<p>The green alga <i>Chlamydomonas reinhardtii</i> (CR) has been explored as the live component of biohybrid microrobots due to its intrinsic motility. However, cell performance depends on physiological state, which evolves with culture age. Using optical tweezers, we quantify the rotational dynamics of individual CR cells across lag, exponential, stationary, and death phases. We reveal a clear performance trajectory: rotation speed and corresponding hydrodynamic torque peak during the mid-exponential phase and decrease as cultures mature. Additionally, counterclockwise rotation consistently generates higher hydrodynamic torque than clockwise rotation. These findings provide quantitative benchmarks linking CR’s motility characteristics to growth phase, offering guidelines for designing living micromachines and establishing rotational dynamics as a sensitive proxy for cellular metabolic health.</p> Graphical abstract <p></p>