Two halves of the same guidelines
WHO's 2020 guidelines ask adults for two separate things each week: 150 to 300 minutes of moderate aerobic activity or 75 to 150 minutes of vigorous activity, plus muscle-strengthening work for all major muscle groups on two or more days. HIIT sits on the aerobic side. The NHS describes it as very vigorous activity, short bursts of maximum effort broken up with rest, and says several short sessions of it can meet the weekly target.
Lifting sits on the other side. The NHS notes that muscle-strengthening exercise is not always aerobic, so it comes on top of your cardio rather than replacing it. To see the kit for both at one club, look at functional training at RPM.
What each one changes
| Question | Strength training | HIIT |
|---|---|---|
| Main change | Stronger muscles, and bigger ones with enough weekly sets | Higher aerobic fitness, measured as maximum oxygen uptake |
| What the research says | ACSM advises progressive loading, adding 2 to 10 per cent once you beat your target reps by one or two | A 2015 meta-analysis of 28 trials found large gains from both HIIT and steady endurance work, slightly larger after HIIT |
| How it feels | Hard sets, with breathing that settles during the rests | Breathing hard and fast, with only a few words possible in each burst |
| How progress shows | More load or more reps at the same effort | The same intervals feel easier, or you manage more rounds |
| Typical session | Around 40 to 60 minutes including rests | Around 15 to 25 minutes of work after a warm-up |
| Skill involved | Technique on each lift, built over months | Low on a bike, higher with sleds, ropes or sprints |
The 2015 meta-analysis covered healthy adults aged 18 to 45. Its authors found that people with lower starting fitness gained more from intervals, which is worth knowing if you are coming back to training. It says nothing about strength, and that is the point: neither format does the other's job.
The recovery cost, and how to manage it
A 2012 meta-analysis of 21 studies compared lifting alone with lifting plus endurance training. The combined groups still gained strength and muscle, but less than the lifting-only groups, and the shortfall grew with how often and how long the endurance sessions ran. Running carried a measurable cost to strength and muscle gains, while cycling did not.
- Keep interval sessions short, since longer endurance sessions went with a bigger cost.
- Use the bike for intervals in weeks when strength comes first.
- Keep leg-heavy intervals off the day after heavy squats or deadlifts.
- Watch your warm-up sets. If they feel heavy and your working weights stall for a fortnight, drop an interval session before you drop a lifting day.
If you only have time for one
| Your main goal | Start with | Then add |
|---|---|---|
| Getting stronger or building muscle | Strength training two or three days a week | One short interval session on a bike |
| Fitter heart and lungs | HIIT or steady cardio | Two strength sessions to cover WHO's muscle advice |
| General health | Both, as WHO advises | Walking on the other days |
| Starting from no exercise | Steady cardio and simple strength work | Intervals once the steady sessions feel routine |
If you are starting from zero, the conditioning from zero guide sets out work-to-rest ratios before you push to maximum effort. If you have a heart condition or another medical condition, speak to a doctor before adding high-intensity work.
Fitting both into an Abu Dhabi week
| Days you can train | Strength | HIIT | One way to lay it out |
|---|---|---|---|
| Three | Two full-body sessions | One | Lift Saturday and Tuesday, bike intervals Thursday |
| Four | Three sessions | One | Lift Saturday, Monday and Wednesday, intervals Thursday |
| Five | Three sessions | Two | One interval block after the lightest lifting day, one on its own morning |
A short interval session suits Friday, when gym hours are shorter and the day often belongs to prayers and family.
The NHS says strength work can go on the same day as aerobic activity or a different one. When both share a visit and strength leads, lift first and finish with five to ten minutes of intervals. The cardio and weights ordering guide covers the other ways round.
Choosing an interval format
| Format | Cost to the legs | Suits |
|---|---|---|
| Spin or upright bike | Low impact, and cycling showed no strength cost in the 2012 meta-analysis | Lifters and beginners |
| Sled pushes on the turf | High, so count it as leg work | An upper-body lifting day |
| Battle ropes | Light on the legs, hard on shoulders and grip | The day after heavy legs |
| Slam balls | Moderate | Short mixed rounds with the ropes |
| Treadmill intervals | Running carried a strength cost in the 2012 meta-analysis | Runners preparing for a race |
Rowers are not confirmed at RPM, so ask before you plan rower intervals.
Lifting and intervals at RPM
RPM is one club, on Level 4 of AD HUB Sports Complex in Al Manhal. The training floor photos show a squat rack with colour bumper plates, barbells, dumbbells and plate-loaded machines. For intervals, the functional area has a turf lane with a sled, battle ropes and slam balls, and spin bikes. The cardio row has treadmills, cross-trainers and an upright bike.
- The women-only Ladies section has its own strength and cardio equipment. Which sections a membership covers depends on the tier, so confirm yours.
- Engine is the tier that adds coached programming, if you want a coach to balance the two for you.
- Group classes run in both sections and the timetable changes, so ask which ones are on.
- RPM offers HYROX-style training on the functional floor as an independent gym, not an official HYROX partner or venue.
Sources
- World Health Organization, WHO guidelines on physical activity and sedentary behaviour (2020)
- NHS, Physical activity guidelines for adults aged 19 to 64
- Milanović Z, Sporiš G, Weston M. Effectiveness of high-intensity interval training (HIT) and continuous endurance training for VO2max improvements. Sports Medicine, 2015
- Wilson JM, et al. Concurrent training: a meta-analysis examining interference of aerobic and resistance exercises. Journal of Strength and Conditioning Research, 2012
- American College of Sports Medicine, position stand: Progression models in resistance training for healthy adults (2009)
Questions, answered.
Will HIIT undo my strength gains?
Not in the 2012 meta-analysis: lifters who added endurance work still gained strength and muscle, just less than those who only lifted. Short sessions on a bike keep the cost lower.
How many HIIT sessions a week?
Many programmes use one or two alongside lifting. The NHS says several short sessions of very vigorous activity can meet the weekly aerobic target, so you do not need more to tick that box.
Is HIIT or lifting better for fat loss?
This guide makes no fat-loss promise for either. Both count towards WHO's weekly activity advice, and a dietitian is the right person to ask about eating for a body-composition goal.
Can I do HIIT on rest days from lifting?
Yes, if it is short and easy on the legs, such as ropes or a bike. If you feel flat the next day, make that slot an easy walk instead.
Is a circuit the same as HIIT?
Not quite. A circuit uses resistance exercises with short rests, while HIIT is bursts of very hard aerobic effort. The heavy sets vs circuits comparison covers circuits.