# Predictive Validity of the Single Leg Hamstring Bridge Test in Military Settings
## 4 Discussion
Furthermore, with the simple inclusion of force plate measurement, this test can be easily transformed into a more thorough and precise isometric posterior chain test [29] that, unlike an isokinetic test, can also be performed in the field. The SLHBT requires little equipment and resources, can simultaneously accommodate testing of several participants [30], and can detect potential bilateral asymmetries. It seems that good hsmrting performance is a characteristic of soldiers with generally good overall physical performance, as they performed better on all physical fitness tests (CMJ and push-ups were non-significant, but have shown the same trend). It may be that soldiers at the lower level of overall physical fitness executed the specific training program only to achieve better results on the APFT (as this test is obligatory for them), while on the other hand, soldiers with good overall physical performance (e.g., who were not worried about passing the APFT successfully) did general functional fitness training with a broad range of diverse physical tasks. It was shown in previous studies [31] that a generalized approach to training could also improve soldiers' scores on the APFT without a specific focus on APFT tasks. This could at least in part explain how hsmrting performance could be related to, e.g., pull-up and/or push-up performance (\(p=0.071\)). Additionally, there is a functional-anatomical connection between the hamstring muscles (biceps femoris muscle; BF) and the sacrotuberous ligament [32] that may also explain the impact of hamstring performance on other upper body exercises where the trunk needs to be stabilized. Furthermore, it has been shown in elite soccer players that strengthening of the hamstrings can influence some explosive activities such as short 5 m and 10 m sprint times and maximal CMJ height [33], showing that hamstring strength can have an influence on other physical performance parameters. Nevertheless, the different nature of the motor test must be acknowledged. For example, the CMJ evaluates the elastic-explosive force, while the SLHBT evaluates unilateral resistance strength, which is why it refers to two different manifestations of producing force. Additionally, EMG (electromyography) studies have shown that trunk muscle activities (i.e., internal oblique, rectus abdominis, erector spinae) are significantly greater during single-leg lift bridge exercise and that such effects can be increased even more with the performance of this exercise on unstable surfaces [34]. The largest effect size was noticed for the difference in a two-mile run, where soldiers with good hsmrting strength, which is associated with better running performance [35], were almost 1 min faster than their counterparts with weak hamstring strength. The single leg bridge exercise and test, as a closed kinetic chain exercise [34], activate the hamstring, gluteus maximus (GM) and gluteus melous muscles [20] with the single leg support adding to the rotational torque in the trunk to additionally increase the activation of the trunk muscles to maintain neutral lumbar position [36]. Higher hamstring performance is also important [37] in cases where the hamstring muscle, as GM main synergists [38], needs to take over because of reduced strength or activation of the GM muscle [39; 40]. Performing deadlifts, front and back squats, lunges etc. (as weight lifting exercises in the functional fitness training program) could also result in better achievement in single leg bridge tests, as these exercises activate gluteal muscles and hamstrings [41; 42], which are also recruited in the single leg bridge task. Incorporating these exercises in military training to recruit and train the muscles of the posterior chain (the hamstrings and gluteal group) may minimize overuse in the lumbar extensors (erector spinae) while reducing the likelihood for injury and enhancing muscular firing patterns [43].