Maximising fitness for teenage males
When it comes to training children and teenagers, growth and maturation is a far more important determinant of training requirements than chronological age, says Toni Reinikainen.
One of the major problems evident in the training of children is a lack of knowledge and experience about how children grow and develop. When it comes to training it is critical to remember that children are not just smaller versions of adults, and that every child develops at a different rate. This is particularly evident between the ages of 12 and 15 years, when vast differences can be observed between individuals of the same age. Trainers and parents must be aware of the individual variations that occur in the physiological capacities of children.
Growth and maturation
Maturation refers to the timing and progress towards a mature state, while growth refers to the measurable changes in physical growth and various body systems1,2. Physical performance measures are related to the growth and maturation of an individual, especially when considering individuals with the same chronological age during pubertal years2.
Growth rate has been shown to be episodic, not necessarily gradual, by Lampl et al. (1992) who measured daily, half-weekly and weekly measurements of infants, and stated that 90 to 95 per cent of normal development is actually growth-free and growth is distinctly a process in incremental bursts3. Growth rate is highest during the first year of life with a gradual decline until the onset of the adolescent growth spurt2. During adolescence growth, stature rapidly increases with a similar growth in body weight2. Physical growth increases rapidly, reaching a peak (peak height velocity) at 14 years in males, then gradually declines and eventually ceases once adult stature is attained4.
Peak height velocity
Peak height velocity has been identified as a key measure for creating optimal individualised fitness programs during the maturation process5. The peak height velocity allows fitness professionals to identify periods of increased growth and program accordingly, as it has been shown that maturation levels will differ greatly between individuals despite having similar chronological ages5. Research has stated that the pubertal growth spurt for boys generally starts around the age of 12 and continues until the age of 176. Peak height velocity is reached at 14 years of age (12.5cm/year) before decelerating to zero at roughly 17 years of age, with the total growth during puberty approximately 28cm6. With such large magnitudes of growth occurring within short periods of time, there is increased risk of musculoskeletal and epiphyseal (cartilage) injury: therefore, it is imperative to monitor and control training load during such periods7.
During growth and maturation, longitudinal studies have shown that the greatest improvement (+70%) in absolute peak oxygen consumption (L min-1) occurs between 11 and 15 years, with a peak improvement coinciding with peak height (13.5 years) and peak weight velocity (13.5 years)2,6,8. Additional studies have noted that oxygen consumption, VO2 (mLkg-1min-1), in boys reaches a maximum around eight years, while marginally declining into early adolescence before leveling off during the remaining maturation process9. Although a decline in relative VO2 max occurs after peak height velocity, it is probably a reflection of the changes in composition rather than aerobic function2. Buono et al (1991) reported VO2 max (ml/kg/min) values across three different school groups aged; 10.6±0.5 years (mean± standard deviation) (47.8ml/kg/min), 12.8±0.6 years (47.6ml/kg/min) and 16.1±1.1 years (48.0ml/kg/min) and found very similar results across the groups.
|Implications for the fitness professional|
Anaerobic power development during childhood has been shown to increase steadily, with an increased rate of improvement at the onset of puberty6,10. Both sprint speed and jumping performance improves dramatically during adolescence, with the peak velocity occurring between the ages of 14 and 15 years9.
The development of speed has been shown to reduce in the interval before peak height velocity showing negative values (-0.6 s.year-1), subsequently indicating a plateau 12 to 18 months after peak height velocity11. Vertical jump shows a relationship with height and occurs at approximately the same time as peak height velocity.
Strength gains have been shown to improve dramatically from childhood to adulthood, with a peak velocity occurring after the onset of peak height velocity, or after approximately 15 years of age. Strength training suggestions provided by the Australian Strength & Conditioning Association (ASCA) recommend the introduction of light resistance and high repetition modified body weight movements with clients aged as young as six years of age provided they have the mental capacity to comprehend and follow simple instructions. Maximal loading (80 per cent+ of 1RM) is not included at any stage of junior development and should not be considered until full growth and maturation of an individual has occurred (18+ years).12
To safely and efficiently train young athletes, it is crucial to understand the many changes that take place during the maturation process and to structure the training programs you deliver accordingly.
Toni Reinikainen, BSc (Sp&ExSc)
Toni completed his Sport & Ex Science honours degree at the University of the Sunshine Coast in 2012 with the topic ‘Chronological development of fitness qualities in elite junior Australian rules footballers’. For more information email firstname.lastname@example.org