Newtonian mechanics demonstrates that the greater the magnitude of ground reaction force generated, or the higher the amount of force that is applied to an object, the quicker the object or body will accelerate (dependent on the mass of the object / body that the force is applied to). Likewise, the greater the amount of torque generated by a muscle, the higher the level of joint angular acceleration. It is therefore evident that the ability to produce high magnitudes of ground reaction force and joint torques within sports is of great importance within sports performance.

However, what also must be considered is the limited time frame in which force and torque can be applied within sports. During locomotion (running, sprinting, changing direction, etc.) or when striking an object or an opponent, an athlete must apply rapid forces within a very limited time duration. Such limited time frames in which to apply force requires the athlete to produce equally rapid muscle shortening velocities, therefore equating to high power outputs in conjunction with: P = F x V

Where P is the power output, F is force generated by the concentric muscular contraction and V is the muscle shortening velocity. Power is defined as the amount of work completed within one unit of time (measured in Watts) and has been identified as a key performance quality within multiple sports.  

The ability to generate optimal power output within a short time frame has previously been linked to adaptations within the musculotendinous unit referred to as tendon stiffness. Tendon stiffness is the ability to quickly utilise kinetic energy during the amortisation phase when landing or when in locomotion (the eccentric to concentric conversion between landing and take-off). Chelly and Denis (2001) previously reported that leg stiffness (when calculated from hopping) was significantly correlated with maximal velocity sprint performance. Likewise, Kukolj et al (1999) previously reported a significant correlation between counter movement vertical jump performance (a test of explosive power) and sprint performance. It is evident that power output is a key performance quality within maximal sprint performance, both in the form of explosive power (e.g. jumping) and via musculotendon stiffness (e.g. locomotion).

Aragón-Vargas and Gross (2019) recently identified power output as a key indicator of vertical jump performance. Similarly, Kamandulis et al (2018) previously identified peak power is a key performance variable in boxing punch performance. It is evident that the ability to produce maximal power is of great importance to vertical jump performance, maximal sprint performance and striking performance, and should therefore be a key focus when preparing athletes that are required to perform such fundamental sporting actions. 

However, the ability to produce large power outputs is not only related to explosive based activities, but also to endurance-based sports. Endurance based athletes are required to produce mechanical work per foot contact, pedal stroke, swim stroke, etc. throughout the duration of a competitive event or training session. This ‘repeated power production’ quality is referred to as power endurance. Research by Spurrs et al (2003) investigated the effects of plyometric training 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 an improvement in running performance and running economy due to an increase in power production via musculotendon stiffness adaptations. It is therefore evident that the ability to produce high power output is of great importance across many sports, and should therefore be a key focus within athlete preparation.