Everything You Need to Know From A to Z — Part 4: S-Z

Here we are at the end. If you've followed this series since Part 1, you've already gone through adaptation, aerobic base, cadence, drills, running economy, fartlek... and now it's time to close out the alphabet. It's no accident that the final letters include some of the concepts that generate the most questions from my athletes: sleep, tapering, lactate threshold, VO2max. These are terms that get used constantly and understood poorly, and that gap is exactly where I tend to see the most expensive mistakes in race preparation.

Let's go letter by letter, no filler.

S is for Sleep

If I had to pick a single underrated variable in recreational running, this would be it. Sleep is where a good chunk of muscle repair happens, where training adaptations get consolidated, and where hormonal regulation takes place. Five straight nights of poor sleep can cancel out the stimulus from an entire week of well-planned training.

There's an interesting link connecting exercise to cognitive function and, by extension, to sleep: running releases cathepsin B, a protein associated with improvements in memory and brain function [PMID:27345423]. It's a reminder that running doesn't just train legs and lungs — it trains the brain too, and the brain needs sleep to consolidate all of that.

Practical tip: prioritize 7-9 hours, especially the nights before quality sessions (intervals, tempo, long runs). If you have to choose between an extra workout at 5am or an extra hour of sleep, sleep almost always wins.

T is for Tapering

Tapering is the progressive reduction of volume (not intensity) in the 1-3 weeks before a major race. It's probably the part of training where the most anxious athletes make the most mistakes — out of fear of "losing fitness," they keep training hard right up until days before the race and arrive exhausted.

The science here is clear: you can cut volume by 40-60% while maintaining intensity, and not only do you not lose fitness, you show up fresher and perform better. Tapering isn't passive rest — it's active rest with a purpose.

Simple rule I use with my athletes: for a marathon, start the taper 2-3 weeks out. For a 5K or 10K, one week is usually enough. Keep a bit of intensity in there (some short reps at race pace) so the legs don't "go to sleep."

U is for Underlying Threshold (Lactate Threshold)

Lactate threshold is the intensity above which lactate starts accumulating in the blood faster than the body can clear it. Along with VO2max, it's one of the two physiological pillars that best predict endurance performance — and unlike VO2max, threshold responds very well to training even in experienced athletes.

Training near threshold (what many call a "tempo run" or "controlled pace") improves your ability to sustain high speeds without accumulating metabolic fatigue. It's the work that separates someone who "can run fast" from someone who "can run fast for a long time" — which is, in essence, what a half marathon or marathon is all about.

Practical tip: a typical threshold session is 20-40 minutes at a "comfortably uncomfortable" intensity — you should be able to say a short sentence, not hold a full conversation.

V is for VO2max

VO2max is the maximum volume of oxygen your body can consume and use during exercise. It's the most studied physiological variable in the history of sport, and while it has a significant genetic ceiling, it can be meaningfully improved with the right training — especially high-intensity intervals.

Here's a relevant data point for anyone training for body composition alongside performance: a study compared HIIT on a bike versus HIIT running in overweight or obese men, and found differences in fat loss and gut microbiota composition depending on the modality [PMID:38233990]. This suggests the running stimulus has specific metabolic effects that go beyond simple calorie expenditure — another reason not to underestimate quality work, even if speed isn't your main goal.

Practical tip: 3-5 minute intervals at an intensity close to VO2max (with recovery of similar duration) are among the most efficient ways to stimulate this variable. You don't need to do these every week — one session every 7-10 days during a specific training block is enough.

W is for Warm-up

The warm-up isn't a formality before "the real work." It's part of the training. A good warm-up raises muscle temperature, improves nerve conduction, prepares the cardiovascular system for the demand ahead, and reduces injury risk.

For easy runs, 5-10 minutes of easy jogging is enough. For quality sessions (intervals, threshold, races), the warm-up should include easy jogging + dynamic mobility + short strides that prepare the neuromuscular system for the speed you're about to demand from it. Skipping this and going straight into a fast interval is one of the most common — and most avoidable — ways to get injured.

