Abstract
High-intensity interval training (HIIT) is of scientific interest due its role in improving physical fitness, but the effects of HIIT on bone health need be carefully explored. Further, it is necessary to know whether HIIT effects on bone health are dependent on the physical activity levels. This may be experimentally tested since we have built a large cage (LC) that allows animals to move freely, promoting an increase of spontaneous physical activity (SPA) in comparison to a small cage (SC). Thus, we examined the effects of HIIT on biophysical, biomechanical and biochemical parameters of bone tissue of C57BL/6J mice living in cages of two different sizes: small (SC) or large (LC) cages with 1320 cm2 and 4800 cm2 floor space, respectively. Male mice were subdivided into two groups within each housing type: Control (C) and Trained (T). At the end of the interventions, all mice were euthanized to extract the femur bone for biophysical, biomechanical and biochemical analyses. Based a significant interaction from two-way ANOVA, trained mice kept in large cage (but not for trained mice housed in SC) exhibited a reduction of tenacity and displacement at failure in bone. This suggests that long-term HIIT program, in addition with a more active lifestyle correlates with exerts negative effects on the bone of healthy mice. A caution must also be raised about the excessive adoption of physical training, at least regarding bone tissue. On the other hand, increased calcium was found in femur of mice housed in LC. In line with this, LC-C mice were more active (i.e. SPA) than other groups. This implies that an active lifestyle without long-term high intensity physical training seems to play a role in promoting benefits to bone tissue. Our data provides new insights for treatment of osteo-health related disorders.
Highlights
High-intensity interval training (HIIT) is of scientific interest due its role in improving physical fitness, but the effects of HIIT on bone health need be carefully explored
Our results show that 10-weeks of HIIT applied 5 times per week can influence bone tissue, as well as change of femoral bone calcium concentrations in mice
The most interesting finding in the study showed high tenacity value for mice living in large cage, but the association of this active lifestyle with HIIT resulted in reduced bone resistance, negatively impacting tenacity for the trained group in LC when compared with the control group living in the same conditions
Summary
High-intensity interval training (HIIT) is of scientific interest due its role in improving physical fitness, but the effects of HIIT on bone health need be carefully explored. LC-C mice were more active (i.e. SPA) than other groups This implies that an active lifestyle without long-term high intensity physical training seems to play a role in promoting benefits to bone tissue. Considering that positive or negative adaptations can be achieved when training protocols are carried out for long periods, it is important to conduct studies to assess the chronic effects of this method This is further strengthened in groups considered to be at high risk, which have problems or physio pathologies that require care when using intense physical exercise. The literature has developed with regard to the effects of physical exercise on bone health, the actual impact of such intensity on this tissue is still not fully understood In this sense, it has been observed that highintensity training can generate significant loss of cortical bone, favoring the appearance of injuries or fractures[17,18]. Performing experiments of this nature in humans is not simple
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