Continuous Running vs High Intensity Training: Why are you still jogging?

The Dark Fleet of Airdynes.

The scientific literature is in agreement, but the abounding number of joggers I see on a daily basis tells of the clear disconnect between this scientific literature and the average exerciser.

Before I get into this, I would like to make a clear disclaimer: I am not out to discourage jogging. There are a number of reasons to go out for a nice jog through the park. What I’m out to do is ask the joggers a simple question: Why are you jogging? If you can answer that logically (and there are a number of ways to do so), then it’s fine by me. I just want you to have thought about it. (*Certain clinical populations and those needing to prepare mentally for a long distance race are hereby dismissed).

So maybe we should start with a more basic question first: why even exercise? Ignoring weight training and its benefits and looking solely at the cardiovascular and respiratory systems (the things dealing with your heart, blood pressure, oxygen consumption, oxygen delivery and the like), numerous physiological improvements can be seen from exercising. You’ll see an increase in muscle oxidative capacity, muscle buffering capacity, and glycogen content, and you’ll see a decrease in blood pressure and resting heart rate as well as a reduced risk for cardiovascular disease and a countless number of other things. The list goes on, of course, but that isn’t the purpose of this post.

In a 2006 study titled “Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance,”¹ researchers found…well the title just ruined my surprise. Researchers found similar molecular and cellular adaptations between interval (high intensity) training and traditional endurance training with a huge difference in training volume (950 kJ of work, including recovery, for the high intensity group vs ~6500 kJ of work for the continuous training group). What’s the reduction in volume mean? It means less overuse injuries and less time spent training (18 – 27 minutes per session vs 90 – 120 minutes per session in this study) while still achieving similar adaptations.

So what’s important in your exercise then? Evidence² has shown a number of physiological and performance criteria can be maintained when exercise is reduced, but is the maintenance due to the frequency, duration, or intensity of training? The intensity. Or simply stated: the effort you’re giving. In a 25-week study done in 1985, 12 subjects were trained identically for 10 weeks then split into separate groups for the remaining 15 weeks. Group 1 held intensity and duration constant while half of the group reduced frequency by 1/3 and the other half of the group 2/3; group 2 held intensity and frequency constant while half of the group reduced duration by 1/3 and the other half 2/3; and group 3 held frequency and duration constant while half of the group reduced intensity by 1/3 and half 2/3.

Guess what happened?

The reduced frequency group continued improving their VO2max, as did the reduced duration group. The reduced intensity group? Their VO2max’s declined rapidly following the reduction. (VO2max is an individual’s maximum capacity to deliver and utilize oxygen. So essentially it’s a direct reflection of your cardiorespiratory health.) Not only did their VO2max suffer, but they also lost the benefits they had seen through their reduced resting heart rate and increased left ventricle size (bigger = better). The bottom line: exercise intensity is important. Reducing your intensity by 2/3 or even 1/3 (going from sprinting to easy jogging or even sprinting to jogging) is sure to be followed by a drastic reduction in exercise benefits.

In a third study, a meta-analysis of studies from 1968 to 2010³, the authors found that interval training improves VO2max (your cardiorespiratory health) to a greater degree (~0.5 L/min vs ~0.2-0.3 L/min) than continuous running while greatly decreasing training volume. So will you see improvements with continuous running? Sure – as I said, there are logical reasons to take on this style of training. But you can see even greater benefits with a significantly reduced training volume (read “reduced number of injuries”) when utilizing interval training.

How about sport performance improvements? In a 2013 study⁴, two different interval training programs were implemented for 6 weeks and compared to a continuous running control group. The supramaximal intensity (sprint training) group, the high intensity, and the continuous running groups were all tested on their 3000m time, 40m sprint time, and repeated sprint ability (6 x 40m repeats with 24 seconds of recovery) before and after the 6 weeks of training. The results were nothing short of…exactly what we would expect at this point in the post: the supramaximal intensity group improved significantly in the 3000m time trial, the 40m sprint, and the repeated sprint test over the control group. The high intensity group improved noticeably over the control group as well, however it wasn’t statistically significant. The control group improved some, but not nearly as much as the high intensity or supramaximal intensity groups, and the control group’s improvement came at a much greater cost.

Yes yes I know, no one likes sprinting. Jogging is much more fun. False. Well, I disagree at least, as does a study titled “High-intensity interval running is perceived to be more enjoyable than moderate-intensity continuous exercise: Implications for exercise adherence,”⁵ in which high-intensity interval running was perceived to be more enjoyable than moderate-intensity continuous running. 

So who cares? You care, of course! As compared to continuous running, interval training elicits similar molecular and cellular improvements, greater VO2max improvements, better left-ventricle growth characteristics, more pronounced speed and repeated sprint ability improvements, and it’s more fun! And all with a significant reduction in mileage and training time.

Back to my question then: Why are you still jogging?

References:

1.     Gibala, M. J. et al. Short-term sprint interval training versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. Journal of Physiology (2006). 901-911, 2005.

2.     Hickson, R. C., C. Foster, M. L. Pollock, T.M. Galassi, and S. Rich. Reduced training intensities and los of aerobic power, endurance, and cardiac growth. J. Appl. Physiol. 58(2): 492-499, 1985.

3.     Bacon, A.P., Carter, R. E., Ogle, E. A., Joyner, M. J. VO2max Trainability and High Intensity Interval Training in Humans: A Meta-Analysis. PLoS ONE 8(9): e73182. doi:10.1371/journal.pone.0073182

4.     Daniel Cicioni-Kolsky , Christian Lorenzen , Morgan David Williams & Justin Guy Kemp (2013). Endurance and sprint benefits of high-intensity and supramaximal interval training. European Journal of Sport Science, 13:3, 304-311, DOI: 10.1080/17461391.2011.606844.

5.     Bartlett, J. D., Close, G. L., Maclaren, D. P. M., Gregson, W., Drust, B., Morton, J.P. High-intensity interval running is perceived to be more enjoyable than moderate-intensity continuous exercise: Implications for exercise adherence. Journal of Sports Sciences (2011). 29(6): 547-553.