Previous research has shown that high intensity interval training (HIIT) improves aerobic and anaerobic capacity, lean muscle level, glucose tolerance, insulin sensitivity in addition to other health/fitness markers.
Researchers from the Division of Sport and Exercise Science at Abertay University in Dundee, Scotland and Leeds Trinity University in Leeds, UK demonstrated for the first time that HIIT needs to be “performed only twice a week to see major improvements in aerobic capacity, functional capacity and metabolic health in a middle-aged population.”
During middle age (defined as 35 to 58 years old), adults typically see an 8 percent drop in both VO2 max (aerobic capacity) and insulin sensitivity per decade. This study showed just 16 sessions of HIIT over an eight week period, with one or two days of rest between each sprint, offset these and other changes seen with aging. The participants in this study experienced a significant increase in VO2max of 8 percent (see Figure 1). Each training session consisted of 10 repeated 6-second all-out cycling efforts against 7.5% of body weight for males and 6.5% for females (on a Monark peak bike Model 894E).
Short duration HIIT continues to show impressive results in health and physical function compared to traditional, long duration, steady state exercise that most people continue to do. Adding in 1-2 days/week of HIIT would seem warranted as a result of this and other well-documented HIIT research.
Simon Adamson, Ross Lorimer, James Cobley, Ray Lloyd and John Babraj (2014). High Intensity Training Improves Health and Physical Function in Middle Aged Adults. Biology, 3(2): 333-344; doi:10.3390/biology3020333
John Babraj Niels Vollaard et al., (2009). Short duration high intensity interval training substantially improves insulin action in young healthy males. Endocrine Disorders 9:3 doi:10.1186/1472-6823-9-3