Swimmers' Shoulder-Hip Coordination Shifts with Pace

The research team wanted to see how shoulder and hip movements work together when swimmers go fast or slow. They used a method called continuous relative phase and a mapping technique called SPM to look at data from 15 top male swimmers. The swimmers performed non‑breathing front‑crawl strokes at two speeds: a 25‑meter sprint and a 400‑meter pace. All the recordings were taken from a previous study, so the scientists could re‑examine the patterns without collecting new data.

At the sprint speed the shoulder no longer leads the hip; instead the hip takes the lead. The phase angle moved from a small positive value at the slower pace to a negative value at the fast pace, and the change was statistically significant. The swimmers also showed more variation in their coordination at the sprint, with a larger standard deviation of the phase angle. The coupling strength between shoulder and hip was weaker during the sprint compared with the longer distance swim.

The differences were not spread across the whole stroke. The recovery phase held most of the changes, while the push phase stayed roughly the same at both speeds. This means that when swimmers need speed they adjust how shoulder and hip roll relate to each other mainly during the recovery part of the stroke. The findings suggest that coordination is not a fixed pattern but adapts to the demands of the pace.

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