What is HIIT?

What is HIIT?

Author: Jake Watson – Strength Coach & Kinesiologist, CSEP – CEP, P. Kin, ESSAM/One Welnness

Why has High Intensity Interval Training (or HIIT) become the fitness trend of the last decade?

What is HIIT?

High Intensity Interval Training or HIIT is a training format that has been adopted from the classic interval based training. The difference being that rather than working at a percentage of your maximal work capacity you are required to work through set training/workout routines at maximal effort. This may mean completing a set routine as fast as possible, for as many times as possible in a given time or on a set time for each activity.

The most recent surge HIIT has seen more of a focus on the involvement and amalgamation of cardio and resistance based training technique. These regimes require you to push yourself in an all-out effort followed by a short and sometimes active recovery, which is then repeated for multiple intervals.

The rise of this newer form of HIIT training can be somewhat paralleled to the popularity of training formats such as Crossfit and P90x. In each modality the rest periods are either set, or governed by the participant’s ability to continuously perform the set routine and require maximal effort throughout the working component.

What happens to your body that’s different to steady-state exercise? And what’s the benefits?

HIIT places a large stress on your musculoskeletal & cardiovascular systems which increases your body’s need for oxygen during the effort phase creating an oxygen deficit to the demand. During steady state exercise an easing of the intensity through a reduction in training output can allow this shortage of oxygen to be replenished.

However due to the short nature of the recovery phase within HIIT training your body doesn’t have time to recover fully before the next interval. This is not only present in aerobic based but also resistance based HIIT regimes and elicits an after-burn effect known as Excess Post-Exercise Oxygen Consumption or “EPOC”. This is a period in which the bodies systems are in an oxygen deficit and in the process of restoring the body back to a resting state. Specifically the body is using the excessive consumption of oxygen to replenish depleted energy stores and fuel the bodies increased metabolism from the increase in body temperature.

These elevated levels of fuel consumption created by EPOC requires the body to breakdown fat stores (the highest form of accessible energy) in response and is the reason why this style of training is so much more effective at burning calories and oxidizing fat than your steady state or regular aerobic exercise.

Why should I include HIIT in my training regime and what’s the evidence?

Current guidelines for weekly physical activity within Canada recommend that people be achieving 150 minutes of moderate activity in a week. However, many people are not achieving this goal weekly, citing several barriers including time as a reason for not achieving the target. HIIT allows for a much shorter time demand but with further benefits.

Recent studies, have revealed as little as 3 HIIT sessions per week, involving 10 min of intense exercise can be extremely beneficial. Demonstrating a consistent improvement in aerobic capacity, skeletal muscle oxidative capacity, exercise tolerance and markers of disease risk after only several weeks in both healthy individuals and those with cardio and metabolic disorders.

These outcomes are prevalent across a cluster of studies into the benefits of HIIT, many of which have demonstrated marked increase in V̇o2 Performance markers and an overall improved capacity in fatty acid oxidation. Which is fantastic news when trying to improve your energy output and performance.

What are some of the performance outcomes from HIIT?

Furthermore it has shown great benefits in reducing risk of Cardiovascular risk factors in particular;

•  Systolic and diastolic blood pressure

•  High density lipoproteins – your good Cholesterols

•  Triglycerides and fasting glucose

How can I start? What do I need to know before my first HIIT session?

Its’ important to ensure that you are well conditioned and taper the exercise routine to your current ability. Too often I come across clients and friends whom have injured themselves from this style of training. The following points can help reduce the risk of injury and help improve your performance within these training formats when starting off.

Active warm-up and mobility – ensure that you’re sufficiently warmed up; this includes a minimum of 5-10mins of light to moderate low impact cardiovascular exercise followed by a regime of active range of motion exercises. These are exercises that involve moving the body’s joints through end ranges actively and can also include placing light resistance through musculature surrounding the joints.

Ensure adequate rest periods between exercises – even if you have set a routine that requires you to perform as many exercises in a given time or your trying complete a routine as fast as possible, if you do not allow for adequate rest to ensure that appropriate technique is maintained then it’s all for nothing. If you feel your technique slipping during an exercise ensure you take a short break or increase the time between exercises.

Taper the session according to your level of fitness – much like the point above if you try a resistance or intensity that is unmanageable throughout your training you will likely lose form and place stress on the vulnerable structures within your musculo-skeletal system. Find the resistance or intensity that tests you but does not result in acute system failure.  

Build that core base- In a resistance setting especially it is important that there be a base level of core strength in which the body can rely on to keep all structures stable throughout the training routine. A poor level of core stability is likely to lead to large demands being placed on the passive structures such as ligaments and intervertebral discs during exercise.

Stretch is best – many of our workplace demands these days require long periods within stationary positions. This can lead to a tightening and shortening of certain musculature structures within the body. To put it simple the muscular structures in your body works like “Ying and Yang” if something is tight or shortened then something needs to be compromised elsewhere to assist this. In addition, more recent research is demonstrating the benefits of regular stretching and its links to improved muscle strength. Make you stretch post workout, your body needs it.