By Jon-Erik Kawamoto
Very little is considered new or radical in the fitness industry these days. Most of the training and programming parameters such as progressive overload, specificity of training and the principle of reversibility have stood the test of time. Training concepts may come and go, but we always seem to fall back on what works best or what proves to be better.
Putting a HIT on Aerobic Exercise
A prime example is long slow distance training or aerobic exercise. Once believed as the go-to training method for fat loss, low intensity training has since been bumped from the top spot and replaced with high intensity training, also known as high-intensity interval training (HIT) or burst training. Commonly associated with cyclical-type exercises, like running and cycling , HIT incorporates hard and easy periods of high and low intensity efforts.
Regular performance of HIT-type workouts have been shown to be effective at reducing body fat, however, “the mechanisms underlying the fat reduction…are undetermined but may include [HIT]-induced fat oxidation during and after exercise and suppressed appetite” . HIT has been found to significantly lower insulin resistance, which increases the body’s capacity for fat oxidation , which basically means, you’re better able at utilizing fat for fuel during workouts (depending on exercise intensity) and in the recovery period, post workout.
Not only great for fat loss, but regular performance of HIT has been shown to enhance both aerobic and anaerobic energy systems simultaneously. HIT has been touted as a time-efficient training strategy because it takes less total time to induce similar metabolic adaptations that are comparable with longer duration endurance-type training [2,3]. For example, similar improvements in work capacity can result from workouts consisting of multiple Wingate Tests, which involves 30-seconds of maximal cycling on a specialized upright bike, performed for several weeks, compared to higher volume, lower intensity aerobic workouts .
It’s Circuit Training, Not Crossfit
Combing two or more exercises together like burpees and deadlifts or chin-ups and kettlebell swings is not “doing” Crossfit; it’s circuit training. Hamilton Nolan said it best in an article he wrote for Gawker.com, “You can’t trademark working out, you #&%kers…you don’t own that sh*t” . Besides, according to Mel Siff , circuit training appeared to be formalized way back in 1953 by R. Morgan and G. Adamson at the University of Leeds in England, meaning that it was around long before Crossfit.
Anyways, considered a complete training system, circuit training is used to develop strength and cardiovascular endurance simultaneously because it involves pairing two or more resistance training exercises together. Since we like making acronyms in the fitness industry, circuit training with minimal breaks is referred to as HIRT (high-intensity interval resistance training)  or HIPT, (high-intensity power training)  in the literature. HIRT and HIPT basically share the same concept where moderately heavy resistance training exercises are paired together with minimal prescribed rest periods, with the goal of maintaining a high power output throughout the duration of the workout [6,7].
Similar to HIT, HIRT and HIPT (follow me here) have all been shown to be effective at improving body composition by increasing the energy required for post-exercise metabolism [6, 7], otherwise known as EPOC (excess post-exercise oxygen consumption) (told you about all the acronyms). However, I’ll take a step back and state that research seems to be equivocal regarding the effects of resistance training on the duration of EPOC as there is hardly any consistency in the resistance training protocols between studies.
Regardless, exercise intensity and duration seem to be very influential factors at determining EPOC duration and magnitude  and it appears that compound exercises performed in a circuit style fashion that focus on loads geared toward muscle building (10-repetition maximum) may optimize post workout metabolism and increase EPOC for several hours , thus leading to more calories burned overall.
Back in 2005, Charles Staley came out with Muscle Logic: Escalating Density Training  – a simple yet effective training system involving high intensity circuit-style training designed to ramp up the calorie burn and your work capacity, all while preserving or increasing muscle mass. Later in 2013, John Romaniello and Adam Bornstein incorporated their version of density training in their New York Times best seller, Man 2.0, Engineering the Alpha .
Essentially, two exercises are performed back to back for a given amount of time. The time frames can vary, but Staley originally planned for 15-minute sets. The recommended weight used is equal to your 10-repetition maximum (RM) but only 5-repetitions are performed in each set. The plan is to go back and forth, performing 5-reps of each exercise, until the time period is over. You would keep track of how many times you go through the circuit and focus on trying to beat that number, without changing the weights, the next time you do that same workout, hence the title, escalating density training.
Hybrid Density Training
Taking the density training approach to the next level, I like to add a 3rd exercise, a 20-second all out sprint. In essence, it’s HIT + HIPT = super high-intensity interval training or SHIT for short (see what I did there??). All jokes aside, the sprint can be performed on a treadmill, spin bike, air dyne bike, prowler, rower or versa climber.
