Research Review By Demetry Assimakopoulos©

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Date Posted:

June 2011

Study Title:

High Intensity Training versus Traditional Exercise Interventions for Promoting Health

Authors:

Nybo L, Sunstrup E, Jakobsen MD et al.

Author's Affiliations:

Section of Human Physiology, Department of Exercise and Sport Sciences, University of Copanhagen; Bispebjerg University Hospital, Copanhagen Denmark; the Institute of Sport Sciences and Clinical Biomechanics, University of Southern Denmark, Odense Denmark.

Publication Information:

Medicine and Science in Sport and Exercise 2010; 42(10):1951-8.

Background Information:

It is well established in exercise physiology research that prolonged moderate intensity exercise can lower the relative risk for several metabolic diseases (4,9,11,12). However, many clients and patients are dissatisfied with this treatment option because they do not have the time to properly implement such training protocols.

Many recent studies have concluded that high intensity interval (HIT) training may show similar results to prolonged moderate intensity training in increasing cardiorespiratory fitness, muscle oxidative capacity (as determined through mitochondrial enzyme activity) and many other health parameters, making HIT a time-efficient strategy for improving health.

HIT is defined as: “repeated sessions of brief, intermittent exercise performed at a high work intensity that involves single efforts that can last from a few seconds up to several minutes. [These] repeated efforts [are] separated by up to a few minutes of rest or low-intensity exercise” (7). The quality and quantity of intervals are extremely variable. They range from high volume-constant load (total volume is similar to a bout of traditional endurance exercise, only performed in intervals) to low-volume, all-out (few short bouts of extremely high intensity training that when summed together create a very low training volume).

Changes in mitochondrial content secondary to HIT have been found in literature as early as 1982 (6). Dudley et al determined that relatively intense, short duration exercise can achieve the change in mitochondrial response that can be seen in typical prolonged endurance exercise.

Similarly, Burgomaster et al (5) concluded as little as six sprint interval training sessions increased muscle oxidative potential and cycle endurance, illustrating the potency of exercise intensity for stimulating improvements in endurance exercise performance. They believe this occurred because of an increase in enzymatic efficiency outside the cell (free fatty acids and blood glucose transport through the cell membrane), inside the cell (speed of glycolysis) and inside the mitochondria (increase in speed and efficiency of many enzymes).

The same group (3) discovered that there were similar muscle glycogen utilization rates (mmol/kg of dry weight), maximal activity of mitochondrial enzymes (citrate synthase and ?-HAD), VO2peak, mean exercise heart rate, and arterial distensibility (mmHG) (13) during and after a low volume sprint interval and traditional endurance training. This further exemplified that HIT can elicit physiological responses that are comparable to prolonged moderate intensity training. While having this knowledge is valuable to personal trainers and clinicians alike, it is important to recognize that this type of exercise is not well tolerated by all populations. With this being said, trainers should pay attention to the response their clients have to their treatment.

When HIT is implemented slowly and methodically, it can be used in a number of different populations. For instance, Schjerve et al (16) compared the effects of HIT to traditional endurance exercise and strength training on improving VO2Max and cardiovascular health in obese patients. The HIT group elicited the greatest change in VO2Max and consequently, the most significant decrease in cardiovascular risk profile, post-study. Tjonna et al in their 2008 study found that HIT was superior to moderate intensity training in reversing the risk factors of metabolic syndrome over the course of 16 weeks (17). Similar results have been found in populations suffering from coronary artery disease (15) and patients undergoing chemotherapy (Adamsen et al, 2009).

Strength training is yet another exercise strategy for promoting health, developing strength and increasing lean muscle mass (10). Strength training can also facilitate osteogenesis, increase bone mass and bone mineral density, thus preventing osteoporosis. High intensity interval running could be considered high-impact exercise and could thus have a positive effect on bone mineral density (8,14). Additionally, it can have an insulin-like effect on muscles in healthy and Type 2 Diabetic patients.

In short, the goal of this study was to clarify how a HIT intervention can influence different health parameters, such as blood lipid profile, glucose tolerance, fat mass, blood pressure and other cardiovascular health markers compared to prolonged moderate intensity training and strength training.

