Intervals VS Steady State
The age old debate
Some will say don’t waste your time with steady state, intervals give you more “bang for your buck”. While others swear by more volume at lower intensity.
Both are right in some ways because…wait for it… it depends!
The Science
At the muscular level, research indicates that interval training surpasses steady-state training in enhancing both the overall quantity and efficiency of mitochondria. Mitochondria, often referred to as the "powerhouse of the cell" from high school biology, provide energy by metabolizing fat and glucose.
Each muscle cell contains multiple mitochondria, which house enzymes (proteins that accelerate bodily reactions). Both interval training and steady-state training produce two effects:
Increase in the number of mitochondria.
Augmentation in the activity of enzymes.
However, interval training yields significantly greater impacts on both factors compared to steady-state training.
In a specific study, the group engaging in steady-state training had to exercise five days a week for 40-60 minutes at 65% of their maximum aerobic capacity to achieve results equivalent to the interval group, which exercised three days a week for 4-6 intervals of 30 seconds each at maximum intensity, with 4.5 minutes between intervals. This showcases the efficiency of interval training in achieving comparable outcomes with less time investment.
There appears to be a tradeoff between the duration and intensity of exercise, where the time-saving benefit of interval training is balanced by the requirement for intense effort in a shorter timeframe.
However, there is one aspect where steady-state training clearly outperforms interval training: maximal cardiac output, which refers to the maximum amount of blood the heart can pump in a minute. In a study comparing interval and steady-state training, it was observed that participants engaging in intervals did not experience an increase in maximal cardiac output, whereas the steady-state group did.
ok, but what doest that mean in application? What will help you achieve your goals better?
Again… it depends!
If you are just starting your fitness journey, I definitely recommend that you ease into things with low to moderate intensity steady state training. I want you to first enjoy yourself and have a positive experience so that you keep going and make exercise a habit. This will help you achieve a stable cardiorespiratory base upon which you can build further improvements in health, endurance, energy, mood and caloric expenditure. When you are ready, you can then slowly start adding some intensity.
Most seasoned athletes will definitely also profit from steady state training:
During the aerobic base phase of their season/training bloc
Throughout their week as active recovery or LSD (Long Slow Distance)
Ultrarunners
As they approach their event, the amount of steady state will usually diminish and athlete will then become more specific with more time spent at goal race pace or faster.
If you are an active person but don’t really have any race plans/specific goals other than health and overall fitness, I would actually recommend to do both. If you are time poor, a High Intensity Interval Training (HIIT) strength circuit three times/week and some walking on days you are not training could be a good option. But remember that everyone is unique and built differently, you might realise that it is a bit too much for you and might want to replace one of the HIIT session by a 90 min bike ride or jog.
It is always a good idea to keep a training journal and note how you feel after each training session/week and see if your program need tweeking or if you are going in the right direction. I personally use the Training Peaks application to log my training.
In conclusion, the age-old debate between steady-state and interval training boils down to a personalized approach based on individual goals and fitness levels. The scientific evidence supports the superiority of interval training in enhancing mitochondrial quantity and efficiency, making it a time-efficient choice for those seeking impactful results in a shorter timeframe. However, the context is crucial, and the application of these findings depends on various factors.