Fast bowler physio

My kid’s a great bowler – Just wait till they hit their growth spurt …

A guide to peak height velocity (PHV) and how we can predict when a child will grow, their increased risk of injury, and the impact on performance in young cricketers.

For many years on the cricket field I have observed many talented kids performing their skills.  Unfortunately I have observed many suffer some nasty injuries and others who suddenly can’t master their art and lose the love of the game.  Others too have been told that they are too little while others dominate due to their size and fall away later when the rest catch up.

The issue of growth maturity is not a new one but the more we understand what stage of maturity a young athlete is at we can work towards reducing injury and improving performance.  Here we will talk about the effect PHV can have on sports like cricket

What is Peak Height Velocity?

Pretty cool term for what simply means the most amount of growing a person will do after their first year of life.  In boys it is normally between 13 to 15 and in girls 11 to 13. It coincides with onset of puberty and can include drastic changes in athletic performance – both good and bad as well as impacting their injury risk.

After our first year of life we steadily decline in the rate of growth (i.e. as in cm we grow each year) until we hit PHV when this sharply increases.  During PHV adolescent boys grow between 5.8 cm to 13.1 cm per year and girls between 5.4 to 11.2 cm per year.

How do we know when it is happening?

You may not need a complicated formula to realise your child is transitioning to adolescence by their behaviours and physical appearances but the great thing we can do with some measures is predict when this will occur, plan for it and create a plan for them to get the best out of their body for cricket performance. 

We calculate the PHV by calculating what is known as maturity offset.  Maturity offset is a number telling us how far away onset of PHV. This is done by taking measures of height, sitting height and weight every 3 months.  Monitoring these changes allows increased accuracy to determine the actual age of onset.  We can also use this to predict their bone mineral content and adult height.  This can be useful in understanding what roles they may be suited to once fully grown.  This will allow the youth cricketer to make adjustments to optimise how their height can work for them in batting, bowling, wicket-keeping and fielding.

I personally use a normative data formula and this formula has increased accuracy when within 12 months of onset when measures are taken at a single point in time.  If you have received a measure and the predicted time is between -1 and 0 that score is pretty accurate providing the tests were done accurately.  The PHV period usually lasts for up to 18 months at which point Peak Weight Velocity occurs.

How does PHV change what we do?

PHV has significant implications for the type of training a child / adolescent should be doing to improve performance and minimise injury.  The exercises and activities done in the pre and during phase have lifelong implications and so what they do now may impact their injuries in their late teens and even their 30’s!!

PHV has significant impact on changing bone and muscle structure as well as coordination, skill development and ability to develop strength, speed and power.  It is beneficial to understand what type of training can and should be done before and during PHV to optimise performance, physical development and risk of injury. 

growth chart

A word on bone strength in young cricketers

Bone strength is a combination of the bone mineral content (BMC) and the size (thickness and radius) of the outer layer of the bone. Bone strength is effectively the bones ability to resist stress and is strengthened through high frequency repetitive exercise.  

  • High Frequency loading includes fast, powerful, jolting style training including landing from jumps and hops for the legs, throwing for the shoulder and fast bowling for the spine
  • When a bone undergoes a high frequency load of up to 100 repetitions (we believe 30 fast bowling deliveries results in 100 repetitions of load to the spine) it adapts the size and BMC nicely over the next 4 to 6 hours and rebuilds stronger bone that can resist more stress. 
  • Changes to the bone size capacity (maximal outer layer radius/thickness) is only available to use in childhood and adolescent years.   
  • In children who have yet to hit puberty or onset of PHV, then they have greater adaptability to building stronger bones with active children demonstrating increases of > 20% of bone strength compared to PHV period (15%) and post-adolescent (5%). 
  • If anyone (adults included) go beyond these 100 repetitions then the bone fails to adapt efficiently.  It is less sensitive and requires a longer rest period to restore the bone building workers work ethic. 
  • Adult level BMC is not achieved until approximately 6-8 years after the onset of PHV.  At this stage the risk of lumbar stress fracture substantially decreases (normally 22 years of age in young males)

Bone Strength Development for cricketers can include:

  • Fast bowling up to 30 balls then complete rest for 4 to 6 hours to develop the lower limb, spine and pelvic bones
    • if you go above the 30 balls longer rest periods are required – sometimes an extra day or 2
    • Harder bowling surfaces (such as concrete) may decrease the threshold for optimal repair, therefore  more rest required
    • Less strength / control in hip, knee or ankle may increase the demand on the spine and therefore decrease the threshold for optimal repair and more rest will be required
  • Jumping and hopping up to 100 times then complete rest for 4-6 hours
  • Throwing at low intensities up to 50 throws

It is important that to get the benefits the complete rest phase is adhered to.  This means that if they have bowled 30 balls for the sake of improving their bone strength they should not go and run and jump for at least 4-6 hours

Note that if you go above these recommendations then longer rest periods are required to benefit from the changes.  We know that sometimes they will bowl or throw more but extra rest is required for the bone-building workers to be able to do their work again –> hence we encourage rest days between bowling sessions but other activities can be done while the spine is building itself up!!

