Inter-limb low-frequency fatigue tracks the distribution of training dose rather than the underlying deficit: a case report from a five-week strength camp in an elite youth footballer
Krótki-Borowicki P, Quiroga B, Hijano J, Siedlecki H, Guerra J, Buchheit M. Inter-limb low-frequency fatigue tracks the distribution of training dose rather than the underlying deficit: a case report from a five-week strength camp in an elite youth footballer. Sport Perf Sci Rep. 2026; Sep; #318:v1.
We have been reading inter-limb asymmetry as a sign of limb status. What if it is (at least partly) just a mirror of how we load each leg?
In our return-to-play series (SPSR #289), an asymmetry that did not close by discharge was read as incomplete recovery. Fair enough, except that in rehab we always load the injured side more. So the two are impossible to separate.
This summer at Optimo Sport, Pawel and the team gave us the context to look at it. A young winger with a 32% hamstring deficit on one side and an ankle sprain on the other. Deliberately asymmetric dosing first, then equal repetitions, then a taper, with Powerdex measured before and after every session.
The asymmetry moved: 9.7% in week 1, 14.9% in week 3, and 1.2% after three light days. One case only, with running introduced in the same week as the peak, so it’s not proof. But enough to stop me reading a single-day asymmetry without looking at the programme first.
The finding I like most is the one we didn’t expect: the limb that gained the most strength (+66% concentric at 60°/s) was also the most variable from one morning to the next. Capacity and readiness are two different things.
Huge credit to Pawel Krótki-Borowicki, who led this, and to Jose, Bernardo, Hubert Juan, and the Optimo staff for the daily data discipline.
Related: LFF in RTP (#289) and modality-specific LFF signatures (#290) on [website]
