Physiology Friday #285: Q&A on Ketones, Creatine, Endurance Nutrition, Heat Training, and More!

Greetings!

In place of this week’s newsletter, I recorded a Q&A session based on questions I’ve received in the last few months. I had so much fun doing it and hope you enjoy listening (and learn something!)

I answer a variety of questions related to training, nutrition, supplementation, and injury prevention; share insights on the use of ketones and creatine; discuss fueling strategies for workouts, and emphasize the importance of mental performance and adaptation. I also cover challenges related to heat training, health concerns associated with high training volumes, and the role of gear in running, as well as advice on weight management while training for performance.

You can find an edited list of questions and my responses below (for those who prefer to read). It’s a bit shorter and punchier for better digestibility.

Nutrition & Supplementation

Exogenous Ketones

Q: How often do you use exogenous ketones? I noticed recovery benefits during ultra training but not with lower volume.A: During peak marathon blocks I currently take 4 shots/week (of Ketone-IQ: two after my hard interval session and two after my long run. I pair them with post‑workout carbs and protein. I generally don’t use them in base phases or at low training volumes.

Q: What are your overall thoughts on ketones, and when/how often do you take them? Worth the investment?A: They’re not a miracle supplement, and many basics move the needle more. For me—solid sleep, nutrition, and training already in place—ketones are a small edge I experiment with mainly post‑workout for recovery. Cost matters, so I focus usage where I feel the most benefit.

Q: Do you use ketones pre‑workout or pre‑race? I’ve heard folks tout recovery benefits most.A: Rarely pre‑race. Occasionally before a long run for a “flow”/focus feel, but for performance I prioritize carbohydrates during the session. My primary use case remains after hard sessions and long runs.

Creatine

Q: Thoughts on creatine? Do you cycle off?A: I take ~5–10 g/day, every day. There’s no need to cycle; creatine isn’t a hormone and doesn’t cause receptor “desensitization.” If you stop for a week or two, your stores remain fairly saturated; after >~1 month off, benefits likely wane.

Q: Do you take creatine on non‑training days?A: Yes—daily. Creatine works via long‑term saturation, not acute timing.

Q: Does timing matter?A: You can take it anytime, but I prefer post‑workout with a meal (protein + carbs). Better blood flow/insulin sensitivity may help uptake and support glycogen/protein synthesis.

Q: What supplements are you taking right now?A: Daily: Omega‑3s (EPA/DHA), creatine, vitamin D, iron (FerroZorb/Thorne), and Tongkat Ali (experimental; no clear effects noticed, no downsides so far). I removed ashwagandha—I felt it sometimes blunted my drive/mood (anecdotal).

Fueling

Q: How do you fuel early‑morning sessions? Two‑hour rides are also hard to fuel.A: I’m not hungry early. I usually start fasted and then take carbs during (gels/drink mix). For 90–120 minutes, I aim ~40–60 g carbs/hour. ≤80‑minute easy runs I often do fasted.

Q: What do you eat right after a workout if you’re not hungry?A: Hot days kill appetite. I lean on Greek yogurt + granola + berries or a smoothie (protein + fruit + greens powder + ice). Cold/sweet options go down easier than “hearty” meals.

Q: You use multiple gel types. How do you choose, and why not Maurten?A: I rotate to avoid palate fatigue and to match purpose: caffeine vs. non‑caffeine; 40 g vs. 20–25 g carb gels; different carb sources (maltodextrin/fructose vs. “real‑food” blends). Current favorites:

* SIS Beta Fuel (40 g, isotonic)—easy to take without water.

* Minted (40 g + ~50 mg caffeine, unflavored)—simple profile.

* BPN GO (25 g, real‑food)—tasty and lighter. Maurten works but the chewable texture isn’t ideal for me at race pace.

Q: Benefits of fueling even “easy” long runs? Downsides of not fueling?A: Fueling easy long runs may not boost performance that day, but it protects recovery by limiting glycogen debt/calorie deficit. I feel better the next day when I fuel a 20‑miler vs. under‑fueling or going fully fasted.

Training & Workouts

Q: First six weeks of a 12‑week marathon block—what quality do you do? Continuous threshold or intervals? Key goal‑pace workout before race?A: Early and late phases look similar: lots of tempo/threshold work, with some shorter, faster reps closer to race day. I prefer continuous threshold (tempos; 2–3 mi repeats) over short reps. Two staples:

* 8–10 miles at marathon pace within a long run (dress rehearsal with fueling/shoes).

* 4–3–2–1 mile cut‑down (pace quickens each block; ~10 total quality miles).

