This Week in Training Science: October 12–18, 2026

The most likely reason progressive overload matters for muscle growth is that it keeps sets close to failure as you get stronger. This is the editors' reading of the evidence, not a settled finding from a specific trial. A fixed load trained hard can still build muscle in the short term, but it becomes a smaller stimulus as you adapt. This brief covers that question, plus evidence-based guidance on Nordic hamstring curls, why soreness fades, and how to move your training history between apps without losing it.

Research Highlights

Progressive overload and hypertrophy

One existing trial speaks directly to how you progress. Plotkin et al. compared adding load against adding reps and found similar muscle growth between the two approaches (Plotkin et al., PeerJ, 2022; doi:10.7717/peerj.14142). How you progress may matter less than whether you keep progressing.

Editorial interpretation (not a study finding): Progressive overload works less like a switch that turns growth on and more like a way to keep effort high as you get stronger. If the load and reps never change, each set gradually ends further from failure as your capacity rises, so the same session delivers less stimulus. Over a few weeks, a consistent load trained hard can still produce growth. Over months, failing to progress quietly lowers the effort of every set.

Many hypertrophy trials are short, recruit untrained participants, and measure growth with ultrasound muscle thickness. Novices respond to almost any reasonable training, so results from these trials may not carry over to trained lifters, who adapt more slowly.

Expert Insights

Two evidence-focused explainers this week covered hamstring injury prevention and why soreness fades:

  • Nordic hamstring curls. The Nordic curl has some of the strongest evidence of any exercise for reducing hamstring strain injuries.

    • A meta-analysis of 15 studies including 8,459 athletes found that programs including the Nordic reduced hamstring injury rates by about 51% (van Dyk, Behan & Whiteley, British Journal of Sports Medicine, 2019).
    • Randomized trials in soccer players support the same conclusion (Petersen et al., American Journal of Sports Medicine, 2011; van der Horst et al., American Journal of Sports Medicine, 2015).
    • The effective dose is smaller than most lifters assume. A systematic review found that low-volume Nordic protocols produced eccentric strength gains similar to high-volume protocols (Cuthbert et al., Sports Medicine, 2020). Presland et al. (Journal of Science and Medicine in Sport, 2018) found similar architectural adaptations, including fascicle length, with low and high volumes.

  • The repeated bout effect. Your second leg day hurts less because the first one triggered adaptations that protect the muscle from damage. Reviews describe three groups of mechanisms (McHugh, Scandinavian Journal of Medicine & Science in Sports, 2003; Hyldahl, Chen & Nosaka, Exercise and Sport Sciences Reviews, 2017):

    • Neural: changes in how motor units are recruited.
    • Mechanical and connective tissue: changes in muscle and tendon stiffness and in the extracellular matrix.
    • Cellular and inflammatory: a changed inflammatory response and remodeling of the muscle cells themselves.

    Soreness is therefore a poor gauge of workout quality. Less soreness does not mean less stimulus.

From the Kenso Blog

Much of this week's content covered switching training apps without losing years of data.

  • Why app switches fail. Switches tend to fail for three reasons:
    • lost history,
    • friction while logging,
    • a new tool that does nothing useful with the data it receives.
  • Data portability. We published step-by-step migration guides from Hevy and Strong, plus a breakdown of what transfers. Here is how import works in Kenso:
    • Free and auto-detected. Settings → Import Workouts accepts Strong CSV, Hevy CSV, or a Kenso CSV/JSON export, up to 10 MB.
    • Exercise matching. Exercises are matched to Kenso's library. Any that can't be matched are listed and skipped before the import runs.
    • Safe re-imports. Importing a newer export only adds new sessions, so nothing is duplicated.
    • Full history credit. Imported sessions count toward PRs, charts, and muscle coverage.
    • Free diagnosis. With at least 6 imported sessions in the last 3 months, Kenso shows a free post-import diagnosis. It covers two things:
      • Muscle balance: where your volume went, plus blind spots. Kenso defines a blind spot as any muscle receiving under half the median volume across your muscles.
      • Strength standing: your best estimated 1RM on key lifts, tiered against strength standards when your sex, bodyweight, and age are known.
    • Turn history into a program. "Bring this into a program" detects the routine in your imported history and builds a Kenso program from it. Your first one is free; more are available on Kenso Pro.
  • Logger vs. coaching layer. Lifters who have used a logger for years already own their data. The open question is whether anything is analyzing it. A practical test: export your history and check whether any tool can tell you which muscles you've undertrained and where your lifts stand. If not, your logger is storing data without coaching from it.
  • Specialized tools.
    • MAPS Prime Pro: We're not aware of an official MAPS Prime Pro integration in mainstream loggers. The practical approach is to log corrective work in the same session as your main lifts.
    • Meet openers: For meet prep, choosing openers in the final eight weeks is best treated as a data problem. A common approach is to pick an opener you could hit for a single at around RPE 7–8 on a bad day, anchored to your recent top singles or estimated 1RM rather than your all-time best.
  • Home gyms for powerlifters. Smart gyms and all-in-one cable trainers have two problems for competitive lifters. Their resistance ceilings often top out well below competitive squat, bench, and deadlift loads, and they don't provide a true free-barbell path for the competition lifts. A conventional setup serves competitive lifters better:
    • power rack with safeties,
    • stiff power bar,
    • enough plates for your top singles,
    • sturdy flat bench,
    • protective flooring or a deadlift platform.

Training Takeaways

  • Progress the load with a clear rule. Once you hit the top of your rep range on all sets at roughly RPE 8 or lower (2 or more reps in reserve), add the smallest available increment. That is typically about 2.5 kg for upper-body lifts and 5 kg for lower-body lifts. Kenso's rule-based double-progression engine applies this logic for you. It recommends weight and rep increases, and flags when a deload is due, based on your logged sets and RPE.
  • Don't judge a session by soreness. Reduced soreness after repeated sessions is an expected adaptation. Track performance trends instead.
  • Add Nordic curls at a modest dose. Low-volume protocols produce eccentric strength adaptations similar to higher volumes (Presland et al., 2018; Cuthbert et al., 2020). Based on those findings, roughly 2 sets of 4–6 reps, once or twice per week, is a reasonable maintenance target. Reach it with a ramp-up: start with a single low-rep set and build volume over the first 2–4 weeks. This limits the heavy soreness the eccentric-focused Nordic causes in new users.

Bottom Line

Keep sets hard by progressing gradually, don't chase soreness, and treat your training history as an asset worth carrying forward.