Quick Answer

Six of the most common strength-training myths do not hold up to research. Lifting weights does not stunt a child’s growth. Muscle soreness is not proof of a good workout. You do not need to train every day to see results. Cardio alone reduces fat but leaves muscle on the table. Static stretching right before a game does not reliably prevent injury. And strength training makes young athletes faster and more resilient, not slower or bulkier. Below, a certified strength and conditioning coach breaks down what the peer reviewed research actually shows for each one.

Myth 1: Does Lifting Weights Stunt a Child’s Growth?

This is one of the most persistent myths in youth sports, and it does not hold up. The American Academy of Pediatrics addressed it directly in its clinical report on resistance training for children and adolescents, published in the journal Pediatrics. The report states that appropriately designed and supervised resistance training programs have no apparent negative effect on a child’s growth or on the health of the growth plates. In prepubescent kids, the strength gains that come from a good program are driven mostly by the nervous system learning to recruit muscle more efficiently, not by dramatic increases in muscle size.

Injury data supports the same conclusion. Rates of injury in supervised, well coached resistance training programs run lower than in most other youth sports, and the injuries that do get reported cluster in unsupervised settings, such as an unsupervised home gym, rather than in programs run by a qualified coach. The real risk to a young athlete is not the barbell. It is bad coaching, or no coaching at all.

Source: Stricker PR, Faigenbaum AD, McCambridge TM. Resistance Training for Children and Adolescents. Pediatrics. 2020;145(6):e20201011. https://doi.org/10.1542/peds.2020-1011

Myth 2: Does Being Sore Mean You Had a Good Workout?

It does not, and chasing soreness can work against you. Delayed onset muscle soreness, usually called DOMS, is a sign that your muscles did something unfamiliar. It is not a scorecard for how effective your training was. Beginners tend to get the most sore while also making the fastest strength and muscle gains in their first few months of training, which is likely where this myth started, but the two things simply happen at the same time without one causing the other. Runners experience significant soreness too, even though running produces far less muscle growth than resistance training does.

Research on muscle damage backs this up. How sore a person feels lines up poorly with the actual microscopic damage happening in the muscle tissue. It is possible to have real muscle damage with very little soreness, and to feel brutally sore with very little damage. On top of that, heavy soreness can reduce how much force a muscle produces in the following session, which can work against your progress rather than for it. Soreness tells you that you introduced a new stimulus. It does not tell you that you built muscle.

Source: Nuckols G. The Science of Sore: DOMS Explained. Stronger by Science.

Myth 3: Do You Need to Train Every Day to See Results?

You do not, and for most people daily training is not even the optimal approach. Decades of strength research support this, including classic studies showing that training a given muscle group once or twice a week can produce strength gains close to training it three times a week. A systematic review and meta-analysis by Schoenfeld, Ogborn, and Krieger, published in the journal Sports Medicine, looked specifically at how training frequency affects muscle growth when total weekly volume is held constant.

The review found that training a muscle group twice a week produced better growth than training it only once a week, but the evidence did not show a clear additional benefit to a third weekly session. In other words, the total number of hard sets you accumulate across a week matters more than how many separate days you spread those sets across. Two or three focused, well structured sessions a week, done consistently for months, will outperform seven rushed and exhausted ones.

Source: Schoenfeld BJ, Ogborn D, Krieger JW. Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy: A Systematic Review and Meta-Analysis. Sports Medicine. 2016;46(11):1689 to 1697. https://doi.org/10.1007/s40279-016-0543-8

Myth 4: Is Cardio Alone the Best Way to Lose Fat?

Cardio is genuinely effective for reducing fat, so calling it a myth outright would overstate things. But it is missing an important piece. A widely cited randomized trial by Willis and colleagues, published in the Journal of Applied Physiology, followed overweight and obese adults through eight months of aerobic training only, resistance training only, or a combination of both. The aerobic only group and the combined group reduced body fat and total body weight by similar amounts, and both outperformed the resistance only group on fat loss specifically.

Where cardio alone falls short is body composition. Only the groups that included resistance training, whether alone or combined with cardio, gained meaningful lean muscle mass. The aerobic only group did not. That distinction matters because muscle is what shapes how the body looks and functions through a weight loss phase, and it plays a real role in long term metabolic health. The scale cannot tell you whether the weight you lost was fat, muscle, or some of both. Cardio is a legitimate tool for losing fat, but pairing it with resistance training is what protects and builds the muscle that cardio alone leaves behind.

Source: Willis LH, Slentz CA, Bateman LA, et al. Effects of Aerobic and/or Resistance Training on Body Mass and Fat Mass in Overweight or Obese Adults. Journal of Applied Physiology. 2012;113(12):1831 to 1837. https://doi.org/10.1152/japplphysiol.01370.2011

Myth 5: Does Static Stretching Before a Game Prevent Injury?

This one lands in the middle, and the honest answer is that the evidence is thin in both directions. A systematic review by Small, McNaughton, and Matthews, published in Research in Sports Medicine, examined the research on static stretching as part of a pre-exercise warm-up and found moderate to strong evidence that routinely doing it does not lower overall injury rates. There was some preliminary evidence that it may help reduce one specific category of injury, damage to muscles and tendons, but that evidence was limited and not consistent enough to treat as settled.

