Resistance Exercise On Skeletal Muscle Mass And Strength In Effects Of 8-week Pre-sleep Casein Intake Combined With Sedentary Healthy Adults

PurposesThe purpose of this study is to: By comparing the effects of casein intake combined with resistance exercise pre-sleep and casein combined with resistance exercise at dinner on skeletal muscle mass and strength in sedentary healthy adults with the same total protein intake,we explored whether there was a specific time effect of protein intake pre-sleep on skeletal muscle mass and strength in sedentary healthy adults.To provide a scientific basis for casein intake pre-sleep as a sports nutrition intervention strategy for sedentary healthy adults.Research methodsThe required sample size was calculated by the G*Power,and a total of 34 sedentary healthy subjects were included according to the trial recruitment and screening conditions and randomised into two groups of 17 each for an 8-week presleep casein intake combined with resistance exercise intervention(RT+CAS)and a dinner intake casein combined with resistance exercise intervention(CAS+RT).Subjects were asked to record their diet 3 days before the experiment using a diet record sheet and to consume a standard meal 1 day before the experiment;at the end of the intervention the diet for the first 3 days of the experiment was aligned with the diet recorded 3 days before the baseline test to reduce diet-induced errors.During the experiment,subjects completed baseline tests(body composition,muscle thickness,muscle strength tests and fasting blood collection)before starting the 8-week intervention.At the end of the intervention,the same tests as those at baseline were performed.Differences in baseline indicators between the two groups were analysed using independent samples t-tests;differences in indicators between the two groups were tested using one-way analysis of covariance;and differences in indicators within groups were analysed using paired samples t-test or nonparametric tests.Two-tailed tests with a significance level of 0.05 were used.Results(1)For body composition,compared to pre-intervention,after the 8-week intervention,CAS+RT and RT+CAS whole-body muscle mass significantly increased by 1.2%(P=0.048)and 1.1%(P=0.003),and lower limb muscle mass significantly increased by 4.8% and 4.6%(P<0.001),while CAS+RT body weight(P=0.023),lower limb body fat mass(P=0.045)and defatted body weight(P=0.026)increased significantly,with no significant change in RT+CAS and no significant difference between groups.(2)For muscle thickness,compared to pre-intervention,after the 8-week intervention,CAS+RT and RT+CAS had significant increases in medial and lateral gastrocnemius muscle thickness(P<0.001,P=0.047)and lateral gastrocnemius muscle thickness(P=0.033,P=0.014),but only RT+CAS had significant increases in anterior tibial muscle thickness(P=0.009)and rectus femoris muscle thickness(P=0.013),CAS+RT had no significant changes,and there was no significant difference between groups;(3)For muscle strength,compared to pre-intervention,after the 8-week intervention,CAS+RT and RT+CAS significantly increased the peak torque of the flexor and extensor muscles of the knee joint at 60°/s and 180°/s angular velocities,with a significant increase of 17.6%(P=0.039)and 21.8%(P<0.001)in the peak torque of the flexor and extensor muscles at 60°/s angular velocities,and a significant increase of 17.9%(P=0.003)and 27.2%(P=0.028)in the peak torque of the extensor muscles,respectively;At 180°/s angular velocity,the peak flexor force distance increased significantly by 26.2% and 36.3%(P<0.001),and the peak extensor force distance increased by 39.60%(P=0.003)and 54.7%(P<0.001),respectively.The improvement of RT+CAS showed a trend that was superior to CAS+RT,with no significant difference between groups.CAS+RT and RT+CAS significantly increased the relative peak torque of knee extensor and extensor at 60°/s angular velocity and 180°/s angular velocity.At the angular velocity of 60°/s,the relative peak torques of flexor muscles increased by25%(P<0.001)and 27.7%(P=0.015),and the relative peak torques of extensor muscles increased by 12.1%(P=0.023)and 18.2%(P=0.001),respectively;At 180°/s angular velocity,the relative peak torque of the extensor muscles was increased by46.5% and 50.8%(P < 0.001),and the improvement of RT+CAS was better than that of CAS+RT,but there was no significant difference between the two groups.RT+CAS significantly increased the relative peak torque of knee flexor by 45.8%(P<0.001)at180°/s angular velocity,while CAS+RT had no significant change.The mean power of CAS+RT and RT+CAS knee flexion and extension muscles increased significantly at 60°/s and 180°/s angular velocities,and the mean power of flexor muscles increased by 20.4% and 25.3% at 60°/s angular velocities,respectively(P<0.001).The average extensor muscle power increased by 20.2%(P=0.001)and25.3%(P=0.002),respectively.At 180°/s angular velocity,the average flexor power increased by 17.6% and 18.3%(P<0.001),and the average extensor power increased by 22.6% and 31.4%(P=0.002 and 0.003),respectively.The improvement of RT+CAS was better than that of CAS+RT,but there was no significant difference between the two groups.The total work of knee extensor at 60°/s angular velocity and the total work of knee extensor and extensor at 180°/s angular velocity were significantly increased in CAS+RT and RT+CAS groups.The total work of knee extensor at 60°/s angular velocity increased by 17.2%(P=0.002)and 21.1%(P<0.001),respectively.At 180°/s angular velocity,the total flexor work increased by 21%(P=0.001)and 25.7%(P<0.001),and the total extensor work increased by 20.9%(P=0.007)and 26.7%(P=0.021),respectively.The improvement of RT+CAS was better than that of CAS+RT.However,there was no significant difference between the groups.(4)For blood indicators,compared to pre-intervention,8-week intervention significantly increased the serum IGF-1 and decreased serum myostatin concentration of CAS+RT and RT+CAS,with serum IGF-1 concentration increased by 11.82%(P=0.001)and 13.28%(P<0.001),and serum myostatin decreased by 4.1%(P=0.001)and 4.9%(P<0.001),respectively,with no significant difference between groups.Conclusion(1)8 weeks of casein intake immediately after dinner and 30 minutes pre-sleep combined with resistance exercise significantly increased skeletal muscle mass of the whole body and lower limbs and muscle strength,and increased serum IGF-1 content associated with muscle synthesis and decreased serum myostatin content associated with muscle breakdown in sedentary healthy adults.(2)the tendency for pre-sleep casein intake combined with resistance exercise to show superiority in terms of the degree and comprehensiveness of improvements in muscle thickness and muscle strength,suggesting that pre-sleep protein intake is an effective nutritional intervention strategy to improve skeletal muscle health in sedentary healthy adults,and that the effects of pre-sleep protein intake on other health indicators need to be further explored in the future.