## 4 Discussion
For the P3 vs. P5 comparison, the VLO in position P3 exhibited a marked peak in EMG activity during the early cycle phase, aligning with findings in P1 and P2. This higher VLO activity in P3 suggests that a lower handlebar and LeMond saddle height may require enhanced knee extension efforts and stabilisation from the quadriceps to maintain control over leg dynamics in the forward-leaning posture. This posture likely increases quadriceps load, similar to the effect observed in P1, emphasising the role of handlebar height in influencing muscle recruitment during the power phase. Similarly, in the P4 vs. P5 comparison, position P4 showed significant differences in early-cycle VLO activity relative to P5, with elevated muscle engagement in this phase. The higher handlebar position in P4, though less aggressive than P3, still places notable demands on the VLO, likely due to the mechanics of knee extension required to sustain leg stability and pedal power. The increased quadriceps activation observed in P4 supports the notion that even modest handlebar height adjustments, in combination with saddle height, can substantially impact muscle activation dynamics. These observations highlight that both LeMond saddle height positions (P3 and P4) elicit heightened VLO activity in the early pedalling phase compared to the customised P5 position. The findings suggest that the personalised adjustments in P5 may offer a more ergonomically favourable setup that reduces the muscular workload on the quadriceps, particularly in the VLO, thus potentially lowering the risk of muscle fatigue and improving efficiency over extended rides. This reinforces the value of custom-fitting approaches integrating handlebar and saddle height to enhance comfort and minimise unnecessary muscle strain for road cyclists [13; 37; 38]. Adjusting these elements based on body dimensions may significantly enhance comfort and reduce pain and musculoskeletal injury risk [2; 37; 38; 39]. In turn, the EMG analysis of the lateral gastrocnemius (LG) muscle across different cycling positions highlights the effect of handlebar and saddle configurations on lower limb activation patterns, with significant variations observed between positions P1, P2, P3, P4, and the custom-fitted position P5. Notably, position P4 elicited the highest LG activity, particularly during the early phase of the cycle (0-25%), followed by consistently elevated muscle engagement throughout most of the pedal stroke relative to P5. This increased activity in P4 suggests that the LeMond saddle height paired with a high handlebar height places substantial demands on the LG, likely due to increased plantarflexion requirements and more excellent calf muscle stabilisation needed to maintain control over pedal force application. In the P1 vs. P5 comparison, position P1 similarly showed increased LG muscle activity during both the initial and late phases of the cycle compared to P5. This elevated activation pattern may be associated with the aft saddle and low handlebar combination, which appears to place additional strain on the calf muscles, potentially stabilising the ankle and foot position during both the force generation and recovery phases. For P2 vs. P5, position P2 exhibited two distinct peaks in LG activity during the early (0-25%) and late (75-100%) phases, indicating a heightened need for plantarflexion and stabilisation at the beginning and end of the pedal stroke. This increased engagement of the LG in P2 suggests that even the high handlebar height, when paired with an aft saddle, may create unique biomechanical demands on the calf muscle to maintain pedal stroke stability. The comparison of P3 and P5 yielded similar insights, with P3 eliciting consistently higher LG activity throughout the cycle compared to P5. This increased muscle activity suggests that the LeMond saddle height with low handlebars amplifies the calf's stabilising role, possibly to counterbalance the forward trunk posture and the associated shifts in lower limb biomechanics.