Improving Running Economy within Endurance Athletes

The demands of long-distance running require athletes to apply large ground reaction forces over the course of the event. Endurance athletes are required to apply such forces within a very limited time scale (e.g. during the contact phase of a running stride) suggesting the forces are required to be applied quickly and repeatedly. A key performance parameter that is vital to this ‘repetitive force and power production’ process is musculotendinous stiffness.   

Tendon stiffness is the ability to produce rapid RFD within the shortest ground contact time possible, and therefore involves very little flexion at the ankle, knee or hip upon landing. As little change in joint angle occurs during tendon stiffness-based movements, most of mechanical work occurs within the tendon rather than the muscle. For example, upon landing from a drop jump plyometric, the muscles that plantar flex the ankle perform a quasi-eccentric-isometric contraction. This means the muscles are being held isometrically within the same position before being eccentrically lengthened under load and can therefore operate at the high force end of the force-velocity curve, whilst the tendon undergoes a rapid stretch-recoil action. The greater the level of tendon stiffness, the greater the RFD and energy economy of the movement, as less actual muscle work is occurring within the muscle itself. Such less energy demand obviously suits endurance-based sports, where muscles are required to produce sub-maximal force over the course of the entire event duration.

Plyometrics & Tendon Stiffness

Spurrs et al (2003) examined the effect of a plyometric training intervention on running performance, musculotendon stiffness and various performance measures. The authors reported significant improvements within the athletes 3 km performance, running economy, vertical jump performance and five bound distance tests. These findings clearly demonstrate the link between improvements in running performance and running economy, due to an increase in power production via musculotendon stiffness adaptations. It is evident that power output is in an important performance quality within endurance-based athletes and should therefore be trained accordingly in conjunction with other endurance-based training.  

Maximal Strength & Tendon Stiffness       

As an endurance-based athlete inevitably fatigues, the amount of force or torque generated will diminish, resulting in a reduction in overall performance. Therefore, the greater the level of force and torque generating capabilities from the outset, the lesser the effect on performance as the force and torque magnitudes decrease. Hence, an athlete will still be able to produce a greater amount of force / torque output when under fatigue, as the initial maximal force and torque levels were greater in the first instance. Ronald et al (1997) reported significant improvements in running economy in long-distance runner’s post strength training intervention. Hence, the favourable musculotendinous anatomical changes brought about by maximal strength training (e.g. an increase in tendon stiffness) in conjunction with speed strength training methods will result in an increase running economy. Aagaard and Andersen (2010) previously reported similar findings when reviewing the literature on strength training within endurance-based sports. The authors concluded that the enhancement in endurance performance is most likely due to increases in size of type IIA fibres, force generating capabilities, rate of force development and overall neuromuscular function.

It is evident that peak force, power production, and tendon stiffness are vital performance qualities within middle and long-distance running athletes. All of which will improve an athlete’s ability to produce repeated sub-maximal force / power output whilst under fatigue, therefore improving an individual’s overall running economy and overall running performance.