On this page
- 2026 at a glance
- What is the ACSM ranking?
- 1. Wearables turned VO₂ max into a daily number
- 2. "HIIT" slipped while named protocols grew
- 3. VO₂ max became the longevity metric
- 4. Zone 2 vs. 4x4 ended in "both"
- 5. Older adults moved to the center
- 6. GLP-1 drugs pushed exercise for weight management up the rankings
- 7. Apps fought watch features for the timer slot
- 8. Low-impact versions and hybrid racing
- What 2026 did not bring
- 2026 by the numbers
- What it means for your training
- Frequently asked questions
Two years ago we called 2024 the year of the Norwegian 4x4, when podcasts and longevity doctors first pushed the protocol into the mainstream. 2026 was the year it settled in. Here are the trends that shaped how people did interval training this year, which data backs them up, and where the hype ran ahead of the evidence.
2026 at a glance
In 2026, interval training shifted from generic "HIIT" to specific, measurable protocols. Wearables were the No. 1 fitness trend for the third year running, VO₂ max became a mainstream longevity metric, and the Norwegian 4x4 (four 4-minute efforts at 85–95% of max heart rate with 3-minute recoveries) became the go-to workout for raising it. HIIT as a category fell from No. 6 to No. 12 in the ACSM 2026 trends survey, while the 4x4 kept turning up in mainstream lifestyle coverage.
What is the ACSM ranking?
Several rankings in this article come from the ACSM Worldwide Fitness Trends survey. The American College of Sports Medicine (ACSM) is the largest sports medicine and exercise science organization in the world. Every year it asks fitness professionals, clinicians and researchers to rate which trends will shape the year ahead, then publishes a ranked list in ACSM's Health & Fitness Journal.
The 2026 edition was published in October 2025 and drew about 2,000 respondents. Its top 10:
- Wearable technology
- Fitness programs for older adults
- Exercise for weight management
- Mobile exercise apps
- Balance, flow and core strength
- Exercise for mental health
- Traditional strength training
- Data-driven technology
- Adult recreation and sport clubs (new entry)
- Functional fitness training
High-intensity interval training placed No. 12. One thing to keep in mind: the survey measures what professionals expect to be popular, not what is effective. A trend can drop in the rankings while the research behind it stays just as strong.
1. Wearables turned VO₂ max into a daily number
ACSM ranked wearable technology No. 1 for 2026, and it was the top pick among respondents aged 65 and older. The practical effect was that millions of people now see a VO₂ max estimate on their wrist. Once a number is visible, people want to move it, and the 4x4 is the most-studied workout for doing exactly that.
Watch estimates are useful for spotting trends but are not lab-grade. Our Apple Watch and Garmin VO₂ max accuracy guide explains when to trust them, and the VO₂ max by age chart puts your number in context.
2. "HIIT" slipped while named protocols grew
HIIT dropped six places in ACSM's 2026 ranking, from No. 6 to No. 12. That does not mean people stopped doing hard intervals. "HIIT" stopped being specific enough to excite anyone. People went looking for a protocol with a name, a research group behind it and a measurable result. The Norwegian 4x4, developed by the NTNU researchers in Trondheim, fits all three.
Compare it with other formats in our 4x4 vs Tabata guide.
3. VO₂ max became the longevity metric
Longevity doctors such as Peter Attia kept pointing to large observational studies, including a 2018 JAMA Network Open cohort of 122,007 patients, that link higher cardiorespiratory fitness with lower all-cause mortality. In 2026 that message reached a mass audience, and the 4x4 got marketed as "the longevity workout."
Keep one caveat in mind: the mortality data is about VO₂ max in general. No trial shows that the 4x4 itself extends lifespan. What the trials do show is that the 4x4 raises VO₂ max efficiently. Read our Attia reality check for the fuller picture.
4. Zone 2 vs. 4x4 ended in "both"
The loud "Zone 2 or HIIT?" debate of 2024–2025 mostly settled into a polarized week: lots of easy, conversational cardio plus one or two truly hard 4x4 sessions. Easy volume builds the aerobic base, and the 4x4 raises the ceiling. Our Zone 2 vs Norwegian 4x4 guide includes a sample week.
