The benefits of high-intensity exercises



If your primary goal is fat loss and you are lacking spare time, nutritionist, trainer and online coach Brooke Turner suggests opting for HIIT classes or programming.

“Higher-intensity training can help you burn more calories in a shorter period of time, while also providing an EPOC (excess post oxygen consumption) or afterburn effect to continue expending energy even after the workout is over,” she says. EPOC is a result of excess oxygen being needed to restore muscle glycogen and to rebuild damaged muscle proteins following an intense session. The result is added calorie burn from the comfort of your couch.   

“The EPOC effect can last up to 12 hours, with some research indicating that there are benefits up to 48 hours after a workout. This leads to a raised metabolism following a session,” adds Turner.

Training which combines heavier lifts with cardiovascular work – such as free-weight boot camps, CrossFit and F45 – may aid in building stamina, strength and power for the right person. Those prone to injury, or beginners lacking proper technique, are generally advised to stick to a less frantic weight training regimen.

“CrossFit workouts are varied functional movements performed at high-intensity, so you can expect to see improvements in all fitness domains. This includes stamina, strength, coordination, flexibility, power, speed, agility, balance, accuracy and endurance,” says trainer and manager of Hive Active, Inshan Sheriff.


“CrossFit programming is constantly varied – you will never have to repeat the same session. This avoids plateau and ensures the body is challenged regularly, encouraging favourable adaptations in the fitness domains and in general health,” says CrossFit competitor and trainer, Isabelle Gosling, who stands by CrossFit as a great mode to build both strength and endurance.

“Once you can move safely and consistently through a range of functional movements, we can increase the intensity of your workouts. Improving intensity or power output allows you to move faster and lift heavier loads without the fear of plateauing. It also has the added benefits of increasing strength, performance, muscle mass and bone density.

Despite its benefits, you shouldn’t ignore your own fitness levels or training needs when it comes to high-intensity weight programming. Class sizes are often large, meaning coaches can miss technique issues or not properly address your individual goals – whether that be building strength and lean muscle mass, improving body composition, staying fit or having fun. Be sure to find classes where your program is tailored.

“CrossFit is a highly-refined system of exercises and training programs that are geared toward the more experienced athlete,” says certified personal trainer and nutritionist, Alex Stewart.

Progression is also an issue. While it’s true that variety can guard against plateaus to some extent, be careful if you are relying on high-intensity weight training alone for a toned physique. Controlled movement patterns concentrating on time under tension – or the amount of time your muscles are under strain during a weight lifting set –have been shown to have benefits for muscle hypertrophy without the same risk of injury. A recent study published in Frontiers in Physiology found that accentuated eccentric loading (AEL) – which involves lowering a weight slowly during the lengthening of the muscle, rather than letting it drop – might be more effective in avoiding a plateau then changing a program week to week.Scientists conducted a ten-week experiment involving three strength-training groups, with the AEL programming noting an increase in force production, work capacity, muscle activation and resistance compared to the other methods.


“HIIT can work to improve your anaerobic capacity and increase your metabolism. The high energy output and short duration recovery involved with HIIT means it is effective for achieving fat loss with the added benefit of improving fitness levels,” says Turner.

“A liploytic effect occurs within the body through the oxidative stress created from a HIIT session. This stress stimulates the release of fat stored in fat cells such as cortisol. Ultimately, fat cells get the message to release stored fat to be turned back into glycogen and burned as fuel.”

And there is research to back it up. A study led by researchers of the University of Wisconsin collected heart rate and perceived exertion data of moderate to very fit women doing two different popular CrossFit workouts. The study found that calorie expenditure averaged 117.2 calories for the first workout and 63.9 calories for the second, with heart rates elevated to an average of 90 per cent and maintained throughout the session. Fitness industry guidelines suggest maintaining a maximum heart rate of 64 to 94 per cent in order to improve cardio endurance, supporting the claim that CrossFit both burns calories and improves aerobic fitness.

On the flip side, one study published by the University of Stirling found that doing fewer reps during high-intensity workouts might lead to improved fitness results: so if weightloss is your primary goal it may be worth opting for a shorter workout, such as BlockFIT.

“It’s based on a functional interval training approach to maximise post workout burning of body fat and address factors such as strength, power, agility and mobility, and address any imbalances, restrictions or weaknesses,” explains managing director of BlockFIT Anna Block.

“Using rival movement patterns and interchanging periods of work and rest, this type of training is known as the most effective and efficient way to lose overall body fat. You don’t need longer than 30 to 45 minutes, and congruent with the level of intensity, a single workout can have the effect of burning body fat for up to 24 hours afterwards.”


If you’re prone to injury, try mixing up your exercise regime with both low- and high-intensity workout sessions to aid recovery – don’t CrossFit six days a week.

“Incorporating too many high-intensity sessions per week can increase the risk of raising your cortisol levels and placing undue stress on the body. Raised levels of this hormone impede fat loss goals,” warns Turner.

“Over-training can lead to injury, increased cortisol levels and in turn can actually lead to weight gain (particularly through your waist) or a decline in the rate at which you reach you fat loss goals.”


“Incorporate a mix of HIIT and lower- intensity sessions into your weekly training programs for maximal results,” says Turner. In other words, work CrossFit or similar high-intensity classes into a more structured, balanced program.

“Periodise or cycle your weights program – try for two weeks at a high weight and low volume, then two weeks low weight and high volume. Progressive overload as you adapt to one weight and your strength increases, can help to keep you improving your strength and avoid reaching a plateau,” says Turner.

Prioritise sleep each night to aid aforementioned recovery.

“Sleep plays a key role in fat loss and is the time in which your body repairs itself,” says Turner.