Interval training is a key part of any successful endurance training program, and with good reason. It’s one of the most effective ways to boost aerobic fitness (VO2max), improve health and endurance exercise performance.
As you might expect, interval training has received a lot of attention from researchers. And research has been unequivocal. Interval training improves your aerobic capacity, muscular endurance, fat oxidation, neuromuscular coordination, exercise efficiency and performance.
Not only has research given us a clear understanding of how effective interval training is. We now know a lot more about how to structure, the most effective interval training sessions.
We know which intensities work best. How different intensities have different training effects. We know that interval length and the total volume of intervals is also important. And we know that how we structure the recovery periods – passive recovery vs active recovery, work to rest ratio etc – is also important. I’ve covered many of these areas, in detail on the following page: high intensity interval training (HIIT).
Whilst this give us important insights into how to structure interval training. It’s not clear whether all athletes gain the same benefit.
But, I thought you just said that interval training is clearly beneficial? It is…but, one area that’s less well understood – how your fitness level affects your response to interval training.
Aerobic fitness (VO2max) and interval training effectiveness
Whilst we know interval training is clearly beneficial. We know less about, how your fitness level affects the level of response to interval training. In particular, do highly trained and moderately trained athletes get the same training benefit? Should they exercise at the same ‘relative’ exercise intensity? And should they use the same recovery periods?
One study, published in The Journal of Sports Medicine and Physical Fitness, looked to answer some of these questions. Here, researchers looked at how an athlete’s level of aerobic fitness, affected the interval training workout (Panissa et al., 2014). In this case, researchers wanted to know whether aerobic fitness affected the effectiveness of the session.
So, how did they do this? Firstly, the athletes completed a high intensity interval running session, consisting of 1 minute of running at the velocity of VO2max (vVO2max), separated by 1 minute of passive recovery. Then researchers analysed how much time athletes spent near their aerobic capacity (above 90%VO2max).
So why 90% VO2max? Simply put, it’s a key training intensity. In fact, research has shown that training between 90 and 100% of VO2max leads to a significant aerobic training benefit. And, by assessing how much time was spent above 90% VO2max, researchers were analysing whether aerobic fitness, affected the effectiveness of interval training.
What did the researchers find?
When your fitness improves, reduce interval recovery time
The main finding of the study, was that the runners with greater aerobic fitness (higher VO2max), spent significantly less time above 90% VO2max. Interestingly, this was despite, all the athletes training at the same ‘relative’ intensity.
So, why was this? The main reason for this, was likely due to improved rates of recovery, amongst the athletes with greater aerobic fitness. Whilst improved recovery is an important training adaptation. It meant they recovered more quickly and spent less time in the important 90% VO2max zone.
So, what does this tell us? In short, the recoveries were too long for the runners with greater aerobic fitness. And, the fitter you are the more attention you need to pay to the recovery periods, during interval training. So, in the same way that you increase the speed, or intensity, of intervals as you get fitter, you also need to reduce the length of recoveries.
Implications for Interval training:
What does this mean for training? Firstly, a one size fits all approach isn’t necessarily the best approach. Individual differences in aerobic fitness, must be considered when planning interval workouts. With this in mind, interval session – including group interval workouts – should be tailored to reflect individual differences in fitness.
In practical terms:
- Athletes with greater aerobic fitness, may need shorter recoveries, or more active recoveries.
- If aerobic fitness is lower, then a longer recovery may be more appropriate.
Whilst, this research looked at VO2max intensity, the same is likely true (and probably more so) for intensities run below VO2max, such as 5k training and 10k pace running intervals.
In particular this has implications for group interval workouts.
Group interval workouts
Group interval sessions often form the main quality workout for club runners. And for good reason, they’re a great way to get the most out of your training. There’s only one problem…not everyone get’s the same training benefit.
During these sessions, athletes train together, running the same intervals. And often using the same recoveries. Whilst, this works for most athletes. The research does highlight that not all athletes gain the same training benefit. And if you’re on either end of the spectrum – high fitness level, or lower fitness level – the training effect will be different.
For athletes, with a high aerobic capacity, the sessions may end up being too easy. And if your fitness level is lower, then these may end up too intense. With this in mind, recovery periods should be altered for individual athletes, based on their aerobic fitness.
An important consideration….just because two athletes, have the same performance level, doesn’t mean they have the same level of aerobic fitness. They might have similar race times, but one has greater aerobic fitness, whilst the other has greater efficiency.
Here, paying attention to heart rate recovery between intervals, can prove useful for checking whether recovery periods are appropriate.
Improving Group Interval Workouts
So, how can you improve group training sessions? A simple approach is to get the athletes with a greater aerobic fitness, to use an active recovery, during interval training. Whereas, those with lower aerobic fitness use a standing recovery.
For me the recovery period has always been an important, and often overlooked, part of training. And to get the most out of interval training, especially when there’s an aerobic focus to the workouts, we can reduce the length of the recovery. Which will help to improve the effectiveness of training. Obviously, this depends on the intensity and purpose of the training session. We also need to consider, whether adjusting the recovery length will negatively affect the work interval.
For athletes with a high level of aerobic fitness, reducing the recovery period, can be the best way to increase the overall intensity and effectiveness of the workout. Helping to ensure you achieve the greatest aerobic training benefit.
Panissa VL, Julio UF, Pinto-E-Silva CM, Andreato LV, Schwartz J, Franchini E. (2014) Influence of the aerobic fitness on time spent at high percentage of maximal oxygen uptake during a high-intensity intermittent running. J Sports Med Phys Fitness. 2014 Dec;54(6):708-14.