While most of the time the focus is on capacities, or how big our engine is, the real key is often how efficient a runner is. Endurance is about supporting speed and being physiologically and biomechanically efficient. Distance runners maximise their mechanics for efficiency of movement.
The three types of efficiency we are concerned with are:
These 3 combine to create total efficiency.
Running economy (RE) is one of the physiological parameters for running performance and used to measure total efficiency.
It uses oxygen intake to represent energy use and is defined by how much oxygen it takes to cover a given distance at a fixed speed. Or, it also relates to the amount of oxygen used by an athlete when running at a constant (submaximal) running speed.
RE significantly correlates with running performance. RE can explain up to 65% of variation in race performance.
RE is a measure of gross efficiency, meaning that it is the result of both internal and external components so that mechanical, neural and metabolic efficiency play a role.
<Short ground contact times,
<higher cadence (greater stride frequency)
<and higher knee and lower ankle stiffness are associated with better RE.
Trained runners who exhibit greater neuromuscular activation prior to and during ground contact, in turn optimizing spatiotemporal variables and joint stiffness will be the most economical runners.
Factors that affect Running Economy
Running economy is one of the most important factors in determining distance running performance.
Up and Down Movement
Uneconomical runners expend more energy bobbing up and down when they run than do more economical runners who tend to glide over the ground with very little vertical oscillation. Excessive up and down movement is a waste of energy.
Muscle capacity to store energy
With each running stride, the muscles of the landing leg store impact energy as they contract eccentrically to absorb the shock of landing. Most of the stored energy is then used during the concentric muscle contraction that propels the body forward during the next stride. We can use elastic recoil provided by the tendons, contribute a significant proportion of the energy for propulsion (35%) at least when running on flat terrain.
Biomechanical efficiency refers to anything that impacts the mechanical cost of running. Factors such as elastic energy storage and return, the mechanics of the stride itself, how the foot lands and the structure of the runner contribute to biomechanical efficiency, how wasteful a movement pattern is. If these factors are optimized, then less energy is required to cover a given distance.
There are several mechanisms that can improve biomechanical efficiency, one of the most important being the Stretch Shortening Cycle (SSC). A spring-like mechanism where a muscle is actively stretched and then immediately contracts. During the pre-stretch portion, energy is stored in the series elastic components of the muscle, then energy is then released during the contraction part. The amount of elastic energy return is dependant on length and speed of the stretch, stiffness of the muscle and the time between the stretch and subsequent contraction.
Muscle stiffness strongly correlates with RE. In general, a stiffer muscle will store more energy and the SSC works best when a stiff muscle is rapidly stretched and contracted with little time in between. Example of this is the calf muscle upon landing and subsequent toe off in running.
Stiffer (measure of leg compliance) muscles surrounding the ankle and knee create an increased SSC response which results in greater force on the subsequent toe off.
We always want to obtain optimal stiffness and energy return. Pre-activation, or tuning of the muscles to prepare for impact before landing is a way to actively manipulate stiffness of the system, resulting in greater storage of elastic energy.
The achilles tendon stores 35% of its kinetic energy. To properly utilize elastic mechanisms, the body needs to be in optimum position biomechanically and the tendons need to be trained to utilize the forces. Rapid movements such as sprinting and plyometrics train the tendons to be better able to utilize the energy.
Running with the ankle more plantar flexed, (more forefoot) allows the subsequent stretch reflex on the calf and Achilles-Calf complex to utilize more elastic energy than landing in a dorsiflexed position at heel strike where the calf complex is already in a stretched position thus minimizing the SSC. Ground contact time is also longer in heel strikers so there is more time between energy storage and release. More energy likely dissipates and is lost.
Maximising Elastic Energy Use
Reactive or plyometric training-Short hops, jumps and bounds with the focus on minimizing the amount of ground contact time will work! Sprinting is about the most specific form of plyometric activity that can be done for runners, yet it is often under-utilized. Doing 60-100m accelerations is a great way to work on using elastic energy. These will train you to reach force development faster, minimize ground contact and optimize the stiffness of the muscles and tendons.
The biomechanical model proposes that an important function of the muscles and of the brain and nerves that control their function, is to maintain the tension in the tendons when stretched at footstrike as well as during the first part of the of the stance phase of the running cycle. This then allows the spring (Achilles tendon and other structures) to be stretched actively. Return of the spring to its unstretched position at toe off then provides a good proportion of the energy needed for the next stride.
Maximising rate of force development so that ground contact time is minimized creates a more efficient runner.
Neural efficiency is an improvement in the communication between the nervous system and muscles themselves. E.g, an improvement could occur via more refined motor programming.
Metabolic efficiency refers to the factors that impact on the production of energy for the muscles to use such as fuel source or oxygen delivery.
It is a balancing act to maximise total efficiency.
The most important thing about strength training is it builds damage resistance. Athletes need muscles with superior efficiency, contractility, elasticity and fatigue resistance. Stronger athletes tend to have reduced risk of injury. Rate of Force (RFD) is of huge importance. Force capability is increased in stronger runners which improves their running economy and therefore overall performance. An increasing body of evidence shows that by incorporating an S&C program of heavy weights and plyometrics increases running economy by 4% (Barnes et al. 2013b; Burgess and Lambert 2010a; Saunders et al. 2004) A stronger and more stable athlete will cover the same distance more efficiently than an athlete with poor running economy.
It will improve neuromuscular function-improved muscular coordination and coactivation, increase the percentage of fast twitch fibres and improve tendon stiffness-all of which contribute to faster more economical running as well as reduced injury risk. Strength training is good practice, we should not dismiss something that has such a positive impact on our running performance and reduces risk of injury by improving mechanics and enhancing athleticism and ultimately prolonging your running career.
Distance runners-don’t neglect pure speed training/hill sprints or strength training, or you will continue to be inefficient over the ground.