Zone 2 or HIIT? Or Neither?

My 58 year old patient walked in yesterday to the treatment room and the first question she asked was if she should start HIIT training. Woah! Hang on, I said to her do you really know what HIIT is? (*See end of article for what HIIT is please).

She said her friends, children and all the fitness influencers she sees extols the benefits of HIIT. Then without batting an eyelid, she said, "What about Zone 2 training?"

That is basically what is happening online. One group says train at Zone 2 while the other says go hard or go home, HIIT is the way to go.  

What do the best in the world actually do? A new study by Sandbakk et al (published in April 2025) investigated elite endurance coaches and their training were not what you expected. These coaches had athletes winning more than 380 international medals in long distance running, biathlon, rowing, cross country skiing, road cycling, swimming, triathlon and speed skating.

All the coaches stick to a traditional periodization model, including a gradual shift towards overall lower training volume and more competition-specific (race pace) training as the competitive period approaches.

Another common emerging feature was an emphasis on high volume low intensity training. Look at the picture above, MOST (80-90 percent) of the weekly training was easy. Here is the key insight, majority of the easy work was not in Zone 2. It was in Zone 1. Slower than what the internet experts are obsessed with. Slower means more sustainable and more adaptation over time. That's how you get stronger. 

True aerobic development is only possible from accumulating volume. It also allows one to recover and handle key sessions. 

This Zone 1 low intensity sessions along with combined with 2-3 weekly "key workout" days consisting of 3-5 intensive training sessions. The sessions are purposeful and focused, with recovery all planned. 

Finally, coaches across all sports focused on getting high training quality by optimizing training sessions by controlling the load-recovery balance to ensure optimal preparations for major competitions.

The athletes go through all the zones (see the above picture), not just high intensity (Zone 5), but also in between. Short, fast intervals and controlled thresholds. The exact proportion is dependent on their competition demands. There were not a lot of really hard anaerobic sessions. 

Why the big difference between these elite coaches and what we see online with all the fitness influencers? Firstly the fitness influencers usually do not compete in races or competitions. They won't be posting so many videos if they do. Train easy, adapt, get stronger does not sell as well as "unlocking this magic Zone of HIIT". High performance is not about shortcuts. It's about accumulating consistency over time. Not as attention catching, but it definitely works.

To sum up, it's mostly sessions of low intensity, with occasionally high sessions adjusted to the individual. Balance stress and recovery and consistency over all else. Now you know.

* Many gyms, fitness influencers and trainers get patients to do what is traditionally circuit training but call it HIIT. Circuit training is like 30 seconds doing push ups, rest a minute, go to another station and perform 30 seconds of high knee lifts, rest a min, 30 seconds of lifting dumbbells etc

HIIT stands for high intensity interval training. Or interval training for short.  Example, you run 15 intervals or repetitions of 400m with a one minute rest in between or the coach will say run 6 x 1km going every 5 minutes (meaning if you run your kilometer in 3:50 min, you get 1:10 min rest before starting again). You can also cycle intervals outdoors or on a trainer with your bicycle attached.

Circuit training does not sound sexy, but HIIT certainly does!

Reference

Sandbakk O, Tonnessen E, Sandbakk SB et al (2025). Best-practice Training Characteristics Within Olympic Endurance SpoRts As Described By Norwegian World-Class Coaches. Sports Med 11:45. DOI: 10.1186/s40978-025000848-3

Run Longer Or Run Faster?

Picture by Richseow from Flickr

Your coach many plan a different variety of training runs for you. You can do a steady long run, threshold runs, add in some fartleks, some hard core intervals / HIIT and of course the recovery runs.

However, it boils down to really just two options if you want to fitter and faster. You can train harder with a higher intensity or you can train more. In an ideal world, I would run long and run hard daily. That doesn't happen of course, otherwise injuries would soon be knocking on your door.

Those two variables, intensity and volume are the "bread and butter" of all training programs for running, cycling, football, all sports really. Sports psychologists would add mental skills training to the mix.

If we had to choose one, which is better? Which gives you more bang for your buck?

