High and low intensity training are very different but both show important benefits depending on one’s goals, desires, and preferences.
Short duration high intensity interval training (also known as HIIT) is a time-effective alternative to obtain health benefits. But, is it better than low to moderate intensity training? There are questions about whether or not high intensity training can replace low to moderate intensity training of long duration – a training strategy known for its high energy expenditure.6 Let’s lay out the facts!
What Is High and Low Intensity?5
In brief, high intensity training is maximal to near maximal effort for a short period of time, without interruption. It usually involves both anaerobic and aerobic energy systems – which has to do with where the energy comes from.
In comparison, low intensity training is a sub-maximal effort. Usually, low intensity exercise relies on aerobic energy systems and aerobic dependent muscle fibers. Also, it is often performed for longer periods of time.
Fiber Recruitment7
Our body has two main types of muscle fibers used for different types of activity. The fiber types are called Type 1 and Type 2. There are two kinds of type 2 fibers, however, for the purpose of this article, let us assume that Type 2 fibers fall in the same category. The speed of contraction is the major difference between both kinds of fibers.
- Type 1 Fibers – Also known as Slow Twitch Fibers. As the name suggests, the contractile speed of these muscle fibers is “slow”. These fibers are mostly used during endurance type training. These fibers are more relevant in low intensity training.
- Type 2 Fibers – Also known as Fast Twitch Fibers. As the name suggests, the contractile speed of these muscle fibers is “fast”. These fibers are mostly used during fast, quick contractile movements of shorter duration due to the higher energy requirements. These fibers are more relevant in high intensity training.
Physiological Effects of Different Intensity Training6
Stronger Bones
“High-intensity interval running may be considered as high-impact exercise and could therefore be speculated to have an effect on bone mineral density”
Nybo et al., 2010 (p.1952)
What is meant by this quote is that with higher impact exercise there are long term benefits that can be promoted. Of those is osteogenesis and better bone mineral composition.
What does this mean? A person doing higher impact and/or high intensity interval running would have stronger bones throughout their lifetime.
Cholesterol5
Moderate intensity training matched with longer periods of exercise relies more on your fat oxidative (fat dependent) systems. Therefore, moderate intensity exercise may allow for a better cholesterol profile.
Why? Long duration, moderate intensity exercise reduces body fat mass because it relies on fat for energy. Consequently, one’s cholesterol profile is likely to improve.
People at Risk for cardio-metabolic disorders3
The benefits of cardio-respiratory fitness are clear when taking part in high intensity activities. High intensity exercise can have substantial positive outcomes to those with coronary artery disease, congestive heart failure, and metabolic syndrome. In fact, improvements in blood pressure and physiological adaptations in the left ventricle have been documented.
People with cardio-metabolic disorders can benefit from the positive changes resulting from HIIT training when there is a large enough stress on their body. While high intensity training creates physiological stress, its effects can be mitigated by the typically shorter duration of these sessions. Therefore, people doing HIIT are encouraged to push as hard as possible during effort.
On top of that, insulin sensitivity is improved with high intensity training. This can be very beneficial for those with diabetes.
“Very short duration high-intensity interval training substantially improves insulin action.”
Nybo et al., 2010 (p.1951)
Alternative for Elderly: Low Intensity Training1
By now, high intensity training seems like a no-brainer. However, it is not easy for everyone to take part in such a training protocol. The mental requirements to push at such a high intensity and the physical strain that this training induces is not possible for everyone.
For example, the elderly population may not be able (or want) to go through the demands of high intensity training. For this population, low intensity training for a longer sustained duration is a great alternative. The low intensity provides a type of exercise that is feasible and still creates improved strength, flexibility, and balance.
The ultimate outcome of such training for the elderly population is improved functional capability. This also means an increase in health-related quality of life and improved independence at an old age.
Note: The benefits of low intensity training are applicable to everyone, not just elderly. If you find more pleasure in doing low intensity exercise, do that. You are being active and this is what counts.
Fat Metabolism in Low Intensity Training4
There are several reasons why low intensity training is beneficial, such as its reliance on fat as its energy source. The fat-burning feature of low intensity exercise is applicable for most people, but especially endurance trained athletes. Endurance athletes use their fat stores more optimally than the average person.
The good news is that anyone can become more of an endurance trained individual. To do so, it would require more training time at low to moderate intensity.
Ultimately, using fat as an energy source is not always healthy depending on a person’s current body composition. Ensuring yourself that your body is properly fed before and after your training will ensure that you continue feeling good and feel like exercising.
Long duration, low intensity exercise can be considered for people with fat loss goals or for those looking to increase lean body mass. However, make sure you seriously consider why you want to lose weight before pursuing this goal.
How to choose Between High and Low Intensity?6
The debate between high and low intensity training is not about which one provides benefits. They both have health benefits regardless of which one a person likes more. High and low intensity training may have benefits that the other does not provide.
For example, low to moderate exercise is more effective in treating hyperlipidemia (in simple terms – high blood fat/lipid density) higher intensity training is less effective in comparison to higher intensity training.
However, short, moderate, and high intensity training can reduce blood pressure and can improve the risk of developing hypertension.
High intensity training is found to be superior for improving maximal oxygen consumption which can translate well for cardiorespiratory fitness (cardio). This would support the idea that cardio is more dependent on training intensity rather than the amount or volume of training.
Combining High and Low Intensity2
As highlighted above, the benefits of either low or high intensity are many. There is no perfect way to achieve certain goals but using a combination of high intensity training and low intensity training is showing promise for many trained individuals and athletes.
As individuals consider improving their training programs to maximize performance, it is almost a certainty that training programs will contain both high and low intensities.
Evidently, people should incorporate all training intensities in a best-case scenario. But the truth is that it is not possible for all and it is not what everyone wants either. So, the best choice is probably the one that makes you keep exercising and improving your health. Try high and low intensity training and find out what works for you!
