Article Title



Masoud Moghaddam1, Carlos A. Estrada1, Tyler W.D. Muddle1, Mitchel A. Magrini1, Nathaniel D.M. Jenkins1, Bert H. Jacobson1, FACSM

1Oklahoma State University, Stillwater, OK

High intensity interval training (HIIT) refers to a group of short bouts separated by rest periods. Intensity and duration of exercise and rest periods are the most significant factors in optimizing HIIT adaptations. Since a 2:1 work-to-rest ratio causes a higher oxygen deficit, a 10s:5s work-to-rest ratio was incorporated to establish a shorter yet potentially effective interval duration. PURPOSE: This study compared the effects of ultrashort (UH) versus short (SH) functional HIIT on body composition, vastus lateralis cross sectional area (VL CSA), anaerobic, and aerobic performance. METHODS: Thirty-four recreationally active participants were randomly assigned to SH (8 males and 9 females) and UH (8 males and 9 females) groups and completed 6 cycles of 6 exercises at ~90% of maximal heart rate (i.e. kettlebell snatches; step-up jumps; jumping jacks; front squat; burpees; high knees) 3 d/wk for 4 weeks. SH was performed with 20s:10s work-to-rest ratio, and a 2-minute recovery between cycles, while UH was completed with 10s:5s work-to-rest ratio, and 1-minute recovery. Fat mass (FM), fat free mass (FFM), VL CSA, Wingate anaerobic capacity (i.e. peak power [PP] and anaerobic power [AP]), and aerobic fitness (i.e. VO2max) were measured before and after the intervention and analyzed with 2-way mixed factorial ANOVAs. RESULTS: FM did not significantly (p>0.05) change, however, both groups significantly (p<0.05) improved FFM (UH: 60.8 ± 15.0 to 61.5 ± 15.2 kg, SH: 54.3 ± 11.5 to 55.5 ± 11.0 kg), as well as VL CSA (UH = 24.8 ± 6.2 to 27.1 ± 6.3 cm, SH = 25.6 ± 5.1 to 27.9 ± 5.5 cm). Additionally, anaerobic (UH: PP = 913 ± 305 to 1033 ± 300 W; AP = 11.5 ± 1.1 to 12.6 ± 1.1 W/kg, SH: PP = 839 ± 162 to 887 ± 181 W; AP = 11.8 ± 1.1 to 12.5 ± 1.2 W/kg) and aerobic capacity (UH: VO2max = 35.8 ± 6.9 to 38.9 ± 6.1 ml/kg/min, SH: VO2max = 39.7 ± 9.3 to 42.6 ± 9.1 ml/kg/min) significantly (p<0.05) increased in both groups. There were no significant (p>0.05) differences between groups. CONCLUSION: These results suggest that HIIT at a 10s:5s work-to-rest ratio can improve physical fitness with a shorter time commitment. Future studies are needed to examine a differential effect of these protocols for men versus women. Since the participants would be best categorized as low-fitness, caution is warranted when extrapolating these results to others with higher-fitness levels.

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