Impact of swimming intensity on spatiotemporal kinematics of lower-limb breaststroke actions in national-level male swimmers: A discrete variable and time-series analysis.
Gourgoulis V, Nikodelis T, et al. • Journal of biomechanics • 2026
Lower-limb action adaptations to swimming intensity in breaststroke are predominantly driven by temporal reorganization and phase-coordination shifts rather than spatial modification of the joint trajectories.
Key Findings
Results
Submaximal breaststroke swimming was characterized by significantly longer absolute and relative durations of the non-propulsive 'leg lift and glide' phase compared to maximal swimming.
Nine competitive male swimmers performed 25-m breaststroke trials at both maximal and submaximal intensities.
The 'leg lift and glide' phase occupied 59.09 ± 5.72% of the kick cycle at submaximal intensity versus 34.45 ± 12.11% at maximal intensity (p < 0.001).
Three-dimensional kinematics were captured using a multi-camera motion analysis system.
The kick cycle was divided into 'leg sweep', 'leg lift and glide', and 'leg recovery' phases.
Results
Submaximal swimming produced 50.3% greater horizontal centre of mass displacement per kick compared to maximal swimming, despite lower swimming velocity.
Horizontal centre of mass displacement per kick was 2.24 ± 0.38 m at submaximal intensity versus 1.49 ± 0.30 m at maximal intensity (p < 0.001).
This difference occurred despite submaximal swimming being performed at a lower swimming velocity.
The greater displacement per kick is attributed to the longer non-propulsive glide phase at submaximal intensity.
Data were analyzed using paired t-tests for discrete metrics and Statistical Parametric Mapping (SPM) for time-series trajectories.
Results
Maximal swimming elicited compressed phase timing with earlier occurrence of peak joint events and higher angular velocities, particularly near phase transitions.
Phase timing was compressed during maximal compared to submaximal swimming.
Peak joint events occurred earlier in the kick cycle during maximal swimming.
Higher angular velocities were observed during maximal swimming, especially near phase transitions.
Greater vertical centre of mass displacement was also observed during maximal swimming.
SPM analysis was applied with normalization to both total kick cycle and individual phase durations.
Results
Joint ranges of motion and segment widths remained consistent across swimming intensities, indicating preservation of spatial movement patterns.
Spatial variables including joint ranges of motion did not differ significantly between maximal and submaximal intensities.
Segment widths were also preserved across intensities.
This consistency indicates that swimmers do not alter the spatial organization of their kick when changing intensity.
Both discrete variable and time-series (SPM) analyses were used to confirm this finding.
Discussion
Adaptations to swimming intensity in breaststroke lower-limb action are predominantly driven by temporal reorganization and phase-coordination shifts rather than spatial modification.
The primary adaptation mechanism identified was temporal: changes in phase durations and timing of peak events.
Spatial parameters (joint ranges of motion, segment widths) were conserved across intensities.
The dual analytical approach of discrete variables and SPM time-series analysis was employed to differentiate temporal from spatial adaptations.
Normalization was applied to both total kick cycle and individual phase durations to enable valid temporal comparisons.
Methods
The study employed a dual methodological approach combining discrete variable analysis (paired t-tests) and time-series analysis (Statistical Parametric Mapping) to characterize breaststroke kick kinematics.
Nine national-level competitive male swimmers were recruited.
Swimmers performed 25-m breaststroke trials at both maximal and submaximal intensities.
Three-dimensional kinematics were captured using a multi-camera motion analysis system.
SPM was applied to time-series trajectories normalized to both total kick cycle and individual phase durations.
The study investigated spatiotemporal kinematics including joint angles, angular velocities, segment widths, and centre of mass displacement.
What This Means
This research suggests that when breaststroke swimmers change their effort level — from a comfortable pace to full-speed — they primarily adjust the timing of their leg kick rather than the shape or range of their movements. The study tracked nine competitive male swimmers using multiple underwater cameras and found that at a relaxed pace, swimmers spend proportionally much more time gliding with their legs extended (about 59% of each kick cycle) compared to when swimming at maximum effort (about 34%). This extended glide at lower intensity allows the swimmer to travel farther per kick cycle (about 2.24 meters versus 1.49 meters), even though they are moving more slowly overall.
At maximum effort, swimmers compress the timing of each kick phase, reach peak positions in their joints earlier in the cycle, and move their legs faster — particularly around the transitions between kick phases. Importantly, the actual range of motion at each joint and how wide the legs sweep stayed the same regardless of effort level, meaning the fundamental shape of the kick is preserved; only the timing changes.
This research matters for understanding how elite swimmers regulate their effort in breaststroke, which is the only competitive stroke requiring simultaneous use of both arms and legs in a symmetrical pattern. The finding that spatial movement patterns are preserved while temporal patterns change could inform how coaches teach pacing strategies and how analysts assess swimmer efficiency. It also suggests that training programs focused on improving race-pace breaststroke should pay particular attention to phase timing and coordination rather than trying to alter the geometric shape of the kick motion.
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Gourgoulis V, Nikodelis T, Gketzenis P, Kasimatis P, Bekiaris A, Koulexidis S. (2026). Impact of swimming intensity on spatiotemporal kinematics of lower-limb breaststroke actions in national-level male swimmers: A discrete variable and time-series analysis.. Journal of biomechanics. https://doi.org/10.1016/j.jbiomech.2026.113372