Adaptations from sprint training are not limited to speed and athletic performance.

Research shows that sprint training leads to a variety of physiological adaptations that translate into all of the following:

  • Improved athletic and functional performance
  • Reduced body fat and improved body composition
  • Improved cardiovascular health markers
  • Lower risk of diabetes
  • Enhanced cognition and brain volume
  • Lower risk of depression
  • Increased pulmonary function

What follows is a summary of each of these benefits from the literature.

Reduce Body Fat and Improve Body Composition

Excess body fat and the metabolic problems that coincide with obesity are an increasing problem worldwide. Exercise is often prescribed as a tool for reducing body fat; however, studies show that the conventional recommendations of using steady-state aerobic exercise are disappointing, being largely ineffective for reducing body fat stores (5). In comparison, studies suggest sprint training may be more effective to produce significant fat loss, especially in overweight populations (33, 54). 

When done against resistance, sprint training has been shown to increase lean mass, which helps sustain metabolic rate during fat loss (23, 50). Additionally, sprint training has been shown to increase insulin sensitivity and lower visceral abdominal fat that is linked to metabolic and heart diseases (50). One factor that contributes to these favorable effects is that sprint training improves metabolic flexibility or the body’s ability to utilize body fat for energy.

From the section on energy systems, we know that burning triglycerides via the Krebs cycle is a complicated and lengthy process (compared to the other energy system options) and the body will rely on glucose stores when not forced to adapt and increase levels of the enzymes necessary for beta-oxidation, or the process whereby fat is used for energy.  Sprint training is one way to improve this process and raise levels of enzymes involved in beta-oxidation (8). For example, in a study of overweight men, performing 6 sprint sessions over 2 weeks resulted in a 3 cm decrease in waist circumference and significant increase in lipid (fat) oxidation (55).

Improve Cardiovascular Health

Sprint training has been shown to improve markers of cardiovascular health in several ways. A study of overweight women showed increased stroke volume, which is the amount of blood ejected from the heart with each best, after 4 weeks of cycling sprint training (52). A series of studies have shown that sprint training benefits people with hypertension, who have heart disease risk factors or are recovering from a heart attack.

Using high-intensity intervals lasting 1 to 4 minutes interspersed with active recovery has been shown to lower blood pressure and convey a range of cardiovascular benefits including improved endothelial function and lower resting heart rate (10, 11). Other research shows interval training may be useful for people with family history of hypertension because it can improve arterial structure and lower chronic inflammation affecting the arteries and heart (9). Moderate-intensity interval training can even be used by heart failure patients: One study found that 3-minute intervals at as high as 80% of VO2 peak for 12 weeks resulted in greater fitness benefits and an increase in cardiac output, while lower markers of inflammation (18).

Increase Cognition & Brain Volume

The brain is a prime target for adaptations from exercise and sprint training is no exception. Studies show it can decrease inflammation in the brain, raise levels of protective hormones and improve learning. In a study of Parkinson’s patients who did moderate-intensity interval training for 8 weeks, brain health status improved, and they experienced a significant reduction in inflammation in the brain (60). Scientists believe exercise stimulates the release of Brain-Derived Neurotrophic Factor (BDNF), which acts as a hormone in the brain and aids learning, while countering oxidative stress.

Interval training has also been shown to improve the learning process. In one study, participants improved their recall of new vocabulary by 20% after interval workouts compared to a control group that did no exercise (58). Researchers theorize intense exercise raises catecholamine hormones and dopamine that stimulate the brain. 

Prevent Depression & Improve Mental Health

Exercise has been identified as a tonic for mental health, improving levels of chemical messengers that regulate mood and cognition. Interval training is no exception, raising levels of the POMC neurotransmitters (commonly known as beta-endorphins) that have a mood-raising effect (26, 59). The benefit extends to lowering risk of depression and anxiety (27, 59).

As to the ideal training intensity for protecting mental health, research is inconclusive on the impact of moderate-aerobic intervals compared to high-intensity and maximal effort sprints on depression. One study found that in university students, both interval and steady-state aerobic exercise reduced depressive symptoms. However, the interval program increased perceived stress, which could be counteractive to optimizing mental health in some populations (41).

