High Intensity Interval Training | Benefits of exercise on Coronary Heart Disease (CHD)

WHAT IS HIIT?

High intensity interval training, or HIIT, is a workout that alternates between intense burst of activity, with fixed periods of less intense activity. It is a form of cardiovascular exercise, which should have short periods of vigorous exercise to make heart rate speed up (Mayoclinichealthsystem.org, 2019).

This form of exercise became mainstream around a decade ago, after physiologists revealed that it could bring significant health benefits (Vox, 2019).

One asset is the improved cardiovascular health and fitness. “HIIT Cardiovascular training is designed to develop a healthier heart and circulatory system”, mentioned by Howard Knuttgen, who is a research associate in physical medicine (Publishing, 2019)

Other benefits include burning a lot of calories in a short space of time, which makes it more efficient. Another is weight loss. One study concluded that doing HIIT three times a week, 20 minutes per workout, had lost 2kgs of body fat in 12 weeks, with no dietary changes (Cross, 2006).

SUGGESTED WORKOUT ROUTINES

ROUTINE COMBINATIONS	REPITITION
30 seconds sprints + 30 seconds rest	10 times
45 seconds jumping jacks + 15 seconds rest	12 times
TABATA STYLE – 20 seconds of work + 10 seconds rest	4 mins

Figure 1– Examples of workout combinations which are repeated multiple times which will range from a duration of 10 to 30 minutes per day. (Healthline, 2019)

Tabata style training is a form of HIIT that consists of 8 ‘rounds’ of an exercise routine which is specifically 20 second ‘on’ and a 10 second ‘off’ method. The total duration of this style is 4mins. (Bodybuilding.com, 2019)

An intensive workout will range from 30 seconds to 3 minutes with short recovery periods from 1 to 5 minutes. During the workout, the heart rate will work between 80-100% (this can be checked through a Fitbit app)(Mayoclinichealthsystem.org, 2019).

It is recommended by the Mayo Clinic that every individual do at least 20-30 minutes’ worth of exercise 5 days a week. If someone has a health condition or not used to HIIT, it is good to work their way up slowly by involving moderate intensity exercise in their first few weeks.

“For optimal heart health, add in two to three days of interval training a week” says Chip Gay (Mayoclinichealthsystem.org, 2019)

EFFECT OF HIIT ON THE HEART

HIIT is powerful as it can reduce the risk of blood clots, and even prevent coronary heart disease. According to recent research, the strength of the heart is built by increasing the pumping capacity. “In order to increase the strength of any muscle, you have to stress it” – Paul Robbins, Specialist with Athletes’ Performance (Google.com, 2019).

CASE STUDY

This study was conducted to investigate the effect of exercise intensity on CHD and cardiorespiratory fitness. 64 men, aged 30-45 who lead a sedentary life were chosen to participate. Participants were all from Canterbury, UK. This investigation was approved by the East Kent Hospitals Local Research committee and the men signed a consent form.

Tested factors – VO2 max, lipid, lipoprotein and fibrinogen concentrations.

Participants were told to maintain their normal dietary habits, and training exercises were prescribed monthly, after a fitness test of all factors. (Physiology.org, 2019)

Figure 2 – Chart which shows the randomised allocation of each of the participants into the Control, Moderate intensity, and High intensity category for investigation. At the end, 42 participants completed the study. (Physiology.org, 2019)

Figure 3 – The VO2 max man value for moderate intensity group ( ·,n = 14) and high intensity group (○,n = 13). (Physiology.org, 2019)

The cardiorespiratory fitness did not alter for the control group, and figure 3 shows the increase in VO2 max between the other two groups. After 24 weeks, the VO2 max increased by 0.38 ±0.14 l/min for the moderate intensity group, and by 0.55 ±0.27 l/min for the HIIT group. After doing repeated measures of analysis for the variance, there has been a significant correlation between the VO2 max score and exercise group (F = 3.37, P < 0.05). This result indicates that VO2 max responded differently amongst both the groups. (Physiology.org, 2019)

Benefit – Doing HIIT, there is an Increase in VO2 max indicating that the oxygen uptake from the body, gets delivered to the muscles of the heart and body, allowing more blood flow, and giving energy during exercise. It also increases the body’s metabolism up to 24 hours after doing intense exercise. (Bicycling, 2019)

Figure 4 – Measurements of cholesterol, Triglycerides and fibrinogen before and after the study. (Physiology.org, 2019)

Significant changes after 24 weeks were observed in HIIT group (P < 0.05). Significant decrease in total cholesterol (-0.55 ±0.81 mmol/l) and LDL (-0.52 ±0.80 mmol/l). This data suggests that HIIT is more effective in improving cardiorespiratory fitness than moderate intensity training. It also suggests that CHD risk factors are dependent on exercise intensity.

