Physiological Determinants of Cycling Performance

Maximal oxygen uptake (VO2max) or peak power output, and lactate threshold are important physiological variables related to endurance performance. To produce the power necessary to pedal and make a bike move requires energy. During distance cycling, the muscles that use oxygen produce most of this energy. A higher maximal oxygen uptake means the generation of more energy, producing more power, thus resulting in a faster cycling speed.

Maximal Oxygen Uptake

In distance running it is best to express VO2max relative to body weight (ml·kg -1·min -1 or ml of oxygen used per kg of body weight per minute), but with cycling it is a bit more complicated. On a flat surface, the energy cost of cycling is proportional to air resistance, which is proportional to the cyclist's total surface area. Smaller cyclists have a greater surface area to mass ratio, providing greater relative air resistance. In a study of cyclists riding on flat ground at the same speed, larger cyclists elicited a 22% lower VO2, as expressed in ml·kg -1·min -1, than smaller cyclists. (Riding in a pack negates this difference.) During mountainous ascents, cyclists slow down, reducing the air resistance, so the primary determinant of energy cost is overcoming the force of gravity, thus lighter cyclists are at an advantage. It also appears that peak power achieved during a max test is a better predictor of performance in road cycling than VO2max. For example, Lindsay et al. (2) found a correlation of 0.84 between peak power and 40-km cycle speed.

Lactate Threshold

Individuals do not exercise at 100% of their VO2max during endurance events. The longer the race, the lower % of VO2max maintained for the duration of the race. Some individuals are able to compete at a higher % of VO2max during a race because they have a higher lactate threshold.

What is lactate threshold?

During physical activity, when all or most of the energy you are generating is produced using oxygen, there is very little lactate in the blood. As you begin to produce a significant amount of energy anaerobically, without oxygen, lactate begins to build up in the blood. Suppose an individual has a lactate threshold that occurs at 60% of their VO2max. At 40%, 45%, 50% and 55% of their VO2max all of their energy is produced aerobically and there is very little lactate in the blood. Then at 60% of their VO2max, the individual begins to produce a significant amount of energy anaerobically, resulting in a significant build up of lactate in the blood.

Lactate threshold occurs at a higher % of VO2max in well-trained individuals (in the range of 70 - 85% of VO2max) than in untrained individuals (40—60% of VO2max). The higher someone's lactate threshold, the higher VO2max they can maintain during a distance race. In our testing, we did not measure lactate threshold. We measured ventilatory threshold (VT 2), the point at which ventilation increases exponentially, which is a good reflection of lactate threshold.

Improvement with Training

Untrained individuals will see a significant improvement in VO2max, peak power output, and lactate threshold with training. These factors, however, don't improve infinitely with training. Although many individuals tend to train by just doing long rides, training at different paces, particularly riding just below, at, and just above your HR at VT 2 is critical for improvement in these factors.

HR- VT 1 and HR-VT 2 have been used to monitor exercise intensity during cycling competition (8). The table below gives the percentage of time spent in each heart rate phase during different types of stages in the Tour de France.

Stage Type Phase 1: HR<VT 1 Phase 2: VT 1 HR<VT 2 Phase 3: HR>VT 2

Flat

85%

14%

2%

Time Trial

7%

40%

53%

Medium Mountain

75%

23%

2%

High Mountain

63%

27%

10%

In an Ironman Triathlon, the heart rate during the cycling portion of the event was not significantly different than the HR at VT 2 . The heart rate was quite steady at 81% of HR max with occasional HRs up to 87% of HR max.

Aerobic FIT

Data from Aerobic FIT can be utilized in two primary ways.

(1) Assessing Personal Improvement: By periodically getting retested, you can compare the results of the tests, and monitor your progress.

(2) Compare Yourself with Other Cyclists: To compare yourself with other athletes we have taken and adapted values from testing based on professional and elite cyclists (United Cycling Federation National Road Team, US National Off-Road Bicycle Association (2, 3, 4, 5, 6, 7).

References

  1. Swain D. P. The influence of body mass in endurance cycling. Medicine and Science in Sport and Exercise 26(1):58-63, 1994.
  2. Lindsay F., J. Hawley, K. Myburgh, H Schomer, T. Noakes, S. Dennis. Improved athletic performance in highly trained cyclists after interval training. Medicine and Science in Sport and Exercise 28(11):1427-1434, 1996.
  3. Coyle E., M. Fletner, S. Kautz, M. Hamilton, S. Montain, A. Baylor, L. Abraham, G. Petrek. Physiological and biomechanical factors associated with elite endurance cycling performance. Medicine and Science in Sport and Exercise 23(1):93-107, 1991.
  4. Lucia A., J. Pardo, A. Durantz, J. Hoyos, J. Chicharro. Physiological differences between professional and elite road cyclists. International Journal of Sports Medicine 19:342-348, 1998.
  5. Martin D., B. McLean, C. Trewin, H. Lee, J. Victor, A. Hahn. Physiological Characteristics of nationally competitive female road cyclists and demands for competition. Sports Medicine 31 (7):469477, 2001.
  6. Tanaka H., D. Bassett Jr., T. Swenson, R. Sampedro. Aerobic and anaerobic power characteristics of competitive cyclists in the US Cycling Federation. International Journal ofSports Medicine 14: 334 338, 1993.
  7. Wilber R., K. Zawadzki, J. Kearney, M. Shannon, D. Disalvo. Physiological profiles of elite off-road and road cyclists. Medicine and Science in Sport and Exercise 29(8): 1090-1094, 1997.
  8. Lu cia A., J. Hoyos, A. Carvajal, J. Chicharro. Heart rate response to professional road cycling: The Tour de France. International Journal of Sports Medicine 20: 167- 172, 1999.