Taking similar parameters from Staley, here’s a template of my Hybrid Density Training (HDT) circuit:
A1. Lower Body Exercise 10 RM - 5 reps
A2. Upper Body Exercise 10 RM - 5 reps
A3. Cardio Sprint 20-sec
Parameters: Repeat A1 through A3 for 20-minutes – I suggest longer than 15-minutes because there are now 3 exercises to cycle through. Keep track of how many rounds you complete.
And here’s a sample workout using the above template:
Circuit A: HDT Circuit
A1. Conventional Deadlift 10 RM – 5 reps
A2. Barbell Bench Press 10 RM – 5 reps
A3. Treadmill Sprint 20-sec
Perform A1 through A3 with minimal rest periods. Keep your form tight and don’t be a hero. Repeat for 20 total minutes and record how many rounds you complete. Try to beat the number of rounds you completed the next time you perform this workout (keeping the weight and treadmill settings the same).
Circuit B: HDT Circuit
B1. High Bar Back Squat 10 RM – 5 reps
B2. Barbell Press 10 RM – 5 reps
B3. Air Dyne Sprint 20-sec
Perform B1 through B3 with minimal rest periods. Keep your form tight and don’t be a hero. Repeat for 20 total minutes and record how many rounds you complete. Try to beat the number of rounds you completed the next time you perform this workout (keeping the weight and air dyne settings the same).
Circuit C*: Density Circuit
C1. Biceps Barbell Curl 10 RM – 5 reps
C2. Decline Dumbbell Triceps Extension 10 RM – 5 reps
*Choose two isolation exercises for circuit C
Perform C1 and C2 with minimal rest periods. Keep your form tight and don’t be a hero. Repeat for 5 total minutes and record how many rounds you complete. Try to beat the number of rounds you completed the next time you perform this workout (keeping the weight the same).
Combing moderately heavy resistance training exercises and high intensity sprints, as in my Hybrid Density Training workouts, can be an effective plan of attack to burn a ton of calories and shed excess fat . Remember to eat a slight calorie deficit and make sure you recover well between workouts. Also, watch your form near the end of the 20-minute sets – it’s not worth getting injured so if your form breaks at rep 3 or 4, move on to the next exercise. For maximum results, perform this type of workout 3 times a week! Good luck.
 Boutcher, S.H. (2011). High-intensity intermittent exercise and fat loss. J Obes, 868305. doi: 10.1155/2011/868305
 Gibala, M.J., & McGee, S.L. (2008). Metabolic adaptations to short-term high-intensity interval training: A little pain for a lot of gain? Exerc Sport Sci Rev, 36, 2, 58-63. doi: 10.1097/JES.0b013e318168ec1f.
 Burgomaster, K.A., Howarth, K.R., Phillips, S.M., Rakobowchuk, M., Macdonald, M.J., McGee, S.L., & Gibala, M.J. (2008). Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans. J Physiol, 586, 1, 151-160.
 Nolan, H. (2012). The problem(s) with Crossfit. Retrieved from http://gawker.com/5928989/the-problems-with-crossfit on August 8, 2013.
 Siff, M. (2003). Supertraining, 6th ed. Denver, USA.
 Paoli, A., Moro, T., Marcolin, G., Neri, M., Bianco, A., Palma, A., & Grimaldi, K. (2012). High-Intensity Interval Resistance Training (HIRT) influences resting energy expenditure and respiratory ratio in non-dieting individuals. J Transl Med, 10, 237. doi: 10.1186/1479-5876-10-237.
 Smith, M.M., Sommer, A.J., Starkoff, B.E., & Devor, S.T. (2013). Crossfit-based high intensity power training improves maximal aerobic fitness and body composition. J Strength Cond Res, Feb 22. [Epub ahead of print]
 Schuenke, M.D., Mikat, R.P., & McBride, J.M. (2002). Effect of an acute period of resistance exercise on excess post-exercise oxygen consumption: Implications for body mass management. Eur J Appl Physiol, 86, 411–417.
 Staley, C. (2005). Muscle logic: Escalating density training. Rodale Books.
 Romaniello, J. & Bornstein, A. (2013). Man 2.0 engineering the alpha: A real world guide to an unreal life: Build more muscle. Burn more fat. Have more sex. HarperOne.
ABOUT THE AUTHOR
Jon-Erik Kawamoto, CSCS, CEP, is a Personal Trainer, Fitness Writer and owner of JKConditioning in St. John's, Newfoundland, Canada. He has contributed regularly to many major health and fitness magazines and websites such as Men’s Health, Men’s Fitness, Muscle & Fitness and Bodybuilding.com. In addition to training clients and writing, Jon is putting the final touches on his master’s degree in exercise physiology at Memorial University.