The Effect of Resistance Exercise Priming in the Morning on Afternoon Sprint Cross-Country Skiing Performance

Purpose: We tested whether a single session of heavy-load resistance priming conducted in the morning improved doublepoling (DP) performance in the afternoon. Methods: Eight national-level male cross-country skiers (mean [SD]: 23 [3] y, 184 [6] cm, 73 [7] kg, maximum oxygen consumption = 69 [6] mL center dot kg-1 center dot min-1) carried out 2 days of afternoon performance tests. In the morning, 5 hours before tests, subjects were counterbalanced to either a session of 3 x 3 repetitions (approximately 85%-90% 1-repetition maximum) of squat and sitting pullover exercises or no exercise. The performance was evaluated in DP as time to exhaustion (TTE) (approximately 3 min) on a treadmill and 30-m indoor sprints before and after TTE (30-m DP pre/post). Furthermore, submaximal DP oxygen cost, countermovement jump, and isometric kneeextension force during electrical stimulation were conducted. Participants reported perceived readiness on test days. Results: Resistance exercise session versus no exercise did not differ for TTE (approximately 3 min above) (mean +/- 95% confidence interval = 3.6% +/- 6.0%; P = .29; effect size [ES], Cohen d = 0.27), 30-m DP pre (-0.56% +/- 0.80%; P = .21; ES = 0.20), 3 0-m DP post (-0.18% +/- 1.13%; P = .76; ES = 0.03), countermovement jump (-2.0% +/- 2.8%; P = .21; ES = 0.12), DP oxygen cost (-0.13 % +/- 2.04%; P = .91; ES = 0.02), or perceived readiness (P >= .11). Electrical stimulation force was not different in contraction or relaxation time but revealed low-frequency fatigue in the afternoon for the resistance exercise session only (-12% [7%]; P = .01; ES = 1.3). Conclusion: A single session of heavy-load, low-volume resistance exercise in the morning did not increase afternoon DP performance of short duration in high-level skiers. However, leg lowfrequency fatigue after resistance priming, together with the presence of small positive effects in 2 out of 3 DP tests, may indicate that the preconditioning was too strenuous.