The Endurance Lab

In this episode of The Endurance Lab, I sit down with Dr. Christian Cheung, an exercise physiology researcher and senior scientist at WHOOP, to explore what the science actually says about cannabis, THC, CBD, running performance, cardiovascular health, sleep, and exercise recovery.
Christian shares findings from his research examining what happens when people exercise after using THC or CBD. One particularly surprising result: participants felt they performed better after THC, even though their actual cycling time-trial performance was worse.
We also discuss why THC can raise your exercising heart rate by approximately 10–20 beats per minute at the same workload, why that doesn't necessarily mean a better aerobic training stimulus, and how cannabis use may affect sleep quality, HRV, and recovery.

➡️ Join The Endurance Lab Inner Circle on Telegram
👉 https://t.me/TheEnduranceLabInnerCircle

🔥 FIND YOUR TRUE ZONE 2 WITH TYMEWEARTymewear Vita Pro measures your breathing in real time to identify your individual physiological thresholds and help you train at the intensity you actually intend to train at.
➡️ Endurance Lab listeners SAVE $100 OFF the Tymewear Pro Training membership
Code: E-LABTW26
👉 https://www.tymewear.com/E-LABTW26

➡️ Listen to my conversation with TimeWear founder Anar Larson:
👉 https://open.spotify.com/episode/5sz25EZjGUHoGSaA38nHwM

CHAPTERS
00:00 Why runners think THC improves performance
01:56 Cannabis, THC, and CBD explained
07:03 Why people run while high
12:04 The surprising truth about THC and endurance performance
18:49 What the cycling performance study revealed
23:29 Why THC raises your heart rate during exercise
32:21 Is exercising with THC safe?
39:11 Does CBD improve performance and recovery?
42:52 Cannabis, sleep quality, HRV, and recovery
46:27 Cannabis and cardiovascular risks after 40

In this episode of The Endurance Lab, I sit down with Dathan Ritzenhein, a three-time Olympian, former American record holder, World Championship medalist, and head coach of On Athletics Club (OAC), to explore the fundamentals of getting faster—and staying competitive—as we age.
Dathan has experienced some of the most influential training philosophies in distance running, working with coaches including Mark Wetmore, Brad Hudson, Alberto Salazar, and the Hansons. Today, he draws on those experiences to coach some of the world's best runners.But what happens when we apply those elite training principles to marathon runners in their 40s, 50s, and 60s?
We explore why consistency matters more than chasing mileage, how to balance training volume and intensity, why masters runners shouldn't abandon speed work, and whether popular approaches like Norwegian double-threshold training make sense for recreational marathoners.
Dathan also explains how he would structure marathon training for a 50-year-old runner with limited training time who's trying to qualify for Boston, including how to organize workouts, long runs, strength training, and recovery.

➡️ Join The Endurance Lab Inner Circle on Telegram
👉 https://t.me/TheEnduranceLabInnerCircle

🔥 FIND YOUR TRUE ZONE 2 WITH TYMEWEARTymewear Vita Pro measures your breathing in real time to identify your individual physiological thresholds and help you train at the intensity you actually intend to train at.
➡️ Endurance Lab listeners SAVE $100 OFF the Tymewear Pro Training membership
Code: E-LABTW26
👉 https://www.tymewear.com/E-LABTW26

➡️ Listen to my conversation with TimeWear founder Anar Larson:
👉 https://open.spotify.com/episode/5sz25EZjGUHoGSaA38nHwM

➡️ On Athletics Club (OAC)
👉 https://www.on.com/en-fi/explore/athletes/oac-global?

Chapters
00:00 Why intensity matters after 40
01:25 Lessons from elite coaches
05:40 Consistency over mileage
11:32 Dathan’s biggest training regrets
16:07 Marathon training for busy runners
20:40 Inside On Athletics Club training
29:30 The long-term approach
36:03 Training for masters runners
43:53 Intensity vs. mileage after 40
47:22 Recovery as you age
50:17 Speed work and strides
55:51 Threshold vs. double threshold
1:00:36 Cross-training for marathoners
1:03:58 Strength training
1:06:09 Lessons from Dathan’s career