What the broader research shows more clearly is that static stretching performed immediately before an explosive activity can temporarily reduce sprint speed and jump height. That does not mean stretching itself is a problem. It means timing matters. Static stretching has a stronger case as a separate practice for building long term flexibility, done after training or as its own session, rather than as the last thing an athlete does before stepping onto the field.

Source: Small K, McNaughton L, Matthews M. A Systematic Review into the Efficacy of Static Stretching as Part of a Warm-Up for the Prevention of Exercise-Related Injury. Research in Sports Medicine. 2008;16(3):213 to 231. https://doi.org/10.1080/15438620802310784

Myth 6: Does Strength Training Make Young Athletes Slower and Bulkier?

This myth is false, and the research points in the opposite direction. The same clinical report from the American Academy of Pediatrics that addresses growth also explains why young athletes do not bulk up the way adults might expect. Prepubescent kids do not yet have the hormonal profile needed to build significant muscle mass, so the strength they gain from a structured program comes primarily from their nervous system getting more efficient at using the muscle they already have. Reviews of youth resistance training have documented meaningful strength increases, often cited in the range of roughly 13 to 30 percent, in preadolescent athletes over programs lasting 8 to 20 weeks, without the added muscle bulk associated with adult lifters.

As for speed, there is no credible body of research showing that strength training slows young athletes down. If anything, the opposite pattern shows up consistently across the youth athletic development literature. Athletes who build a foundation of strength tend to show better gains in explosive qualities like sprinting and jumping than athletes who skip strength work entirely. A stronger young athlete is a faster, more resilient athlete, not a slower one.

Source: Stricker PR, Faigenbaum AD, McCambridge TM. Resistance Training for Children and Adolescents. Pediatrics. 2020;145(6):e20201011. https://doi.org/10.1542/peds.2020-1011

None of these six verdicts comes from gym folklore. They come from peer reviewed research and standing position statements from major medical and sports science organizations. If you are in the Rockville area and want a training program built on what the evidence actually supports rather than what sounds alarming online, that is the approach we take at Prepare for Performance. Which of these six myths surprised you the most?

 

 

Frequently Asked Questions:

Does lifting weights stunt a child’s growth?

No. The American Academy of Pediatrics states that appropriately designed and supervised resistance training has no apparent negative effect on growth or the growth plates in children and adolescents. Strength gains in young kids come mainly from improved nervous system coordination, not muscle bulk, and supervised programs carry lower injury rates than most other youth sports.

Does being sore after a workout mean it worked?

No. Muscle soreness shows that you introduced a new or unfamiliar stress, not that you built muscle. Soreness correlates poorly with actual muscle damage, and heavy soreness can temporarily reduce the force your muscles produce in the next session, which can hurt progress rather than help it.

Do you have to train every day to see results?

No. Research on training frequency shows total weekly training volume matters more than how many days you train. A systematic review found that training a muscle group twice a week produced better growth than once a week, with no clear extra benefit from a third weekly session.

Is cardio alone the best way to lose fat?

Cardio does effectively reduce fat, but it does not build or preserve muscle the way resistance training does. A randomized trial found aerobic only and combined training reduced fat by similar amounts, but only groups that included resistance training gained meaningful lean muscle, which matters for long term body composition and metabolic health.

Does static stretching before a game prevent injury?

The evidence is thin. A systematic review found moderate to strong evidence that routine static stretching does not lower overall injury rates, though it may help prevent some muscle and tendon injuries specifically. Stretching right before explosive movement can also temporarily reduce sprint speed and jump height, so timing matters.

Does strength training make young athletes slower and bulkier?

No. Prepubescent athletes lack the hormonal profile needed to build significant muscle bulk, so strength gains come from improved neuromuscular coordination instead. There is no credible research showing strength training slows young athletes down, and the broader evidence points toward stronger athletes developing better speed and resilience, not less.

 

 

References

1. Stricker PR, Faigenbaum AD, McCambridge TM. Resistance Training for Children and Adolescents. Pediatrics. 2020;145(6):e20201011. https://doi.org/10.1542/peds.2020-1011

2. Schoenfeld BJ, Ogborn D, Krieger JW. Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy: A Systematic Review and Meta-Analysis. Sports Medicine. 2016;46(11):1689 to 1697. https://doi.org/10.1007/s40279-016-0543-8

3. Willis LH, Slentz CA, Bateman LA, et al. Effects of Aerobic and/or Resistance Training on Body Mass and Fat Mass in Overweight or Obese Adults. Journal of Applied Physiology. 2012;113(12):1831 to 1837. https://doi.org/10.1152/japplphysiol.01370.2011

4. Small K, McNaughton L, Matthews M. A Systematic Review into the Efficacy of Static Stretching as Part of a Warm-Up for the Prevention of Exercise-Related Injury. Research in Sports Medicine. 2008;16(3):213 to 231. https://doi.org/10.1080/15438620802310784

5. Nuckols G. The Science of Sore: DOMS Explained. Stronger by Science.

6. American College of Sports Medicine. Mythbusting: Youth Resistance Training.