Self-Selected Pacing during a 24 h Track Cycling World Record
The Cyclist The cyclist (35 years, 76 kg, 1.86 m, body mass index (BMI) 22 kg/m2) is an experienced ultra-endurance cyclist. To date, he has won several long-distance cycling races. For instance, he holds the record for the fastest Crossing of America in the “Race across America” (RAAM) in 2014 in 7:15:56 d:h:min with an average cycling speed of 26.43 km/h. RAAM crosses the United States from west to east (4860 km and 35,000 m of altitude). In 2015, he set a world record in the 24 h road cycling event, where he cycled 896 km at an average speed of 37.33 km/h .
The Event At noon on October 14, 2017, the cyclist started his record attempt in the Tissot Velodrome  in Grenchen, Switzerland. The track is a 250 m long and 7 m wide oval built out of wood. Temperature in the velodrome was kept constant at ~20 °C, and humidity was low at ~30% throughout the whole event. The previous record was set on October 8–9, 2010, by Marko Baloh (Slovenia) at the Montichiari Velodrome in Brescia, Italy, by completing 3615 full laps of 250 m and covering a full distance of 903.76 km . The cyclist used a conventional time trial bike (Shiv, S-WORKS, Specialized) with a disc wheel. He used Roval wheels  with specially made Turbo Cotton tires. The front brake was omitted for the purpose of aerodynamics; a brake lever and one chain ring had to suffice. The chainwheel had 53 sprockets, while the gear rim pinion had 11–23 sprockets. He changed the gears only to change the pedaling frequency. Power output in W was measured using Power2max NG (Saxonar GmbH, Waldhufen, Germany) , which the participant had also used in his last record race. After each hour, the accumulated distance was recorded. The athlete tried to maintain the power output of 230–260 W. Lap times were recorded electronically.
Results At the beginning of the attempt, the athlete cycled at an average speed of 41 km/h. His support team provided him food and drinks, mainly consisting of water, isotonic sports drinks, and green tea. They provided 400–500 kcal of energy per hour. After 2–3 h, the cyclist suffered from digestive problems, most likely due to the position on the time trial bike. To solve the problem of digestion, the support crew gave him more green tea plus Coca Cola® and Ensure®. After the first two hours, he already had his first problems when low back pain occurred. Moreover, an incident of serious emotional distress after two hours of cycling was recorded by his support team. During the night, he had problems with drowsiness, and the support crew gave him coffee and non-caffeinated chewing gum. He made his first stop of 2.5 min for a toilet break after 21:53 h:min of continuous cycling. Up to this point, he had consumed 15 L of fluids. After 23 h of cycling, he broke the existing world record. In the last hour, he tried to increase his cycling speed .
The cyclist covered 941.873 km and completed 3767 laps in 24 h. After 23 h and 10 min, he broke the existing world record. The cycling speed was 39.2 ± 1.9 km/h (range 35.5–42.8 km/h), and the power output was 214.5 ± 23.7 W (range 190.0–266.0 W). The number of laps per hour was 157.0 ± 7.5 (range 142–171), and the time per lap was 22.98 ± 1.07 s (21.05–25.35 s).
Figure 1, Figure 2 and Figure 3 show the relationship of speed, power, and number of laps, respectively, with the distance. In all cases, a negative correlation was observed, ranging from large (i.e., power output) to very large (i.e., cycling speed and number of laps) magnitude. These correlations indicated a positive pacing strategy, i.e., a decrease in cycling speed across the event. Furthermore, four phases could be identified using visual inspection of the nonlinear regressions in the figures of speed, power, and number of laps completed per hour during the race: the first phase lasting from the start till the fourth hour with a relatively stable cycling speed; the second phase from the fourth till the ninth hour, characterized by the largest decrease in cycling speed; the third phase from the ninth hour till the 22nd hour, showing relatively small changes in cycling speed; and the last phase from the 22nd hour (approximately after a 2.5 min break for toilet) till the end, presenting a final end spurt. In addition, cycling speed correlated significantly with power output (Figure 4).
When we compared cycling speed (Figure 1) and power output (Figure 2) between the two attempts, we could see that cycling speed was higher in track cycling compared to road cycling, whereas the opposite trend was shown for power output (Table 1). Considering cycling speed (Figure 1), power output (Figure 2), and the correlation between the two (Figure 4), the goodness of fit was stronger for track cycling, highlighting the influence of “other” factors (e.g., temperature, wind) of road cycling. It should be highlighted that the relationship between power output and cycling speed was linear outdoors and curvilinear indoors.
Discussion In this case report, we analyzed self-selected pacing during a 24 h track cycling world record. As hypothesized, the athlete’s new world record in 24 h track cycling was better than his world record in 24 h road cycling although his power output was lower. When we compared the two 24 h cycling world records, he had improved on the existing world record in track cycling (903.76 km) held by Marko Baloh by ~38 km (4.2%); in 2015, he had improved on the existing world record in 24 h road cycling of 834.77 km, set in 2004 by the Slovenian Jure Robič, by ~61 km (7.4%).
The performance in the 24 h track cycling was 45.577 km better than in the 24 h road cycling. For the world record attempt in 24 h road cycling, he was riding at a mean cycling speed of 37.34 km/h and achieved an average power output of 250.2 W , while the mean cycling speed in the 24 h track cycling world record was 39.2 ± 1.9 km/h with a mean power output of 214.5 ± 23.7 W. It should be highlighted that the cycling speed did not correlate perfectly with the power output. The absence of a perfect relationship between cycling speed and power output should be attributed to the fact that power output depends not only on cycling speed but also on the bicycle’s design, the cyclist’s size and position, and environmental factors, such as wind and road surface [37,47]. In the corresponding world record in road cycling, the decrease in cycling speed and power output throughout the laps could be modeled linearly, and the ambient air temperature and wind speed were related to cycling speed for the whole event. In that event, the air temperature was 13 °C at the start and dropped to 2 °C in the night at 03:00 a.m.; a low temperature is associated with fast speed and vice versa . It is well known that environmental influences, such as heat  and cold , have an influence on pacing in cycling time trials, with hot temperatures inducing larger decrease in performance, i.e., a more positive pacing. However, heat and cold seem to influence performance differently . A review of the influence of environmental factors (e.g., temperature and wind) on cycling performance concluded that ambient temperature and wind exerted a small effect in outdoor events, whereas power output seemed to be maintained at moderate temperatures during indoor trials .
For cyclists competing in the RAAM, the change in temperature and altitude had an influence on cycling speed and power output, with temperature having a positive and altitude having a negative influence on power output for all finishers . In the actual track cycling event, the athlete had no problems with temperature (constant at 20 °C) or wind (no wind), remained in the same sitting position throughout the 24 h, and was therefore able to ride faster (1.86 km/h faster) with a lower power output (35.7 W less on average). The higher cycling speed at a lower power output was most probably due to the surface of the velodrome, which is smoother than the asphalt of a road. A smoother surface decreases rolling resistance compared to asphalt, and a cyclist can consequently attain faster speed for less power output. Moreover, a cyclist can adopt a more aerodynamic position indoors than outdoors with a lower cross-sectional area in a thermostatically controlled environment, reducing wind resistance against a constant air pressure and thus increasing speed [4