Boys' Resistance Training: Strength Rose in 9 Weeks, Muscle Thickness Did Not Differ
In short
In a randomized controlled trial of 68 boys aged roughly 11 to 14 doing two lower-body resistance sessions a week for nine weeks, the training groups improved isometric mid-thigh pull peak force more than controls (p = 0.042), while quadriceps muscle thickness did not differ between groups. No difference between prepubertal and pubertal boys was detected, but power to find one was limited. In young lifters, strength gains show up before muscle size does.
The researchers split 68 boys into prepubertal (mean age 11.58) and pubertal (mean age 14.28) groups using maturity offset estimates, then randomized each into resistance training or active control, giving four groups.
What did they do?
The training groups did lower-body resistance training twice a week for nine weeks. Controls simply continued regular soccer training. Strength was measured with the isometric mid-thigh pull and hypertrophy with muscle thickness, so this tested maximal force in a static pull rather than a one-rep max.
Did strength increase?
Yes. The time-by-intervention interaction for peak force was significant (p = 0.042), with larger improvements in the training groups. Strength gains in youth are largely attributed to neural adaptation, and this result is consistent with that explanation.
Did the muscles get thicker?
No clear difference. The interaction was not significant for rectus femoris and vastus intermedius thickness (p = 0.295) or for vastus lateralis (p = 0.711). The three-way interaction with maturity was not significant either, but the authors note these analyses had limited power. That reads as “this study could not tell,” not “there is no difference.”
How should you read it?
Nine weeks is short and the study used one lower-body protocol. The safe conclusion is that this protocol increased peak force in prepubertal and pubertal boys. It does not settle whether hypertrophy occurs or what happens long term. For coaching, set expectations that strength comes first and visible change comes later.
Strength appears in the logbook before it appears in the mirror, which is the case for keeping steady records even when nothing feels different. Why the same program produces different results in different people is covered in why training response varies.
This study measured isometric force, not a one-rep max. It is not a basis for maximal attempts in young people, and training should be supervised by a qualified coach.
Frequently asked questions
Do prepubertal children gain strength from resistance training?
In this trial the combined training groups improved peak force more than controls (p = 0.042). No difference between prepubertal and pubertal boys was detected, though power was limited.
Does resistance training build muscle in teenage boys?
Here, quadriceps and vastus lateralis thickness did not change significantly more in the training groups than in controls. Nine weeks is also a short period to judge.
Why does strength rise in young lifters?
Strength gains in youth are largely attributed to neural adaptations. Evidence for muscle growth in prepubertal youth remains inconsistent.
What training did the boys do?
Two lower-body resistance sessions a week for nine weeks, while controls continued their regular soccer training. Strength was measured with the isometric mid-thigh pull.
Source: PubMed