Effects of Eight Week High-Intensity Interval Training Program Followed by a Six Week Detraining on Healthy Adult Gym-Users

Background: The literature has reported that high-intensity training (HIIT) can effectively improve maximum oxygen uptake (VO2 max) and body composition (BC). Still, contradictory results are reported regarding its impact of HIIT training and post-period detraining on gym users. Objective: This study aimed to verify how eight weeks of HIIT affects VO2 maximum and BC in healthy gym users. Additionally, the effect of a six-week detraining period was verified. A group of 10 gym-users (mean ± SD age: 29.03 ± 6.18 years) volunteered for this randomized controlled trial (RCT). Method: A HIIT program that included exercises such as jumping air squats, burpees and jumping jacks was applied over eight weeks. After this period, a six-week detraining period was applied. To measure changes in VO2 max, the Queen’s College Step Test (QCST) was applied, while a bioimpedance scale was used to measure BC. Results: Eight weeks of HIIT seem to show a tendency to increase VO2 max and cause positive changes in BC (p ≤ 0.05) with the exception of two variables (i.e., fat-free mass and fat mass). Furthermore, the results suggest that 6 weeks of detraining may negatively affect gains resulting from the training program, particularly in VO2 max and body mass index (BMI) p ≥ 0.05. Conclusions: Eight-week HIIT program incorporating short-duration explosive exercises can positively affect VO2 max and BC in adult gym users.