We do know that interval training can be used for a variety of populations. In heart failure patients undergoing an aerobic interval training program, there was a significant reduction in depression that lasted after the training program ended, whereas a control group that did no exercise experienced an increase in depression after the study period completed (27). Finally, when schizophrenic patients performed a 15-minute interval training workout that used body weight exercises interspersed with rest, mood and mental health scores both improved (59). 

Increase Lung Function & Circulation

The respiratory system is not a limiting factor in supplying oxygen to working muscles, and this system experiences the fewest adaptations of all the physiological systems of the human body in response to exercise. In healthy people, lung volume, lung capacity, and respiratory rate change very little in response to training (26). However, in unhealthy individuals or those with inflammation of the respiratory system, exercise can have a substantial impact (35). In Individuals with compromised lung function such as those with emphysema, active smokers, or COPD (Chronic Obstructive Pulmonary Disorder), interval training has been shown to improve pulmonary function and respiration. In one study, COPD patients in their 80s who did a combination of strength and interval training had significant improvements in fitness and a 14% increase in the vital capacity, a marker of lung function (20).

Improve Fitness & Oxygen Consumption

Oxygen consumption (also known as VO2) is a physiological measurement of how well the body uses oxygen to power physical activity. It is used to assess aerobic endurance and overall fitness. VO2 max is the measurement of the maximum amount of oxygen that an individual can utilize during intense or maximal exercise. Theoretically, the more oxygen that can be used during intense exercise, the more ATP you can produce via the oxidative aerobic system.

Although typically used to measure aerobic capacity, studies show that even very short bursts of interval training can significantly improve VO2 max. One study that compared the effect of 5-second, 15-second, and 30-second repeated maximal effort sprints performed on a non-motorized self-propelled treadmill found that all groups improved VO2 max (36). The longer 30-second sprints produced the largest increase in VO2 max of 8.7%, whereas the 5-second sprints elicited a moderate increase of 4.3%. The scientists concluded that sprint training is a viable method for improving oxygen uptake. The peak speed generation of very short sprints sufficiently stimulates mechanisms underlying both aerobic and anaerobic adaptive response.

Increase Endurance & Work Capacity

In addition to improving VO2 max, interval training produces adaptations in the muscles that benefit for endurance athletes. Glycogen is the stored form of carbohydrates in the muscles that is used to power exercise. Interval training increases glycogen storage in the muscle by as much as 20% (26). Another benefit is an increase in muscle buffering capacity of up to 50%, which is the ability to metabolize lactate and hydrogen ions that lead to a decrease in contractile force when they accumulate (26).

Interval training also stimulates the fast-twitch muscle fibers that are not trained with lower intensity exercise, increasing speed and power capacity (26). Together these adaptations can result in faster competition times: In one study, trained cyclists who included maximal sprint workouts twice a week in training reduced time trial performance compared to a control group that continued with their regular training (12).

 

Improve Power

Power is the ability to express strength quickly. It is defined by the equation Power = Work/Time, where Work is the volume of work performed divided by the length of time it takes to complete it.

Power is an essential trait both for athletes and for the elderly who need to preserve capacity and avoid falls. For athletes training for power, the goal is to train the body to utilize the stretch-shortening cycle, which is the elastic component of the muscle. For the elderly, the purpose of training is geared at sustaining muscle, stimulating the higher threshold motor units in the muscles, and maintaining function of the central nervous system. Interval training can accomplish both, although the details of the protocols will be different and relative to the individual.

For athletes, maximal effort sprints and plyometrics that train the stretch-shortening cycle will increase power and performance. For older adults, cycle, walking, or intervals on another cardio machine can be effective. For example, in a study of life-long sedentary older men (age 62), performing cycling intervals increased power and lean muscle mass after a 6-week low-frequency training program (44).

 

RESSOURCE CENTER

Our bibliography with the latest studies about High Intensity Interval Training.