Effects Of High-intensity Interval Training On Physical Fitness And Biochemical Parameters Related To Bone Metabolism In Normal-weight Compared With Overweight Female College Students

Objective:Advances in technology have led to the increasement in screen time and decrement in physical activity,leading to increase in young people obesity.High-intensity interval training（HIIT）has been popular among young people as a weight-loss training method in recent years.However,most studies of HIIT in young women only focus on the improvement of body composition and physical fitness,little is about the effect of HIIT on the bone health among young women accompanied by weight-loss and fat reduction.In view of the duality of the impact of body mass index on bone,this paper aims to compare the effects of 8-week HIIT intervention on the physical fitness and bone health related indicators in normal weight and overweight female college students,providing a scientific theoretical basis on revealing the mechanism of weight loss and fitness though exercise.Methods:Participants in this study were all voluntary and recruited from one college.A total of 34 female students were included in the sports program.Of these female students were divided into two groups based on body mass index（BMI）,a normal weight group（NW;18.5 kg/m²≤BMI<24kg/m²;n=18）and an overweight group（OW;BMI>24kg/m²;n=16）.Of the 34 participants pre-selected,12 dropped out of the sports program due to personal issues.Thus,a total of 22 students entered our HIIT protocol.During the study,one participants was excluded due to frequent no-shows and then dropped out,there were finally22 participants who（NW,n=12 and OW,n=10）finished our program.Total training program was designed for 8 weeks,3 sessions per week on cycle ergometer supervised in laboratory.Each training session consisted of a 5-min warm-up at 60W and 5-min cool-down stage at50W～60W.The main stage consisted of six repetitions of 3-min cycling at 85～90%VO₂max interspersed by periods of active recovery of 2-min cycling at 35～45%VO₂max.The cycling speed of 60±5rpm would be maintained throughout each training session.HR would be monitored all the time and RPE would be record 5 times during each training.Training progression was carried out by increasing the intensity of work from the 5th week（5%increase of the VO₂max every 2 weeks）.All participants were examined for blood parameters,body morphological indicators,physical fitness and anaerobic capacity at the baseline and the end of the study.During the intervention,all subjects’diet was not controlled,but their daily diet and normal activity（except the intervention activity）were required to remain unchanged.The experimental data were analyzed by IBM SPSS（version 26）.Results:1.Compared with pre-exercise intervention,the body fat percentage,fat mass,fat mass in Android region and Gynoid region of NW group and OW group were all lower after 8-week exercise intervention（p<0.05）.Muscle mass didn’t change in both groups.BMI,waist circumference and waist-to-height ratio were also significantly lower in OW group than pre-exercise intervention（p<0.05）,while there was no significant change in NW group.There was no statistical difference between the two groups in other parameters（p>0.05）.2.Compared with pre-exercise intervention,25（OH）D showed a dramatical improvement in both groups（p<0.01）.Fasting insulin and insulin resistance index in NW group and fasting glucose in OW group were significantly decreased（p<0.05）.There was no statistical difference on the change percentage of other blood indicators between two groups（p>0.05）.3.Compared with pre-exercise intervention,the standing long jump and 10-second quadrant jump performance were significantly improved in both groups（p<0.05）;VO₂max and 400-meter running was significantly increased in NW group only（p<0.05）,there was no significant change in OW group（p>0.05）.The change rate of VO₂max in NW group was significantly higher than that in OW group（p<0.05）,but there was no significant difference in the rate of change of other parameters between the two groups（p>0.05）.4.Compared with pre-exercise intervention,the peak power in two groups improved remarkably after exercise intervention（p<0.05）,the average power saw a significant growth in NW group（p<0.05）,and there was no significant change in other indicators.There was no significant difference between the two groups in the percentage change of other anaerobic capacity parameters（p>0.05）.Conclusion:1.Under the same amount of exercise,8-week HIIT intervention can reduce body fat percentage and fat mass for normal weight and overweight female college students,but the8 weeks exercise intervention could not significantly increase the muscle mass,lean body mass and bone density in normal weight and overweight female college students.2.Under the same amount of exercise,8-week HIIT intervention can improve the25（OH）D level of normal and overweight female college students,but not their OC levels.3.Under the same amount of exercise,8-week HIIT intervention can improve the lower extremity explosive power、speed endurance and lower extremity sensitivity in normal weight and overweight female college students,but can improve the cardiovascular fitness in normal weight female college students only.4.Under the same exercise amount,8-week HIIT intervention can improve anaerobic capacity in normal-weight and overweight female college students.