 0.8 vs 3.5 ± 1.1; p < 0.001). Whereas significant decreases were noticed in TRAP5b in boys (7.3 ± 3.4 U/l vs 6.4 ± 3.5 U/l; p < 0.05) and in girls (3.9 ± 1.6 U/l vs 3.3 ± 1.5 U/l; p < 0.05). Testosterone/cortisol -ratio increased significantly in boys (p < 0.05), but there was no change in girls. The significant physical performance improvements in boys were in 20 m sprint (p < 0.05), standing 5-jump (p < 0.01), and Cooper (p < 0.05). In girls significant improvements were only in standing 5-jump (p < 0.05). No significant changes occurred in the control group. The increases in osteocalcine and osteocalcine/TRAP5b -ratio in the power group were significantly greater than in the control group (p < 0.05; p < 0.05). The decreases in TRAP5b in the endurance group were significantly greater than in the control group (p < 0.01). The power group improved in maximal strength significantly compared to the endurance group (p < 0.001) and the control group (p < 0.01). Also the increase in standing 5-jump of the power group was significant compared to the endurance group (p < 0.01). The improvement in Cooper test of the endurance group was significant compared to the power group (p < 0.05). Discussion and conclusion. Bone turnover remained in the anabolic state during the 6-month training period for boys and girls as bone formation marker levels increased and resorption levels decreased. Thus, it can be hypothesized that the anabolic state is beneficial for increases in bone strength and bone mass. Bone resorption marker, TRAP5b, decreases with age. That may suggest that as puberty progresses, bone turnover slows down. The bone formation marker/bone resorption marker -ratio may be used to explain bone anabolic/catabolic-state in training. For practice, it is important to add high impact jumps and bounds and heavy strength training in the training plans of athletes regardless of their events to increase their bone strength.