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 Like A Snail To Go Fast?

I recently read a story about Alex Karp. Yes, that Alex Karp, who is the founder of Palantir Technologies, a tech company that specializes in data intelligence. Karp is 55 years old, but has 7 percent body fat! At his age, that is an extremely low level of body fat. That's the body fat level Michael Phelps had when he competed at the 2008 Beijing Olympics and won 8 gold medals.

Karp is a tech billionaire though, not a young Olympic gold medalist. He says he does not *diet nor starve himself. His fitness comes from 5 hours plus of cross country ski training a week.

What can we learn from Karp's training so that we too can benefit? Karp says he spends 90 percent of the time going at the speed of a snail! Whether you are running or cross country skiing, Karp advises going at the "slowest pace a human can run for as many hours as you can afford. And then once, preferably twice, a week, you're doing speed intervals."

Karp's training is all about sheer distance, just put in the miles he says. No speed or intensity, except when doing his intervals. He started training like this when the Covid pandemic hit. He was already in reasonably good shape before. But since he had lots of time, he became very disciplined about training in that format. He saw results after 18 months, and especially huge results after 36 months. 

Karp says he learned this training regime from athletes in Norway. Norway has won the most number of Winter Olympic medals for cross country skiing. Going slowly like a snail most of the time helps build a cardio base so that it allows you to go fast when you have to. Like when doing intervals or when racing. 

This form of training is also known as low intensity steady state training (LISS), the exact opposite of high intensity interval training (HIIT). LISS is the tortoise compared to HIIT's hare. When you go for a jog/ run, long walk, bike ride where you can easily hold a conversation, you are performing LISS. For those who need a number, this is usually between 50 to 60 percent of your maximum heart rate. 

Like HIIT, LISS can also help you burn fat, build endurance and increase exercise capacity. However the time you need to spend doing it to achieve those results is typically much longer. LISS can help you recover from those high intensity workouts while supporting your larger fitness goals. Exactly like what Karp is doing. 

For many of us who exercise and train, our hard sessions are not usually not hard enough and our easy (or recovery) sessions are not easy enough. This is why some athletes use a heart rate monitor (HRM) to train. This ensures that you know the correct intensities. Ben Pulham from Coached Fitness has been advocating training with a HRM for a long time. BUT, you have to really adhere to the readings, otherwise it will not be effective. With Singapore's climate, you really have to go a lot slower.

Yes HIIT can be super effective, but also incredibly stressful on the body. Do it too often and you'll increase your risk of overtraining and injury which will hinder your progress and shortchange your results. 

Alex Karp says it took him at least 18 months before he saw results. Can you be that patient? You have to, if you want results. If HIIT is a calorie scorcher, then LISS is a slow simmer where calories are still burned even if you don't emerge from your workouts drenched in sweat. 

Research also shows that those who engage in low intensity exercise are more likely to stick to their plan compared to those who attempt to accomplish the same goals in half the time with HIIT (Forster et al, 2015). The subjects found HIIT "less enjoyable".

Then, there's also the engagement factor. For some people, running, walking, cycling or swimming for a few minutes can feel endless. Me? I love the long, slow runs and rides.

Reference

Forster C, Farland CV, Guidotti F et al (2015). zthe Effects Of High Intensity Interval Training Vs Steady State Training In Aerobic And Aerobic Capacity. J Sp Sci Med. 14(4): 747-755. PMID: 26664271

*The biggest adjustment Karp made was dropping added sugar in his diet. He used to eat lots of chocolate, and had sugar in his coffee and tea. However, on special occasions and if he's traveling and finds a really nice Danish, he will eat it.

Keep Jogging Or Rest?

Picture by Richard Seow

For those of you old enough to remember former Singapore runner, Syed Ahmad Taha - he's the last Singaporean runner to run the 10,00m on the track in under 33 mins before Soh Rui Yong in 2012, and Melvin Wong in 2015 at the Singapore SEA Games. Syed ran the 10,000m in 32:41 min in 1990.

I remember watching him do interval training (the original HIIT) at the old National Stadium back in 1988. When I was a teenage runner, those intervals we did certainly did not have such a fancy name like HIIT. 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).

Syed Ahmad Taha was doing 25 x 400m with a 60 seconds rest and he would be lying on the track recovering while you could see his heart thumping away. He would spring back up as his coach told him to get ready for the next rep. No super shoes, no super spikes back then in 1990. Respect!

A quick question for all runners before reading the rest of this article. During your track intervals training, do you normally continue to jog/ run after the interval or just rest before starting the next rep?

Well, no prizes for guessing that this post compares active recovery (jog/ run) versus passive recovery (lying down or slow walk) between repeats during interval training.

The study had well trained runners do 4x 2:00 minute at their maximum aerobic speed at an outdoor track, with a 2 minute rest or 2 minute jogging between the intervals.