X is for eXcess Training (Overtraining)

Yes, we had to stretch the letter a bit, but the concept is too important to leave out. Overtraining syndrome happens when training stress consistently outpaces the body's capacity to recover, without enough adaptation time between stimuli.

This is where a topic that's evolving quickly in sports science comes in: biomarkers. There's growing interest in using specific biological markers to detect accumulated fatigue and overtraining risk before it turns into injury or illness [PMID:41922043]. It's not yet a widely accessible tool for recreational runners, but the direction is clear: the future of training monitoring won't rely only on how you feel, but on objective data that backs up that feeling.

While that technology becomes more accessible, the classic warning signs still hold up: persistently elevated resting heart rate, insomnia, irritability, and stalled or declining performance despite training more. If you notice two or three of these signs together for more than a week, it's time to cut back, not push through.

Y is for You (the athlete you are, not the one you were or wish you were)

This letter is more philosophical than physiological, but it's one I repeat most often in coaching sessions. One of the most common mistakes I see — in new runners and veterans alike — is training according to the athlete they were five years ago, or the one they imagine they "should" be, instead of the one they actually are today, with the body, time, and recovery capacity they have today.

This is especially relevant for masters runners. There's evidence that the hearts of older endurance athletes respond differently to prolonged exercise than those of younger athletes, showing cardiac adaptations tied to aging combined with decades of training [PMID:40667749]. It's not worse or better — it's different, and training should reflect that difference. Competing in the 3000m in the masters 45-49 category myself, I adjust my volume and recovery quite differently than I did at 25. Ignoring this doesn't make you more disciplined — it makes you more likely to get hurt.

Practical tip: train by comparing yourself to your own progression, not to your past self or someone else's Strava feed.

Z is for Zoning In on Stride Mechanics

We close with the stride — the complete movement pattern between one foot strike and the next. Stride length, cadence, and ground contact time are the three variables that define your running technique, and all three change naturally with speed: there's no universal "perfect stride," only an efficient stride for each pace and each body.

A common mistake is artificially lengthening the stride to "run faster" — this almost always increases ground contact time and injury risk (especially in the shin and knee), because the foot ends up landing well ahead of the center of mass, acting like a brake with every step.

Practical tip: instead of forcing stride length, work on cadence (steps per minute) and let stride length grow naturally alongside the power you build through strength and speed training.

Closing the Alphabet

Four parts, twenty-six letters, and one underlying message: running, properly understood, isn't a collection of tricks — it's a system where every piece, from how you sleep to how your foot lands, affects all the others. You don't need to master all twenty-six concepts to run well. You need to understand the three or four that are currently limiting your progress the most, and work on them with patience.

If there's one thing I've repeated across all four installments of this series, it's this: details matter, but not all of them matter equally, and not all of them matter right now. The skill of good training — and of a good coach — lies in identifying which ones do, at the moment they do.

Thanks for sticking with this whole series. See you on the track, on the road, or on the trail.

References

• Frandsen J, Aaroe M. Cardiac Effects of Prolonged Endurance Exercise in Young and Older Athletes. Scand J Med Sci Sports. 2025. [PMID:40667749]
• Siebers M, Bizjak DA. Exercise biomarkers. Adv Clin Chem. 2026. [PMID:41922043]
• Couvert A, Goumy L. Effects of a Cycling versus Running HIIT Program on Fat Mass Loss and Gut Microbiota Composition in Men with Overweight/Obesity. Med Sci Sports Exerc. 2024. [PMID:38233990]
• Moon HY, Becke A. Running-Induced Systemic Cathepsin B Secretion Is Associated with Memory Function. Cell Metab. 2016. [PMID:27345423]
• Fokkema T, van Damme AADN. Training for a (half-)marathon: Training volume and longest endurance run related to performance and running injuries. Scand J Med Sci Sports. 2020. [PMID:32421886]