1. It’s not as effective for weight loss
“HIIT does not appear to be as effective as moderate-intensity continuous exercise in reducing body weight,” says Dr Paul Chiam, senior consultant cardiologist at The Heart & Vascular Centre.
It is important to keep in mind that a combination of high-intensity workouts, strength training and a healthy diet is the best way to achieve weight loss. In addition, a study in the American Journal of Clinical Nutrition found that people ate
more after a high-intensity session than those who did lower-intensity exercise.
Dr Chiam also adds that there is some evidence that high-intensity workouts may not be as effective in improving lipid (cholesterol) profiles compared with moderate intensity exercises.
2. It could worsen existing heart problems
High-intensity workouts are not advisable for those with pre-existing heart conditions. According to Dr Chiam, this includes those with narrowing or blockages in the arteries, those who’ve had heart attacks, have had previous heart artery angioplasty or bypass surgery, and those with heart muscle disease.
This goes for people with undiagnosed heart diseases as well. If you are worried or unsure if you have a condition, you should consult your physician for a health assessment.
Dr Chiam also notes that there is a “theoretical higher risk” of a heart attack when engaging in high-intensity exercise. “The intense bursts of exercise at or near maximum capacity place the heart under great stress.” However, in healthy individuals, the chance of a heart attack is rare.
3. It could raise your blood pressure
“Patients with high blood pressure should also avoid this kind of exercise regimen as the intense bursts of exercise raise blood pressure significantly,” says Dr Chiam.
When doing high-intensity exercise, your heart works harder and your blood pressure rises. In healthy and fit individuals, this usually occurs for a short period and blood pressure returns to normal.
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If you have high blood pressure, your physician may first put you on medication to lower it. Those with very high blood pressure should consult their physicians before attempting any new exercises.
4. You run the risk of injury
HIIT involves alternating short periods of intense anaerobic exercise with less-intense recovery periods. “An example would be to perform short bursts of hard sprinting alternating with short periods of jogging. This would not be suitable for everyone,” says Dr Chiam.
“The intense bursts of exercise at maximum or near maximum exercise capacity, for example during sprinting, may increase the risk of sports injuries,” he says.
While the exercise itself may not be inherently dangerous, poorly executed workouts can be harmful. If you’re doing a HIIT exercise class at the gym, make sure to follow your trainer’s instructions and avoid trying complex moves without supervision.
Dr Chiam also advises those who are prone to skeletal, joint and muscle injuries or those with skeletal and joint deformities to avoid high-intensity exercise.
5. You’re overexerting your body
People often make the mistake of trying to push themselves too hard during exercise. If you feel the workout is overly strenuous, dial it down, or, if it’s an exercise clasee, let your trainer know so you can go at a pace that is challenging but not pushing you over your limits.
Make sure you get adequate sleep, food and hydration before heading for an intense workout.
Overexertion could lead to undesirable effects. “If the person experiences severe giddiness, vomiting or severe chest pain that persists after completion of the exercise, medical advice should be sought,” says Dr Chiam.