Investigating the Effects of Infrared Therapy on Bone after High-intensity Treadmill Exercise Training

Summary

Prolonged high-intensity treadmill exercise training inhibits bone formation and promotes bone resorption in mice, resulting in decreased bone mass. Here, we present a protocol to examine the effects of infrared therapy on high-intensity exercise-induced alterations in bone metabolism. Further mechanistic studies are required to elucidate the underlying molecular pathways.

Abstract

Bone tissue is an important load-bearing organ of the human body. Moderate exercise enhances bone mass through mechanical loading, while high-intensity exercise may suppress it. Infrared therapy improves circulation, reduces pain/inflammation, and aids tissue repair. This paper presents a protocol to elucidate the modulatory effects of infrared therapy on high-intensity exercise-induced skeletal metabolic disorders and their molecular mechanisms. In this study, 24 6-week-old mice were randomly divided into control (CTR, N = 8), high-intensity treadmill exercise training (HIT, N = 8), and infrared therapy after high-intensity treadmill exercise (IRT, N = 8) groups. The latter two groups were trained for 8 weeks. In the first week, the mice underwent treadmill acclimation training. In the second week, the mice exercised at the rate of 24 m/min for 50 min, which increased at the rate of 1 m/min and 10 min every week until it reached 28 m/min for 80 min, with a gradient of 5° for 6 days. At the fifth week, HIT group mice were subjected to whole-body infrared therapy intervention, with the temperature controlled between 42 °C and 45 °C. The whole treatment process lasted ~40 min, 3x a week. Results showed that in the HIT group compared with those in the CTR group, the bone volume/total volume and trabecular number were significantly decreased, the trabecular separation was significantly increased, the osteogenic-related genes of Atf4, Runx2, and Ocn were downregulated, and the osteoclast-related genes of Ctsk and Mmp9 were upregulated. The micro-CT results of the IRT group mice showed no significant difference, but the osteogenesis-related genes Alp, Atf4, Runx2, Ocn, and Osx were upregulated in the femur. In addition, the osteoclast-related gene Ctsk was downregulated. Long-term high-intensity treadmill exercise may reduce bone mass. While infrared therapy does not affect bone mineral density, it may improve bone metabolism.

Introduction

Osteoporosis (OP) is one of the most common systemic metabolic bone diseases, particularly prevalent among the elderly, and represents a major global health issue¹. OP is characterized primarily by decreased bone mineral density (BMD), bone quality, and bone strength, which increases the risk of bone fractures². The prevention and treatment of OP are crucial for improving human quality of life, encompassing approaches such as pharmacological therapy, adequate intake of calcium and vitamin D, reduction of smoking and alcohol consumption, and early physical exercise to increase and maintain peak bone mass level

Protocol

This study received ethical approval from Shanghai University of Sport's Laboratory Animal Ethics Committee (No. 102772023DW016) and complied with national/institutional animal research regulations. Twenty-four 5-week-old male C57BL/6 mice were housed in an SPF-grade animal facility at the Shanghai University of Sport. Mice were housed at 22 ± 2 °C, 40-70% humidity with 12 h light/dark cycles and provided ad libitum food/water. All biological materials, including bones, blood, and RNA extraction reagent-treated samples, should be collected in Biohazard Level II autoclave bags, sterilized at 121 °C for 60 min prior to disposal, with proper d....

Results

Fatigue due to prolonged high-intensity treadmill exercise training
We established a long-term high-intensity platform running exercise model to study the skeletal changes under exercise and the effects of infrared therapy on bones (Figure 1A). At the end of the intervention, mice were observed for changes in body weight. Compared with the body weight of the mice in the CTR group, no significant change was determined in the HIT group, while a significant decrease occurre.......

Discussion

Of all metabolic bone diseases, OP is the most common and a major global public health problem¹¹. OP arises when osteoblastic and osteoclastic functions are dysfunctional, and its prevalence is high¹⁸. Exercise has been increasingly emphasized by physicians and researchers as a potential strategy for the prevention and treatment of OP considering its low cost and few adverse effects and its great potential in the future treatment and prevention of OP. The mechanisms by whic.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Far infrared therapy instrument	Cofoe Medical Technology		Infrared radiation was then applied as a heat source to warm the blood in the subcutaneous capillary network. The therapy temperature was controlled between 42 °C and 45 °C, and the entire treatment lasted approximately 40 min, 3 times per week
Micro-CT	SCANCO Medical AG	VIVACT80	Micro-CT scanning was performed to assess parameters of the trabecular bone in the left femur, including BV/TV, Tb.N, Tb.Th, Tb.Sp, and cortical thickness (Ct.Th).
Mouse treadmill	Anhui Zhenghua Biological Apparatus Facilities Co., Ltd		High intensity treadmill running in mice
Paraffin embedding machine	Leica		The paraffin embedding machine can embed tissues
paraffin slicer	Leica		The paraffin microtome can slice tissues
PrimeScript RT Reagent kit
SPSS
Tribromoethanol		Avertin
TRIzol	Accurate Biology	AG21101/AG21102