What could be improved from this study?

As well as male participants, females could have been included in this study, to assess if there is a difference in response of exercise intensity on CHD.
More participants, at least 1000 would have given a lot more data to conclude the study and give a more accurate set of results.
These results are for a particular age group, having different age range groups could show if age has a significant effect on the ability of doing HIIT for CHD.
This study consists of participants of one area in the UK. An ethnic/area diversity should be used to increase validity.

Unlike this study, another study by Paul T. Williams showed that CHD is independent of HIIT as part of the National Runners Health Study. Results suggested that the adjustment for physical activity had little effect on the decrease of CHD deaths. He argues that cardio fitness is a CHD risk factor however, largely independent of physical activity, in which more tests and clinical screenings are warranted (Garcia-Gathright et al., 2015).

IS IT SAFE?

Research on HIIT is encouraging, especially for heart patients and older adults. Cardiac rehab is vital for heart patients. Through a HIIT scheme, patients can improve their health conditions. Before starting it, heart patients and people with low fitness must check with the doctors to ensure they are fit enough/what kind of regime is best (Vox, 2019).

Written by Soummeiya Nithiananthan (17829788)

References

Aamot, I., Forbord, S., Gustad, K., Løckra, V., Stensen, A., Berg, A., Dalen, H., Karlsen, T. and Støylen, A. (2013). Home-based versus hospital-based high-intensity interval training in cardiac rehabilitation: a randomized study. European Journal of Preventive Cardiology, 21(9), pp.1070-1078.

Bicycling. (2019). Performing Intervals Twice a Week Can Help You Live Longer. [online] Available at: https://www.bicycling.com/health-nutrition/a27105274/higher-fitness-linked-to-lower-death-heart-disease/ [Accessed 13 Dec. 2019].

Bodybuilding.com. (2019). Ask The Ripped Dude: What The Heck Is Tabata Training? | Bodybuilding.com. [online] Available at: https://www.bodybuilding.com/content/ask-the-ripped-dude-what-the-heck-is-tabata-training.html [Accessed 13 Dec. 2019].

Cross, J. (2006). MEDLINE, PubMed, PubMed Central, and the NLM. Editors’ Bulletin, 2(1), pp.1-5.

Garcia-Gathright, J., Oh, A., Abarca, P., Han, M., Sago, W., Spiegel, M., Wolf, B., Garon, E., Bui, A. and Aberle, D. (2015). Representing and extracting lung cancer study metadata: Study objective and study design. Computers in Biology and Medicine, 58, pp.63-72.

Google.com. (2019). [online] Available at: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=2ahUKEwiOpLvoqqvmAhUdQRUIHVp6CKgQFjAEegQIDRAJ&url=https%3A%2F%2Fbestlifeonline.com%2Fhiit-workout-heart-health%2F&usg=AOvVaw1DCEmqVCUT1rOerXqS-ycj [Accessed 13 Dec. 2019].

Healthline. (2019). 7 Benefits of High-Intensity Interval Training (HIIT). [online] Available at: https://www.healthline.com/nutrition/benefits-of-hiit#section1 [Accessed 13 Dec. 2019].

Mayoclinichealthsystem.org. (2019). Interval training for heart health – Mayo Clinic Health System. [online] Available at: https://mayoclinichealthsystem.org/hometown-health/speaking-of-health/interval-training-for-heart-health [Accessed 13 Dec. 2019].

Nuffieldhealth.com. (2019). What is HIIT training? | Nuffield Health. [online] Available at: https://www.nuffieldhealth.com/article/what-is-hiit-training [Accessed 13 Dec. 2019].

Physiology.org. (2019). Changes in cardiorespiratory fitness and coronary heart disease risk factors following 24 wk of moderate- or high-intensity exercise of equal energy cost | Journal of Applied Physiology. [online] Available at: https://www.physiology.org/doi/full/10.1152/japplphysiol.01310.2004 [Accessed 13 Dec. 2019].

Publishing, H. (2019). Interval training for a stronger heart – Harvard Health. [online] Harvard Health. Available at: https://www.health.harvard.edu/exercise-and-fitness/interval-training-for-a-stronger-heart [Accessed 13 Dec. 2019].

Tucker, A. (2019). A Sweaty 24-Minute Cardio Workout You Can Do In Your Living Room. [online] SELF. Available at: https://www.self.com/story/a-sweaty-24-minute-cardio-workout-you-can-do-in-your-living-room# [Accessed 13 Dec. 2019].

Vox. (2019). How to get the most out of your exercise time, according to science. [online] Available at: https://www.vox.com/science-and-health/2019/1/10/18148463/high-intensity-interval-training-hiit-orangetheory [Accessed 13 Dec. 2019].