In my opinion, yes. The difference is subtle, but there is a difference.
Now, labels can be just words, and, in the fitness industry, words (in this case, acronyms) often get distorted by clever marketing.
Before comparing the acronyms, let’s remind ourselves of the principle of specificity: The body makes specific adaptations to imposed demands. Now, I call it “pop” and my wife calls it “soda”, so, quite possibly, what I call “HIIRT” another may call “HIRT”. We have to look closely at what the exerciser is being asked to do, rather than what the exerciser/trainer is calling the exercise. We need to understand the intent of the exercise and the expected physiological response.
I define high-intensity interval resistance training (HIIRT) as a series of exercise super-sets performed at rather low intensities (I know this sounds a bit contrary) and high repetitions [e.g., ³ 10 reps or as many reps as possible (AMRAP) in a prescribed time-frame) with little rest between super-sets. The intent of this exercise is to burn calories and build skeletal muscle endurance. Cardiorespiratory endurance is only minimally affected. Some trainers refer to this kind of exercise as “metabolic conditioning”, which to most seems to imply the targeting of anaerobic endurance. CrossFit founder, Greg Glassman, actually defines metabolic conditioning as “conditioning exercises intended to increase the storage and delivery of energy for any activity”1. His intent is to avoid “specificity of adaptation”, which is arguable, but it is clear from his definition that metabolic conditioning is a more general, albeit catchy, term for any type of conditioning workout. In the end, specificity rules and the exerciser will adapt according to the stimulus.
I define high-intensity resistance training (HIRT) further along the strength-endurance continuum. While both HIIRT and HIRT are, technically, “circuit training”, I consider HIRT to be more along the line of old school Nautilus training (1970’s). Nautilus training generally involved a circuit of roughly 12 machine exercises arranged from large muscles to small muscles performed to momentary muscular failure for just one set. The point was to totally exhaust the muscle and promote muscle hypertrophy and strength. It is an effective way to train, albeit with some limitations. HIRT can also be done with free weights, and is often in the form of high-intensity (i.e., heavy) weights lifted to near-failure (leaving 1-2 repetitions “in the tank”) in the form of 2- to 3-exercise super-sets (micro-circuits). Such training is better for hypertrophy than strength because volume is the focus over intensity (again, we slightly misuse the term “high-intensity”). These also add an element of time-efficiency to the workouts, as time spent resting between sets is filled with another exercise.
Consider the goals when deciding between HIIRT and HIRT. If the goal is strength and hypertrophy, consider “high”-intensity/”moderate”-volume HIRT. If you prefer less hypertrophy and more fat-burning, consider ”moderate”-intensity/”high”-volume HIIRT. Both will increase the post-exercise energy expenditure. HIRT, however, favors muscle hypertrophy, whereas HIIRT favors fat loss. Neither is likely to have a significant impact on cardiorespiratory endurance.
Whichever acronym you or your trainer uses, consider the goal(s) when selecting exercises, intensities (i.e., weights), repetitions, sets, and recovery times.
Be your best today; be better tomorrow.
Carpe momento!
1 http://journal.crossfit.com/2003/06/metabolic-conditioning-jun-03.tpl