Training with your kids? Make sure it's child’s play

James Marshall explains why children aren’t simply ‘mini adults’ and shows how to put together some child-friendly training options that will benefit you and your children

The recent rise in recreational running is epitomised in the ‘parkrun’ phenomenon. This simple, free and elegant concept has proven very popular with 1.75million people registered in the UK, with 90,000 running each week^{Parkrun UK submission to Public Parks Inquiry blog.parkrun.com/uk/2016/10/09/parkrun-public-parks-inquiry/ d.o.i. 11/11/16}. Many of you reading this may be included in this demographic, and might well use the parkrun as a weekly or monthly measure of performance over 5km.

Some readers may have children that they take to either junior parkrun (2km) or the normal 5km run. As parkrun themselves have said “parkrun is actively encouraging participation among young people by establishing a series of junior parkruns exclusively for those aged between 4 and 14 years of age”^{Parkrun UK submission to Public Parks Inquiry blog.parkrun.com/uk/2016/10/09/parkrun-public-parks-inquiry/ d.o.i. 11/11/16}. But, is that what children should be doing at that age? Whilst the idea of a healthy family is great, are adults unwittingly forcing children to do what is right for the adults, rather than what is right for the children?

Children aren’t mini adults

The great exercise physiologist David Costill has stated that “growth, development and maturation of the organism are expressions that label the steps on the way towards adulthood”^{Wilmore, J. H., D. L. Costill, and W. L. Kenney. “Cardiorespiratory adaptations to training.” Physiology of sports and exercise. Human Kinetics, Champaign 220 (1994)}. In other words, children aren’t simply mini adults. If you ever watch children play in a park or school playground you will see how they move naturally. They do lots of short, intermittent bursts, usually in different directions and anaerobic in nature. What they don’t do is work for long periods doing the same thing in the same direction like steady state aerobic work^{Pediatric Exercise Science, 25, p508-514 (2013)}. Yet, as children grow and develop, they are able to sustain longer work efforts if required - such as during a testing session or for a 600m race. This improvement takes place in pre-pubertal children without any ‘aerobic training’ of the kind undertaken by adults who wish to improve their times.

In a study on Polish children doing the Cooper Test (how far they can walk or run in 12 minutes) girls were found to increase their distance covered up to the age of 13 and then plateaued but boys continued to improve up to the age of 16^{Studies in Physical Culture and Tourism Vol. 13, Supplement p127-129 (2006)}. This study looked at results in 1985 and then in 2005. You can probably guess that both groups declined over 20 years: girls by 100-200m and boys by 100-300m. In other words, the children were less fit in 2005 than their predecessors in 1985.

When this decline in fitness is talked about anecdotally a lot of emphasis is placed on school sport or physical education. But what about the parents’ responsibility? A study in the Netherlands looked at children’s activity outside, again from 1985-2005^{Personal Communication with study author Honore Hoedt. Scottish Athletics Conference (2016)}. They found that in 1985 the average child was playing outside for 30 hours per week, but in 2005 that had dropped to only five hours per week (figure 1). This has a huge effect over time; a 15 year old in 2005 walking into an athletics club, would have played outside for 12,250 fewer hours than his 1985 counterpart!

---

FIGURE 1 PLAY HISTORY OF 2005 VS. 1985 ADOLESCENT

Average hours playing outside	1985 Child	2005 Child	2015 Child
Per week	30	5	?
Per month	1500	250	?
Per decade	15000	2500	?

NB: data for 2015 cohort is not yet available but would be expected to continue the downward trend

---

How does playing improve endurance performance compared to taking your child running? Many researchers have found reasons beyond aerobic capacity to explain the improvement in endurance as children grow older: some are easy to measure; others are difficult, but still important. Whilst aerobic capacity undoubtedly plays some part (see box 1) much of the improvement comes from non-aerobic factors, which can (and are) developed through child friendly activities such as play.

Non-aerobic factors

Most of these factors are trainable, but size does matter. An increase in body size (rather than a relative rise in VO2max) is largely responsible for the improvements in endurance performance as children grow^{Res. Q. 48 p270-279 (1977)}. Extra height means a greater stride length, all else being equal, will lead to an improved endurance time in growing children. This is important to remember when training children: their times will improve with growth if they keep active, so be careful when justifying a specific training regime as the reason for improvement.

In a study that analysed standardised school fitness tests in the US, the researchers found that that VO2max was indeed significantly associated with 600-yard and 1-mile run times in 7 to 12-year-old subjects^{Pediatric Exercise Science 1, p313328 (1989)}. However, so were height, body fat percentage, and 50-yard dash times. The two factors that were the most significant determinants for both runs were body fat % and 50 yard dash time – ie children who were the least fat and ran the quickest over 50 yards also got the quickest mile and 600 yard times.

In another study on slightly older children, researchers showed that 60% of variance in 2km run times for children aged 10-14 was down to anaerobic factors as measured by the Wingate test^{Int. J. Sports Med. 5 p67-73 (1984)}. The Wingate test is a maximal effort test on a bike for 30 seconds measuring power output. Those children that did best on the bike for a short burst also performed best on the longer run.

---

BOX 1: AEROBIC CAPACITY AND THE DEVELOPING CHILD

For years researchers have looked at the correlation between maximal aerobic capacity (normally expressed as VO2 max) and endurance performance^{Pediatric Exercise Science 1, p313328 (1989)}. One of the reasons we know so much about VO2 max and children’s endurance performance is that it is quite easy to measure. This means a lot is published and talked about aerobic power, and therefore training programmes can becomes skewed towards the ‘research’. For example one study found that trained child cyclists were found to have a VO2max of 58.5mls/kg/min while untrained children had a VO2 max of 45.9mls/kg/min^{Acta Physiol Scand 175, 85–92 (2002)}.

