Finding time to exercise

Weight loss

Researchers from Australia conducted a research review investigating the effects of high-intensity interval training (HIIT) on fat mass, VO2 Max (a measure of aerobic fitness) and insulin sensitivity. Reduced insulin sensitivity results in consistently high blood sugar, which can lead to type 2 diabetes.

The studies included in the review varied slightly in their interventions, but typically participants completed short bursts of exercise for 30 seconds, 3 times a day, 3 times a week for 2-24 weeks. The exercise was either running on a treadmill or cycling on a stationary bike. Findings demonstrated that fat mass significantly decreased, VO2 max increased, and insulin sensitivity increased.

But how does HIIT compare to less intense, longer periods of exercise, such as running? One clinical trial compared:

A) Control group (little exercise)

B) HIIT group (3 weekly 20-minute workout sessions of HIIT)

C) Steady exercise (3 weekly 40-minute workout sessions of cardio)

over 15 weeks and measured the impact on weight. They found that both group A) and C) demonstrated no weight loss, whereas the average weight loss in group B) was over 2kg and significantly more than the other groups. Groups B) and C) showed an increase in VO2 max.

A potential explanation for these findings is that HIIT has a positive impact on certain stress hormones released by the kidney that accelerate fat oxidation. This means HIIT might encourage your body to ‘burn’ more fat over regular aerobic exercise. So, any form of exercise can improve your fitness levels but if weight loss is your goal, HIIT could be more effective than longer, less intense periods of exercise.

 

Key points:

• All types of exercise are beneficial for your fitness and health.
• Short bursts of high-intensity exercise are more effective for weight loss than longer periods of less intense exercise. 

Blood sugar control

Blood sugar levels are controlled by the hormone insulin. Insulin regulates blood glucose (sugar) levels by signalling to the body to remove glucose from the blood and store it as glycogen in our muscles and liver for when we need it. If our bodies become resistant to insulin and blood glucose levels are consistently high, there is a risk of developing type 2 diabetes.

The trial mentioned above demonstrated how HIIT improved insulin sensitivity. The more sensitive we are to insulin, the better our blood glucose control.

The changes in insulin sensitivity were significantly related to the changes in weight. Since insulin resistance and weight gain are usually interlinked, HIIT has huge potential benefits for those with prediabetes or type 2 diabetes.

Key point:

• Short bursts of high-intensity exercise positively impact blood sugar levels.

Heart health

The British Medical Journal published a large meta-analysis of research that compared HIIT with lower-intensity, longer periods of exercise in individuals living with chronic diseases where unhealthy lifestyle was the main contributing factor (such as type 2 diabetes). Results indicated that HIIT was more beneficial to heart health than lower-intensity, longer periods of exercise.

The researches suggested that stiffness of the arteries plays a large part in cardiovascular problems (heart attacks, strokes etc). They suggested that when the short bursts of exercise are of a high enough intensity, it promotes elasticity of the arteries, which in turn reduces the risk of heart attacks and strokes. This was supported by numerous studies in the review that found increased nitric oxide release in HIIT groups, which seems to promote elasticity of the arteries.

Key point:

• Short bursts of high-intensity exercise may reduce the risk of cardiovascular problems more than longer periods of less intense exercise. 

How to incorporate HIIT into your day

Whether you exercise regularly or are completely new to it, below are some simple ways to include short bursts of exercise into your daily routine.

Beginner

The moment you wake: star jumps – 1 minute

Mid-morning coffee: wall push-ups (edge of table/kitchen counter/wall) – 1 minute

Lunch break: squats – 1 minute

When you get home: jogging on the spot – 1 minute

Intermediate

The moment you wake: mountain climbers – 1 minute

Mid-morning coffee: push-ups – 1 minute

Lunch break: squat jumps – 1 minute

When you get home: running on the spot – 1 minute

Advanced

The moment you wake: crossover mountain climbers – 1 minute

Mid-morning coffee: push-ups with clap – 1 minute

Lunch break: lunge jumps – 1 minute

When you get home: burpees – 1 minute

Take home message

• It is a myth that you have to exercise for long periods of time for it to be effective.
• Shorter, more intense bursts of exercise appear to be more effective for weight loss,  blood glucose control, and heart health.
• It is easy to fit in small amounts of HIIT exercise throughout the day by doing as little as a minute here and there.