REF-1301 · Thomas et al., 2018 · Medicine & Science in Sports & Exercise · Paper · PubMed

Do heavy squats or sprints need 72 h before my next maximal effort?

In 10 male athletes, fatigue cleared by 72 h after heavy squats and sprints, by 48 h after jump squats. Nerve-stimulation markers, not endurance performance (B-).

Main caveat: Read from the abstract only; the athletes' sport and training history, session order, washout, magnitudes and the definition of "resolved" could not be checked.
limited, mixed evidenceMeasured on trained athletes

Thomas and colleagues tested the common assumption that maximal-effort sessions must be separated by at least 48 h because they fatigue the central nervous system.

Ten male athletes completed three sessions that required maximal efforts with different loading: heavy resistance exercise (10 × 5 back squats at 80% of one-repetition maximum), jumping (10 × 5 jump squats) and maximal sprinting (15 × 30 m).

Before, immediately after and 24, 48 and 72 h after each, they measured neuromuscular function with electrical stimulation of the femoral nerve and single- and paired-pulse magnetic stimulation of the motor cortex, with responses recorded from the knee extensors, and self-reported fatigue on a visual analogue scale.

Each session produced fatigue that resolved by 48 h after jumps and by 72 h after squats and sprints. The potentiated quadriceps twitch force — a measure of muscle function — was reduced for 48 h after all three. Voluntary activation was reduced for 24 h after jumps and sprints and for 48 h after squats; no other changes in central nervous system function were seen.

The authors conclude that such sessions need up to 72 h to recover fully, but that the fatigue is not mainly central.

Our reading: one of the few direct sources of a 72-h figure, and it is session-specific — heavy squats and sprints, not jump squats — and measured as force capacity, so it supports a long gap before maximal work rather than before every quality endurance session.

Protocol

Participants: n = 10 male athletes; sport, age, training level and strength-training history are not given in the abstract.
Familiarity: not stated whether the athletes regularly did heavy squats, jump squats or sprints (likely, as athletes; our inference).
Sessions (crossover): STR — 10 × 5 back squats at 80% 1RM; JUMP — 10 × 5 jump squats; SPR — 15 × 30 m maximal sprints. The order, randomisation and washout between sessions are not given in the abstract.
Measures: pre, post, 24, 48 and 72 h — electrical stimulation of the femoral nerve (potentiated quadriceps twitch force), single- and paired-pulse transcranial magnetic stimulation of the motor cortex (voluntary activation and cortical measures), responses from the knee extensors; self-reported fatigue on a visual analogue scale.
Funding and interests: not stated in the abstract; PubMed indexes the paper as "Research Support, Non-U.S. Gov't" without naming the source.

Key Results

Time to recovery after each session (abstract):

MeasureHeavy squats (10 × 5 at 80% 1RM)Jump squats (10 × 5)Sprints (15 × 30 m)
Fatigue resolved by72 h48 h72 h
Potentiated quadriceps twitch force reduced for48 h48 h48 h
Voluntary activation reduced for48 h24 h24 h
Other central nervous system measuresno differencesno differencesno differences
The abstract does not say which measure defines "fatigue resolved" (maximal voluntary force, the composite of measures or the self-reported scale), and gives no magnitudes, SDs or confidence intervals.
No endurance or sprint performance test was taken during recovery.

Mechanisms

Measured: the lasting impairment was peripheral (twitch force down for 48 h after all three sessions); voluntary activation recovered within 24-48 h; cortical measures did not change.
Authors' interpretation: the 48-h rule between maximal sessions is not justified by central nervous system fatigue; recovery is set mainly by muscle function and can take up to 72 h after heavy resistance and sprint sessions.
Inference: jump squats recovered faster than both heavy squats and maximal sprints; external load alone cannot explain it, since unloaded sprints took as long as heavy squats (the abstract gives no mechanism).

Practical Application

Do heavy squats or sprints need 72 h before my next maximal effort? In 10 male athletes, fatigue cleared by 72 h after heavy squats and sprints, by 48 h after jump squats. Nerve-stimulation markers, not endurance performance (B-).
Use 72 h before a sprint, a power or ramp test or a race after a heavy squat or a maximal sprint session (this study's time course for force capacity).Not from this paper; the base's own practice: a familiar heavy lift ≥24 h before threshold or VO2max work and ≥48 h before a sprint or a test; a new or damaging one ≥48 h before quality; new and damaging ≥72 h before maximal running (SYNTH-31, which notes that this study's 72 h may also apply before a sprint or a test after a familiar heavy squat session, where its rule keeps 48 h); steady endurance or tempo is fine in the 24-48 h damage window and testing is not (SYNTH-23, on REF-701: muscle damage cut sprint and incremental peak power, not time-trial output).
Light, explosive jump work recovers by about 48 h (this study). Not from this paper; the base's own practice: plyometrics not within about 48 h before a key session (SYNTH-45), which this time course supports for jump squats.
"CNS fatigue" is not the reason to space sessions — the measured deficit was in the muscle (this study's conclusion).

Limitations

Read from the abstract only; the athletes' sport and training history, session order, washout, magnitudes and the definition of "resolved" could not be checked.
n = 10 men; neuromuscular markers only, no performance test during recovery.
Three specific sessions (heavy squats 10 × 5 at 80%, jump squats, 15 × 30 m sprints); lower volumes, other loads or a familiar routine may recover sooner.
Funding and conflicts of interest: not stated in the abstract or the PubMed record.
How this entry was checked and changed
Why this level

crossover with n = 10 (rubric B), lowered a step because the outcomes are neuromuscular markers (evoked twitch force, voluntary activation, cortical measures, self-reported fatigue), not endurance performance, and because it was read from the abstract (the Northumbria repository URL listed by OpenAlex no longer resolves; the successor portal is behind a bot-check page)