High-intensity interval training (HIIT) and creatine supplementation reduce endurance strength and mineralization of bone tissue

Abstract Purpose The aim of the present study was to investigate the effects of an HIIT protocol on the bone mineral density (BMD), mechanical strength, and bone mineralization of animals supplemented with creatine. Methods Forty male Wistar rats, 60 days old, were used. The animals were divided into four groups: (1) control (C), (2) creatine (Cr), (3) training (T), and (4) training + creatine (TCr). The animals in the Cr and TCr groups were supplemented with creatine monohydrate (2% of daily feed weight). The T and TCr groups performed an HIIT protocol, 5x/week, for 12 weeks, with the treadmill at a 15° inclination. The running protocol was performed at 60% of the Vmax obtained in the maximum effort test for 3 min, followed by 4 min of running at 85% of the Vmax. At the end of the experiment, the animals were euthanized, and samples of the tibia were collected. Subsequently, bone densitometry analyses were performed to determine the BMD and Raman spectroscopy to observe bone mineralization. The three-point mechanical test was also used to determine bone strength (Fmax). Results The results showed a reduction in the TCr group for mechanical strength (Cr vs TCr) and for the analyzed minerals (C vs TCr) ( p < 0.05). Conclusion HIIT added to creatine supplementation led to decreases in mechanical strength and the mineralization of the tibia.