Issue #3: Training Adaptation

✍️ Author’s Note

Welcome to this edition of the Threshold Lab newsletter! I’m Stephen Pelkofer, an experienced HYROX athlete with a men’s pro personal best of 59:41 and men’s pro doubles best of 51:39. If you want to learn about my story and how I got here, check out this Instagram post here.

The goal of this newsletter each week is to pick a training topic related to running or HYROX, do deep research into it, and provide actionable protocols that the reader can take away and apply to their training immediately. Let me read the research, listen to the experts on podcasts and youtube, and then give you the tools to make it work for you.

👨‍💻 Introduction

Topic: Training Adaptation

Hybrid athletes, runners, and HYROX competitors are all trying to achieve performance improvements in either strength, endurance, or both. Long-term improvements in either requires a solid grasp of how training adaptation works. How long does it take to see improvements? Why do plateaus happen? In this issue we’ll explore the science of adaptation, timelines for physiological adaptation to occur, and how these can depend on the training age of the athlete.

🔬 Deep Dive

Adaptation takes time. There is no cheating the system. When you start a new training block, your body doesn’t just magically transform after one hard workout. The physiological adaptations follow a timeline. While some changes do happen fast, others require weeks or months of consistent work. With time, discipline, and a little bit of structured variety and progression, anyone can change their body and performance.

On the endurance side of things, improvements can happen fast initially. One study saw VO₂max jump about 5% in just 1 week of daily high-intensity cardio (and ~44% increase after 10 weeks of training) [1]. That sounds incredible, but the dramatic early gains are usually in untrained individuals with a lot of room for improvement. In contrast, an elite endurance athlete who has been training for years might squeak out a very small percentage improvement over a similar training block. Adaptations like capillary growth in muscles, mitochondrial enzyme increases, or improved lactate threshold tend to accrue gradually over months or years of steady training, with diminishing returns as you get fitter. The key message: if you’re new to endurance exercise, expect significant jumps early on, whereas the veterans have to grind for smaller wins.

On the strength side, the timeline involves both neural adaptations (improvements in the nervous system's efficiency in recruiting and coordinating muscles) and muscular adaptations (physiological changes within the muscle tissue itself, such as hypertrophy). When you first start lifting, you often get stronger almost session to session in the first few weeks. This doesn’t mean you put on 5 pounds of muscle in a fortnight (shoutout the swifties) → your nervous system is just learning to recruit your existing muscle fibers more efficiently. The rapid early strength gains in novice lifters are largely neural and result in improved coordination of muscle firing and motor unit recruitment [1]. Strength training is a skill, and your body gets better at that skill quickly.

Muscle hypertrophy (increasing muscle fiber size) lags a bit behind the neural adaptations. While a measurable increase in muscle size can happen in the first few weeks of a new training program, the most significant muscle growth typically becomes evident after 8-12 weeks of consistent training [2]. This is why you need to stick with a hypertrophy program for a couple of months to really see changes. Early on, you’re laying the neural groundwork, but the visible muscular changes come later.

Like most things in fitness, the adaptation timing really depends on the training age and athletic background of the athlete. Novice athletes often improve rapidly in response to almost any consistent training stimulus. Experienced athletes see slower rates of change and likely need a totally new stimulus to see anything drastic change in a short training block. A veteran marathoner training for the Olympic trials is trying to find ways to shave off seconds or a couple minutes over a ~2 hour event, whereas a novice runner can improve 30+ minutes between two marathons.

There is a balance between consistency and introducing new stimulus. Improvements in fitness require consistently showing up, repeating the same workouts and exercises, and progressing slowly over time. However, you should not just do the same routine endlessly for weeks and months on end. Any athlete, regardless of fitness and experience level, will hit a plateau if they don’t make structured changes in their programming. More on this in the lab notes ⬇️

🧪 Lab Notes

In every issue of this newsletter, the “Lab Notes” are going to be the protocols that you can apply to your training and routine right away. The goal of this section is to translate the science into actionable steps for the reader, whether you’re a recreational runner/HYROX competitor, or someone pushing the limits of their peak potential.

• Consistency trumps everything else

  • The best workout plan is the one that you can stick to long term

  • Do not hop between workout plans every few weeks

  • There are no magic workouts that make you elite

  • Don’t get too comfortable doing the same thing forever – new adaptations will require progressive overload and a new stimulus eventually

• Specificity with slight variation

  • The longer you’ve been training, the more you need patience and smart programming to see marginal gains

  • Train specific qualities (like maximal strength, or aerobic endurance) long enough to get results, but present the body with new challenges once it adapts to the old one

  • Identify a weakness, build programming to address that weakness, and progress it intentionally over 6-8 weeks

  • Every so often, experiment with varying the exercises you are using in your core lifts

    • Barbell lunges → bulgarian split squats

    • Back squat → box squat or front squat

• Repeat key workouts a few times each year

  • Including a “testing week” in time periods outside of race prep is a good approach to see if you have improved on key markers

  • For HYROX athletes, this might include time trials such as: 10k run, 2k ski, 2k row, 5k ski, 5k row, 100 burpee-to-plate for time, ½ HYROX

• Adaptation happens during rest

  • All the hard training in the world won’t yield results if you don’t allow time for recovery

  • I will do a future deep dive on recovery and why it is critical for training and performance, but just remember that recovery is literally where and when adaptation takes place

  • The best recovery = good sleep and nutrition (not ice baths and sauna)

😁 Work with Me

I have helped many athletes either achieve a new PR or prepare for their first race. Fill out the 1:1 intake form below if you want a free consult – you can also signup for a free call with me directly through this booking link here.

That’s it for this edition of the Threshold Lab. If you enjoyed this and found it useful, please share it with a friend!

What I Read and Researched for this Issue

• [1] Time Course of Physiological and Anatomical Changes: NSCA's Essentials of Tactical Strength and Conditioning

• [2] Adaptations to Endurance and Strength Training: David C. Hughes, Stian Ellefsen and Keith Baar

• [3] Science of Running podcast: The difference between direction and magnitude of training adaptation