Do Sprinters and Jumpers Differ in the Acute Countermovement-Jump Response to Isometric Conditioning Protocols? An...

Sprinters and jumpers differ in their force-velocity demands, so this exploratory study compared their acute countermovement jump (CMJ) response to isometric conditioning.

Twenty-two competitive track and field athletes (10 sprinters, 12 jumpers; 19.1 ± 3.3 y) were alternately allocated from a randomised list to a 3 × 5 s isometric knee-extension or isometric half-squat (n = 11 each). Discipline was not manipulated, and no control condition was included. CMJ height was assessed from flight time by frame-by-frame video analysis, with take-off and landing timestamps read to the nearest 0.01 s. The best of three jumps was the primary trial summary. Percentage change (ΔCMJ) was the primary outcome.

Sprinters increased (+2.40 ± 4.46%) whereas jumpers decreased (-2.02 ± 6.44%). Discipline and protocol were analysed jointly in one additive model. The protocol contrast was small and imprecise (-0.25 percentage points [ISO-SQ relative to IKE], 95% CI -5.50 to 5.00; p = 0.921). The unadjusted discipline difference was non-significant (4.42 percentage points, 95% CI -0.46 to 9.30; p = 0.074) and the parallel Mann-Whitney U test was borderline and implementation-dependent (p = 0.043-0.050). After age adjustment it attenuated to +2.51 percentage points (95% CI -2.65 to 7.66; p = 0.320), whereas age remained associated with ΔCMJ (-0.86% per year; p = 0.042). Post hoc averaged trial summaries gave larger contrasts.

The primary comparison was inconclusive and materially attenuated by age adjustment but directionally consistent across trial summaries and protocols. The observed discipline-dependent pattern is hypothesis-generating and requires confirmation in adequately powered, controlled trials.