## 4 Discussion
Another notable finding was that the BF, representing the posterior thigh and hamstring group, showed low muscle activation (the least of all muscles). This suggests that the Eccentron exercise is not particularly effective for engaging the hamstrings. A likely explanation for this low activation lies in the biomechanics of the movement such that during the eccentric phase, the knee angle progressively decreases, resulting in the hamstrings shortening rather than lengthening. Since eccentric loading is most effective when a muscle is lengthening under tension, this shortening action likely reduces the mechanical load placed on the hamstrings, thereby limiting their activation. This pattern of low hamstring activation is consistent with findings by [PERSON] et al. [22], who observed low hamstring and soleus muscle activity across various squat exercises, regardless of center-of-gravity adjustments. Their work suggests that hamstring under-activation during closed-chain lower limb squat press- or leg press-based tasks may be a broader phenomenon beyond the specific isokinetic eccentric leg press movement studied here. Perhaps the most comparable study relating to the isokinetic aspect is the [PERSON] et al. study. Using a novel squat testing device that performs \"isovelocity\" movement via a motorized system, [PERSON] et al. [12] demonstrated that during both concentric and eccentric squat movements, the hamstrings exhibited lower EMG amplitudes compared to quadriceps muscles, supporting the notion that multi-joint lower limb exercises, especially during an eccentric movement, may inherently result in differential muscle recruitment patterns, favoring some muscles over others. This aligns with our finding of consistently low BF activation despite the eccentric loading, also providing support for the idea that certain posterior chain muscles may be under-recruited during multi-joint closed-chain eccentric tasks like the Eccentron exercise. However, this pattern may not apply uniformly across all posterior chain muscles. For example, the gluteus muscle group, which lengthens during hip flexion in the eccentric phase, would be expected to exhibit heightened activation. This preferential engagement of the quadriceps (and possibly gluteus) muscles during this form of eccentric exercise may have important clinical implications given these two muscle groups play a primary role in eccentric control when attempting to prevent/counteract a fall. One limitation of the present study is that it did not include EMG assessment of the gluteus muscle group, leaving this interpretation speculative. Future research should include gluteal EMG data to confirm whether these muscles are more engaged than the hamstrings during the Eccentron-based exercise. From a practical standpoint, these findings have important implications for exercise programming. When the Eccentron is used as a primary lower body exercise, it may not sufficiently target the hamstrings. Therefore, it would be advisable to include additional exercises that specifically recruit the hamstrings (such as Nordic hamstring curls, leg curls, etc.) to ensure a balanced posterior chain development and to reduce injury risk. Additionally, the relatively high standard deviations observed in some EMG parameters highlight notable inter-individual variability in muscle activation patterns, which may have practical significance for customizing eccentric training or rehabilitation programs to individual needs and movement strategies. This is especially relevant given that exercises such as the Nordic hamstring curl have been shown to elicit significantly higher EMG activity in the hamstrings compared to other modalities [23], and that eccentric hamstring exercises are indicated as important for reducing hamstring-related injuries [24]. The GM muscle exhibited relatively low muscle activity during the Eccentron exercise, which is somewhat unexpected.