At age 49, Marilyn Tarkalson ran a 2:58 marathon, breaking 3 hours after previously running 3:21 and 3:14. Now, at age 50, she’s still trying to get faster.
In this conversation, we break down exactly what changed in Marilyn’s marathon training, nutrition, recovery and mindset. Whether you’re trying to run a sub-4 marathon, sub-3:30 marathon, qualify for Boston, break 3 hours, or simply run a faster marathon after 40, Marilyn’s progression offers a fascinating look at what it can take to keep improving as a masters runner.
Marilyn explains how she structures her training using a base → support → specific approach, how she built toward 50–60 mile weeks, why strides and speed work remain important as we age, and how she incorporates threshold training, marathon-pace workouts and long runs. We also discuss how she balances harder training with injury prevention and recovery.
But training was only part of her breakthrough. Marilyn says nutrition was the starting point. She explains how moving toward a whole-food plant-based diet affected how she felt and recovered, what she eats as an endurance athlete, and how she thinks about nutrients such as iron, ferritin, B12 and vitamin D.
We also get into strength training for runners over 40, recovery, sleep, HRV, menopause and HRT, and the mindset shift that took Marilyn from believing a sub-3 marathon was impossible to running 2:58 at age 49.
Perhaps most importantly, Marilyn doesn’t believe her best running necessarily has to be behind her. At 50, she’s still developing as an athlete and is now chasing an even faster marathon.
If you’re a masters runner, midlife runner, marathon runner over 40 or over 50, or you’re simply wondering how to improve your marathon time as you get older, this conversation is a reminder that meaningful improvement can still be possible with consistent training, recovery, nutrition and patience.

➡️ Join The Endurance Lab Inner Circle on Telegram
👉 https://t.me/TheEnduranceLabInnerCircle

🔥 FIND YOUR TRUE ZONE 2 WITH TYMEWEARTymewear Vita Pro measures your breathing in real time to identify your individual physiological thresholds and help you train at the intensity you actually intend to train at.
➡️ Endurance Lab listeners SAVE $100 OFF the Tymewear Pro Training membership
Code: E-LABTW26
👉 https://www.tymewear.com/E-LABTW26

➡️ Listen to my conversation with TimeWear founder Anar Larson:
👉 https://open.spotify.com/episode/5sz25EZjGUHoGSaA38nHwM

🏃 Work with Andrew / Run Elite Coaching:
👉 https://www.andrewsnowcoaching.com

CHAPTERS
00:00 From 3:21 to a 2:58 marathon at age 49
00:51 Marilyn’s running journey — and years of getting injured
06:12 How she went from 3:21 to breaking 3 hours
07:00 Training vs nutrition vs mindset: what changed the most?
10:32 What Marilyn eats as a plant-based marathon runner
14:05 How changing her diet affected recovery and performance
22:46 How she trained to run a sub-3 marathon
29:32 Marathon-specific training and marathon-pace workouts
34:18 Why speed still matters for runners over 40
41:54 Balancing speed work, recovery and injury prevention
46:41 Strength training for runners as they get older
54:26 Recovery, HRV, sleep and training fatigue
1:01:43 Why she’s chasing a 2:54 marathon at age 50

How do you run a faster marathon after 40?
Whether your goal is to break 4 hours, run a sub-3:30 marathon, qualify for Boston, or eventually run a sub-3 hour marathon, Andrew Snow argues that the answer may have far less to do with adding harder workouts—and far more to do with building the foundation required to support them.
Andrew Snow is a running coach and author of Run Elite, a book that takes training principles used by elite runners and translates them for recreational athletes. In this conversation, we explore how runners in their 40s, 50s and beyond can apply those principles to marathon training while dealing with limited training time, recovery capacity, work, family and the realities of getting older.
We break down Andrew’s base → support → specific approach to marathon training, why he prioritizes training frequency and mileage before harder workouts, how much running you may actually need to reach your marathon potential, the role of strides and hill sprints, marathon-pace training, long runs, nutrition, recovery and race specificity.
Andrew also explains why a runner trying to go from a 4-hour marathon toward sub-3 may need to think in terms of years rather than another 12- or 16-week marathon training plan—and why building a much bigger aerobic foundation could ultimately be the key to running your fastest marathon.
If you’re trying to figure out how to run a faster marathon, how to break 4 hours, how to run a sub-3:30 marathon, how to run a sub-3 marathon, or how to keep improving as a masters runner, this conversation offers a very different way of thinking about long-term marathon performance.

➡️ Join The Endurance Lab Inner Circle on Telegram
👉 https://t.me/TheEnduranceLabInnerCircle

🔥 FIND YOUR TRUE ZONE 2 WITH TYMEWEARTymewear Vita Pro measures your breathing in real time to identify your individual physiological thresholds and help you train at the intensity you actually intend to train at.
➡️ Endurance Lab listeners SAVE $100 OFF the Tymewear Pro Training membership
Code: E-LABTW26
👉 https://www.tymewear.com/E-LABTW26

➡️ Listen to my conversation with TimeWear founder Anar Larson:
👉 https://open.spotify.com/episode/5sz25EZjGUHoGSaA38nHwM

