SENSIBLE STRENGTH TRAINING FOR PRE-ADOLESCENTS

Safe and productive youth strength-training programs based on research results show which strength-training protocols are best-suited for children.

A pervasive problem of childhood obesity exists today. But the two tactics most often employed for overweight adults — dieting and endurance exercise — are less likely to be effective for children. Generally speaking, preadolescents should not follow low-calorie diets, and they will usually not perform adult-style aerobic exercise (20 to 60 minutes of continuous treadmill running, stationary cycling, stair climbing, etc.).If you observe children at play, you will typically see brief periods of high-effort activity, followed by similar periods of low-effort recovery. Like puppies, they run fast and rest, run fast and rest. The activity best suited to childrens’ exercise characteristics, and the one that provides the greatest potential for improving their body composition, is strength training. A basic and brief program of sensible and supervised strength exercise is a safe and effective means for changing overweight kids into fit kids.

Youth strength-training research

Several studies prove the efficacy of strength training for children. A recent eight-week strength-training study was conducted with fifth-grade students.5 After performing body composition assessments on 176 fifth graders, 42 boys and girls with the highest percentage of body fat were selected as research subjects. Twenty-two children were placed in the exercise program, and 20 children served as a closely matched control group.

The exercisers performed about 20 minutes of free-weight strength training and about 20 minutes of active games twice a week under the supervision of their physical education teachers. The strength-trained youth improved their body composition almost twice as much as their peers (5.5 pounds vs. 2.9 pounds) (see Table 1). These findings indicate that a brief program of strength exercise may increase muscle development beyond that associated with normal growth processes. A similar study conducted with 11-year-old figure skaters using weight-stack machines produced almost the same results, especially the gain in lean weight following the strength-training program.6

In addition to enhanced muscle development, a year-long study with nine-year-old girls demonstrated a 6 percent greater increase in bone mineral density for those who performed strength exercises compared to those who did not train.4 Contrary to the unfounded fear that strength training is harmful to growing bones, this research suggests that sensible strength exercise significantly enhances skeletal development in preadolescent girls.

Although it is possible for a child to incur musculoskeletal injury while performing strength exercise, this has never occurred in my 15 years of conducting youth strength-training programs. Likewise, there are no reports in the research literature of serious injuries to preadolescent participants in supervised youth strength-training programs. For injury prevention, adherence to sound exercise principles and competent adult supervision are the key components of safe and successful youth strength-training experiences.

In 1993, a youth strength-training study was completed that produced an unprecedented 74-percent increase in overall muscle strength in 10-year-old children.1 The exercisers developed almost six times as much strength as the control subjects during the two-month training period (see Table 2).

The exercise protocol in this study was the DeLorme-Watkins system, consisting of three progressively heavier training sets with 10 to 15 repetitions each. The first set used 50 percent of the child’s 10-repetition maximum (10 RM) weight-load for 10 repetitions, and served as a first level warm-up. The second set used 75 percent of the child’s 10 RM weight-load for 10 repetitions, and served as a second level warm-up. The third set was performed with the child’s 10 RM weigh-toad for as many repetitions as possible. When the child completed 15 repetitions with this weight-load, the resistance was increased by 5 to 10 percent.

Another strength-training program used the Berger system.2 This exercise protocol required three sets with the child’s six-repetition maximum (6 RM) weight-load. After two months of training, the 10-year-old boys and girls increased their upper- and lower-body strength by an average of 47 percent. While this was a significant gain, it was considerably less than that attained with the DeLorme-Watkins program. Based on these two studies, two warm-up sets followed by one hard exercise set with a moderate weight-load (10 to 15 repetitions to fatigue) may be more effective for building strength in preadolescents than three hard exercise sets with a heavy weight-load (6 repetitions to fatigue).

A third study eliminated the sets variable, and strictly examined the effects of resistance/repetitions on youth strength development.3 This time, one set of six to eight repetitions using a relatively heavy weight-load was compared to one set of 13 to 15 repetitions using a moderate weight-load. The children who performed 13 to 15 repetitions made significantly greater increases in muscle strength and muscle endurance than those who performed six to eight repetitions (see Table 3).

These results indicate that preadolescents, unlike adults, may respond better to strength-training protocols that use more repetitions with moderate resistance than those that use fewer repetitions with heavy resistance. This may be related to the neuromuscular component of strength development in untrained children, with more exercise repetitions eliciting more motor learning. Of course, the risk of injury is further reduced by training with moderate weight-loads, making this exercise protocol doubly beneficial.

This training program (one set of 13 to 15 repetitions) was used with female figure skaters between eight and 13 years of age.6 Because these young athletes skated several days a week, their strength training was limited to 10 exercises, one or two days per week. The one- and two-day-per-week exercisers attained such similar results that the data was combined. After 10 weeks of training, the 26 skaters (mean age 10.5 years) increased their upper-body strength by 40 percent, their joint flexibility by 6 percent and their jumping performance by 11 percent. All of the participants expressed personal satisfaction with the strength-training program, and their skating coaches reported improved athletic ability on the ice.

