Re-Examining Pacing Profiles in Elite Cross-Country Olympic Mountain Biking: The Influence of the Start Loop and Performance Level.

PURPOSE: Current literature characterizes cross-country Olympic mountain bike pacing as a "positive strategy" (fast start followed by decline or stabilization). However, this interpretation may be confounded when a start loop (SL), a structurally distinct initial lap included to facilitate positioning, is analyzed with subsequent laps. This study aimed to (1) quantify the influence of the SL on interlap pacing variability and (2) characterize pacing across performance quartiles. METHODS: Lap-by-lap timing data were analyzed for 934 elite finishers (543 men, 391 women) across 10 major 2024 events (World Cups, World Championships, and Olympic Games). Seven events included an SL, while 3 did not. Lap speeds were normalized to each athlete's mean race speed and analyzed using generalized estimating equations to assess lap effects and lap × performance quartile (first vs fourth) interactions. Interlap variability was quantified using coefficient of variation (CV). RESULTS: When only structurally comparable laps were considered, interlap variability was consistently low. Races without an SL showed low variability (median CV < 1.0%), and similar values were observed when the SL was excluded (median CV 1.1% in men and 1.2% in women). Including the SL increased variability approximately 7-fold (median CV 8.5% men and 10.9% women; P < .05). Lap × performance quartile interactions were event-dependent and small. Lower-performing finishers tended to start relatively faster and finish relatively slower than top performers. CONCLUSIONS: Excluding the SL reveals relatively stable interlap pacing in elite cross-country Olympic mountain biking with limited between-lap variations, whereas its inclusion substantially inflates variability and accentuates apparent fast-start behavior.