📘 Andrew Snow’s book — Run Elite:
👉 https://www.runelitebook.com/

🏃 Work with Andrew / Run Elite Coaching:
👉 https://www.andrewsnowcoaching.com

CHAPTERS
00:00 Can you still make a huge marathon breakthrough after 40?
00:30 Why runners plateau — and how to start improving again
05:34 Should you increase mileage or change your training first?
13:08 How much mileage can a runner actually tolerate?
19:18 Autophagy, fasting and recovery for runners
25:20 The best fueling strategy for endurance performance
29:44 Nutrition fundamentals for runners
37:28 The missing ingredient: marathon-specific training
40:00 Inner Circle: The highest-ROI workout for time-crunched runners
44:50 Andrew’s Base → Support → Specific training model
57:55 How much marathon-pace training should you actually do?
1:22:49 Putting it all together: building your marathon training plan

#MarathonTraining #RunningAfter40 #Marathon #MastersRunning #Running #Sub3Marathon #BostonMarathon #EnduranceTraining #RunFaster

In this episode of The Endurance Lab, I sit down with Dr. Greg Grosicki, Staff Research Scientist at WHOOP, to explore the science of HRV and HRV-CV and, more importantly, how runners can actually use these metrics to make smarter training decisions.
We break down why higher HRV is generally better while lower HRV-CV is generally better, why your seven-day HRV trend can tell you something very different from today's reading, and what different combinations of HRV and HRV-CV may reveal about recovery, adaptation and accumulated training stress.
We also get practical. What should you do when today's HRV is suppressed but you feel great? When should HRV actually cause you to change a planned interval workout? What happens to HRV-CV during a hard training block or taper? And can these metrics help runners recognize when they're adapting well versus drifting toward excessive fatigue?
For runners over 40, we also explore an especially interesting question: how do HRV and autonomic stability change as we age? Greg discusses research showing age- and sex-related differences in HRV-CV, what may happen after around age 40, and whether exercise and fitness could help attenuate some of the age-related decline in HRV.
In this episode, we cover: what HRV-CV actually measures; HRV vs HRV-CV; why HRV should be compared to your own baseline; whether wearable HRV measurements can be trusted; heat stress and HRV; daily HRV vs seven-day trends; four HRV/HRV-CV training scenarios; when to train hard versus back off; HRV-CV as a marker of adaptation; what happens during overload and tapering; HRV recovery and resilience; how HRV-CV changes with age; autonomic aging; and how Zone 2 and high-intensity training affect HRV.

➡️ Join The Endurance Lab Inner Circle on Telegram
👉 https://t.me/TheEnduranceLabInnerCircle

🔥 FIND YOUR TRUE ZONE 2 WITH TYMEWEARTymewear Vita Pro measures your breathing in real time to identify your individual physiological thresholds and help you train at the intensity you actually intend to train at.
➡️ Endurance Lab listeners SAVE $100 OFF the Tymewear Pro Training membership
Code: E-LABTW26
👉 https://www.tymewear.com/E-LABTW26

➡️ Listen to my conversation with TimeWear founder Anar Larson:
👉 https://open.spotify.com/episode/5sz25EZjGUHoGSaA38nHwM

➡️ Previous Endurance Lab HRV episode with Dr. Marco Altini
👉 https://youtu.be/D6ZPuaMaEgs

➡️ HRV-CV research discussed in the episode:
Grosicki et al. — “Heart rate variability coefficient of variation during sleep as a digital biomarker that reflects behavior and varies by age and sex”
👉 https://pubmed.ncbi.nlm.nih.gov/41309064/

Chapters
00:00 Higher HRV vs lower HRV-CV
00:30 Using HRV to guide running training
02:21 What is HRV-CV?
08:57 The science behind HRV-CV
12:03 How new is HRV-CV?
13:48 Dr. Greg Grosicki’s journey to WHOOP
19:31 What is WHOOP?
20:43 Sleep, recovery and strain
27:42 How WHOOP uses recovery data
31:04 Inner Circle: Can you trust HRV from sports watches?
35:15 How heat stress affects HRV
37:06 Daily HRV vs 7-day HRV vs HRV-CV
39:59 Two runners with the same HRV — but very different recovery
44:09 Four HRV + HRV-CV training scenarios
47:47 The HRV-CV warning sign
49:55 How to use HRV to decide whether to train hard
53:28 When good HRV can still be misleading
54:14 Is HRV-CV a measure of adaptation?
55:16 Why low HRV-CV isn't always good
57:19 What happens to HRV-CV during hard training?
58:25 How high is too high for HRV-CV?
1:00:49 What should happen to HRV-CV during a taper?
1:01:30 HRV recovery and resilience
1:03:30 What happens to HRV-CV as we age?
1:05:44 Autonomic aging and HRV
1:08:03 How training can improve HRV and HRV-CV