Resting (rather than jogging during the rest period) enabled the runners to work harder and spend more time at peak VO2. This is the whole point of interval training, to spend more time running in the 90-100 percent VO2 max region. The rest allowed the runners to suffer more. Perceived effort by the runners after each run was also lower with rest in between. The researchers concluded that complete rest is preferable for this type of workout. 

Some points to note. The runs were done at identical running speed. The runners may be able to run faster if they were allowed to run the interval at their own pace with a jog recovery since jogging (low intensity exercise) keeps the blood flowing, which eliminates lactic acid quicker to enable you to go faster at the next rep).

Lactate (or lactic acid) levels were only measured after the workout was over, lactate levels were significantly higher (6.93 vs 6.24 mmol/ L) while the runners rested. 

The question I'm pondering on is whether to make your workout harder or easier? Is standing still to rest better since your muscles are filled with lactic acid and you get to practice running in that state? 

Or is jogging better since you can train your body to eliminate lactic acid quicker form your bloodsteam and thus enabling you to run faster. Perhaps, you can do complete rest while training for your next race this year and do the jogging rest for the same race next year and see which gives a better race timing. Definitely a good study topic for researchers.

If your goal is to run each rep as quickly as possible, then you are better off resting or just walking a little, if the recovery time is a minute or under since resting helps to restore phosphocreatine, which fuels your sprints and the starting stages of your longer runs. (This is why some athletes that require frequent sprints in the sport - hockey, basketball, football etc take creatine) which can be a separate post.

However if your rest period is 2 minutes or longer, light jogging may possibly help you run faster since you are actively clearing lactic acid and other metabolites.

Reference 

Sanchez-Otero T, Tumil JL, Boullosa D et al (2022). Acive Versus Passive Recovery During An Aerobic Interval Training Session In Well-trained Runners. Euro J Appl Physiol. 122(5): 1281-1291. DOI: 10.1007/s00421-022-04926-2.

Isometric Exercise Training Trumps HIIT

Isometric glutes and quads training

An article in the Straits Times last year showed that an increasing number of Singaporeans have hypertension or high blood pressure. 

This is not just in Singapore, hypertension is a global health problem that is largely treated by anti-hypertensive medication. However, even though anti-hypertensive medication is mostly effective, other than being costly over the long term, it has adverse side effects and also poor adherence rates. My own grandmother used to take one pill a day, then she reduced the dose to half herself before stopping altogether.

Traditionally, moderate intensity aerobic exercise is currently recognised as the recommended modality for managing blood pressure problems. Current exercise compliance to benefit long term cardiovascular risk is also poor. Hence, a different approach may be needed to manage hypertension.

The paper referenced below investigated the effects of isometric exercises versus high intensity interval training (HIIT) to find out which is more effective at reducing resting and ambulatory blood pressure (BP).

Both IET and HIIT were found to be effective, however IET was significantly more effective at reducing resting BP compared to HIIT. Systolic and diastolic BP were reduced by 8.50 mmHG and 4.07mmHG after IET versus 2.86 mmHG and 2.48 mmHG following HIIT.

HIIT lessened the resting heart rate significantly by 3.17 beats per minute (bpm) versus 1.34 bpm for IET. 

Duration of exercise, subject's medication status and time of diagnosis of hypertension had no effect on the results.

Compared to HIIT, IET had superior results in the management of resting BP with reductions similar to or greater than anti-hypertensive medication. HIIT was still found to be highly effective at reducing resting BP and may have wider physiological benefits than IET since it was more effective at reducing resting heart rate. 

Teaching patients to use IET to reduce hypertension should definitely be considered. Most of the studies that studied IET used hand grip exercises for the upper limb and stationary wall squats or leg extension for the lower limb. Cycling intervals were the most common for HIIT studies.

The authors concluded that getting patients with hypertension to do IET for controlling their blood pressure should be considered, while HIIT better for maintenance of good health.

Now you know IET trumps HIIT when it comes to lowering blood pressure.

Reference

Edwards J,  De Caux A, Donaldson Jet al (20). Isometric Exercise Versus High-Intensity Interval training For The Management Of Blood Pressure: A Systematic Review And Meta-Analysis. BJSM. DOI: 0.1136/bjsports-2021-10442.

*Thanks to Megan for getting me the article

Instead Of Complaining About Wearing Face Masks..

He wore a mask, I didn't - posed lah ;) 

Almost daily during the circuit breaker (CB) period last year, my older boy and I went out to ride our bikes since there were hardly any cars on the road.  Most of the time we had our cloth face masks on. Needless to say, we found riding uphill more difficult when having them on. 

Made it to the top of Mt. Faber

Newly published research backs this up. Researchers had 28 young (18 to 29 years) and healthy participants perform 2 maximal exercise tests on a treadmill. One with and one without a cloth face mask.

