Fuelling and hydration
Eating for the work, and the framing we refuse to use with juniors.
Carbohydrate is the currency of a long match
Tennis is intermittent and can go on for hours. Muscle glycogen is the fuel that runs out, and when it does, both movement and decision making degrade. Intake scales with the work, not with bodyweight alone: a heavy training day and a rest day are not the same problem.
| Day type | Rough carbohydrate guide | Practical version |
|---|---|---|
| Light or recovery | 3 to 5 g per kg bodyweight | Normal meals, carbohydrate at each |
| Moderate, 1 to 2 hours on court | 5 to 7 g per kg | Add a carbohydrate snack around sessions |
| Heavy, or a tournament day | 6 to 10 g per kg | Deliberate fuelling before, during and after |
During play, 30 to 60 g of carbohydrate per hour is a common target once a match passes about an hour. Bananas, sports drink, gels and dried fruit all work. What matters is that the athlete has practised it before a match, because the gut needs training too.
Protein for adaptation
Protein supports repair and adaptation. Around 1.4 to 2.0 g per kg bodyweight per day is the usual range for a training athlete, spread across meals rather than concentrated in one. Roughly 0.3 g per kg per feeding, every 3 to 4 hours, is a simple way to do it.
Hydration
Tennis is often played in heat, and sweat rates in a junior match can exceed a litre an hour. Losing more than about 2 percent of bodyweight in fluid measurably affects performance, and more than that affects thermoregulation and judgement.
- Weigh before and after a hot session to learn an individual sweat rate. It varies enormously between athletes.
- Sodium matters in heavy sweaters. Water alone over a long hot day can dilute blood sodium, which is dangerous.
- Urine colour first thing in the morning is a crude but usable check.
- Drink to a plan on tournament days rather than to thirst, because thirst lags behind loss during play.
Underfuelling is the real risk in junior sport
Low energy availability means not eating enough to cover both training and the basic business of growing. Sustained, it affects bone health, hormonal function, immunity, mood and performance. In a growing athlete the consequences can be long lasting. The syndrome is described in the literature as relative energy deficiency in sport, or REDs.
Athlivate watches for patterns such as repeatedly skipped meals or persistent underfuelling on heavy days, and flags them to staff. It does not tell a 15 year old anything about their eating. That conversation belongs to a dietitian.