We all want simple workouts that deliver results, and that’s why the 21-15-9 format has become a staple in high-intensity functional fitness. Originally a CrossFit workout, it involves completing one or two movements for 21 repetitions each, then 15, and finally 9.
The descending structure strikes a perfect balance between volume and intensity, letting you push hard early while maintaining momentum as the reps drop. It keeps workouts straightforward, efficient, and mentally manageable, whether you’re new to fitness or a seasoned athlete. Juris Vjacirs, personal trainer and specialist CrossFit coach at Ultimate Performance, outlines the benefits of the 21-15-9 format, how long a workout should take and some simple movement combinations.
What is the 21-15-9 workout?
21-15-9 is one of CrossFit’s most recognisable and widely adopted workout formats. The structure is straightforward: you complete one or two movements for 21 repetitions each, then repeat those movements for 15 reps, and finally finish with 9 reps.
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The format is intentionally simple, but the training effect is far from basic. ‘Because the reps decrease each round, you’re able to maintain momentum and push the pace, which creates a surprisingly high cardiovascular and muscular training stimulus,’ says Vjacirs. ‘It’s a time-efficient way to get a lot of work done in a short period, and the descending rep scheme keeps the workout mentally manageable even as the intensity ramps up.’
How do you do the 21-15-9 rep scheme?
‘To complete a 21-15-9 workout, you start by choosing the movements you want to pair – these can be bodyweight, weighted, or a combination of both,’ says Vjacirs. You then work through the rounds of 21, 15, and 9 reps as efficiently as possible while maintaining good technique.
‘Many people begin the first round with a steady pace to avoid early fatigue, then naturally pick up speed as the reps drop. The aim is to keep rest breaks short without compromising form. Because the structure is so adaptable, it’s accessible to beginners who may scale the movements, while still offering a serious challenge for more advanced athletes pushing for speed and intensity.’
Where did the 21-15-9 workout structure come from?
This rep scheme originates from the early days of CrossFit programming. ‘Founder Greg Glassman developed it to deliver short, intense workouts that feel psychologically achievable,’ Vjacirs explains.
‘The format has been used in some of CrossFit’s most iconic benchmark workouts, including Fran – a CrossFit standard workout consisting of 21-15-9 thrusters and pull-ups – and has since become a staple within functional fitness due to its blend of intensity, simplicity and approachability.’
Once the first and highest-rep round of 21 is complete, athletes feel a sense of progress, knowing the toughest section is behind them. That built-in motivation encourages continuous effort throughout the session.
Benefits of the 21-15-9 workout
21-15-9 works so well because it’s both simple and highly scalable. Vjacirs outlines the following benefits.
- You can adapt every element, from the movements and weights to the pace and rep count, making it suitable for any fitness level.
- Many variations require no equipment at all, which is ideal for at-home training or outdoor sessions.
- As all the numbers are multiples of three, the rounds are easy to break up into smaller sets of three to make them easier and more manageable if necessary.
- For beginners, the structure offers a gentle introduction to intensity: the descending reps naturally build confidence as the workout becomes more manageable with each round.
- The short duration helps keep sessions focused, efficient and easy to fit into a busy schedule, while still delivering a powerful training effect.
How long does a 21-15-9 workout take?
A standard 21-15-9 workout is usually done ‘for time’, or as fast as possible. Typically, it lasts between 4-10 minutes, though the exact duration depends on the exercises you choose and your level of experience, explains Vjacirs. ‘Bodyweight-focused versions tend to be faster, while workouts involving heavier loads or more technical movements can push toward the upper end of that range.
‘Regardless of the variation, the goal of the 21-15-9 structure is to deliver a short, sharp burst of effort that maximises intensity without requiring a long-time commitment.’
Example 21-15-9 workouts
- Classic CrossFit (Fran workout) pairing
• Thrusters
• Pull-ups - Beginner-friendly, equipment-free
• Air squats
• Sit-ups - Conditioning-focused
• Burpees
• Kettlebell swings - Strength-based option
• Deadlifts
• Hand-release push-ups - Mixed variation
• Dumbbell snatches
• Box jumps