Pertinent Results:

Both the high intensity interval training (INT) and the prolonged moderate intensity (MOD) interventions succeeded in increasing VO2Max. The INT group’s scores increased to a greater degree than the MOD group in the experimental time frame. The strength training (STR) group did not have a significant increase in VO2Max from pre- to post-treatment. The INT group’s increase in VO2Max score was significantly higher than the other two treatment groups, post-study.

Systolic blood pressure was reduced by 8mmHg in all treatment groups. Heart rate and diastolic blood pressure were decreased to a greater extent in the MOD group, than in the INT group. Capillarization remained unchanged in the INT group, but increased significantly in the MOD group. Heart rate during walking and during submaximal running reduced similarly in both the MOD and INT groups.

There was no change in fat oxidation during walking or submaximal walking in the INT group, despite an increase in cardiovascular fitness level and a decrease in rating of perceived exertion at submaximal loads. Similarly, fat oxidation did not change for any of the other groups during walking. However, fat oxidation increased during submaximal running for the MOD group.

HDL, LDL, total cholesterol and the HDL:total cholesterol level remained unchanged for the INT group. The HDL:total cholesterol level significantly decreased for the MOD group, and lowered in the STR group, but not to a statistically significant amount.

Fasting blood glucose and the concentration of blood glucose post-ingestion of 75mg of glucose (OGTT) reduced similarly in INT and MOD groups. However, these values did not change in the STR groups and the CON. There was no change in insulin levels in any of the three groups.

The MOD group showed a decrease in total body weight and an increase lean body mass. The STR group increased their body weight. No significant changes were found in any of the above categories in the INT group.

Clinical Application & Conclusions:

  • High intensity interval training is effective for improving cardiorespiratory fitness and glucose tolerance in untrained subjects. Training intensity is more important than training volume for increasing cardiovascular fitness.
  • High intensity interval training also has a positive effect on systolic blood pressure, creating yet another way to counteract the onset of hypertension. However, it was not more effective than prolonged moderate intensity training or strength training. The clinical result of a decrease in systolic blood pressure and mean arterial pressure is independent of the improvement in cardiovascular fitness.
  • High intensity interval training is less effective than prolonged moderate intensity training and strength training at treating obesity and hyperlipidemia.
  • Strength training is more effective at increasing lean body mass and bone mass, than high intensity interval training.
  • Prolonged training appears to be most efficient at improving lipoprotein levels (9). This means that training volume may be more important than training intensity at changing one’s blood lipid profile. These results relate to the greater decrease in body fat elicited by the MOD group, as opposed to the INT group.
  • For individuals diagnosed with the metabolic syndrome and overweight patients, integrating high intensity training into an exercise program is more effective than a program that only includes prolonged moderate intensity physical activity.
  • High intensity training with a lower training volume is as effective at improving glucose tolerance when compared to moderate intensity training with a higher training volume. When the training intensity is close to maximum, at least 40 minutes of training per week is needed to elicit the same results as training for 150 minutes per week at a moderate intensity.
  • Lean bone and muscle mass increased after strength training. They did not improve after high intensity interval or prolonged moderate intensity training.

Study Methods:

The study consisted of 36 untrained men who had not participated in regular physical exercise for at least 2 years. They were a mean age of 31 years, non-smokers and without any diagnosis of cardiovascular or metabolic disease.

The participants were separated into 4 groups: 1) those who had to perform high intensity interval running (INT; n = 8); 2) those who performed strength training (STR; n=8); 3) those who performed continuous running at a moderate intensity (MOD; n=9); 4) a control group who performed no exercise (CON; n=11). The participants who were randomly selected into one of the exercise groups completed a 12 week training regimen. Those in the control group went about their lives normally for the duration of the study. Prior to and after the intervention, the study participants were subjected to an exercise test, an oral glucose tolerance test (OGTT), measurements of blood pressure and blood lipid profile, and a muscle biopsy test to determine capiliarization and metabolic enzyme concentration levels.

