Can you be good at both running and cycling?

Last year at this time, we revealed some astonishing stories of cyclists who became high-level runners. We presented some surprising examples of Tour de France legends who tried their hand at running with immediate excellent results. But the question we would like to ask this time is whether what applies to these examples is possible with all types of cyclists? And is it also possible the other way around? Can a sub-2h10 marathon runner win a regional cycling race with only a few months to prepare?

By Jean-François Tatard – Photos: Depositphotos.com / DR

What we would like to highlight first are the differences in terms of systemic responses between the two sports. Such as VO2max, anaerobic threshold, heart rate, and what is called economy (economic pedal stroke in cycling or economic stride in running). But also to check, depending on the two practices, how the body responds from a ventilatory and neuromuscular point of view. And right away, what seems obvious is that for VO2max, there would be more positive physiological transfers from running to cycling than the other way around. And also that maximal and submaximal heart rates are different between the two activities. As for efficiency, it is higher in running. Ventilation seems more altered by cycling due to mechanical constraints. Central fatigue and the decrease in maximal strength are more significant after prolonged effort in running than in cycling. These are our initial, more or less well-founded observations…

Specific adaptations, and transferable ones

It should be noted that cyclists and runners will develop both specific adaptations unique to their sport and transferable adaptations. Some are positive and facilitate cross-training, while others will make the transition from one activity to another complicated. The differences between cycling and running can be understood in two distinct ways: first by comparing systemic responses such as heart rate, whether related to maximal or submaximal intensities. Then, in a second step, by observing other underlying adaptation mechanisms.

Fat oxidation is a first example. In this sense, oxidation is more significant for intensities above 50% of VO2max in running than in cycling. Moreover, the intensity corresponding to this maximal oxidation is higher in running than in cycling. So, we oxidize more lipids for a given intensity and exercise duration, and we consume them over a wider intensity range in running than in cycling.

These metabolic differences influence the determination of the lactate threshold in the discipline in which one primarily trains. However, the difference seems to be more significant in runners who are more penalized on the bike than cyclists on a treadmill, for example. This is accompanied by a greater sensation of fatigue and discomfort in runners who use an indoor trainer than for cyclists who use a treadmill.

What we also notice during an exercise test is that the results are more usable for a cyclist doing a treadmill test than for a runner on a bike. Also, we notice that the maximal HR is generally 5% higher in running than in cycling (e.g., 170 on the bike for 180 on foot for the same subject). The relationship between HR and VO2 is also different depending on the activity. Certainly because it is influenced by body position or environmental conditions.

The efficiency we mentioned earlier is higher in running compared to cycling. And it is likely that this difference comes essentially from the phenomenon of absorption and then restitution of elastic energy, particularly in the elastic component of joints such as the knee, ankle, or pelvis. This phenomenon exists in running but not in cycling. And in fact, the energy cost of running is proportional to the ground contact time.

Running places greater demands on the cardiovascular system

On the other hand, it is well known that at an intensity around 60-70% of VO2max in both cycling and running, a drop in blood pressure can be observed, but respiratory muscle fatigue is greater in cycling for the same cardiac intensity. And another factor altering ventilatory responses in cycling indirectly stems from the fact that the efficiency of the muscle pump is lower. In fact, the venous compartment perfusing the leg muscles, particularly those of the calves, functions as a second heart. By contracting, the muscles compress the veins and promote the return of venous blood to the heart. The muscle pump is all the more effective when the movement is rhythmic and accompanied by strong, repeated contractions, as in running. The lower efficiency of the muscle pump in cycling limits venous return to the heart and therefore also leads to a lower pulmonary blood volume than in running.

When starting endurance training, the increase in VO2max primarily comes from an increase in maximal cardiac output. In both cycling and running, cardiac output is a major factor in VO2max, but it is generally higher in running than in cycling, which partially explains the differences in VO2max generally observed between the two sports. Furthermore, cardiac output is greater in running, and the efficiency of the peripheral muscle pump is also superior. In conclusion to this component: running activity places greater demands on the cardiovascular system than cycling.

Muscular factors determine the sensation of difficulty in cycling

According to a study we found in Sport & Vie magazine (Sport & Vie Hors Série number 23: Pour en finir avec les idées reçues sur le coeur du sportif), it has been suggested that the physiological differences observed between cycling and running would essentially stem from the subjective perception of the difficulty (or arduousness) of the effort, which would be greater in cycling, where it seems more determined by muscular factors, whereas in running, central and/or metabolic information would prevail.

In running, the decrease in strength is proportional to the duration of the exercise, whereas this is much less evident in cycling.

The muscle contraction regimen being different between cycling (essentially concentric) and running (stretch-shortening type and therefore integrating an eccentric phase), the structural alterations and nervous adaptations under the effect of fatigue are also very probably different. In running, the decrease in strength is proportional to the duration of the exercise, whereas this is much less evident in cycling. This comes from different contributions between central (nervous) fatigue and peripheral (muscular) fatigue between cycling and running. In long-duration events, a decrease in the level of central activation has been observed in running, whereas this manifestation of central fatigue was not reported in cycling. However, this activation deficit was observed in cycling at high intensity.

We are also observing a rather new phenomenon in current practices among runner athletes, who are tending towards using cycling to reduce running mileage and the associated risks of muscle and tendon injuries.

Finally, running promotes lipolysis more than cycling. In fact, gym coaches advise running on a treadmill rather than pedaling on a spinner. The downside is that prolonged exercise is more accessible in cycling (supported sport) than in running (strong joint stresses). The solution undoubtedly lies in alternating between the two.

In conclusion

It was not a match between the cyclist who starts running and the runner who starts cycling, and which of the two has the best chance of succeeding, that interested us most. Moreover, the question is, in our opinion, too provocative, even simplistic, and the notion of result is very relative. But we still tried to animate the debate and arbitrate with our own interpretation of the different physiological components put to the test in each of the two activities. And thus, cycling and running have significant differences, and in reality, where we don’t necessarily expect them. In terms of ventilatory adaptations, for example, or neuromuscular or metabolic ones. It should therefore be specified that the objective here was above all to better benefit from each of these characteristics to promote development in the sport that interests us at the moment we want to practice it…

Finally, we do not all have the same natural predispositions for cycling or for running. And it is absolutely not obvious that a good cyclist will make a good runner, and a good runner a good cyclist. This depends more on innate physiological criteria. But the most important thing is that each of us finds pleasure and fulfillment in the sport he or she has chosen this morning upon waking, regardless of the performance.

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