5. Older adults moved to the center
Fitness programs for older adults ranked No. 2 in ACSM's 2026 survey. The 4x4 has unusually strong evidence here. The Generation 100 trial (BMJ, 2020) randomized 1,567 Norwegians aged 70–77, and the high-intensity interval group improved VO₂ peak the most. Mortality was lowest in that group too, though the difference was not statistically significant. If you are over 50, start with our HIIT after 50 guide.
6. GLP-1 drugs pushed exercise for weight management up the rankings
"Exercise for weight management" ranked No. 3 in ACSM's 2026 survey, its highest position ever, as GLP-1 medications such as Ozempic and Wegovy spread. The consensus advice: pair the medication with resistance training and enough protein to protect muscle, and use cardio such as the 4x4 for heart and metabolic health. See preventing muscle loss on GLP-1s.
7. Apps fought watch features for the timer slot
Mobile exercise apps ranked No. 4 in 2026, down from No. 2 the year before, as watches built in more guided workouts. Apps kept an edge on structure: preset 4x4 timers, heart-rate zones calculated for you, and progress history. Our fitness apps overview covers the landscape.
8. Low-impact versions and hybrid racing
Two practical shifts showed up across forums and coaching content:
- Lower-impact 4x4s. Rowers, bikes, incline walking and step-ups replaced running for many people, keeping the intensity without the pounding. See the rowing and treadmill settings guides.
- HYROX and hybrid racing. HYROX grew quickly through TikTok and Instagram, and HIIT-style conditioning is central to preparing for it. Our HYROX beginner plan uses the 4x4 as the aerobic engine.
What 2026 did not bring
No major new Norwegian 4x4 trial was published in 2026. Most coverage still relies on the same foundations: Helgerud et al. (2007), where 4x4 training raised VO₂ max by about 7% in eight weeks, and Generation 100. Many "2026 updated" articles online repackage that older research, and some quote numbers that do not match the original papers. When a claim matters to you, check the study.
2026 by the numbers
| Signal | 2025 | 2026 |
|---|---|---|
| Wearable technology (ACSM) | No. 1 | No. 1 (3rd year running) |
| High-intensity interval training (ACSM) | No. 6 | No. 12 |
| Mobile exercise apps (ACSM) | No. 2 | No. 4 |
| Fitness programs for older adults (ACSM) | Top 5 | No. 2 |
| Exercise for weight management (ACSM) | Top 10 | No. 3 (highest ever) |
| Landmark new 4x4 trials | None | None |
What it means for your training
The lesson of 2026 is simple: pick a proven protocol, measure it and stay consistent. Whether 2027 keeps that direction is already visible in ACSM's new survey. Read our 2027 fitness trends outlook. To act on it, start the 12-week Norwegian 4x4 plan for 2027 in January and retest your VO₂ max at the end.
New to the protocol? Begin with the beginner's guide and set your zones with the heart rate calculator.
Frequently Asked Questions
What is the ACSM fitness trends ranking?
It is an annual survey by the American College of Sports Medicine (ACSM). Fitness professionals, clinicians and researchers rate which trends they expect to shape the coming year. The 2026 edition surveyed about 2,000 respondents and was published in October 2025. It measures expected popularity, not how effective a workout is.
Was HIIT still popular in 2026?
Yes, but it was less of a headline. ACSM's 2026 survey ranked HIIT No. 12, down from No. 6 in 2025, and the 2027 survey kept it at No. 12. Interest shifted from generic HIIT toward named, research-backed protocols such as the Norwegian 4x4.
What was the No. 1 fitness trend of 2026?
Wearable technology, for the third year in a row in ACSM's 2026 survey. Watches that estimate VO₂ max were a big reason people went looking for a workout that raises that number.
Was there new Norwegian 4x4 research in 2026?
No landmark 4x4 trial appeared in 2026. The protocol still rests on NTNU's earlier work, including Helgerud et al. (2007) and the Generation 100 trial (2020) in adults aged 70–77.
Should I combine Zone 2 and Norwegian 4x4?
For most people, yes. A polarized week with mostly easy Zone 2 cardio plus one or two 4x4 sessions became the default advice in 2026. See our Zone 2 vs 4x4 guide.
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