# Short vs. Long Bouts of All-Out Rope Skipping: Effects on Metabolic and Perceptual Responses
## 4 Discussion
This suggests that the participants had already achieved or were close to their maximal rate of output at this time point. Subsequently, the RERs gradually decreased over the next 30 s, indicating a shift from a carbohydrate-dominant to a fat-carbohydrate combination as the energy source. However, as the Skip-3 min continued, its RER gradually increased to a higher ratio (>1.0) until the cessation of exercise, indicating a heavier reliance on glycolysis and oxidation pathways. The contribution of aerobic metabolism during Skip-3 min (84.86% of VO2 max) was similar to that observed during high-intensity cycling (ranging from 72% to 85% of VO2 max) [30]. Exercise intensity at about 70% of VO2 max was discovered to reflect the switch of the principal metabolic demand from aerobic to anaerobic [31], indicating that Skip-3 min required a substantial anaerobic energy supply. Apart from the metabolic responses, our study revealed a lesser level of perceived exertion and muscle soreness when a shorter all-out skipping bout was applied. This finding is consistent with a recent study on HIIT, which found that shorter HIIT bouts are perceived as less effortful than longer intervals, even when the overall workload is the same [20]. Additionally, the distribution of muscle soreness may also affect the extent of exercise exertion. In rope skipping, localized muscle soreness is likely due to metabolic acidosis during exercise [32], which seems to be more pronounced in the lower limbs, especially the calves. There are several possible explanations for these findings. Firstly, maintaining postural stability during exercise requires the activation of major muscle groups throughout the body. Skippers with higher skill levels tend to adopt a more kyphotic posture during speed events, which may reduce the jump height and flight time and allow for faster skips [33]. Although the lower extremities play a major role in rope skipping, skippers also need to coordinate and stabilize different body regions for effective skips. Consequently, it is important to consider the overall muscle involvement in rope-skipping events. Secondly, participants with limited rope-skipping experience may have higher average ground contact impacts, leading to increased muscle soreness scores. Studies have shown that adults performing bilateral jumping exercises can produce ground impacts of 2.87-5.39 times their body weight, depending on their relative jump height [34]. However, experienced skippers can limit these impacts to three times their body weight or less [35]. As a result, eccentric muscle contraction of the calf might be increased to cushion these impacts, leading to localized muscle soreness in the calf. Future studies could incorporate a force platform to investigate this issue further. An additional important finding of our study is that the E-rope demonstrated high levels of concurrent validity and between-day reliability, indicating that it is a reliable and valid tool for measuring rope-skipping performance. The accuracy of the E-rope was highly correlated with the counting of an IJRU judge, and the MDC was calculated for the E-rope, allowing users to determine meaningful changes beyond measurement error. It is noteworthy that the E-rope moderately overestimated the actual number of skips counted by the judge. This may be due to the E-rope assuming that a successful skip is completed when the rope finishes a loop at the bearing of the main handle. Therefore, the rope may have completed a loop just before the participant tripped over it, resulting in overestimation. However, the E-rope is still considered a useful tool for remotely monitoring and encouraging rope-skipping training, particularly when traveling. With interactive mobile technology and knowledge of the metabolic responses during rope skipping, coaches and teachers can remotely advise skippers' performance and prescribe exercise programs.