Each participant runs to complete exhaustion as the treadmill speed and incline is increased every 3 minutes and the time to exhaustion is recorded. This is used to estimate VO2 max levels. Heart rate, blood pressure, rate of perceived exertion and the participant's perceptions of wearing a face mask while running were also recorded.

Key findings were that cloth face masks reduced run time to exhaustion by 14 percent and VO2 max by 29 percent. With masks on, the participants felt more short of breath and claustrophobic at higher exercise intensities compared to not wearing masks. Blood oxygenation levels (Sp O2 levels) were also lower when cloth face masks were worn. The reduced levels of oxygen in the blood show a definite physiological effect. 

The more effective the mask in filtration capacity (the more protection for the wearer), the more it will affect exercise performance. Take home message is that using a mask during exercise does make it a lot harder. The researchers recommend that exercise time, frequency and especially intensity be modified when wearing a cloth face mask.

The researchers also cautioned that their findings of impaired performance with cloth face masks may be in part due to the perceived discomfort. Meaning, the participants were less motivated to keep running at higher treadmill speed and incline. 

My racing days are long gone, but if I were still training and competing, I'll probably don a cloth face mask while training (sometimes) to up the intensity a few notches so that when I race without a cloth face mask, I'll be hard to beat. That's just like respiratory muscle training. But that is just me. Please do not take this as training advice! 

Reference

Driver S, Reynolds M, Brown K et al (2021). Effects Of Wearing A Cloth Face Mask On Performance, Physiological And Perceptual Responses During a Graded Treadmill Running Exercise Test. BJSM. epub first 13 April 2021. DOI: 10.1136/bjsports-2020-103758.

Aerobic Exercises Key To Aging Well?

Me on the left. Picture by Jeffrey Keng from Cycleworx

Slightly more than a year ago, I wrote that strength training may be just as important (if not more) than aerobic exercises. Why? Strength training has been found to decrease rates of early and cancer related death.

And earlier this year I disagreed with a funded study by Les Mills International when the article suggested that lifting weights was more beneficial for losing weight compared to running or cycling (aerobic exercises).

Now, some new research seems to show that aerobic exercises (like running, cycling, rowing or swimming) can make our cells younger. That same study found that weight training may not cause the same physiological changes in our cells.

Way back in 2009, a study found that competitive middle-aged runners had extended telomeres compared to inactive people of the same age. What are telomeres? All of us have telomeres at the tips of our chromosomes. Telomeres help protect our cells from damage and have been found to shorten and fray as a cell ages.

Many of the researchers in that 2009 study came together for this recent study to investigate whether exercise would change our telomeres.  They also wanted to know what type of exercise were needed and whether intensity played a part. It is hypothesized by the scientists that exercise helps lengthen the telomeres.

The researchers recruited a group of healthy middle aged men and women who did not exercise. They were tested for  their aerobic fitness and telomere length. In addition, blood markers of telomerase (an enzyme that influences telomere length) were tested as well.

Some in this group were randomly assigned to continue with their lives as normal as a control group. They did no exercises.

Others started a supervised program of brisk walking or running for 45 minutes three times a week or a high intensity interval program of four minutes of strenuous exercise followed by four minute rests with this repeated four times.

A third group took up weight training, doing a circuit of resistance exercises three times a week.

Heart rates were monitored and the exercise program was carried out for six months. Results were tested after this and all the subjects who exercised were found to be more aerobically fit.

At molecular level however, there were differences. Those who did the aerobic exercises and interval training had much longer telomeres than before starting the exercise program and more telomerase activity.

Those who weight trained and those in the control group (who did not exercise) had no change in telomere length. Some even had shortened telomere lengths.

Those who did weight training produced less nitric oxide, which is thought to affect telomerse activity and contribute to lengthening telomeres.

Even though weight training was strenuous, overall heart rate was lower compared to running in the study. This results in less blood flow and probably less physiological response from the blood vessels.

The researchers suggested that exercise needs to be aerobically taxing to extend telomere length and slow cellular level aging. In this aspect, endurance exercise was clearly ahead of resistance training.

The findings do not indicate that weight training does not combat aging as it also helped improved fitness, which itself is a very important indicator of longevity.

Like I wrote before, current research shows that both strength training and aerobic exercises are necessary to be healthy and functional. So run, bike or lift weights, (or whatever exercise you prefer) as they are all beneficial, it's much more important to keep moving.

I wanna for live a long time, so I lift weights too

References

Werner CM, Furster T et al (2009). Physical Exercise Prevents Cellular Senescence In Circulating Leococytes And In The Vessel Wall. Circulation. 120 (24): 2438-2437. DOI: 10.1161/CirculationHA.109.861005.

Werner CM, Hecksteden A (2018). Differential Effects Of Endurance, Interval And Resistance Training On Telomerase Activity And Telomere Length In A Randomized Controlled Trial. Euro Heart J. ehy585. https://doi.org/10.1093/eurheatj/ehy585.