Neural adaptations: fast software changes

Three weeks of stalled squats. The conventional answer is to switch programs because you've crossed into intermediate territory. The data says something else. In Part 3 of the Progressive Loading series, Dr. Jordan Feigenbaum and Dr. Austin Baraki walk through why the standard novice / intermediate / advanced framework runs into trouble in real training, what the four adaptive systems are actually doing across a training career, and why most of what gets called a stall is impatience with the noise floor at your current strength level.

This is Part 3 of the Progressive Loading series. Part 1 covered why loading should react to demonstrated adaptation. Part 2 covered RPE-based autoregulation and the artificial-momentum approach. Today is the mechanism layer.

Pre-order our book, Signal: barbellmedicine.com/signal

Timestamps

• 0:00 - Why your lifts aren't moving
• 1:52 - The novice / intermediate / advanced framework, three claims to test
• 13:23 - What 17 years of powerlifting data show about how long you keep getting stronger
• 32:28 - How getting stronger actually works (four systems on four clocks)
• 38:00 - What early growth is actually made of (the Damas 2016 deuterium study)
• 50:33 - The connective tissue lag and why early-training injuries happen
• 58:32 - Why heavy lifting works for bone density (and why "walk on a treadmill" advice misses)
• 1:05:10 - Why new lifters get hurt 3 to 10 times more than experienced lifters
• 1:12:56 - Fatigue is at least four different things (and most coaches treat it as one)
• 1:26:19 - The CNS fatigue myth (and what the data actually says)
• 1:33:52 - When the bar isn't moving: how to actually diagnose a stall
• 1:45:51 - Takeaways and next week's tease: leptin and low testosterone

What we cover 

- The novice / intermediate / advanced framework: three claims and why each one fails the data test

- The 17-year IPF strength curve and what the no-kink finding does and does not establish (Latella 2024)

- The four adaptive systems and their separate timescales (neural, muscle, connective tissue, bone)

- What early growth actually is, including the deuterium-oxide finding that most week-3 size is fluid (Damas 2016)

- Why connective tissue lags muscle by six to eight weeks, and why that produces patellar tendinopathy four months in

- The 9.5 vs 0.74 to 3.3 injury rate gap between novice and experienced CrossFit participants

- The CNS fatigue myth and the Skarabot 2018 finding that locates the fatigue in the muscle, not the brain

- Why the LIFTMOR trial result (heavy lifting for bone density in women in their 60s and 70s) is being missed by primary care

- A practical decision tree for stalls: environment first, then load, then program

- Tease for next week: leptin, the HPG axis, and the metabolic driver of low testosterone almost nobody connects

Resources 

Training Plateau Action Plan (free): https://www.barbellmedicine.com/training-plateau-action-plan/

Progressive Loading article series: https://www.barbellmedicine.com/blog/progressive-loading/

Beyond Progressive Overload (Part 2 article): https://www.barbellmedicine.com/blog/beyond-progressive-overload/

BBM Programs and Coaching: https://www.barbellmedicine.com/

Support our work on barbellmedicine.supercast.com

Latella C et al. Using powerlifting athletes to determine strength adaptations across ages in males and females. Sports Med. 2024. https://pubmed.ncbi.nlm.nih.gov/

Del Vecchio A et al. The increase in muscle force after 4 weeks of strength training is mediated by adaptations in motor unit recruitment and rate coding. J Physiol. 2019. https://pubmed.ncbi.nlm.nih.gov/30644584/

Lecce E et al. Resistance training-induced adaptations in the neuromuscular system. J Physiol. 2025.

Balshaw TG et al. Neural adaptations after 4 years vs 12 weeks of resistance training. Scand J Med Sci Sports. 2019. https://pubmed.ncbi.nlm.nih.gov/30474171/

Skarabot J et al. Voluntary activation and agonist EMG amplitude in resistance-trained men. J Appl Physiol. 2021.

Roberts MD et al. Mechanisms of mechanical overload-induced skeletal muscle hypertrophy. Physiol Rev. 2023.

Damas F et al. Resistance training-induced changes in integrated myofibrillar protein synthesis are related to hypertrophy only after attenuation of muscle damage. J Physiol. 2016. https://pubmed.ncbi.nlm.nih.gov/27219125/

Damas F et al. Early resistance training-induced increases in muscle cross-sectional area are concomitant with edema-induced muscle swelling. Eur J Appl Physiol. 2016. https://pubmed.ncbi.nlm.nih.gov/26280652/

Lazarczuk SL et al. Mechanical, material and morphological adaptations of healthy lower limb tendons. Sports Med. 2022. https://pubmed.ncbi.nlm.nih.gov/35657492/

Kubo K et al. Time course of changes in the human Achilles tendon properties. Eur J Appl Physiol. 2012. https://pubmed.ncbi.nlm.nih.gov/22105708/

Watson SL et al. High-intensity resistance and impact training improves bone mineral density in postmenopausal women: the LIFTMOR randomized controlled trial. J Bone Miner Res. 2018. https://pubmed.ncbi.nlm.nih.gov/28975661/

Aasa U et al. Injuries among weightlifters and powerlifters: a systematic review. Br J Sports Med. 2017. https://pubmed.ncbi.nlm.nih.gov/27445362/

Prieto-Gonzalez P et al. Injuries in novice participants during an eight-week start-up CrossFit program. Int J Environ Res Public Health. 2020. https://pubmed.ncbi.nlm.nih.gov/32155747/

Kanayama G et al. Tendon rupture in body builders. Sports Med. 2015.

Enoka RM, Duchateau J. Translating fatigue to human performance. Med Sci Sports Exerc. 2016. https://pubmed.ncbi.nlm.nih.gov/27015386/

Behrens M et al. Fatigue and human performance: an updated framework. Sports Med. 2023. https://pubmed.ncbi.nlm.nih.gov/

Halperin I et al. Accuracy in predicting repetitions to task failure: scoping review. Sports Med. 2022. https://pubmed.ncbi.nlm.nih.gov/

Skarabot J et al. Neuromuscular fatigue and recovery after heavy resistance, jump, and sprint training. Eur J Appl Physiol. 2018.

Garcia-Ramos A et al. Greater neuromuscular and perceptual fatigue after low-load to failure than heavy-load to failure. 2024.

Minor, Brian MS, CSCS1; Helms, Eric PhD, CSCS2; Schepis, Jacob3. RE: Mesocycle Progression in Hypertrophy: Volume Versus Intensity. Strength and Conditioning Journal 42(5):p 121-124, October 2020. | DOI: 10.1519/SSC.0000000000000581

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