Group Training Culture
How a warm-up works, and how to structure one for a group class
A warm-up is the lighter activity that comes before the main part of a session. Its job is to prepare the body for that specific work. The research supports warm-ups mainly as a way to improve performance in the session that follows. Their role in preventing injury is narrower. The injury evidence comes from programmes repeated over many weeks, not from a single warm-up.
What changes in the body
A review of warm-up mechanisms by McGowan and colleagues groups the effects into four kinds:
- Temperature effects. Muscle and core temperature rise.
- Metabolic effects. Oxygen uptake is already raised when the main work starts, and oxygen uptake kinetics, the speed at which oxygen use rises to meet a new workload, become faster.
- Neural effects. Brief, intense muscle contractions can temporarily improve the force and speed of the actions that follow. This is called post-activation performance enhancement.
- Psychological effects. The review also lists effects on mental readiness for the task.
Passive warming, such as warm clothing or a heated room, raises body temperature without using up energy stores. An active warm-up produces larger metabolic changes, which is one reason it's the usual choice before training.
What the research shows for performance
A 2010 meta-analysis of 32 warm-up studies included only warm-ups that involved more than stretching. Warming up improved performance on 79% of the outcomes measured, and the authors found little evidence that it causes harm. They also noted that well-controlled randomised trials were scarce, so the size of the benefit in a particular setting is uncertain.
David Bishop's review of active warm-ups describes the conditions behind the benefit:
- Efforts lasting from about 10 seconds to several minutes improve when they begin in a relatively non-fatigued state with oxygen uptake already raised.
- A warm-up that is too intense, or followed by too little recovery, can impair short explosive efforts because the muscles' immediate energy stores haven't been replenished.
- A brief burst of the specific activity can add a further benefit for some tasks.
- Warmth gained during a warm-up needs maintaining if an unavoidable delay follows, especially in cold conditions.
The common thread is that a warm-up should leave you warm and ready, not tired.
The three layers of a warm-up
In 2026, 23 warm-up researchers from 12 countries published an international consensus using the Delphi method, in which experts rate statements over several rounds until agreement reaches a set threshold. The panel described a warm-up in three layers. Applied to a group class, they look like this:
| Layer | Purpose | Class example |
|---|---|---|
| General exercises | Raise temperature and heart rate | Easy rowing, cycling or skiing |
| Specific exercises | Rehearse the session's movement patterns | Lunges, squats, hip hinges, light wall-ball throws |
| Conditioning activities | Short, intense efforts to trigger post-activation performance enhancement | A short sled push at working load, a hard 15-second row |
The class examples are an illustration, not part of the consensus. The panel also agreed that the right warm-up depends on the sport and the individual. A consensus records expert agreement rather than new trial data. Heavy strength sessions also need progressively heavier warm-up sets of the main lift, which a general warm-up doesn't replace.
Static stretching and performance
A systematic review of stretching in healthy, active people found that static stretching immediately before a test reduced performance by an average of 3.7%. The authors suggest reduced muscle activation as a possible cause. The effect depended on the dose:
- Holds of 60 seconds or longer per muscle group: performance fell by 4.6%.
- Holds shorter than 60 seconds: performance fell by 1.1%.
- Stretching followed by dynamic activity: no clear effect on performance.
Gains in range of motion from any type of stretching usually lasted less than 30 minutes. Short static holds are therefore reasonable when someone needs more range for a movement, as long as dynamic work follows and the main block starts soon after. Long holds before heavy or explosive work cost performance.
Warm-ups and injury risk
The Delphi panel found no support for the idea that a warm-up protects against injury in that day's session. It did accept that some exercises included in warm-ups may lower injury risk over the long term.
The clearest evidence comes from football. A meta-analysis of randomised trials in recreational and sub-elite football examined FIFA 11+, a structured programme of running, strength, balance and jumping exercises. Teams that used it had about 39% fewer injuries overall. The players repeated the same programme throughout a season. The result applies to that kind of consistent programme in football and doesn't show that any single warm-up prevents injury. For a gym, the defensible approach is a short, fixed set of landing, balance and strength drills repeated every week.
How heart rate behaves during a warm-up
Heart rate lags behind changes in effort, so a reading can take a minute or two to catch up with a new pace. Starting values also differ between people, depending on resting heart rate and recent activity.
In Pulz8, Zone 1 (Warm Up, gray) is below 60% of maximum heart rate and Zone 2 (Easy, blue) runs from 60% to just below 70%. With a stored maximum of 185 beats per minute, Zone 2 starts at 111 and Zone 3 at about 130. The maximum is often an estimate, so the boundaries are approximate. During the general layer, most tiles should rise steadily from gray toward blue. They don't need to reach the same colour at the same moment.
Short conditioning efforts behave differently. Heart rate often peaks after the effort has ended, so movement quality and perceived effort are better guides than the colour. An unusually high reading at a familiar easy pace can reflect heat, poor sleep, illness, caffeine or a loose sensor strap, and the number alone can't tell these apart. The article on sleep, stress and readiness explains how to interpret it.
Key points
- Build intensity gradually and finish the warm-up without fatigue.
- Rehearse the movements the main block will load.
- Add a few short, sharp efforts close to the session's intensity.
- Keep static holds under 60 seconds and follow them with dynamic movement.
- Keep the gap short between the warm-up and the main block.
- Repeat a fixed set of injury-prevention drills every week rather than lengthening a single warm-up.
Sources
- McGowan CJ, Pyne DB, Thompson KG, Rattray B. Warm-up strategies for sport and exercise: mechanisms and applications. Sports Medicine, 2015.
- Fradkin AJ, Zazryn TR, Smoliga JM. Effects of warming-up on physical performance: a systematic review with meta-analysis. Journal of Strength and Conditioning Research, 2010.
- Bishop D. Warm up II: performance changes following active warm up and how to structure the warm up. Sports Medicine, 2003.
- Boullosa D et al. International expert consensus on warm-up protocols for athletes: a Delphi study. International Journal of Sports Physiology and Performance, 2026.
- Behm DG, Blazevich AJ, Kay AD, McHugh M. Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review. Applied Physiology, Nutrition, and Metabolism, 2016.
- Thorborg K et al. Effect of specific exercise-based football injury prevention programmes on the overall injury rate in football: a systematic review and meta-analysis of the FIFA 11 and 11+ programmes. British Journal of Sports Medicine, 2017.
Heart rate is a training signal, not medical advice. If something feels wrong during a warm-up, such as chest pain, dizziness or unusual breathlessness, stop and seek medical help.