May 10, 2021

Increasing your Power Index for Strength & Conditioning

Don Babbitt, Associate Head Track & Field Coach, University of Georgia

In the sporting world, the main reason for partaking in a strength and conditioning program is to provide a benefit to athletic performance. One of the critical features of a good strength and conditioning program will be a strong transferability to sports performance which, hopefully, will be as high as possible. For power athletes in team sports such as football and rugby, and for power events like the field events, or sprints in track and field, gains in strength and conditioning will often lead to some type of tangible increase in sports performance.

The key question one must with regard to their strength and conditioning program is how to monitor your training to make sure what you are doing will actually transfer over into sports performance. One metric that may help keep your training on course and in perspective is monitoring the Power Index of the athlete as they go through their supplemental training for specific sports performance. This way the athlete will be informed if their ability to move and produce power by pushing off the ground is being enhanced. The ability to express power in this manner is utilized by power athletes in both team and individual sports and can be a key determinant of success in these types of sporting activities. 

How to Calculate the Power Index

The Power Index is a simple measure that is determined by calculating the square root of the athlete’s body weight (in pounds) and multiplying it by the square root of their vertical jump (in inches). There are other more sophisticated forms to measure power indices, such as the reactive strength index (RSI), or the use of the new MyJump2 app, but the power index only requires some form of scale to measure body weight and the basic tools to measure a vertical jump, which can be as simple as chalk or water, and a wall. Perhaps the most important benefit that the power index can provide is the ability to keep the tendency to focus one’s strength and conditioning regimen on maximal strength production in check. All too often, many athletes in power-based sports either intentionally, or unintentionally, chase maximal lifting numbers in the weight room in their quest to become bigger, faster, and stronger. This default toward training for absolute strength can be understandable in that maximal weight lifting performance is seemingly very easy to quantify, and can provide immediate feedback as to whether you are improving (by successfully lifting more weight), or not.

Why the Power Index Can Be Helpful

When focusing purely on large weightlifting numbers, there are a number of other performance variables that can be inadvertently compromised by the athlete if the focus becomes too narrow on just absolute strength. These performance variables can include significant changes in body weight, flexibility, mobility, and coordination in non-weight training tasks. Changes in these variables can end up decreasing the transferability of the weight training gains, which can lead to decreased sports performance. By monitoring the power index, which is a function of both bodyweight and vertical jump, the coach and/or athlete, will be able to keep a close watch on sudden or drastic changes in the body weight to strength ratio. Since the technical portion of monitoring the power index is performing the vertical jump, the reliability of the test will be higher than most tests since it is very simple in technical execution, and allows for very little improvement in performance that can be caused by skill acquisition.

Examples of Power Index Development

A typical example of how a power index can be gradually increased is provided in Figure 1. In this example, a typical power athlete will start with a bodyweight of 264 pounds and a vertical jump of 24”. After a training block of 3-5 weeks focused on hypertrophy and strength development they will gain roughly 2 to 2.5% body weight while keeping their vertical jump stable. By virtue of keeping the vertical jump stable and increasing their body weight, they will effectively increase their power index by about a little over 1%. When a subsequent 3-5 week training block is performed, with the focus now adjusted toward speed/power development and sharpening of performance, the same athlete will drop the 2-2.5% body weight they gained in the first training cycle, while seeing the vertical increase 4% due to the loss in body weight. This will see the athlete gain another 1% in their power index during this training block. These training blocks can be repeated again to keep the improvement of the power index going up (see Figure 1), without drastic swings in body weight that could affect other areas of sports performance such as execution of sport technique.

Figure 1: 

A real-life example of the development of the power index along with the development of sports performance can be seen in Figure 2. This figure shows the performance progression of Reese Hoffa, who was a 4-time world #1, two-time World Champion and Olympic bronze medalist in the shot put. You can see that his early power index increases came from a simultaneous improvement in vertical jump along with an increase in body weight, while the power index was maintained in the second part of his career as he got older by maintaining a higher body weight with a slightly reduced vertical jump (see Figure 2).

During this time, he was able to improve his shot put performances each year for 11 straight years until he achieved his first #1 world rankings in 2006 and 2007. At this point, he kept his power index steady at about 95 and continued to maintain his high level of throwing which saw him go on to collect two more world number rankings in 2012 and 2014.

Figure 2: Power Index Progression of Reese Hoffa

For more examples of power indices at the elite performance level, men’s shot putters from the sport of track and field have some of the highest power index readings in the sporting world. They compare very favorably with the power index readings of the NFL’s best defensive lineman who have similar body types and sports performance needs (being of large size with quick powerful bursts of movement against a resistance). Power Index readings of 95+ are considered elite for these types of sports performers and thought to be typical results for a top men’s shot putter or NFL defensive lineman. Tables 1 and 2 provide power indices for these two athlete groups.

Table 1:

 Table 2: 

Considerations for Power Index Testing

In monitoring the power index throughout the year, it is important to have reliability in the testing measures and to administer tests to calculate the data for the power index in consistent settings. Normally, you will take measurements for bodyweight and vertical jump at the end of a training block or mesocycle during an unload week. This will allow for a proper amount of recovery so that the athlete is being tested when they have had a chance to rest up. If the athlete is tested while in different periods of recovery and/or fatigue, it will skew the test results. The bodyweight test should always be administered when the vertical jump test is administered (on the same scale each time) to ensure the proper alignment of variables so the measurement of the power index is consistent.

» ALSO SEE: Basketball Strength Training — Make Your Next Season the Best Season

To conclude, when training large power athletes in sports like track and field and football where there is no weight limit, training for the improvement of the power index may yield better and more applicable results instead of just gaining mass, or lifting more weight. Many athletes fall into the trap of just increasing lifting gains and think that this alone will provide the extra power they are hoping to develop. Lifting improvements are easy to measure so they are a very attractive way to train, but these gains may not necessarily transfer to desired sports performance in many cases. Weight training improvements can also be due to skill acquisition or gains in mass, which may help to lift results but hinder mobility and sport-specific speed. Increasing the power index can be a good measure of both speed and strength which is the real combination that power athletes are looking to develop.