Training intensity: is higher better, even for beginners?

We get more clues when we look at ‘energy-expenditure matched’ training programs. In these programs, two groups of athletes perform either higher-volume/moderate intensity or higher-intensity/lower volume training programs in which the total weekly energy expenditure in training is the same in both cases. When looking at non-responders, a 2021 study found that in a direct comparison of moderate intensity training with energy-matched HIIT, there was a greater effect on VO2max and a lower non-responder rate for HIIT⁽¹⁰⁾. 

However, in another study looking at 60-minute endurance training sessions performed 1-3 times per week, all those who were classed as non-responders DID achieve good training adaptations when two further training sessions (another 120 minutes) were added per week⁽¹¹⁾. Unfortunately though, this study didn’t contain a comparison group of participants who switched to smaller volumes of higher-intensity training, so it’s hard to draw concrete conclusions.

New FINDINGS

To try and get some answers as to which really is the best endurance training method to ensure a good training adaptation always occurs, a new study by German scientists provides a fascinating insight⁽¹²⁾. In this study, researchers compared the training adaptations produced by a 26-week moderate-intensity steady state walking/jogging running program with one that was matched for total energy expenditure but where the intensity was upped after 10 weeks then again at 18 weeks.

Thirty-one recreationally active and healthy, but untrained participants performed 50-minute training sessions of either walking, jogging or running (depending on base fitness) three days per week for 10 weeks. The moderate intensity used was 55% of heart rate reserve. Heart rate reserve (HRR) is given by the following formula: HRR = max heart rate – resting heart rate. So for example, take a 40-year old where the predicted maximum heart rate is 220 – 40 = 180bpm. If his/her resting heart rate is 70bpm, HRR is therefore 180bpm – 70bpm; ie 110bpm. Training at 55% of HRR in this case would mean training at 70bpm + 55% of 110bpm = 70 + 60.5bpm = 130.5bpm (call it 130bpm!).

How two training modes were compared

All 31 participants followed this training program for the first 10 weeks after which they were randomly split into one of two groups:

• Higher intensity/lower volume - After week 10, the participants increased intensity to 70% HRR and the length of their training sessions was reduced accordingly to ensure that their energy expenditure remained identical to weeks 1-10. After week 18, they switched to HIIT training. This was performed with a 10-minute warm-up at 70% maximum heart rate followed by 4 x intervals of four minutes at 95% max heart rate, each interspersed with 3 minutes at 70% max heart rate, followed by a cool-down at the same intensity. Although the sessions were shorter, the total energy expenditure in all workouts was matched to that during weeks 1-10.
• Same intensity/same volume – These participants simply maintained the same routine as before, training at 55% HRR. Because their intensity had not increased, they maintained exactly the same training volume and session durations throughout weeks 1-26.

In both groups, treadmill testing took place before and at regular intervals throughout the 26-week period to determine heart rates for a given submaximal speed and VO2max. The treadmill was set to a constant incline of 0.5% starting at 4.0kmh and every 3 minutes, speed was increased incrementally until voluntary exhaustion. Responders and non-responders in each group were also identified at various points during the intervention. To be a responder, participants had to experienced a gain in VO2max of at least twice the maximum day-to-day variation that always occurs when testing VO2max (yes, some days your body just performs better than others!). Non-responders had gains that were less than twice this variation.

What they found

The results were very clear cut. Let’s summarize them as follows (see figure 1 also):

• After 26 weeks of training the ‘higher intensity/lower volume’ group improved their VO2max levels significantly (by 3.4mL/kg/min). Moreover, this VO2max gain was observed throughout the 26 weeks.
• In the ‘same intensity/same volume’ group, gains were minimal and non-significant (0.4mls/kg/min), and while there were initial gains during the first 10 weeks, these were offset by declines later on in the 26-week period.
• In the ‘same intensity/same volume’ group, 52% of the participants were classified as VO2max responders and 48% as non-responders after 10 weeks.
• After a further 16 weeks of training (ie at 26 weeks) at this same intensity/volume, the number of non-responders stayed exactly the same at 48%. In other words, for those who had failed to respond to the moderate-intensity program after 10 weeks, the next 16 weeks of the same program produced absolutely zero gains in VO2max! 
• In the ‘higher intensity/lower volume’ group, the number of responders to training grew steadily and reached 87% by the end of the 26 weeks. In particular, from weeks 10-26, the rate of responders grew from 53% to 87%. Contrast this with the ‘same intensity/same volume’ group where there was zero increase in responders after week 10!

^{Top row = week 10, middle row week18 and bottom row week 26. Each bar represents one participant. Grey bars = non-responders; black bars = responders. Vertical size of bar = gain or drop in VO2max at that time point. Note how in the high intensity group (right hand side), the number of non responders drops steadily as time progresses, whereas the same is not true for the moderate intensity group.}

Practical implications for novice athletes

Unlike most previous studies, this one consisted of a training intervention for six months – not just a few weeks. It is highly relevant therefore when trying to answer the question of what works best for considering endurance in novices over the longer term. The clear conclusion from this study is that in relative novices commencing and endurance program, a more intense approach increases the rate of response in VO2max to endurance training, even when the total energy expenditure is held constant. Remember, training more intensely without increasing total energy burn means that less time is spent training – not more.

What this research also tells us is that while a steady state approach can yield improvement for the first couple of months or so, maintaining this approach beyond 10 weeks appears to be fruitless, even for beginners. In plain English, even those who are relatively untrained will reach an endurance fitness plateau quite quickly. Even more importantly, it tells us that when performing a moderate-intensity, steady-state program, quite a few novice athletes will make only minimal gains, and continue to make minimal gains as long as they stick to this approach.

In terms of putting together an endurance training program for a novice athlete, it seems prudent therefore to restrict the initial moderate-intensity, steady-state period to a maximum of ten weeks, and then switch to something more intense. Remember, this higher-intensity training does not need to be performed in addition to moderate-intensity session. Instead it replaces it. Remember too that gains on a higher-intensity regime can be expected even when no extra energy expenditure occurs (ie training volume is cut). This bodes well for program compliance and keeping athletes fresh and injury free!

“When performing a moderate-intensity, steady state program, quite a few novice athletes will make only minimal gains, and continue to make minimal gains as long as they stick to this approach.”

Of course, over a longer period of time, training volumes can be ramped up while retaining high intensity work. Indeed, this is to be encouraged at higher levels of endurance competition where muscle economy becomes important for turning in good performances – see this article for an in-depth discussion of why muscle economy matters. 

How should you move to a more intense phase of training after the initial 10-week period? In this study, firstly the steady state pace was upped to 70% HRR (and distance covered reduced accordingly). For example, a runner covering 4 miles in 50 minutes initially could increase the pace to cover that same distance in 40 minutes (which would keep total energy expenditure approximately the same). After another couple of months, some intervals can be introduced for some or all of the sessions. Repeats of 4-minute intervals at or slightly above 90% maximum heart rate would be a good place to start.

In the meantime however, the purpose of this article is not so much to prescribe a training program, but to emphasize that even novice athletes can and should quickly jettison the one-pace, steady-state, moderate intensity approach that is all too often observed in beginners, even after many months of training. When it’s time to make gains, it’s time for some intense thinking!

^References

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