Do you like cycling? Have you ever wondered what factors influence your cycling performance? Well, in this post I’m going to tell you some things you may not have known about the biomechanics and physiology of cycling. Read on and find out how to improve your pedaling technique! All this with bibliographic references so that you can read more scientific literature on the subject.
Introduction
Pedaling is a skill that depends on several factors, including dead center, efficiency and crank length. Dead center refers to the moment when the tangential force applied to the pedal is minimal during the pedaling cycle (Aziz et al., 2014).
Efficiency is the quotient between the total mechanical work and the useful work to move the bicycle forward (García-López, 2009). The length of the crank influences the range of motion of the joints involved in pedaling (Rivero et al., 2013). These factors have been studied by various authors, who have analyzed their relationship with different pedaling styles (Cejuela, 2007), with the performance level of cyclists (Broker, J. P. 2003; García-López, 2009; Sanderson, D. J. 1991; Santalla, A., Naranjo, J., & Terrados, N. 2009) and with the measurement of the force applied to the pedal using specific devices (Kitawaki & Oka, 2013). The purpose of this text is to offer a professional and informative approach to these aspects, respecting the original references.
The keys
Cycling is an activity that involves dynamic interaction between the rider, the bicycle and the environment. To avoid injury and improve performance, it is essential to choose the right bike components, such as handlebars, saddle, crank, etc., and to adopt a good pedaling technique. (Quintana-Duque, Dahmen, & Saupe, 2015)
Pedaling is a key aspect: it consists of a circular motion with a repetitive pattern of force application. However, the force exerted on the pedals is not uniform throughout the pedaling cycle, but varies according to the angle of the crank. (Quintana-Duque et al., 2015). Therefore, pedaling technique depends to a large extent on variations in the force applied to the pedals. (Quintana-Duque et al., 2015). Although there is no agreement on what is the optimal pedaling technique, every cyclist can learn and train different pedaling techniques on a roller or cycleergometer. (Quintana-Duque et al., 2015).
Techniques
Cycling is a sport that requires good pedaling technique to optimize performance and efficiency. There are different ways of pedaling, but the best known are piston pedaling and round pedaling.
Piston pedaling consists of applying force only in the downward phase of the pedal stroke, leaving two dead spots at the top and bottom of the cycle (Cejuela, 2007).
Round pedaling, on the other hand, seeks to take advantage of the entire pedaling cycle, applying force in both the descending and ascending phases, eliminating dead spots (Cejuela, 2007). To facilitate this type of pedaling, systems such as oval cranksets, Rotor cranks or independent cranks have been developed (Cejuela, 2007; Lozano et al., 2006). However, there is controversy as to whether round pedaling is really more efficient than piston pedaling. Some studies claim that round pedaling increases pedaling efficiency by up to 30% by involving more muscles and reducing fatigue (Cavanagh and Sanderson, 1986). Other studies, however, question the existence of round pedaling and argue that there is no evidence that pulling up on the pedal improves performance (Alvarez, 1995; Gregor, 1976; Hoes et al., 1968; Lanfortune et al., 1983). What does seem clear is that pedaling efficiency is highly dependent on the rider’s ability to maintain regular and smooth crank rotation (Kitawaki et al., 2012).
Dead spots
Dead spots are those moments in the pedaling cycle when minimal tangential force is applied on the pedal (Aziz et al., 2014). There are two types of dead centers: the top dead center, which occurs around 0 degrees of pedaling (Top Dead Center), and the bottom dead center, which occurs around 180 degrees (Bottom Dead Center). Some innovative systems have attempted to reduce the time the connecting rod spends in these dead spots. For example, oval chainrings aim to reduce the internal load by reducing the dead center of force application in the crank system. However, although some studies have claimed otherwise, the most recent research on oval chainrings indicates that they do not improve pedaling efficiency (Lozano et al., 2006). Another outstanding case is that of Rotor cranks (Lozano et al., 2006), which modify their angle to reduce pedaling dead spots. The Rotor system allows that before one pedal finishes its thrust phase (0º-180º) the other has finished the recovery and is positioned ahead of the perpendicular (+- 18º). In this way, the connecting rod is ready for the thrust phase (Lozano et al., 2006).
The Dead Spot Score (DSS), which measures the degree of fluidity of the rotational movement of the foot in relation to the axis of the pedal. The DSS indicates the presence of dead spots in the pedal stroke, i.e. moments in which there is a loss of energy due to an inefficient transfer of force to the pedal. These dead spots can be due to a variety of factors, such as improper movement pattern, incorrect posture or excessive heel strike. According to the manufacturer of the device that measures DSS, cyclists with smooth pedaling have low DSS values, implying higher efficiency and lower fatigue (“Dead Spot Score Explained (part 1)”, 2020)(https://blog.leomo.io/dead-spot-score-explained-part-1-13baeb515f83).
The length of the connecting rods
The subject of crank length and its influence on rider performance has been the subject of numerous scientific studies. Some of the aspects that have been analyzed are power, cadence, oxygen consumption, joint angle and muscle pattern. Some of the most relevant findings are summarized below:
- A study comparing 120 mm to 220 mm cranks found that 145 mm and 170 mm cranks produced the highest peak power, with no significant differences between them (Martin & Spirduso, 2001).
- Another study that evaluated the effect of crank length on metabolic expenditure concluded that there was no difference between 150 mm, 165 mm, 170 mm and 175 mm cranks. However, longer cranks increased flexion and range of motion of the hip and knee, which could have negative consequences on the patellofemoral joint and muscle recruitment. Therefore, it was recommended to opt for the shorter connecting rod in case of doubt (Ferrer-Roca et al., 2017).
- A study that analyzed changes in joint angles at different powers found that the ankle was the only joint that consistently changed its motion. This could affect pedaling efficiency and the development of Dead Spot Syndrome (DSS) (Garcia-Lopez, 2009).
These results show that crank length is a factor that can influence rider performance, but that there is no universal optimum measurement. The choice of the right crank will depend on the individual characteristics of each rider, as well as his or her goals and preferences. Today’s technology allows for precise, customized measurements that can help optimize bike fit and improve comfort and pedaling efficiency.
