# Applying Force Plate Technology to Inform Human Performance Programming in Tactical Populations
## 6 Monitoring Force Asymmetries  
Although some have used interlimb asymmetries to indicate injury risk [93], the evidence remains largely unclear as to the magnitude of bilateral \"deficiencies\" that would place an individual at risk. The inconsistencies in reported asymmetries are mainly driven by the variability between individuals caused by numerous factors. For example, asymmetries from acute injuries that alter mechanics and force-producing capabilities may exist, to some degree, for several years after the injury [94]. The extent of the chronic increase in asymmetries is dependent on the rehabilitation process but is also more likely to occur  
Figure 8: Example of percent change plots for monitoring neuromuscular fatigue across weekly to bi-weekly training. CMJ, countermovement jump; LCMJ, loaded CMJ; DJ, drop jump; LDJ, loaded DJ; ISOT, isometric strength test. following major injuries requiring extensive surgeries. Nonetheless, an asymmetry from an injury likely suggests the individual is favoring the healthy side, subsequently placing more physiological stress on the healthy limb. This compensatory movement pattern may result in elevated injury risk if it is not properly managed through structured rehabilitation and training progressions, which may be informed by close monitoring of force plate assessments throughout the recovery process. Likewise, specializing in a sport or occupation may encourage the development of asymmetries from repetitive tasks in which asymmetries are likely advantageous. The most common example of asymmetries is noted in baseball pitchers, with a dominant arm and leg being natural development for increased performances. In this case, the asymmetry that may be more concerning is the balance of muscle strength around the joint rather than between limbs or declinations in strength capacities within limb segments or ranges of motion over time. Lastly, smaller-scale factors may also influence asymmetries, such as anthropometrics (i.e., limb length differences) and physiology (i.e., lean body vs. fat mass differences). As with the aforementioned performance and fatigue assessments, the ability to monitor asymmetries will rely on accurate baseline measurements. To start, identify the sensitivity of tests for detecting asymmetries, such that single-leg jumping tasks may highlight larger magnitudes of asymmetries than bilateral jumping tasks for the same individual [95]. Furthermore, the individual must face the correct direction on the force plate to consistently orient the left and right limbs for consistently accurate calculations. The learning curve to performing tasks, such as single-leg jumps, makes consistency between trials an important factor to consider. Wide ranges of asymmetries may occur, with some trials favoring the right, while other trials favor the left side, which clearly complicates insights derived from back-end data analysis. However, the average asymmetry across all trials may be closer to 0% and thus not concerning as the individual is capable of spreading the workload across limbs. Conversely, practitioners should be more alarmed when individuals consistently display a large asymmetry across several metrics, trials, and time points. Moreover, to truly understand asymmetries, analyses of metrics from various phases of a movement (i.e., concentric and eccentric actions of the CMJ), as well as various movements, are necessary across all populations of interest as they likely vary. For example, an individual may be more protective of rapid or heavily loaded movements, which will be shown more for certain tasks. Nonetheless, information regarding asymmetries can be useful when addressed in an appropriate manner. For example, a law enforcement officer may have a 5% asymmetry in the lower limbs at baseline, but due to carrying unevenly distributed weight on their duty belt (i.e., firearm on the right leg), the asymmetry increases to 15% over two years on duty. This may be an indication to intervene in the training program and prescribe measures to improve this asymmetry.