Pre-PHV (a negative maturity offset number)

For children not yet at PHV this is an excellent opportunity to prepare them for better skills, speed and bone development. During this period their bones adapt exceptionally well to optimising the size of the bones they develop. This is the window of opportunity to develop a robust spine!!

For our young cricketers, especially fast bowlers it is encouraged that they work on

• Supervised plyometric exercises including jumping and hopping to improve bone strength and balance / stability
• Supervised technical sprint and speed training, including change of direction and agility
• Unweighted / body weight or low-resistance supervised lifting techniques so they are better prepared to take advantage of hormone adaptations once the reach onset of PHV
• Sport specific skills

The key in this phase is regular monitoring of the maturity offset (time to PHV) for when it gets between 0 and -1 the accuracy for onset of PHV is accurate and we can plan their training based on their maturity status.

An example of a beginners exercise program for cricketers.  Those that are pre-PHV should focus on quality movement and then once PHV starts and the basics are achieved weights can be added slowly.  P360 does recommend that resistance exercises be prescribed and supervised by a qualified coach or health professional.

Maturity Status

Maturity status refers to the developmental/biological age of the child relative to their chronological (actual) age.  Effectively when they commence PHV.  The average age of PHV onset in boys is 14 years and in girls is 12

  • Late maturers are 1 year behind average PHV onset (boys >15, girls > 13)
  • Early maturers are 1 year before average PHV onset (boys < 13, girls < 11)
  • Normal Maturers are between 1 year before and 1 year after average PHV onset

Early maturers

  • Tend to have a higher risk of overall injury
  • Tends to be more related to muscle and tendon issues. 
  • may have increased muscle development and less conditioning and skill development to use it
  • may be faster relative to others of the same age and therefore run more in training and games
  • Tend to dominate the sport as they are competing against kids of lower biological age even though they are the same age
  • Important to focus on skill development and commence strength programs earlier

Late maturers

  • May not have the necessary muscle development to be doing higher intensity training
  • May not have the growth plate closures expected for others of the same chronological age
  • Osteochondral issues such as Osgood Schlatter’s (pain at the bottom of the patellar tendon) tend to be more prominent in late maturers. 
  • Tend to be the kids who struggle to “hit them off the square” and don’t generate lots of bounce when they bowl or power when they throw
  • Important not to push too hard in lifting weights and would best be comparing their strength tests to other children of the same biological age even if they are younger

The onset of PHV (a positive maturity offset number less than 1.5)

In the first year after onset of PHV adolescents are more likely to suffer traumatic injuries (such as rolled ankles and twisted knees). Why is this so?

Firstly understand what is happening.  The adolescent has increased hormones including testosterone which allows those in their PHV period to develop extra muscle bulk and strength.  The catch?  They are more susceptible to adolescent awkwardness, which occurs in about 25% of active children.  Adolescent awkwardness results in slower running times, slower bowling, lack of foot work while batting, dropped catches and inability to move to the ball in the field.  This is because these adolescents are learning to use different muscles in different ways with limbs at different lengths!!

Our answer traditionally has been make them run further, catch more, bowl more, bat more and yell at them for being lazy!

Unfortunately, there is no easy answer here as this is where we as coaches and parents have to take a deep breath and know that they will pass through this phase.  The consequence though is kids losing interest in the sport or developing an overuse injury (such as Osgood Schlatter’s or a low back stress fracture) or an acute injury such as a dislocated finger or torn hamstring muscle.

It is important in the PHV stage that they focus on

  • Supervised strengthening programs to build strength and muscle
  • Integrate bone strength development training with bowling demands (i.e. continue to bowl to build the spine but respect the rest period)
  • Sport specific skills to meet the strength and size changes

The Take Home Message

It is extremely beneficial to understand a youth athletes maturity status when commencing a cricket specific training program.  This will help in understanding the variability in a youths cricket performance and in the short term help prevent the development of injuries.  The benefits of targeted training will pay off with the potential to reduce the risk of nastier injuries such as stress fractures which are the biggest time loss injury in young cricketers.  What they do now literally shapes the way their spine will work.

  • Don’t be discouraged if your child is a late maturer and hasn’t hit PHV as yet as they can focus into other significant skill development
  • If an early maturer focus on getting strength to make sure the bodies muscles become stronger
  • All children should focus on developing stronger bones through a targeted program

Please note that youth strength and rehabilitation programs should be individualised to the athlete based on everything discussed in the article and assessed during a testing / assessment procedure.  We highly recommend that exercises are supervised and prescribed by a strength and conditioning and/or physiotherapist with experience in youth athletes.

To show your interest or to register for the P360 Youth Cricketers Program from July 2021 please submit your details below and we will provide you with a free maturation and adult height estimation.

Aaron Lewis – High Performance Physiotherapist is Level 2 CNSW Representative Cricket Coach and a focus on Cricket injuries, for queries or to book a consultation to discuss a cricket performance screening please contact Aaron directly.

Join the P360 Cricketers Youth Program

BAppSc (Phty) Masters (Sports PHTY) APAM

High-Performance Sports & Exercise Physiotherapist, Director

Aaron Lewis is a Physiotherapist with a focus on Achilles tendon, ACL tears, hamstring, and Upper limb throwing and lifting pathology. He is also the founding director and senior consultant Physiotherapist at Performance 360.

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