Outside of the training, the individuals assigned to the 3 experimental groups were asked to function about their normal lives. However, before days where tests were being performed, the subjects were asked to refrain from imbibing alcohol and exercise participation for 48 hours before the resting measurements were taken.

Measurement and testing:

The subjects were familiarized to the blood pressure and exercise tests prior to their administration .Fasting glucose, lipoproteins, resting heart rate, and blood pressure measurements were all taken in a fasted state. Furthermore, mean arterial pressure was determined using the equation: (1/3 x systolic pressure) + (2/3 x diastolic pressure).

Exercise testing:

A standardized treadmill test was performed. It consisted of 6 minutes of walking at a speed of 6.5 km/h and 6 minutes of submaximal running at an intensity of 9.6 km/h. This was followed by a 15 minute rest period. After this rest period, an incremental running test was performed until exhaustion. Oxygen consumption and respiratory exchange ratio were measured during the last 3 minutes of walking and subsequently during the last 3 minutes of treadmill running. VO2Max (maximal oxygen consumption) and maximal heart rate were defined as the peak value reached during the incremental running test. Respiratory exchange ratio and steady state VO2 were used to determine fat oxidation levels. These measurements were done during walking at 6.5 km/h and during submaximal running at 9.5 km/h.

Oral glucose tolerance test (OGTT) and muscle biopsies:

The subjects fasted for 24 hours and refrained from vigorous exercise for 48 hours prior to the test. Prior to the OGTT blood was extracted for the purposes of measuring fasting insulin, glucose levels, plasma fatty acids, HDL cholesterol and plasma triglyceride concentrations. Venous blood was extracted from the anti-cubital vein prior to and 15, 30, 60, 90 and 120 minutes after ingestion of 75 g of glucose. In addition to these measurements, body weight and bone density (using dual x-ray absorptometry) were measured.

Muscle biopsies were taken from the vastus lateralis, prior to and post-training. These were analyzed for capillaries, maximal citrate synthase and beta-hyroxyacyl-CoA dehydrogenase activity using histochemistry.

Training protocol:

All training groups exercised 3 times a week, save the INT group, who only participated in an average of 2±.01 sessions per week (INT total exercise time over the course if 12 weeks was 480 minutes). Those in the high-intensity training group first warmed-up with 5 minutes of light jogging. The warm up was followed by 5 intervals of running at 95% of their max heart rate (this measurement was taken at the end of the 2 minute bout).

Those who were selected to the MOD group performed 1 hour of continuous running at 80% of their heart rate max (this translates to approximately 65% of VO2Max). This amount of training corresponded to a total training time of approximately 1800 minutes.

Subjects allotted to the STR group performed 60 minutes of exercise, 3-4 sets of 12-16 reps for the first 4 weeks, then 6-10 reps for the following 8 weeks. Each set was followed by 1 minute of rest. This protocol was followed for a total of 12 weeks. The exercise protocol consisted of squats, hack squats, incline leg press, isolated knee extension, hamstring curls and calf raises. The individual loads were changed to match progressions in muscular strength. The average heart rate over the course of the exercise bout was approximately 50% of max heart rate.

Study Strengths / Weaknesses:

Weaknesses:
  • How were VO2Max and RER determined? The methods for determining either of these were not described.
  • The small number of participants does not permit the conclusion that high intensity interval training is less or as effective than prolonged moderate intensity training at lowering blood pressure and mean arterial pressure or at increasing fat oxidation enzyme activity. With more subjects, the researchers may have found different results.
  • There were only 2 measurement points – one at the beginning and one at the end. More data points are needed to truly understand the relationship between exercise and the dependant variables.
  • Cardiac output during exercise was not measured. The results lent themselves to an increase in cardiorespiratory fitness via cellular means. To gain a true understanding of this topic, oxygen transport needs to be examined as well.
Strengths:
  • There were a number of different variables that were examined
  • The length of the study was sufficient to elicit cardiovascular changes

Additional References:

  1. Adamsen L, Quist M, Andersen C, Møller T, Herrstedt J, Kronborg D, Baadsgaard MT, Vistisen K, Midtgaard J, Christiansen B, Stage M, Kronborg MT, Rørth M. Effect of a multimodal high intensity exercise intervention in cancer patients undergoing chemotherapy: randomised controlled trial. BMJ Oct 13, 339: B3410, 2009.
  2. Babraj JA, Vollaard NB, Keast C, Guppy FM, Cottrell G, Timmons JA. Extremely short duration high intensity interval training substantially improves insulin action in young healthy males. BMC Endocr Disord. 2009;9:3–11.
  3. Burgomaster KA, Hughes SC, Heigenhauser GJF, Bradwell SN & Gibala MJ. Six session of sprint interval training increases muscle oxidative potential and cycle endurance capacity in humans. J Appl Physiol, 2005. 98: 1985-1990.
  4. Burgomaster KA, Howarth KR, Phillips SM, Rakobowchuk M, MacDonald SL & Gibala MJ. Similar metabolic adaptation during exercise after low volume sprint interval and traditional endurance training humans. J Physiol. 2008. 586: 151-160.
  5. Booth FW, Winder WW. Highlighted topic: Role of exercise in reducing the risk of diabetes and obesity. J Appl Physiol. 2005; 99(1):3–4.
  6. Dudley GA, Abraham WM & Terjung RL. Influence of exercise intensity and duration on biochemical adaptations in skeletal muscle. J Appl Physiol 1982: 53: 844-850.
  7. Giballa M., Ontario Society for Health and Fitness H&M: General Meeting of Members. November 2009.
  8. Guadalupe-Grau A, Fuentes T, Guerra B, Calbet JA. Exercise and bone mass in adults. Sports Med. 2009;39(6):439–68.
  9. Hawley JA. Exercise as a therapeutic intervention for the prevention and treatment of insulin resistance. Diabetes Metab Res Rev. 2004;20:383–93.
  10. Knuttgen HG. Strength training and aerobic exercise: comparison and contrast. J Strength Cond Res. 2007;21(3):973–8.
  11. Paffenbarger RJ, Hyde R, Wing A, Lee I, Jung D, Kampert J. The association of changes in physical-activity level and other lifestyle characteristics with mortality among men. N Engl J Med.1993;328(8):538–45.
  12. Pedersen BK, Saltin B. Evidence for prescribing exercise as therapy in chronic disease. Scand J Med Sci Sports. 2006;16(suppl 1): 3–63.
  13. Rakobowchuk M, Tanguay S, Burgomaster SA, Howarth KA, Gibala MJ & MacDonald MJ Sprint interval and traditional endurance training induce similar improvements in peripheral arterial stiffness and flow mediated dilation in humans. Am J Physiol Regul Integr Comp Physiol 295:R236-R242, 2008.
  14. Rector RS, Rogers R, Ruebel M, Widzer MO, Hinton PS. Lean body mass and weight-bearing activity in the prediction of bone mineral density in physically active men. J Strength Cond Res. 2009;23(2):427–35.
  15. Rognmo Ø, Hetland E, Helgerud J, Hoff J & Slørdahl SA. High intensity aerobic interval exercise is superior to moderate intensity exercise for increasing aerobic capacity in patients with coronary artery disease. Eur J Cardiovasc Prevention Rehab 11: 216-222, 2004.
  16. Schjerve IA, Tyldum GA, Tjonna AE , Stolen T, Loennechen JP, Hansen HEM, Haram PM, Heinrichs G, Bye A, Najjars SM, Smith GL, Slordahl SA, Kemi OJ & Wisloff U. Both aerobic endurance and strength training programs improve cardiovascular health in obese adults Clin Sci 115: 283-293, 2008.
  17. Tjonna AE, Lee SJ, Rognmo O, Stolen TO, Bye A, Haram PM, Loennechen JP, Al-Share QY, Skogvoll E, Slordahl SL, Kemi OJ, Najjar SM & Wisloff U. Aerobic Interval Training Versus Continuous Moderate Exercise as a Treatment for the Metabolic Syndrome Circulation 118: 246-354, 2008.