Q: Strength training—do you follow a program (e.g., StrengthLog)?A: Not a strict program. I do simple bodyweight/dumbbell work a few times weekly (push‑ups, pull‑ups, DB variations). It’s minimal but helps durability.

Q: Go‑to bike workouts to improve running?A: Mostly aerobic intervals like 3–4 × 15–20 min @ ~80–85% FTP. Great marathon‑effort proxy. Otherwise lots of easy spinning to replace a Zone‑2 run.

Q: Downsides of adding biking in a marathon block? Overtraining risk?A: It’s not a free lunch—still a stressor. I adjust cycling down if run volume rises. That said, easy rides can be low‑cost aerobic work or recovery.

Q: Swimming instead of biking for cross‑training?A: Personal bias: I don’t enjoy swimming. It’s fine for fitness, but I find less direct transfer to running than cycling.

Q: Bike vs. elliptical for cross‑training?A: Elliptical mimics upright mechanics better, but I can produce/measure higher quality work on the bike. Preference and ability to hit the intended load should decide; I still prefer the bike.

Q: Are treadmill and pavement biomechanics different?A: Yes. Outdoors you propel over ground; on a treadmill the belt moves under you. Effort at a given pace often feels easier on the treadmill.

Injury Prevention & Recovery

Q: How do you prevent injury with 12–15 hr/week of training?A: No magic: sensible load management, don’t go hard daily, keep form a priority, do some strength, and stay generally active/robust.

Q: How do you decide whether to run with pain?A: I use a mental pain scale. If symptoms hit ≥4–5/10, persist after a few days off, or worsen, I shut it down and assess. Don’t push through vague pain that lingers (e.g., multi‑week hip pain)—get it checked.

Mental Performance & Adaptation

Q: Do you have a mental performance routine?A: Nothing formal. I practice self‑talk and “flow” during workouts. I also value training alone regularly to build self‑reliance for race discomfort.

Q: Progress from fitness vs. pain tolerance—what’s mattered more lately?A: Both. I’m fitter and more efficient/durable. Durability = less decline late in races. Learning to sit with discomfort and read physiology (breathing/HR cues) has been huge.

Heat & Environmental Training

Q: How do you handle brutal Southern heat (Austin, TX)?A: Basics: start early, hydrate, fuel, dress smart, and adjust expectations. Use effort, not pace. Heat acclimation helps, but it never feels easy.

Q: Should heat inputs (sauna, hot baths) be avoided on recovery days since heat is a stressor?A: Heat is real stress. Sometimes I substitute a workout with 30–45 min sauna on an easy day. Just count it in total load and listen to fatigue.

Q: You log sauna sessions—do you count them as training time?A: Yes, but I don’t always adjust running unless overall load feels high. In Texas summers I often skip sauna—the daily outdoor heat load is plenty.

Health & Physiology

Q: Does high volume make you reconsider due to coronary calcification or AFib risk?A: I follow the research closely. AFib risk seems higher in longtime endurance athletes; coronary calcium findings are mixed and confounded. Personally, multiple cardiac tests have been normal. I’m 32 and will keep monitoring, but it hasn’t led me to avoid endurance training.

Gear & Equipment

Q: Are “super shoes/trainers” just fun, or do they help on easy mileage too?A: They can reduce musculoskeletal load and may let you train more at lower cost if you run well in them. I wouldn’t use them 100% of the time, but ~75–80% of weekly mileage in super trainers can be reasonable for some runners.

Q: How do you carry water on runs?A: In heat I use belts (e.g., Nathan; “Nerd Belt”) or a light running vest (CamelBak) with front bottles and storage. Handhelds work but I prefer hands‑free. I also plan routes with refill stops when possible.

Weight Management & Performance

Q: Can I lose ~30 lb while building mileage/speed for a January marathon, working full‑time?A: Possible, but performance fueling and caloric deficit are at odds. Two paths:

* Concurrent, slow loss: ~200–500 kcal/day deficit (≈0.5 lb/week), prioritize carbs for training and protein for recovery.

* Staggered approach (preferred for smaller losses): Lose weight in an off‑season, then train at maintenance for performance. Either way: gradual, protein‑forward, and performance‑aware.

Training Symptoms

Q: I feel shaky only on Zone‑2 runs despite “fueling well.” Why?A: I experienced this and traced it (via CGM) to reactive hypoglycemia from eating carbs ~20–30 min pre‑run. Insulin was peaking just as muscles were pulling in glucose, dropping blood sugar. Fixes that worked for me:

* Start fasted, then take carbs ~20–30 min into the run; or

* Eat ≥60 minutes before (or immediately before, if you tolerate it). Cycling vs. running differences may vary individually—experiment with timing.

This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit www.physiologicallyspeaking.com/subscribe