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Cold Plunges Probably Aren't Doing What You Think

  The cold plunge became the ultimate biohacker flex. The research paints a much more complicated picture — and for lifters, it might actually be counterproductive. Cold water immersion went from a niche recovery tool used by elite athletes to a mainstream wellness trend seemingly overnight. Social media is full of people climbing into ice baths at dawn, filming their gasping reactions, and claiming benefits ranging from reduced inflammation to improved focus to accelerated fat loss. Cold plunge tubs are now a multi-billion dollar market. It made ACSM's trending fitness list in 2025. The appeal is understandable. There's something viscerally satisfying about doing something uncomfortable and believing it makes you better. And cold exposure does have real physiological effects — it triggers a norepinephrine release, vasoconstriction, and an acute stress response that genuinely makes you feel alert and energized. But "it makes you feel good" and "it improves your t...
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Lengthened Partials: The Biggest Training Trend of 2025 Doesn't Live Up to the Hype

 Every fitness influencer told you to train in the stretched position for maximum growth. The actual data is far less dramatic than the headlines suggest.

If you follow evidence-based fitness content at all, you've been bombarded with lengthened partials over the past year. The concept took over YouTube, Reddit, and every training program from RP Strength to Jeff Nippard's channels. The claim was bold — training at long muscle lengths through partial range of motion is superior to full range of motion for muscle growth. Not just different. Superior.

Dr. Mike Israetel called stretch-mediated hypertrophy one of the most important discoveries in training science in years. Fitness influencers restructured entire programs around it. People started doing half-rep incline curls and deep-stretch flyes as if full range of motion was suddenly obsolete.

Then the research caught up to the hype. And the story it tells is a lot less exciting.


Photo by Samuel Girven on Unsplash

Where the Hype Came From

The theoretical basis for stretch-mediated hypertrophy is real and well-established. Mechanical tension at long muscle lengths activates signaling pathways — particularly the titin-based mechanosensing cascade — that stimulate muscle protein synthesis. Animal studies have demonstrated this convincingly for decades. Stretch a bird's wing with a weight and the muscle grows dramatically.

The human research picked up steam with a study by Pedrosa et al. (2023) published in the European Journal of Sport Science, which found that training at long muscle lengths produced greater hypertrophy than training at short muscle lengths in the leg curl exercise. Maeo et al. (2022) published similar findings in Scandinavian Journal of Medicine and Science in Sports showing greater muscle growth from exercises emphasizing the stretched position of the hamstrings.

These were well-designed studies and the findings were legitimate. The problem is what happened next — a classic case of fitness culture extrapolating a modest, specific finding into a universal training revolution.

What the Newer Research Actually Shows

Here's where the narrative gets complicated. Wolf et al. (2025) — a study co-authored by Brad Schoenfeld, Jeff Nippard, and other prominent researchers — compared lengthened partials directly to full range of motion training in trained individuals. Published in the European Journal of Sport Science, this study found that lengthened partial repetitions produced similar muscular adaptations to full range of motion repetitions. Not superior. Similar.

That's worth repeating because it directly contradicts the narrative that dominated fitness media for over a year. When lengthened partials were compared head-to-head against full ROM in trained lifters — the population that actually cares about optimizing hypertrophy — the advantage disappeared.

Schoenfeld and Grgic (2020) had already laid the groundwork for this in their review published in SAGE Open Medicine, noting that while training at longer muscle lengths shows promise, the overall body of evidence doesn't support abandoning full range of motion training. The effect sizes in most stretch-mediated hypertrophy studies were small, often around 6-7% at best, and many studies had methodological limitations including small sample sizes and short durations.

A meta-analysis by Pallarés et al. (2021) in Sports Medicine further reinforced that full range of motion training generally produces equal or greater hypertrophy compared to partial range of motion training — a finding that directly complicates the "just train the stretch" messaging.

Why the Hype Outpaced the Science

This is a pattern that repeats itself in fitness culture. A legitimate finding gets published. It shows a modest effect in a specific context. An influential content creator picks it up and amplifies it. Then a dozen other creators make videos about it because it's trending. Within weeks, a nuanced finding about hamstring training at long muscle lengths has been transformed into "lengthened partials are the best way to train everything."

The mechanism that drives this isn't malicious. Content creators are incentivized to present findings as more significant and more actionable than they actually are. A video titled "New Study Shows Modest Effect of Muscle Length on Hypertrophy in One Exercise" doesn't get clicks. "The Most Important Training Technique for Muscle Growth" does.

The result is that millions of people restructured their training around an effect that, when tested more rigorously, turned out to be marginal at best and nonexistent in some contexts. Meanwhile, the fundamentals that actually drive long-term hypertrophy — progressive overload, sufficient volume, adequate protein intake, and training close to failure — got pushed to the background in favor of the shiny new thing.

What This Means for Your Training

None of this means you should avoid training in the stretched position. There's nothing wrong with emphasizing long muscle lengths in your exercise selection — movements like incline curls, deep chest flyes, Romanian deadlifts, and overhead tricep extensions are excellent exercises. They've always been excellent exercises.

What you should probably stop doing is sacrificing range of motion to chase the stretch. If you're doing half-rep preacher curls at the bottom because someone told you that's where "the growth happens," you're making your training worse, not better. The research consistently shows that full range of motion training is at minimum equal to, and often better than, partial range of motion for overall muscle development.

The practical takeaway is straightforward — choose exercises that load the target muscle through a full range of motion, including the stretched position. Train them progressively, close to failure, with adequate volume. Don't abandon good programming principles to chase a marginal effect that the most recent and well-controlled studies can't even reliably replicate.

The Takeaway

Stretch-mediated hypertrophy is a real physiological phenomenon. The idea that training at long muscle lengths has specific benefits is supported by the literature. What is not supported is the claim that lengthened partials are a breakthrough technique that should fundamentally change how you train. The effect is small, inconsistent across studies, and disappears entirely in some direct comparisons with full ROM training.

The biggest lesson here isn't about muscle length at all. It's about how fitness media turns incremental science into revolutionary content — and how easy it is to reorganize your training around hype rather than fundamentals.

Sources:

  • Pedrosa, G.F. et al. (2023). Training at Long Muscle Lengths Leads to Greater Hypertrophy Than Training at Short Muscle Lengths. European Journal of Sport Science.
  • Maeo, S. et al. (2022). Greater Hamstrings Muscle Hypertrophy but Similar Damage Protection After Training at Long Versus Short Muscle Lengths. Scandinavian Journal of Medicine and Science in Sports.
  • Wolf, M. et al. (2025). Lengthened Partial Repetitions Elicit Similar Muscular Adaptations as Full Range of Motion Repetitions. European Journal of Sport Science.
  • Schoenfeld, B.J. & Grgic, J. (2020). Effects of Range of Motion on Muscle Development During Resistance Training Interventions. SAGE Open Medicine.
  • Pallarés, J.G. et al. (2021). Full Range of Motion Versus Partial Range of Motion Training for Muscle Hypertrophy. Sports Medicine.
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