Influence of Circadian Rhythm on HIIT’s Effects on Cardiovascular Endurance, Muscular Endurance and Body Composition among Sedentary College Students

The purpose of this study was to examine the influence of circadian rhythm on HIIT’s effects on cardiovascular endurance, muscular endurance and body composition among TARUC college students. Healthy subjects of both genders (10 males, 15 females) participated in this study and completed 6 weeks of HIIT intervention program. The subjects were assigned to either Morning Group (MG) or Evening Group (EG) according to their Morningness – Eveningness Questionnaire (MEQ) score. Testing parameters for cardiovascular endurance was 20-M shuttle run test, muscular endurance were 1-minute push up and curl up test and body composition was Inbody. Results showed that both groups had a significance improvement (p < 0.05) in cardiovascular endurance (MG 30.43 ± 5.02 to 32.64 ± 5.25, EG 27.77 ± 5.35 to 30.09 ± 6.24 VO2 Max) and both muscular endurance test, 1-minute push up (MG 30.67 ± 11.97 to 45.83 ± 11.58, EG 25.54 ± 6.27 to 38.54 ± 11.03) and 1-minute curl up (MG 28.17 ± 9.91 to 41.08 ± 10.84, EG 24.15 ± 7.39 to 32.69 ± 7.18). MG benefited more in core muscular endurance gain compared to EG. Body composition showed no significant improvement. In conclusion, only muscular endurance for the core had more gain in the MG when comparing training in the morning and evening.