# The Reverse Lunge: A Descriptive Electromyographic Study
## 4 Discussion
### Muscle Activity Categorization Thresholds  
Standardization of peak muscle activity into activation categories was essential to understand the utility of each muscle during the bodyweight reverse lunge, and to best allow clinicians to dose the exercise properly based on therapeutic goals. [PERSON] et al. designated 0-20% of MVIC as low-level muscle activation, 21-40% of MVIC as moderate-level activation, 41-60% of MVIC as high-level activation, and greater than 60% of MVIC as very high-level activation [17]. According to [PERSON] et al., EMG activity greater than 40% of MVIC is expected to produce strength gains [17]. [PERSON] et al. used the same muscle categorization thresholds in their EMG study of core muscle activation during Swiss ball and traditional abdominal exercises [18]. They state that muscle activations greater than 60% of MVIC may be more effective in strengthening and muscle activations, while less than 20% may be more effective for enhancing endurance [18]. For this discussion, we adopted the suggestion offered by [PERSON] et al. where 40% of MVIC is considered the threshold for a potential strengthening stimulus and less than 40% of MVIC is considered an endurance stimulus [17]. The two muscles which achieved a strengthening stimulus in their mean peak percent of MVIC were the lead limb RF (105.67% of MVIC) and the stationary limb GMed (49.2% of MVIC). Of note, the mean peak percentage for the lead RF, which exceeded 100%, is likely due to not achieving a true maximum contraction during MVIC testing. The investigator that offered resistance to the RF may have been unable to elicit the fullest contraction of the muscle. The strengthening threshold was attained due to the forceful extensor torque required by the lead RF to rise from max descent and return to the starting position. The GMed acts as a pelvic stabilizer in a single limb stance (closed chain) [19]. As the stationary limb moves forward and the mass of the body is shifted onto a single limb, there is a high level of muscle activation required of the stationary limb GMed to maintain a level pelvis. The stationary limb RF (36.16%), lead and stationary limbs BF (36.61%, 17.11%), lead limb GMed (34.29%), and lead and stationary limbs GMax (34.88%, 36.61%) were in the moderate-level activation category and did not meet the strengthening threshold. This may be due to a lack of stimulus imposed upon these muscles as the reverse lunge in this study was only performed with bodyweight resistance and therefore these muscles were only recruited at the level needed to produce an endurance or stabilizing level stimulus. During data collection, participants were instructed to perform the lunge to the commands of \"step, down, up, step\", utilizing both limbs during the knee extension phase. Due to the nature of this standardization, there may have been less weight acceptance onto the stationary limb during the rising half of the lunge, decreasing the required demands of these muscles. It is unclear what would have happened if the two limbs moved at their own pace or more forcefully since this was not investigated. Regarding the lead limb muscles, there was a low demand placed on the lead limb BF during the hip extension phase (36.11%). As a primary knee flexor, this muscle only contracted enough to clear the foot during the swing phase to reach ground contact. Furthermore, since the reverse lunge movement is performed in the sagittal plane and the GMed functions mainly in the frontal plane, it was not required to work to a great degree throughout the lead limb motion (34.29%) during the reverse lunge. A study by [PERSON] et al. found that the lead limb GMed mean of the average percent of MVIC muscle activity was 81% during side-lying hip abduction (a frontal plane movement) versus 48% and 42% for the transverse (side) and forward lunges (the closest sagittal plane movement to the reverse lunge) [6]. The findings related to the forward and transverse lunges by [PERSON] et al.