Your body adapts to the stress you impose on it, as long as it is manageable and progressive. Your aerobic system is the foundation of everything — from a fast 5K to a marathon.

💡 80% of your weekly volume should be at easy intensity (zone 2). If you finish every easy run destroyed, you are not building base — you are accumulating fatigue.

Accumulated volume of easy miles over weeks and months, not days. The evidence on half marathon and marathon is clear: more volume associates with better performance, but injury risk rises if it grows too fast. (PMID:32421886)

💡 Progress volume by a maximum of 10% per week. Unload every 3-4 weeks.

Masters runners need to pay more attention here. A trained heart is not the same one you had at 25 — and recent research on cardiac effects of prolonged endurance exercise confirms that optimal volume changes with age. (PMID:40667749)

💡 After 40: full cardiovascular check-up if significantly increasing volume. Monitor your resting heart rate daily.

Rest is not the absence of training. It is an active part of training. When you run you create the stimulus. When you rest — especially when you sleep — your body repairs and adapts stronger.

💡 Never two high-intensity workouts on consecutive days. Masters (35+): consider an extra recovery day between hard workouts.

One of the most underestimated factors. Metabolic heat production during a marathon can exceed the body ability to dissipate it, especially in heat and high humidity. (PMID:11547895)

💡 At 77F (25C) with humidity you can lose 3-5% of performance vs ideal conditions. Adjust your target pace before you start.

For marathon: 30-60g of carbohydrates per hour starting at minute 45-60 of racing. Practice your strategy in at least 4-5 long runs before race day.

💡 Never improvise nutrition on race day. What you have not trained does not exist in competition.

📚 This is Part 1 of 4

Upcoming editions will cover letters G-M, N-R and S-Z. Save this thread — by the end you will have the complete science-runner alphabet.

The blog includes the full analysis of each letter with studies, exact nutrition and hydration numbers, and Henri reflection as an active masters coach and competitor.

Coach Henri

USATF Coach · Masters 45-49 · PMPRunning