What Is the Best to Improve VO2max? HIIT or SIT?

Lack of time is seen as a barrier to maintaining a physically active lifestyle. As a countermeasure, interval training has been suggested as a time-efficient strategy for improving health, primarily due to its potential to increase cardiorespiratory fitness [1].

A systematic review and meta-analysis of two interval training protocols, HIIT (high-intensity interval training) and SIT (sprint interval training) was conducted to investigate which promotes greater gain in cardio-respiratory fitness of VO2max (maximum volume of oxygen your body can consume and utilize during intense exercise) [2]. Classification suggested by Bucchet and Laursen (2013) [3] was used, which considers SIT to be short-duration efforts lasting less than 60 seconds, while longer-duration efforts (> 60 seconds) are considered HIIT.

Studies comparing the effects of HIIT and SIT protocols were selected from the PubMed (MEDLINE), Scopus and Web of Science databases. A total of 19 studies were included in the final meta-analysis after screening. No significant differences were found for the VO2max gains when comparing HIIT and SIT protocols in the meta-analysis [2].

The prescription of either HIIT or SIT is complex and involves the manipulation of several variables, including duration of the effort and recovery phases, intensity of effort and recovery, and total number of efforts/recovery, which are expected to reflect changes in the metabolism and adaptations of organic systems [4]. Some factors to consider are that despite similar increases in VO2max for HIIT and SIT, these protocols may lead to different magnitudes of other adaptations related to aerobic fitness, such as neuromuscular, musculoskeletal tension, cardiovascular work, anaerobic glycolytic energy and cardiac autonomic stress, causing adaptations in other variables besides VO2max [5,6,7].

HIIT and SIT are time-efficient protocols that lead to similar gains in cardiorespiratory fitness. Thus, the choice between these training protocols should be made according to the availability of time, aptitude to perform intense physical activity and the specificity of the physical conditions of each individual to practice exercise. Future studies are encouraged to compare the effect of manipulation of other training variables, such as recovery time, number of bouts and different types of HIIT exercises (running, cycling, rowing, boxing, swimming, etc.), using equalized caloric expenditure and/or the total work performed for a comprehensive comparison between HIIT and SIT protocols. [2]

References

1. Rosenblat, M.A.; Perrotta, A.S.; Thomas Scott, G. Effect of High-Intensity Interval Training Versus Sprint Interval Training on Time-Trial Performance: A Systematic Review and Meta-analysis. Sports Med. 2020, 50, 1145–1161.

2. de Oliveira-Nunes SG, Castro A, Sardeli AV, Cavaglieri CR, Chacon-Mikahil MPT. HIIT vs. SIT: What Is the Better to Improve 𝑉O₂max? A Systematic Review and Meta-Analysis. International Journal of Environmental Research and Public Health. 2021; 18(24):13120

3. Buchheit, M.; Laursen, P.B. High-intensity interval training, solutions to the programming puzzle. Sports Med. 2013, 43, 313–338.

4. Laursen, P.B.; Shing, C.M.; Peake, J.M.; Coombes, J.; Jenkins, D. Interval training program optimization in highly trained endurance cyclists. Med. Sci. Sports Exerc. 2002, 34, 1801–1807.

5. Krustrup, P.; Mohr, M.; Bangsbo, J. The slow component of oxygen uptake during intense, sub-maximal exercise in man is associated with additional fibre recruitment. Pflüger’s Archiv. Gesamte Physiol. Menschen Tiere 2004, 447, 855–866.

6. Batacan, R.B., Jr.; Duncan, M.J.; Dalbo, V.J.; Tucker, P.S.; Fenning, A.S. Effects of high-intensity interval training on cardiometabolic health: A systematic review and meta-analysis of intervention studies. Br. J. Sports Med. 2017, 51, 494–503.

7. Poon, E.T.-C.; Little, J.P.; Sit, C.H.-P.; Wong, S.H.-S. The effect of low-volume high-intensity interval training on cardiometabolic health and psychological responses in overweight/obese middle-aged men. J. Sports Sci. 2020, 38, 1997–2004.