The 20km cycling time-trial (TT20km) is an ecological test that simulates competition conditions and allows the investigation of how thoracoabdominal movements and whole-body kinematics adapt during a self-paced effort. Although the physiological adaptations of cyclists are well documented, little is known about the evolution of thoracoabdominal movement, joint angles of the upper and lower limbs, and their synergies throughout the trial, in order to observe the adjustments made to cope with increasing power demands and high perceived exertion. The central aim of this work was to describe and evaluate all movements performed by an experienced master cyclist during a TT20km. To achieve this, the study was organized into three specific objectives: (i) to characterize thoracoabdominal breathing patterns in experienced master cyclists and examine their stability from rest to exercise; (ii) to describe and analyze changes in upper and lower limb joint angles, across the three planes of motion, between the beginning and the end of the test; and (iii) to identify upper and lower limb synergies through Principal Component Analysis (PCA) and compare them between the start and the end of the test. Nine participants performed a TT20km on their own bicycles mounted on a stationary trainer. Respiratory movements and whole-body three-dimensional kinematics were captured using a multi-camera motion analysis system. For thoracoabdominal analysis, the percentage contribution of each compartment to total volume (superior thorax, inferior thorax, and abdomen) was calculated, as well as correlation coefficients between them, both at rest and during the TT20km. Joint angles were normalized to the pedaling cycle (0–100%). Comparisons between the beginning and the end of the test were conducted using Statistical Parametric Mapping (SPM), while synergies were analyzed by PCA and also compared using SPM.