These findings indicate that a basic and brief strength-training program is effective for improving selected fitness parameters and performance factors in female figure skaters. It also appears that a single weekly exercise session is sufficient for attaining significant strength development in young athletes who are concurrently participating in sports training and competition.

Youth strength-training guidelines

Based on the research findings, following are recommendations for safe and productive youth strength-training programs:

1. Select basic exercises for the major muscle groups. This could be as few as four multiple-muscle exercises, such as leg presses, chest presses, pull-downs and shoulder presses. The program could also consist of as many as 12 single-muscle exercises, such as leg extensions, leg curls, hip adductions, hip abductions, chest crosses, back pullovers, lateral raises, bicep curls, tricep extensions, abdominal curls, low back extensions and calf raises.

2. Have the youth perform approximately 12 exercise sets per training session. For example, three sets each of a four-exercise program, two sets each of a six-exercise program or one set each of a 12-exercise program.

3. Have children use a resistance that permits between 10 and 15 properly performed repetitions to muscle fatigue.

4. Increase the weight-load by 1 to 3 pounds whenever 15 repetitions can be completed in good form.

5. Make sure young people perform every repetition through a full range of joint movement, from a position of comfortable muscle stretch to a position of complete muscle contraction.

6. Have them perform every repetition with controlled movement speed, taking approximately two seconds for each lifting action, and two to three seconds for each lowering action.

7. Train youth two or three non-consecutive days per week. For children actively involved in sports, a single weekly training session should be sufficient.

8. Progress gradually and consistently. This can be facilitated by recording every training session on simplified workout cards.

9. Include aerobic activity and flexibility exercises in every training session, using group games whenever possible to enhance student involvement and enjoyment.

10. Provide competent instruction and supervision by qualified adults throughout every exercise class. For best results, try not to exceed a ratio of five children to one adult instructor.

Contrary to the fear that strength training is harmful to growing bones, research suggests that strength exercise enhances skeletal development.

Table 1. Changes in body composition for exercisers and control subjects over eight-week assessment period (42 subjects, mean age 11 years).

	Group Percent Fat	Lean Weight	Fat Weight	Body Composition
Exercise	-2.7%*	+2.5 lbs*	-3.0 lbs*	5.5 lbs
(N=22)
Control	-1.9%*	+1.5 lbs	-1.4 lbs*	2.9 lbs
(N=20)

*Significant change (p<0.05)

Table 2. Changes in muscle strength for exercise and control subjects after eight weeks of strength exercise (23 subjects, mean age 10 years). Exercise Group (N = 14) Control Group (N = 9)

10 RM Strength in kilograms	Pre		Post	% Change		Pre		Post	% Change
Leg Extension	12.9		21.2	64.5*		12.1		13.8	14.1
Leg Curl	10.4		18.5	77.6*		12.0		13.6	13.2
Chess Press	15.2		25.0	64.1*		13.4		15.0	12.5
Overhead Press	7.5		14.1	87.0*		7.8		8.8	13.1
Bicep Curl	4.7		8.3	78.1*		4.8		5.3	12.2
Mean % Change				74.3					13.0

*Significant two-way interaction (p<0.05)

Table 3. Effects of an eight-week youth strength-training program using higher repetitions and lower weightloads vs. using lower repetitions and higher weight-loads (43 subjects mean age 8 years).

Variable	Control group (no training)	Low rep group (6-8 reps)	High rep group (13-15 reps)
Leg Extension Strength	+13.6%	+31.0%	+40.9%
Chest Press Strength	+ 4.2%	+ 5.3%	+16.3%*
Leg Extension Endurance	+ 3.7 reps	+ 8.7 reps	+13.1 reps*
Chest Press Endurance	+ 1.7 reps	+ 3.1 reps	+ 5.2 reps

*Significantly different from low rep group (p<0.05)

REFERENCES

1. Faigenbaum, A., L. Zaichkowski, W. Westcott, L. Micheli and A. Fehlandt. The effects of twice-a-week strength training program on children. Pediatric Exercise Science 5: 339-346, 1993.

2. Faigenbaum, A., W. Westcott, L. Micheli, A. Outerbridge, C. Long, R. LaRosa Loud and L. Zaichkowsky. The effects of strength training and detraining on children. Journal of Strength and Conditioning Research 10(2): 109-114, 1996.

3. Faigenbaum, A., W. Westcott, R. LaRosa Loud and C. Long. The effects of different resistance training protocols on muscular strength and endurance development in children. Pediatrics 104(1): 1-7, 1999.

4. Morris, F., G. Naughton, J. Gibbs, et al. Prospective ten-month exercise intervention in premenarchael girls: Positive effects on bone and lean mass. Journal of Bone and Mineral Research 12(9): 1453-1462, 1997.

5. Westcott, W., J. Tolken and B. Wessner. School-based conditioning programs for physically unfit children. Strength and Conditioning 17: 5-9, 1995.

6. Westcott, W., and S. Ramsden. Specialized Strength Training. Exercise Science Publishers: Monterey, Calif., 2001.

Wayne L. Westcott, Ph.D., is fitness research advisor at the South Shore YMCA in Quincy, Mass., and author of 21 books on strength training.