Thoughts about Youth Weight Training

Sorry, I did not have the time and patience to provide references for everything. If you are interested in something specific, just ask.

Disclaimer - I am not a doctor or scientist. I do have a reasonable level of education on training science, both from my own research and the Henselmans PT Course.

Why ?

The physical performance of today's children has declined compared to previous generations, as evidenced by studies. I observed in my son's judo class that maybe one out of ten kids does push-ups with proper form.
Kids are spending less time playing outside, thanks to the inexorable tractor beams of "Weapons of Mass Distraction" such as TV, Internet, video games and social media.
As a result, the rate of child obesity is increasing.
Typical youth sports are not sustainable in adulthood - weight training can be continued indefinitely.
Weight training can enhance sports performance, and possibly reduce injury risk. (REF)
Weight training can help increase bone density, and possibly help prevent osteoporosis later in life.
Weight training is a good alternative for "unathletic" kids who don't have talent or interest in typical team sports.
Weight training can be continued through adult life. I like to call it a "life sentence to hard labor".

The prepubertal years: a uniquely opportune stage of growth when the skeleton is most responsive to exercise? (Shona L. Bass, 2000).
A six-year longitudinal study of the relationship of physical activity to bone mineral accrual in growing children: the university of Saskatchewan bone mineral accrual study (D A Bailey, H A McKay, R L Mirwald, P R Crocker, R A Faulkner 1999).
Secular trends in physical fitness and body size in Lithuanian children and adolescents between 1992 and 2012 (Tomas Venckunas, Arunas Emeljanovas, Brigita Mieziene, Vida Volbekiene 2016).

When ?

In my opinion, the earlier, the better.
An early start (say around 8 to 10 years of age) will allow time to learn proper technique and set habits before puberty.
Training can then be intensified during adolescence.

Kids can't grow muscles before puberty ? Research shows that significant strength gains are possible at any age. (REF). Typical studies are probably too short (or not intensive enough) to show hypertrophy, but young gymnasts and Giuliano Stroe demonstrate that it is possible.

How ?

The typical recommendation is to start with body weight training before lifting weights. In today's reality, many kids cannot perform push-ups with proper form, and are too weak to even think of doing pull-ups.

Adjustable dumbbells are affordable. Exercises are usually easy to learn given some basic cues. Dumbbell training also develops stabilizing muscles, and is sometimes safer than training with barbells (e.g. flat bench press).

In my opinion, barbell training is more suitable for older lifters. Barbells and a rack are quite an investment. Exercises tend to be more technical, and are best learned under the direct supervision of a coach or trainer. Olympic lifts require extensive technique practice and good mobility (e.g. deep squat, front rack position).

Machines are expensive, and only found at gyms. Most machines are designed for adults, and will not have the adjustment range to fit smaller kids.

Cable pulleys can be set up at home at low cost (about $50). Typical cable stacks at the gym are problematic for beginners as they don't allow weight adjustment in small increments. The DIY version can be loaded with small plates.

Where ?

Commercial gym - most gyms require a minimum age of 14 or 16 years, and are not cheap. Introduction or supervision is usually minimal, if any.
School gym - this depends on the school, usually only available at the high school level. If you are lucky there will be coaching.
Group classes, for example Crossfit Kids. Often expensive, and one weekly session is not enough for good results. Difficult to have a group class fit for widely varied individual capabilities.
At home. Limited equipment, no or limited supervision by parents or friends. A basic setup consists of:
- Adjustable dumbbells and weight plates
- Bench (or just a sturdy box)
- Carpet or mat to protect the floor
- Pull-up bar
- optional - EZ curl bar
- optional - DIY cable pulley

How to learn ?

At school - we can all dream. Rarely a part of PE curriculum, or too late.
As part of sports training - this will only benefit kids participating in a sports team.
At a gym - as mentioned above, the minimum age gets in the way. I have yet to see a gym that offers more than a cursory introduction to training.
From a personal trainer - at typical personal trainer rates, this will only be an option for well-to-do families.
Internet - mostly Youtube. It is difficult for beginners to identify good content - this should be curated.
Books - there is precious little written for the people that matter (kids).