That was exactly what two groups of researchers were debating over a recent article published recently. The paper investigated whether exercise intensity trumps volume to promote increases in skeletal muscle mitochondria (power generators of our cells).

With more mitochondria in our cells, the stronger we become, so the debate was whether running faster or running longer is better at boosting endurance.

Nice to do a long run here

Those in favor of high intensity training explained that when comparing training programs where subjects do an equal amount of work, those training at higher intensities and lower volume see the biggest gains in mitochondria. That group also suggested that vast majority of people are unwilling or don't have the time to spend long periods of time doing high volume training anyway (Gibala et al, 2019).

The second group of researchers presented evidence of a combined analysis of 56 studies that showed a strong relationship between total training volume and mitochondrial changes suggesting that volume is really the key variable (Bishop et al, 2019). That same analysis did not find any significant relationship between intensity and mitochondrial changes.

The second group also conceded that higher intensity exercise will result in a greater mitochondrial response per minute of exercise. This is a crucial point as we live in a time where everything competes for our time and attention. Getting stronger and fitter in less time may be more efficient for people to meet their fitness goals (Gibala et al, 2019).

In competitions however, we race to see who can be the fastest runner, cyclist etc, not who spent the least amount of time training. Those of you who train to race would definitely do a combination of long slow distance, interval/ HIIT training and medium paced runs. I did all of the above anyway when I was still competing.

And I can tell you many roads lead to the podium. Since both intensity and volume helps trigger mitochondrial adaptations, you should do which you enjoy and helps you improve more.

There are times I really enjoy the camaraderie of doing long runs and long rides. However I also love that adrenaline rush, the release of endorphins I get when putting the hammer down while running or cycling hard.

If you do the same long slow runs or interval training over and over again, it will eventually lead to diminishing returns. Or it will drive you crazy. I know I will go nuts if I just do long slow distance and nothing else.



References

Bishop DJ, Botella J and Granta C (2019). Cross Talk Opposing View: Exercise Training Volume Is More Important Than Training Intensity To Promote Increases In Mitochondrial Content. J Physiol. DOI: 10.1113/JP277633.

MacInnisMJ, Skelly LE and Gibala MJ (2019). Cross Talk Proposal: Exercise Training Intensity I More Important Than Volume To Promote Increases In Human Skeletal Muscle Mitochondrial Content. J Physiol. DOI: 10.1113/JP277634.

I wish I can fly ....

Bike Intervals Can Help You Run Faster

Our training machines

Looks like you gotta spend some time riding furiously on your (stationary) bike if you wanna run faster. All you need is 15 minutes to spare.

A recent study showed that with the right kind of high intensity training on a stationary bike, you can run faster.

The researchers tested runners on a treadmill with a 3 km time trial and split them into four groups. Three groups trained on a stationary bike for two weeks in addition to their regular running routine while a control group just maintained their regular running routine.

The runners did six interval sessions on the stationary bikes in all. Each runner completed six 10-seconds all out efforts. Each group varied the amount of rest between intervals. Rest ranged between 30 seconds to 80 seconds to two minutes rest for the runners. Including warm up and cool down, the session took less than fifteen minutes.

The results showed that the group with the shortest period of rest had the best results. The 30 seconds rest group ran about three percent (or about 25 seconds) faster!

Both the 80 seconds and two minute rest groups did not have any significant improvement in the 3 km time trial. There was no change in the control group.

The researchers attributed the improvement in performance to the elevated heart rate in the 30 second rest group. The short rest prevented the runners from recovering fully making each successive interval more difficult. Their muscles had to adapt faster to the increased load which helped them run faster in the subsequent time trial.

The authors recommend this workout as cross training to avoid injuries. Since stationary cycling also reduced training volume, it is a time efficient way of training as well. Runners who are injured can use this to maintain their fitness while recuperating.

When the weather does not permit you to run outside, you can still ride.

Reference

Kavaliauskas M et al (2015). High-intensity Cycling Training: The Effect Of Work-to-rest Intervals On Running Performance Measures. J Str Cond Research. 29(8): 2229-2236. DOI: 10.1519/JSC.0000000000000868.

Pedaling furiously while it was raining outside

My wife pedaling furiously 5 weeks after giving birth