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Habiba from Peckham asks:
‘What’s more important in a workout: the time I put in or the effort?'
Expert: Dr Rebecca Robinson, consultant in sports and exercise medicine at the Centre for Health and Human Performance.
Whether you’re embarking on a new fitness regime this month or building on an existing exercise habit, you’re no doubt feeling inundated by exercise right now.
But quite aside from weighing up the relative benefits of working out in a gym versus your living room and frantically Googling 'Fire Hydrants', there’s a perennial question that troubles even the most experienced of exercisers: the time/effort balance.
Likewise, a slow, steady jog on a Saturday morning can be just the tonic for an anxious mind (not to mention an aggy boss). So which approach is more superior?
How long do you need to spending work out in order to get the benefits?
To reap the rewards of everything from better heart health to stronger bones, organisations like the World Health Organization (WHO), the US Center for Disease Control (CDC) and our very own NHS have given us a pretty simple target to shoot for: 150 minutes of moderate activity per week, 75 minutes of vigorous activity or a combination of the two.
For context, that’s five 30-minute moderate workouts per week, or five 15-minute vigorous sessions – mix and match as you will.
The former is really anything that raises your heart rate a bit, and encompasses everything from scrubbing the shower with a podcast for company to lapping your local park with a good pal and a strong coffee. For a handy way to remember what constitutes a moderate workout, you should be still be able to talk, but not sing, according to the NHS.
What are the health benefits of focusing on time?
Studies confirm that there’s something in those manageable values. One, published in JAMA Internal Medicine, that analysed the exercise habits of 660,000 people, found those who exercised one to two times the recommended daily amount had a 31% lower mortality risk than those who didn’t exercise at all; those doing two to three times that much exercise saw a 37% lower risk, which peaked at about 39% lower risk of mortality at five times the amount.
Time spent sweating also counts in matters of mental health; a 2016 study in the Journal of Neuroscience found that 20 minutes of exercise could help boost brain chemicals glutamate and GABA – two neurotransmitters vital for memory and mood.
How can I build a workout based on time?
New to exercise and looking to improve your fitness and strength? Lower-intensity, time-based workouts are a great place to start. So says Dr Rebecca Robinson, consultant in sports and exercise medicine at the Centre for Health and Human Performance and Women's Health Collective Expert Panellist.
‘Increasing the time you spend exercising, slowly but steadily, will get the cells within the muscles - the mitochondria - to develop,’ she explains. ‘Greater mitochondria density is important in endurance, but also metabolically.’
Why? Think of mitochondria as the battery packs in cells. They generate most of the chemical energy needed to power the cell's biochemical reactions. In other words, they convert energy from the food you eat into energy your body can use to move.
‘You’ll often hear athletes, particularly runners, talking about building a “base” – time spent building up mileage before they’re ready to push the intensity,’ adds Dr Robinson. Think: Couch to 5k – where the goal is time spent on the move, rather than bursts of all-out effort.
The same applies to most forms of exercise, she adds, whether you’re a runner, a cyclist, or lifting in the gym. ‘Building a base means conditioning that system, including the muscles, ligaments and tendons, which is essential in preventing injury. Because, while quick, high-intensity blasts can be good, is your body ready for that?’
OK, so duration is important. But what about the effort you put in?
There’s a reason HIIT has featured in the top five on the American College of Sports Medicine fitness trends list since 2014. The movement typically features short bursts of all-out intensity (with heart rate at 85% of your max – subtract your age from 220 to get yours) interspersed with periods of rest.
‘High-intensity sessions can be really useful to push the body’s physiology above its current level, shocking it a little bit in a controlled way,’ adds Dr Robinson says.
What are the health benefits of focusing on effort?
Completing intense workouts will drive physiological changes because, put simply, the body thinks, “If I have to work this hard, I’m going to need to adapt”.’
To get more specific, here's what's going on in your body:
The left ventricle of your heart gets thicker and stronger
Your lungs develop more alveoli (the little air sacs that transfer oxygen to the blood)
Your cells develop more capillaries to better facilitate oxygen transfer
Your central nervous system learns to recruit more muscle fibres
The density of those muscle fibres increases
This happens with any exercise of course, but once you reach a certain level of fitness, you might find yourself hitting a plateau – your body has adapted enough to meet the needs of your usual sessions.
This is particularly true when it comes to strength training, says Rory Knight, trainer at the audio-led fitness platform WithU. ‘Muscles require progressive overload to grow, which means consistently increasing intensity through weight, reps, sets,’ he explains.
But HIIT is also a hit when it comes to fat loss, since it’s an efficient way to burn calories – up to 30% more than other forms of exercise performed for the same time, a 2015 study in the Journal of Strength and Conditioning Research found.
One reason is the EPOC effect, or excess post-exercise oxygen consumption. In a nutshell, exercising at this intensity, even if just for short bursts, puts enough strain on the body that returning to its natural resting state (homeostasis) also requires serious work.
How so? Tasks like lowering body temperature, re-oxygenating blood and lowering heart and breathing rate require energy, meaning you’re burning calories post-workout, too.
If all that’s not enough to convince you to up the ante, hitting the government-recommended time targets isn’t the only way to reduce your risk of early death; adding a little intensity goes a long way.
In a study published in JAMA, researchers weighed up spurts of vigorous exercise and sustained moderate exercise, and the former came out on top. Of those who met standard exercise guidelines each week, those who described at least 30% of their exercise as 'vigorous' had a 9% lower risk of mortality than those who only did moderate exercise all week. If more than 30% was vigorous, the lowered risk jumped to 13%.
So what’s more important in a workout: time or effort?
While all the evidence points to intensity for the win, you probably already know that working all out in every session can actually be counter-productive.
‘HIIT workouts are only as good as your ability to recover from them and generate the changes that result from pushing your body close to its limits,’ says Bryce Hastings, physiotherapist and head of research at Les Mills, who’s been involved in several studies on the subject.
In fact, too much high-intensity work could lead to what Hastings calls overreaching and others call overtraining. Symptoms include a plateau or drop in training progress, injuries, feeling unwell more often, disrupted sleep, low mood and feeling exhausted rather than energised after exercise.
Since HIIT also triggers the release of the stress hormone cortisol, those suffering from high stress or anxiety already would be better off giving it a miss.
So is there such a thing as a sweet spot? ‘Generally, we recommend spending 4-9% of your total training volume in the 90% Max HR plus range,’ adds Hastings.
If you’re looking for significant changes in body composition, he suggests aiming for two to three moderate cardio sessions, two strength sessions and two short (no more than 30-minute) HIIT workouts per week, plus a full rest day which could include low-intensity stretching.
For Knight, while longer sessions and higher intensity workouts have a place in any plan, there’s another factor that outweighs both: consistency.
As Dr Robinson puts it, ‘Ultimately it’s about finding a structure that you enjoy, and one that you’ll be able to stick to.’ The best workout? The one you’ll get out of bed for.
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