Risks ?

Young bones are softer, and break more easily than stiffer adult bones. On the other hand, young tendons and ligaments are more resilient.

Growth plates - the standard objection. This has been debunked by science. In practice, the peak loads in even heavy lifting are much less than impact forces in dynamic sports.
Falling weights - easily avoided through proper housekeeping, suitable gear (e.g. dumbbells with spin lock collars), and some education. Most kids are smart enough not to drop heavy things on their toes.
Overstrain - this can be avoided by rules against doing heavy, low repetition lifts.
The overall injury rate in weight training is VERY low. (REF)
Improved strength and stability may reduce the injury rate in other sports. (REF)

Finally, the risks in weight training should be compared with the considerable long-term risks of obesity and poor physical and metabolic fitness !

When can my Child start lifting weights + Part 2 - articles by Dr. Horschig / Squat University
Does lifting weights stunt growth ? - article by Barbell Logic
Physeal injuries in children's and youth sports: reasons for concern? (D Caine et al, 2006).

Kids vs. adults

As kids develop, their nervous system and metabolism changes. In particular...

Younger kids store less glycogen in their muscles, and overall are not as good at anaerobic glycolysis.
Their metabolism can run off fat up to a higher threshold, comparable to trained endurance athletes.
Kids can burn circulating glycogen (e.g. from sports drinks) at a higher rate than adults - but this is not needed for typical weight training.
Research does not agree on the relative strength per cm2 of muscle cross section. In some studies, kids are weaker, in others, stronger (gastrocnemeus = probably well exercised through bouncing around).
The lower rate of glycolysis means that kids build up less lactate, and thus won't fatigue as quickly.
During puberty, some insulin resistance is observed.

The young athlete: some physiological considerations (Oded Bar-Or, 1995).
Are Prepubertal Children Metabolically Comparable to Well-Trained Adult Endurance Athletes? (Sebastien Ratel, Anthony J Blazevich 2017)
Oxidation rate of exogenous carbohydrate during exercise is higher in boys than in men (Brian W Timmons, Oded Bar-Or, Michael C Riddell 2002)
Nutritional Considerations for Performance in Young Athletes (JohnEric W Smith, Megan E Holmes, Matthew J McAllister 2015) - I don't quite agree with their recommendations on carbs...
Protein intake and nitrogen balance in male non-active adolescents and soccer players (N Boisseau, C Le Creff, M Loyens, J R Poortmans 2002) - balance at a daily intake of 1.57g Protein / kg of body mass.
Metabolic and hormonal responses to exercise in children and adolescents (N Boisseau, P Delamarche 2000)
Gastrocnemius muscle specific force in boys and men (Christopher I Morse et al, 2007).

How should kids train ?

Higher frequency training (2x per week or more) seems to be more effective.
Kids recover more quickly than adults, shorter rest periods can be used.
Some recommend to increase training volume by no more than 10% week on week.
In my opinion, given their metabolic characteristics, kids could train like women, with higher volume / shorter rest intervals than adult men.

Strength training recommendations for the young athlete (Jeffrey M Vaughn, Lyle Micheli 2008).
Effect of rest interval length on bench press performance in boys, teens, and men (Avery D Faigenbaum et al, 2008).

Growth spurts

Osgood-Schlatter (knee pain) and Sever's Disease (heel pain) can be particular concerns during this sensitive phase. "Growing pains" in these areas should not be taken lightly. Now - at the tender age of 55 - my doctor tells me that I have Osgood-Schlatter on my knees. An earlier diagnosis could have been helpful...

It can make sense to reduce training volume and intensity during this time. Light, but full ROM training may be valuable to encourage muscles to lengthen.

Nutrition (protein, vitamins, minerals) should be on point to support optimal physical growth. Mine probably wasn't - which is why I put such an emphasis on nutrient-rich food in my nutrition chapter.

Pathophysiology of Osgood-Schlatter Disease: Does Vitamin D have a Role? (note the high prevalence of Vitamin D deficiency even in a sunny country like Tunisia)