How to harness the power of the world's most efficient workout
You've probably seen them at your local gym—the small groups moving through what looks like a whirlwind of exercises, flipping tires, swinging kettlebells, and performing bodyweight movements with barely a rest between sets. This isn't just another fitness fad; it's part of a training revolution sweeping the fitness world.
Imagine combining the heart-pumping intensity of a sprint session with the muscle-building power of weightlifting, all packaged into a single, time-efficient workout.
By definition, HIMT encompasses "all styles of high-intensity combined aerobic, resistance and/or bodyweight exercise" performed at a vigorous intensity 1 . What makes HIMT unique isn't just its intensity, but how it blends different exercise modalities into a seamless, integrated experience.
You might know HIMT by some of its other names—CrossFit®, high-intensity functional training (HIFT), circuit training, or bodyweight high-intensity interval training 1 . Researchers have identified at least 85 different terms used to describe these training methods in scientific studies 1 .
Typically separate cardio and strength training
Focuses primarily on cardiovascular exercises like cycling or running
Combines strength, cardio, and often bodyweight exercises in varied combinations
HIMT offers a time-efficient solution for people struggling to fit both aerobic and resistance training into their busy schedules 6 .
Beyond efficiency, participants often report finding these workouts more enjoyable and motivating than traditional exercise routines 8 , potentially leading to better long-term adherence.
As HIMT's popularity exploded in gyms and fitness centers, scientists noticed a troubling pattern: we didn't really know how to consistently prescribe these workouts for optimal results. The very characteristics that made HIMT appealing—its variety, intensity, and complexity—also made it incredibly difficult to study and standardize.
Researchers termed it "previous heterogeneity in exercise prescription and reporting" 1 . In plain language: everyone was doing HIMT differently, and everyone was describing it differently too.
The research community needed to map this uncharted territory—and that's exactly what a team of scientists set out to do through a comprehensive systematic mapping review 1 .
To solve the HIMT puzzle, researchers conducted an exhaustive analysis of the existing scientific literature, following rigorous systematic review standards 1 . Their approach was both massive and meticulous:
37,090 records initially retrieved from multiple databases
220 studies meeting inclusion criteria for detailed review
246 individual HIMT protocols analyzed against established exercise reporting templates
The team employed a categorical analysis framework based on:
This allowed them to systematically examine every aspect of how HIMT was being prescribed and reported across the scientific literature.
The results of this massive undertaking revealed a field in its infancy, characterized by enthusiasm but lacking standardization.
| Aspect Analyzed | Finding | Significance |
|---|---|---|
| Terms used for HIMT | 85 unique terms | Field fragmentation complicating communication |
| Most common format | Consistent exercise selection in circuits | Practical preference for structured variability |
| Intensity reporting | Inconsistent and often below guidelines | Questionable whether "high-intensity" truly high |
Perhaps most surprisingly, the review found that "a large proportion of studies prescribed 'high-intensity' exercise at a level lower than the American College of Sports Medicine criteria for high-intensity" 1 . This raised important questions about what exactly constituted "high intensity" in many HIMT programs.
| Rank | Outcome Category | Examples |
|---|---|---|
| 1 | Cardiovascular health | VO₂ max, heart rate variables |
| 2 | Perceptual outcomes | Enjoyment, motivation, perceived exertion |
| 3 | Body composition | Body fat percentage, muscle mass |
| 4 | Biochemical outcomes | Blood lactate, hormone levels |
The mapping review also revealed that a "large proportion of previous HIMT research was experimental in design" 1 , indicating that while the field was growing rapidly, it was still establishing its foundational evidence base.
So how do researchers study something as complex as HIMT? The mapping review identified key tools and methods that are essential for proper HIMT prescription and research.
| Tool Category | Specific Tools | Purpose & Function |
|---|---|---|
| Intensity Monitoring | Heart rate monitors, RPE scales | Ensure exercise meets high-intensity thresholds |
| Training Variables | Rep counts, timed circuits, work-to-rest ratios | Standardize and replicate protocols |
| Outcome Measures | VO₂ max testing, body composition scans, strength tests | Quantify training effects |
| Reporting Guidelines | CERT template, PRISMA-ScR | Standardize research reporting |
The Consensus on Exercise Reporting Template (CERT) emerged as particularly important—this checklist helps researchers completely describe their exercise interventions, ensuring that studies can be properly understood, evaluated, and replicated 1 .
For measuring intensity, researchers rely on both objective tools like heart rate monitors (with high-intensity defined as >77% heart rate maximum) and subjective measures like the Rating of Perceived Exertion (RPE) scale 6 .
When it comes to outcomes, the toolkit is diverse because HIMT itself targets multiple fitness domains simultaneously. From blood lactate tests that measure metabolic stress to jump height measurements that assess power output.
The mapping review doesn't just identify problems—it charts a clear path forward for both researchers and fitness professionals.
Researchers should follow established guidelines like CERT to improve reporting rigor 1 . This would allow for meaningful comparisons between studies and more confident conclusions about what works.
The review calls for "actively involv[ing] practitioners in implementation studies to improve ecological validity" 1 . In other words, we need to bridge the gap between laboratory research and real-world application.
Future studies should focus on "outcome measures [that] should be accessible in practice and reflect common training goals of participants" 1 . This means measuring what matters to actual HIMT participants, not just what's easiest to measure in a lab.
While the research continues to evolve, the current evidence suggests several practical guidelines for those designing or participating in HIMT programs:
Ensure workouts truly meet high-intensity criteria through proper monitoring
Don't get caught up in branded terminology—focus on the fundamental principles of exercise selection, volume, and intensity
Factors like supervision, location, and group dynamics may be as important as the exercises themselves
While HIMT thrives on variation, tracking progress requires some consistency in exercises and measurements
The research also hints at why HIMT has proven so popular despite the scientific uncertainties: it aligns with how people naturally prefer to move. As one research group noted, young people "naturally engage in intermittent activities" and often find high-intensity exercise enjoyable 8 .
The systematic mapping review represents a crucial first step in transforming HIMT from a popular trend into an evidence-based training method.
Previous studies have "demonstrated positive effects of HIMT on health and performance outcomes" 1 , including improvements in cardiovascular health, body composition, and muscular fitness 6 .
The enjoyment and motivation associated with HIMT participation 8 suggest it could be a powerful tool for combating the problem of exercise adherence.
In a world where lack of time remains a primary barrier to regular physical activity 9 , time-efficient workouts that people actually enjoy could be transformative for public health.
The HIMT prescription puzzle hasn't been fully solved yet, but we now have the pieces spread out on the table—and researchers are starting to see how they fit together.
As the science progresses, we move closer to being able to consistently prescribe the right combination of exercises, intensity, and volume to help everyone from elite athletes to weekend warriors achieve their fitness goals more efficiently and enjoyably than ever before.