ForumDosing & Titration

Any other long-distance athletes out there?

10 replies8 peopleApr 17, 2026☆ Follow
Summary

How does retatrutide affect heart rate, endurance, and fueling needs for hikers, runners, and cyclists training on a deficit?

Athletes on reta report modest RHR increases that often stabilize, earlier bonking on long efforts tied to larger calorie deficits rather than the drug itself, and preserved lifting strength. Low-carb users note they adapt using fat and ketones without issues, while others emphasize pre-effort carbs or gels to maintain output. Experiences vary by dose timing and individual adjustment periods, with some splitting doses to smooth effects.

What this discussion establishesWhere people disagree

Whether carbohydrates are required for reta efficacy or merely for sustaining high-mileage efforts

Still open

How max HR shifts over time or at higher doses for mixed LSS and HIIT athletes

Nothing here is advice.

10 replies · 8 people
RustKettle12archiveopening postApr 17

Hey everyone, question for the high-mileage crowd. I hike long distances most weekends, usually 25-35 miles with 2000-2800 ft of climbing, and I also powerlift three times a week. I began reta after gaining noticeable fluff over the past year from perimenopause, and the results have been strong. Started March 25 at 162 lb at 5'10.5" on 1 mg weekly split into two 0.5 mg shots; today I'm at 148. Lifting numbers have held up fine, nothing beyond what a normal cut would cause. After nearly four weeks the effects on RHR and HRV have been small, with resting rate moving from 46 bpm to 49-51 and HRV dropping just a few points. Calories dropped as expected but macros stayed decent. I've handled long hikes on cuts before, yet the bigger deficit now seems to make me bonk sooner. Yesterday with good weather and normal pre-hike food I expected at least 25 miles easily, but mad

SlowPebble71archiveApr 17

Just started myself so I can't really compare yet, but being in a calorie deficit will likely cut into strength and endurance somewhat. I'm doing a backyard ultra tomorrow and it will be interesting to see how it goes, though since I'm only on 0.25 mg of Reta so far I doubt it will change much.

RustKettle12archiveApr 17
↳ replying to @SlowPebble71

Backyard ultra people always amaze me. My own hikes stay interesting because the scenery and terrain keep changing, so watching runners loop the same course for 30 miles or more shows how much grit that takes. A runner friend did a 100-mile backyard ultra last year and I wondered about his sanity. You'll have to let me know how it goes!

QuietSignal61archiveApr 17

I always make sure to eat plenty of starches the night ahead plus first thing that day. Otherwise I might run dry partway through and need to crawl home with nothing but powder and liquid sloshing in my gut.

RustKettle12archiveApr 17
↳ replying to @QuietSignal61

I've followed a low-carb diet for epilepsy for over ten years, so my system runs efficiently on ketones and fat. Once fully fat-adapted my hiking stamina actually improved. Plenty of people here claim carbs are needed for reta to work, but that hasn't matched what I've seen. My best hike ever, 45 miles, was done fasted. This feels more like a total daily calorie and fueling question than anything about reta.

SlowLantern46archiveApr 17

Cyclist here trying to figure out fueling for longer rides. Twenty-five miles today doesn't really test it. My idea is to take a few gels an hour before the ride since absorption slows down. Pre-hike fueling is probably similar to pre-ride. Get ahead of it with gels, honey, and so on.

AmberBramble94archiveMay 6

I wanted to chime in quickly as someone new to Reta who runs long distances. I run six days a week and averaged 50-60 miles weekly over the past six months, with longer runs on Saturdays. Leg issues the last couple months cut my mileage. Since starting Reta I've noticed my RHR feels higher than I'd like and that makes me anxious, but my body seems to be settling and it's not as noticeable now. Staying in zone 2 during runs is tougher, though the spikes aren't as bad as they were in the first month. I haven't gone beyond 12 miles in one run since beginning, but I'm hoping for 16 this weekend if energy allows. Dosing 2 mg once a week, technically every six days to keep Monday timing, and thinking about splitting because effects seem to fade around day five. Overall pleased so far.

SteadyTimber22archiveMay 6

Yesterday I nearly took part in a half marathon.

RustKettle12archiveMay 7
↳ replying to @AmberBramble94

That lines up with what I've seen on double-digit mileage, though my RHR has only crept up a little across seven weeks on reta at 1 mg split in two doses. Most of my hikes stay in zone 2-3 and hit zone 4-5 on climbs, yet now I feel wiped out around 10 miles when 25-30 used to be normal before bonking. Lifts are holding up okay, not setting records but keeping volume solid. Down 20 lb with body fat at 16 percent, so the early bonking on hikes might just be my body saying to ease off and fuel better.

WryCompass65archiveMay 7

How is everyone's max HR, or do you avoid pushing into the upper zones? I've seen the same HRV and RHR shifts, but my max HR has also moved upward in proportion to the RHR change. I do a lot of mountain biking that can be steady endurance or high-intensity intervals depending on whether I'm doing distance or VO2 max sessions.

PlainTimber48archiveMay 7

Can't speak to reta since I'm on Tirz and have only used that, staying at 2.5 mg without going higher. I'm just maintaining and have held the same weight for six-plus months. I run over 40 miles and ride over 100 miles a week while lifting three days. I've only noticed lower HR and quicker times, but I also fuel properly and pay attention to hydration. Long runs take 70-90 g per hour.

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