## 4 Discussion
### Chronic Effects  
Another relevant finding of the present scoping review is related to the chronic effects of muscle strength training on the physical fitness of boxers [18; 19; 21; 22; 60; 61; 63; 68]. [PERSON] et al. [19] reported improvements in the maximum 1 RM strength in the bench press and squat exercises, in addition to increases in trunk flexion and extension strength at 30\({}^{\circ}\)/s and increases in isokinetic power of the left arm and upper arm right in extension at 180\({}^{\circ}\)/s through a 16-week specific training for boxers that included multi-joint upper and lower limb strength exercises with free weights, core exercises, glyometric exercises (jumps and throwing medicine balls) and a boxing-specific interval training. The above demonstrates the improvements in physical fitness that can be generated through varied muscle strength training specific to boxers in addition to boxing interval training. In this sense, it has been suggested that a concurrent training modality not only improves sprint capacity and endurance, but also improves the anaerobic threshold level. Therefore, the specific boxing training in this study provided positive results, improving the specific fitness of boxers [86]. Also, training combining free weights and elastic bands has been reported to improve upper body power levels in seven weeks [87], similar to the findings of [PERSON] et al. [19]. Conversely, muscle strength training with free weights in combination with glyometric exercises has shown positive effects in other combat sports. [PERSON] et al. [37] found increases upper and lower limb maximal strength, as well as increases in SJ and CMJ height and a reduction in the time of the specific lunge action in fencers, supporting the findings of the present study [19]. [PERSON] et al. [18] reported increases in power production for the half-squat exercise and for the bench press exercise after a training program with the OPL in elite amateur boxers. In a similar study, [PERSON] et al. [63] during a week with three training sessions through OPL observed improvements of 8% in the impact force of the punch, executing three exercises (bench press, half-squat and SJ loaded). This provides valuable information for coaches to regularly include exercises such as half-squats and SJ loaded, as increases in lower extremity power can be directly transferred to the impact force of the punch, making it a useful and effective training strategy in very short training periods, which can be an advantage in some competitive settings, such as pre-combat phases, when athletes commonly present significant decreases in power and striking performance due to reduced body weight [88]. It has been shown that the power produced by combat athletes in the bench press and SJ loaded exercises is closely related to the impact and acceleration of the punch [15]. This is relevant, given that the power of the legs has a fundamental role in the performance of the punch [15; 16]; specifically, the transmission of force at high speeds from the lower to the upper extremities has proven to be essential to generate greater impact forces [15; 16; 89; 90]. Continuing with the findings reported in the physical fitness of boxers, [PERSON] [21] observed improvements in upper body explosive strength in female boxers through the test of pushing a solid ball sitting in a horizontal position after traditional muscle strength training of 12 weeks with multi-joint upper and lower limb exercises and strength training focused on speed with upper body exercises. These findings are relevant, since they show that female boxers, like male boxers, can benefit from using a muscle strength training program to improve their physical performance in boxing. In this sense, as mentioned in the previous section, an increase in the speed and power of straight punches was also reported in female boxers.