Veggie Blog

Gym advice travels fast, and much of it is repeated without ever being checked. A few of the most popular training rules, such as “always do 12 reps,” “three sets is the magic number” and “never let your knees go past your toes,” are worth a closer look. The research is clearer on some of these than you might expect.

Do you need 12 reps to build muscle?

No. A 2017 systematic review and meta-analysis of 21 studies compared low-load training (60 percent of your one-repetition maximum or less) with high-load training. It found that gains in maximal strength were greater with heavier loads, while muscle growth was similar across a wide range of loads. The authors concluded that maximal strength benefits come from heavy loads, while muscle hypertrophy can be achieved equally across a spectrum of loading ranges. Note that in these studies the sets were carried to momentary failure. In practice, it means that a mix of heavier sets of lower reps and lighter sets of more reps is fine, and you can vary them. See the full abstract if you are curious.

Is three sets the rule?

Three sets is a reasonable number, but there is nothing special about it. The 2026 position stand of the American College of Sports Medicine, which summarized 137 systematic reviews with more than 30,000 participants, found that strength was enhanced by 2 to 3 sets, lifting heavier loads (80 percent of one-repetition maximum or more), and training at least twice a week. Muscle growth was enhanced by higher weekly volumes of 10 or more sets. It also found that training to momentary muscle fatigue, equipment type, exercise complexity and set structure did not consistently change results. The simple conclusion is that healthy adults should do progressive resistance training, adding load or volume over time, and keep it up. How you split the work matters less than doing it regularly.

How many exercises per muscle group?

You may have read that three or four exercises per muscle group is too many and that you should do 30 to 50 reps in total. I could not find a source for those specific numbers, and the position stand points the other way: weekly sets matter for growth. If you are a beginner, one or two exercises per muscle group, done well, are plenty. Add sets later as you progress.

Should your knees stay behind your toes?

This is one of the oldest gym rules, and a 2003 study tested it. Researchers had seven weight-trained men do parallel barbell squats with and without a barrier that stopped the knees moving past the toes. When the knees were restricted, knee torque fell from about 150 to 117 newton-meters, but hip torque rose from about 28 to 303 newton-meters, and the trunk leaned further forward. The authors concluded that restricting the knees may reduce stress on the knees, but forces are probably transferred to the hips and low back, and that proper joint loading during the squat may require the knees to move slightly past the toes. This was a small study of seven men, so treat it as a reminder that technique is about balance, not a single rule. Read the study abstract.

What should you do instead?

Use a weight you can control, keep a full range of motion, increase the load gradually and stop a set if your form falls apart. If you have a joint problem or an old injury, ask a doctor or a qualified trainer to check your squat. For a plan to follow, see full-body workouts in two or three sessions a week, and fitness for men: cardio, strength and safer training for more on safe training. Our guide to preventing sports injuries has twelve habits worth building.