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Glycogen Window

The Glycogen Window is the 30-to-60 minute period immediately following high-intensity match play during which the body is most efficient at absorbing carbohydrates and synthesising muscle glycogen — the primary energy substrate for the anaerobic glycolytic demands of tennis.

Missing this window creates a compounding "energy debt" that degrades performance in subsequent matches of a tournament.

Why Glycogen is Primary

Tennis relies heavily on the anaerobic glycolytic system — the pathway that breaks down glycogen (stored glucose) in the muscles to produce ATP rapidly without oxygen, powering the explosive 3–10 second bursts of a rally. Between points, the aerobic system partially recharges this system.

When glycogen stores are depleted: - The anaerobic system cannot produce ATP at the required rate for explosive first steps and full-power groundstrokes - The aerobic recovery between points becomes less effective, as glycogen is also required for the aerobic pathway's function - The Performance Cliff accelerates — physical fatigue manifests first as reduced leg drive, then as kinetic chain breakdown

The Window Protocol

30–60 minutes post-match: Consume high-glycemic index (GI) carbohydrates during this window — white rice, pasta, or specialised recovery drinks. High-GI foods produce a rapid glucose spike that the maximally depleted muscle glycogen stores absorb immediately.

Protein synthesis: 20–30g alongside or within 2 hours: The violent eccentric loading of rapid deceleration and footwork causes microscopic muscle fibre tears throughout a match. High-quality protein (whey, chicken, soy) initiates Muscle Protein Synthesis (MPS) — the repair process that rebuilds these fibres. Without adequate protein, the muscle damage accumulates as soreness and reduced contractile capacity for the next match.

Fuelling Timing Table

Phase Primary Nutrient Goal
Pre-match (2–3 hours) Low-GI carbohydrates Sustained energy; avoid insulin spike at match start
Mid-match (changeovers) High-GI carbs + electrolytes Immediate glucose for ATP-PC recharge
Post-match (0–60 min) High-GI carbs + protein Rapid glycogen resynthesis + tissue repair

Alcohol and the Window

Alcohol after a match competes directly with the glycogen window: - The liver prioritises alcohol clearance over glycogen resynthesis — the "gas tank" stays empty while the toxin is processed - Alcohol inhibits the mTOR signalling pathway responsible for MPS — post-match muscle protein synthesis is reduced by up to 37% - Alcohol is a diuretic that exacerbates the dehydration already present post-match

If a player chooses to consume alcohol, the protocol is: restore hydration and complete the post-match meal first, then consume alcohol if at all — never within 48 hours of a major tournament match.

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