The Runner's Glossary, Part 3: From N to R

We're continuing the glossary. If you made it here from parts 1 and 2, you've already built a vocabulary base that will help you read your own training with more judgment. This third installment covers N through R, and it's a dense stretch: this is where "core," "overtraining," "periodization," and "threshold pace" live — some of the concepts that generate the most questions in the consultations I get.

As in previous installments, the goal isn't to memorize definitions. It's to understand why each term matters when you're planning your season.

N for Núcleo (Core)

Core work isn't "doing crunches to look good." It's the system that transfers force between your upper and lower body while you're running at speeds where your foot touches the ground for a fraction of a second. A weak core won't hurt you directly, but it will show up as a knee collapsing inward, a hip dropping on each footstrike, or a stride falling apart in the final third of a long race.

At CFSC, I work on this with anti-rotation and anti-extension exercises (planks, Pallof press, dead bugs) rather than traditional crunches, because what you need in a race is to resist movement, not generate it.

Practical point: two 15-20 minute sessions per week are enough if you're consistent. You don't need more volume — you need to stop skipping them.

N for Periodized Nutrition

You don't eat the same way during base training as you do during race week. Periodized nutrition adjusts carbohydrates, protein, and timing based on each block's training load. In high-volume weeks or weeks with interval work, carbohydrate availability becomes more critical; in recovery weeks, you can allow yourself more flexibility.

O for Overtraining Syndrome

This is one of the most misused terms in recreational running. Most runners who say they're "overtrained" are actually poorly recovered or acutely fatigued — not in the clinical overtraining syndrome, which is a deeper, slower-developing condition involving hormonal suppression, disrupted sleep, and a performance decline that persists for weeks or months even with rest.

Recent research on exercise biomarkers [PMID:41922043] is relevant here: there's growing evidence that recovery status can be monitored with objective markers, not just subjective feeling. This doesn't mean you need bloodwork to train well, but it does validate something I've been insisting on for years: heart rate variability, sleep quality, and appetite are earlier, more reliable signals than "I feel tired," which can mean almost anything.

Practical point: if your performance drops for more than two weeks despite reduced volume, and it's accompanied by disrupted sleep, irritability, or loss of motivation to train, that's a real warning sign. Don't try to sort it out alone — talk to your coach or a health professional.

O for Overstriding

When your foot lands well ahead of your center of mass, you generate a braking force on every stride. It's one of the most common causes of knee pain and premature fatigue in runners who "feel like they're running fast but tire out fast." It's not fixed by consciously shortening your stride — it's fixed by increasing cadence a few steps per minute, which naturally brings your contact point closer to your body.

P for Periodization

If I had to pick the single most important concept in this whole glossary, it would be this one. Periodizing means organizing training into blocks with distinct objectives — base, specific, competition, transition — instead of doing "the same thing but harder" every week.

A plan without periodization doesn't fail because the runner isn't trying hard enough. It fails because there's no logical sequence: fatigue accumulates without moments of assimilation, or you reach your goal race having never touched your target pace. Classic periodization (Matveyev) is still a useful framework, but in modern practice it's combined with undulating approaches, where intensity varies week to week within the same block to avoid plateauing.

Practical point: if your training plan doesn't have a clear objective for each 3-4 week block, you don't have a plan — you have a list of workouts.

P for Pronation

Pronation is the foot's natural movement on landing, rotating inward to absorb impact. For years, "corrective" shoes were sold on the idea that overpronation was an enemy to eliminate. Current biomechanical evidence is far more nuanced: pronation is a normal mechanism, and forcing its correction with rigid footwear doesn't consistently reduce injuries in controlled studies.

Practical point: choose footwear based on comfort and how your body responds during trial weeks, not based on a pronation category assigned to you at a store.

Q for Fat Oxidation (Quema de Grasa)

The ability to use fat as fuel at moderate intensities is what allows you to run long distances without relying exclusively on limited glycogen stores. This capacity is trained — literally — by running in low zones consistently. It's the physiological reason why base training at conversational paces isn't "wasting time," but rather building the metabolic engine you're going to need on marathon day.

R for Threshold Pace (Ritmo de Umbral)

Threshold pace corresponds roughly to the intensity you could sustain for 60 minutes in an all-out effort — the point where lactate production starts to outpace your ability to clear it from your blood. Training in this zone improves your ability to sustain demanding paces for longer without accumulating metabolic fatigue.

It's different from VO2max, which we work at higher intensities and for shorter intervals. The common mistake is training threshold too often and too hard, turning what should be a controlled stimulus into an exhausting session that compromises the entire following week.

Practical point: one or two threshold sessions per week, totaling 20-40 minutes of specific work, is enough for most recreational and competitive runners.

R for Active Recovery

It's not synonymous with total rest. Active recovery — easy jogging, walking, light mobility work — keeps blood flow moving without adding significant load, and in many cases it speeds up the dissipation of perceived fatigue compared to absolute rest. The key is in the word "active": if your recovery jog ends up being a disguised workout, you've defeated the purpose.

R for Cardiac Risk in Prolonged Exercise

This letter interests me particularly as a masters competitor. Evidence on the cardiac effects of prolonged endurance exercise in younger and older athletes [PMID:40667749] shows that the trained heart undergoes real structural adaptations — chamber dilation, changes in diastolic function — that are generally beneficial, but that require long-term follow-up, especially in masters athletes who accumulate decades of high volume.

This isn't a reason to stop running long distances. It's a reason to get periodic cardiology checkups if you compete in endurance events consistently over the years, particularly past age 40. The relationship between cardiovascular health, hormone levels, and body composition is also well documented in the endocrine literature [PMID:26590935], and it reinforces something I keep repeating to my masters athletes: strength training and body composition management aren't "extras" at this stage — they're part of long-term cardiovascular protection.

Practical point: if you're over 40 and consistently training for half marathons or marathons, an annual EKG and cardiology consult are a reasonable investment, not an overreaction.

R for RPE (Rate of Perceived Exertion)

The perceived exertion scale remains, despite all the watches and sensors available, one of the most underrated tools out there. It lets you train by feel on days when heart rate is skewed by heat, stress, or a bad night's sleep, without losing control of intensity. A runner who learns to calibrate RPE well ends up more self-sufficient than one who depends exclusively on the numbers on their wrist.

Wrapping Up This Stretch

From N to R we covered programming concepts (periodization), physiology (fat oxidation, threshold pace), and long-term health (cardiac risk). If there's a common thread, it's this: the training that works isn't the most intense — it's the best sequenced and best monitored. The next installment closes out the glossary with S, T, U, V, W, X, Y, and Z.

References

• Siebers M, Bizjak DA. Exercise biomarkers. Advances in Clinical Chemistry, 2026. [PMID:41922043]
• Frandsen J, Aaroe M. Cardiac Effects of Prolonged Endurance Exercise in Young and Older Athletes. Scandinavian Journal of Medicine & Science in Sports, 2025. [PMID:40667749]
• Traish AM, Zitzmann M. The complex and multifactorial relationship between testosterone deficiency (TD), obesity and vascular disease. Reviews in Endocrine and Metabolic Disorders, 2015. [PMID:26590935]