For many years, VO2max has been measured and compared to endurance performance in both adults and children^{Res. Q. 48 p270-279 (1977) Sports Exer. 20:319-330, (1988)}. In adults, weight is usually stable and there is a correlation between VO2max and endurance performance - ie if you have a higher maximal aerobic capacity, you are likely to have a higher endurance performance (race time). But this correlation is less apparent in children; in adults, 2-mile run times have been highly correlated with V02 max^{Res. Q. 42 p54-59 (1971)} but in children aged 10-17 years, 2-mile run times are much less correlated with VO2max^{Med. SciJ. Sports Med. 25:10-17, 1985}.

Children’s weight increases year to year as they grow, therefore the kg part of ml/min/ kg is important. Children show an increase in endurance performance year on year, but their VO2 max doesn’t increase to the same degree because their weight is changing (see figure 2). In non-weight bearing activities such as swimming and cycling however, relative weight is obviously less of a factor than in running. Here, aerobic training has been shown to make an improvement in children. Research shows that heart size increases along with an increase in total blood volume^{Acta Physiol Scand 175, 85–92 (2002)}.

Figure 2: Changing aerobic capacity in developing children

---

Is running better than doing nothing?

Well-meaning parents often assume this is the case and use it as a justification for taking their children on long runs. But this is a false dichotomy - there are more options than just steady state running or sitting in front of a screen. It’s true that compared to their peers who are just ‘active’, there are some definite health benefits for children who run. One study looked at 9-10 year old girls who were members of the local athletics club  and compared them to their peers who just participated in school related activities^{Physical Education and Sport 13(3) p363 – 370 (2015)}. The girls who trained at the athletics club were (unsurprisingly) better at the 800m time trial than their peers, and also better at squats. However, there was no difference between the two groups for co-ordination in the air, baton twirling or push ups (skill and upper body strength tests). The athletics training had not improved these other components of fitness, so whilst it is good, it is far from the complete answer.

The problem is that formalising training too early (eg 6-mile runs with mum or dad) without incorporating elements of ‘playing’ can increase the chance of injury for your child. A study looking at 1206 teenage sports participants found that there were three big risk factors for getting injured^{Br J Sports Med 48 p611 (2014)}: specialising in one sport, indulging in too much organised activity and playing too much sport too soon (see figure 3).

Also, research shows that burnout is more likely if too much training is applied too early, with the wrong stimulus^{J. Hum. Sport Exerc. 4(3) p262-271(2009)}. In other words, will your child still be doing endurance training in twenty years’ time, away from your influence as a parent? Looking at the evidence, it’s clear that the ‘it’s better than doing nothing’ argument, only takes you so far. As the children are growing and developing, they need the opportunities for their bodies and motor skills to develop. Speed, neuromuscular control and skill are best optimised earlier in childhood. Aerobic power and endurance on the other hand can be developed at a later stage - as many masters endurance runners can testify^{Competitive Sport in the Second Half of Life as Exemplified by Track and Field Master Athletes [In German]. 1st ed. Ko¨ln (Germany): Sport und Buch StrauQ, p. 128 (1993)}.

---

FIGURE 3: RISK FACTORS FOR INJURY IN ACTIVE CHILDREN^{Br J Sports Med 48 p611 (2014)}

Speed, neuromuscular control and skill are best optimised earlier in childhood. Aerobic power and endurance on the other hand can be developed at a later stage

---

Training like a child

If you want to spend more time with your child doing healthy activities, why not train alongside them, rather than making them train alongside you? Children play more like sprinters train rather than how middle or longdistance runners train. So as an endurance athlete wanting to train occasionally with your kids, you should consider adding some of these sprint-type training sessions to your plan.

And lest you think that this is ‘wasted’ training time, bear in mind that studies looking at health in sprinters have found that sprint training (consisting of high intensity efforts for 30 seconds or less) boosts maximal oxygen uptake and insulin sensitivity, while lowering blood pressure, and waist and hip circumference (ie body fat reduction)^{BMC Endocr. Disord. 9(3) p1-8 (2009) Metabolism. 59(10) p1421-8 (2010) J. Physiol. 588(15) p2961-72 (2010) J. Appl. Physiol. 94(6) p2406-13 (2003) Exerc. Sport Sci. Rev. 43(1) p57-64, (2015)}.

In addition, there are some benefits from sprint training that endurance-only training may not produce. For example, bone mineral density (BMD) is higher in sprinters and middle distance runners compared to the normal population, whereas endurance runners sometimes have less BMD^{Osteoporosis Int. 24(7) p2033-42 (2013) Aging Male 13(2) p133-41 (2010)}. This may have something to do with the type of training that sprinters do: more resistance work and jumping actions for example. Adding in some sprint training could therefore enhance bone health.

---

PRACTICAL IDEAS

Here are some ideas that could help add some freshness to your training, but more importantly, help your child develop their fitness in a way that is appropriate to their age and stage of development.

---

SUMMARY

As a healthy, fit person who endurance trains, you will probably be more concerned with your children’s fitness than most parents. Wanting to spend more time with them and encourage them to lead a healthy and active lifestyle is a worthwhile endeavour. However, children aren’t mini adults; they have a small window of opportunity in which to fully develop certain parts of fitness such as skill, speed, flexibility and co-ordination^{Perceptual & Motor Skills: Motor Skills & Ergonomics 117 (2) p470-483}. Limiting their training to just running - and slow, long running at that - will hamper their future chances of doing other sports well, or indeed hinder the development of their maximum running speed. But by training alongside them and encouraging them to have vigorous active play, you will be able to spend quality time with them, have fun and develop yours and their fitness in different ways. This will help keep you fresh for your sport too!