What is HIT (and why it's not HIIT)?

The short answer

Two acronyms, one letter apart, two completely different protocols. High Intensity Training (HIT) - a slow, controlled, one-to-one strength protocol, distinct from HIIT (High Intensity Interval Training). One asks a muscle to work slowly to controlled failure on a machine. The other asks the heart and lungs to handle repeated short bouts of near-maximal effort with brief rest.

Both ask for effort. That is where the overlap ends. The rest of this article is the longer version: where each came from, what each formally is, why lay media blurs them, and what we run on the floor in East Finchley.

What HIT is, and where it came from

HIT is a strength training protocol popularised by Arthur Jones, the founder of Nautilus, in the 1970s. Jones set out his thinking in the Nautilus Bulletins and in regular articles in the bodybuilding press of the decade. The protocol he argued for was brief, infrequent and effortful: typically one set per exercise, taken slowly to controlled muscular failure, with several days of recovery between sessions. The stimulus is muscular; the goal is strength.

The lineage from Jones is short. Mike Mentzer's Heavy Duty (1979) and Ellington Darden's writing extended and codified the approach through the 1980s. In 1982, Ken Hutchins, working on a Nautilus-sponsored osteoporosis study at the University of Florida, developed the SuperSlow protocol - the ten-seconds-up, ten-seconds-down cadence we still run. SuperSlow was designed from the start for fragile spines and low-bone-density bodies, not bodybuilders, which is part of why the cadence carries so well into work with older clients today.

The textbook definition has stayed steady for fifty years. Brief, infrequent, high-effort. One set per exercise to controlled failure. Full recovery between sessions.

What HIIT is, and where it came from

HIIT is a cardiorespiratory protocol. The most-cited reference point is a 1996 study by Izumi Tabata and colleagues at the National Institute of Fitness and Sports in Kagoshima, published in Medicine & Science in Sports & Exercise. The study tested 20 seconds of all-out cycling at roughly 170% of VO2max, alternated with 10 seconds of rest, repeated for four minutes (eight cycles), on Japanese national-team speed skaters. The protocol has been informally known as "Tabata" ever since.

From the 2000s onward, Martin Gibala's lab at McMaster University in Hamilton, Ontario has shown that very short bouts of intense cycling produce cardiorespiratory adaptations comparable to much longer steady-state sessions. That is the takeaway most lay readers will have absorbed from a decade of fitness-press coverage.

The core definition follows from the design. Repeated near-maximal bouts of work, short rests, on cardio equipment or in bodyweight movement patterns, eliciting aerobic and anaerobic adaptation. HIIT done well is a legitimate tool. It is just not a strength training protocol.

Why they get confused

Three reasons, none of them anyone's fault.

First, the acronyms share "high" and "intensity". Both ask for effort, and most readers reasonably assume two terms with three of four letters in common mean roughly the same thing.

Second, "interval" tends to drop out of headlines. A magazine piece about a "high-intensity workout" can mean either protocol, and often does not commit to which.

Third, many gym classes labelled "HIIT" mix interval cardio with brief resistance work - kettlebell swings between rounds, push-ups in a circuit. As a workout, that is fine. As a label, it muddies a line that was already faint. Tabata himself has remarked in later writing that his original protocol was designed to stress the cardiovascular system of elite speed skaters and was not intended as a general fat-loss or fitness format; the popular uses of "Tabata" rarely match the original 20-on, 10-off, four-minute structure.

The acronyms are genuinely close, and lay-media usage has drifted. That is worth saying calmly, not correctively.

How to tell which one you are doing in any given session

A short, practical checklist. If most of the answers point one way, that is what is happening.

• Equipment. Resistance machines, free weights, a single strength machine you stay on for a couple of minutes - HIT-shaped. A bike, a rower, a treadmill, a skipping rope, or a circuit of bodyweight moves - HIIT-shaped.
• Cadence. Slow and continuous, with no pause and no momentum - HIT. Fast, repeated bursts of effort - HIIT.
• Rest length. Days of recovery between full sessions - HIT. Seconds of rest between bouts within a session - HIIT.
• Target tissue. A specific muscle group loaded to failure - HIT. The heart, lungs and metabolic system stressed across the whole body - HIIT.
• What is measured. Weight on the stack, time under load, range of motion - HIT. Heart rate, watts, perceived breathlessness, intervals completed - HIIT.

Both can sit inside a sensible week. They are not in competition. They simply ask different tissue for different work.

What we run, and why

What we run at Ultimate Strength is HIT. One 45-minute session a week, by appointment, one to one, in a private studio in East Finchley, North London (N2). Each repetition takes ten seconds up and ten seconds down. Each exercise is a single set taken to controlled muscular failure, with six to seven days of recovery between visits. The equipment is MedX, Nautilus and Cybex. The work is brief; the appointment is not, because calibration, written records and careful setup between machines take time that the work itself does not.

The longer version of the methodological case - super-slow cadence set against interval cardio, who each suits, why we chose HIT in practice - is in the sibling piece, Super slow vs HIIT . The wider description of our method is on our approach , and the floor itself, machine by machine, is on the gym . Yoram is the coach on every session.