Alyssa Bialowas

Research poll after research poll, male and female adults express that one of the biggest barriers they face to frequent exercise is lack of time. One common assumption is that exercise and physical activity at moderate-intensity for a long period is the superior way to burn fat and improve your overall body composition, which is heavily debated. High-intensity interval training (HIIT) is the most time-efficient form of exercise to adapt body composition and improve various health-related indices in adults at various ages.

HIIT improves body composition and improves the maximal aerobic fitness in women of all shapes and sizes, at various health and fitness levels. Five ways that HIIT improves body composition in women:

1. HIIT increases muscle oxidative capacity in overweight women;
2. Increases the capacity for fat oxidization during exercise in women;
3. Lowers cardiometabolic risk in healthy women;
4. Optimizes glycemic control in women with type II diabetes;
5. Increases exercise performance in women over the long-term.

Lets define a few these terms for clarity –

Muscle oxidative capacity – the muscle’s maximal capacity to use oxygen consumed per gram of muscle per hour. The activity of oxidative enzymes affect oxidative capacity, and these very simple enzymes play very complex roles in our mitochondria.

Fat oxidization – a process by which the stored, massive lipid molecules are broken back down into triglycerides and fatty acids (big lipid molecules breaking down into their smaller parts).

Cardiometabolic risk – chances of having diabetes, heart disease or stroke.

Glycemic control – typical levels of blood sugar in a person with diabetes.

Improvements in Muscle Oxidative Capacity, Body Composition and Exercise Performance

In a study by Gibala et al. (2013), women who stated to exercise less frequently and who are by definition overweight, participated in a long-term 15-week fitness intervention that compared moderate-intensity exercise and HIIT. HIIT was more effective than moderate-intensity continuous exercise at reducing whole body fat mass. In their fitness intervention, researchers were interested in the effects of eating a meal before or after the HIIT intervention, and found that fasted-state exercise was more effective in improving body composition, muscle oxidative capacity, and greater insulin sensitivity in overweight women.

Related Article: 90 Seconds A Day of HIIT Might Be All You Need

The study showed that skeletal muscle mitochondrial and glucose transport capacity (muscle oxidative capacity) increased over a 6-week training period. In addition, this study showed that body fat percentage in overweight women decreased following the HIIT training program. Similarly, low volume HIIT was found to increase muscle mitochondrial capacity and improves glycemic control in women with type II diabetes.

Increased Capacity for Fat Oxidation During Exercise in Women

Researchers in the field have long studied the effects of HIIT on body composition in adults. In 2007, Bonen et al. found that in moderately active women, HIIT increased the capacity for fat oxidization during exercise in only a two-week period. They studied eight women participate in seven HIIT sessions and examined mitochondrial enzyme activities, fatty acid transport proteins, skeletal muscle fuel content, and metabolic, hormonal, and cardiovascular responses to exercise. They found that exercise whole body fat oxidization increased 36% after HIIT, and after two weeks of HIIT sessions, whole body and skeletal muscle capacity for fatty acid oxidization during exercise in women.

Related Article: How HIIT Changes Our Body

No matter how old, healthy, fit, overweight, or living with a more serious health issue, HIIT improves body composition in all women and increases exercise performance in women over the long-term. This means improvements in your cardiovascular fitness and your overall health, which will boost your mental and social well-being.

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References

Bonen, A., Galloway, S., Heigenhauser, G., Spriet, L., and Talanian, J. (2007). Two weeks of high intensity aerobic interval training increases the capacity for fat oxidization during exercise in women. Journal of Applied Physiology, 102, 4, 1439-1447.

Gibala, M., Gillen, J., Ludzki, A., Percival, M., and Tarnopolsky, M. (2013). Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women. Obesity Research Journal, 21, 11, 2249-2255.