With the rise in popularity over the last few decades of HIIT, CrossFit and other high intensity forms of training, many people have come to believe that the harder they work, the more results they’ll get, or that if they don’t leave the gym feeling destroyed, they’ve somehow not trained hard enough.
I’d like to take some time to partly dispel that myth, talk about the pros and cons of working at high intensity, plus how to think about and regulate your training intensity.
Energy System Training:
The first thing to realise is that when performing conditioning work, you should be thinking of it as energy system training, recognise that we have 3 energy systems, and think about which you are training. The 3 energy pathways are:
1. The ATP / Creatine Phosphate System (also known as Alactic Anaerobic) – The first 10-20 secs of very intense exercise uses ATP available in the muscles. Once the available ATP is used, phosphocreatine is used to reform ATP, but this is usually spent within 15 secs.
2. The Glycolytic System (also known as Lactic Anaerobic) – The second pathway, the glycolytic pathway, is used for fairly intense exercise, ranging from 15 secs to 3 minutes. Glucose stored in the muscle, mainly from dietary carbohydrates, is used to form the ATP. This pathway is also responsible for the lactic acid build up in our muscles, which creates fatigue.
3. The Oxydative System (or Aerobic) – For less intense exercise bouts which are longer than 3 minutes, the oxidative pathway is primarily used. This energy system requires oxygen and uses fat to produce ATP for longer, sustained exercise. The oxidative system is slower, but more efficient.
Eventually, all 3 energy systems should be trained. However, my stance is that, for most people concerned with health and longevity, the aerobic system should be prioritized to improve first, because of the health benefits it confers.
The problem is that most people who do HIIT or CrossFit training go at it too hard to be using their aerobic system effectively. They go out at such a pace that the Glycolytic system has to be used and it’s taxed so much that a lot of lactic acid is built up in the muscles. This in turn means the aerobic system can’t perform well. Just watch a class performing a 20 minute workout in most CrossFit gyms and you’ll see people get slower and slower over the course of the workout. If they were truly doing aerobic work (the best energy system for that length of workout), it should be done at a sustainable pace that you can maintain for the whole duration.
When you choose to deliberately train the CP or Glycolytic systems, the work periods should be short (as described above). However, the rest periods must be longer, as those systems need more time for full recovery, to clear lactic acid and return to equilibrium, before performing another very high intensity work interval.
Working for 40 secs, then resting 20 secs, is a classic scheme I’ve seen in HIIT classes. But what I’ve observed is that the trainers taking the sessions usually encourage the participants to go as hard as they can. This always leads to a decreasing output each subsequent set. This, again, is a sign that you’ve gone too hard for that work:rest ratio. If you wanted to repeat that work at that intensity, you’d likely need more like a 1:5 ratio (rest 3 mins 20 secs), or even more. And if you wanted to keep the work:rest ratio at those times, you should be telling participants to go at a gentle aerobic pace (not much faster than if they were not taking any rest at all), so they can repeat the work outputs each set.
Regulating intensity and listening to your body:
Another downside of performing all your workouts at high intensity is that I believe it encourages you to develop a habit of ignoring your body. I believe this is a mistake. The meta theme of the Fitness for Life programme is to re-connect to yourself. We do this through teaching you to i) re-connect to your body through movement, ii) fuelling that body with great nutrition and iii) re-connecting you to your sense of self through mental and emotional fitness training.
“Re-connecting to your body through movement” doesn’t mean punishing your body, or demanding more of it than it has to give every time. It means listening to your body, tuning in to it, deepening the mind body connection.
I believe that how we feel physically, emotionally and intellectually tends to go through cycles (for both men and women). So, on days where you’re feeling below par, I always say come into the gym anyway, but back off. Treat it as an energising workout / active recovery. Perform some movement, but don’t push the intensity. Doing this will encourage recovery (the body loves movement) but without fatiguing it further.
Then, when you’re feeling great, and you feel ready to challenge yourself, you can raise the intensity and explore the thresholds of the energy system you’re working on that day.
I believe this approach promotes health and longevity, plus long term fitness progress, because it minimises the risk of burnout or overtraining.
Playing the Long Game:
My guess is that at least part of the trend towards high intensity is related to the drive for efficiency in training. People are more and more time poor, with work hours getting longer, and many families both parents having to work full time to support a family etc. They naturally want to think that their precious time they’re giving to training is getting the most return. Much of the marketing for fitness regimes taps into this problem (you’ve probably seen adverts for workouts that promise results in only 10 mins x 3 times a week). Again, I think there’s a wiser way of thinking about this.
I utterly empathise with the feeling of being time poor. Since having kids, my wife and I still both work full time, and it’s tough to fit everything into life. But what’s worked for me, and one of the things I often tell my clients, is to focus on what you can achieve in the next 2 years, rather than in the next 2 months. This shift in thinking takes load of pressure off, but still keeps you moving forwards and improving. If you add tiny incremental improvements together over a period like that it adds up to a lot of improvement, but the changes are manageable and sustainable. A coach I follow describes this as working on a shallow trajectory towards a distant horizon.
Conclusions:
Whilst it is necessary to approach thresholds of your energy systems to stimulate improvements, it’s important to recognise which energy system you’re trying to improve and get the intensity right for that system. You also need to get the rest periods dialled in for full recovery to maximise the effectiveness of your training session.
Training should be thought of as an act of kindness towards yourself, as self-love, not as punishment. Deepening your connection to your body will lead you towards health and the joy of being in your body for your lifetime.
Applying patience to your journey will make it more enjoyable and, I believe, deliver greater gains in the long term.