I’ve been using the vertical jump for many years to monitor my athletes. I started with a simple Vertec system, and eventually purchased a contact mat. A contact mat is a relatively simple device that allows vertical jump to be calculated based on flight time. Today I use the gold standard measurement device called force plates, which are able to measure a subject’s ground reaction force during a vertical jump. Using some simple math, I can calculate many different variables including peak power, average power, peak velocity, impulse and peak force. The exact relevance of these variables is beyond the scope of this blog, so if you want to learn more, email me or attend one of my seminars!
In my early days, I would often notice random and unexplainable changes in vertical jump height. After a plyometric training block, vertical jump would go down, and at the start of a training block vertical jump would occasionally reach a peak value! One of my close friends and fellow strength coaches Stu McMillan also recorded vertical jump heights over an entire summer in some of his elite bobsleigh and track athletes, and found many discrepancies with what he expected from a performance standpoint.
Needless to say, I had a tough time explaining these results until I realized the sensitivity of the vertical jump for monitoring the fatigue of the neuromuscular system. Vertical jumping requires high rates of force development and power production during vertical jumping is depending on motor unit firing rates and intermuscular coordination. A certain type of neuromuscular fatigue called low frequency fatigue can persist for many days following a training block, and can affect explosive force production and force production at submaximal loads (Figure 1).
Figure 1: Changes in the Force Time Curve After Exhaustive Knee Extension. Notice the change in the slope and the total area under the curve.
Now here’s the interesting application: by studying various aspects of a force curve from vertical jumping tasks I can better design training programs, tapering and peaking cycles, and monitor my athletes to ensure they don’t get too buried during a training cycle. One variable I use to evaluate preparedness is rate of power development (Figure 2).
Figure 2: Theoretical changes in Rate of Power Development.
By monitoring rate of power development over a training cycle, I can better design my training program and prepare my athletes for competition. Consider graph below of a competitive fighter in the lead-in period before a fight. You can clearly see how rate of power development follows the expected physiological state of the fighter as he cuts weight, rehydrates and recovers for the day of the fight.
Figure 3: Rate of Power Development During a Taper
To summarize, vertical jumping isn’t always a performance measure. It can also be used as a marker of preparedness and can greatly improve our understanding of how an athlete adapts to a training stress.