Strength and Conditioning: Kinematics and Kinetics

If you're a personal trainer aiming to become a strength and conditioning coach, biomechanics isn't optional. Two branches of it in particular — kinematics and kinetics — sit behind almost every decision you make about performance and injury prevention.

Kinematics vs kinetics

They sound similar and get muddled constantly. The distinction is simple:

• Kinematics is the study of motion without considering the forces that cause it. It deals with displacement, velocity and acceleration.
• Kinetics is the study of motion and the forces causing it, including torque and power.

One describes what the movement looks like. The other describes what's driving it.

Kinematics in sports performance

In sport, kinematics is used to analyse how an athlete moves so you can improve their technique and performance. As an example, Honert et al. (2018) investigated how toe joint stiffness affects walking biomechanics. They found that varying toe joint stiffness changed the centre-of-mass dynamics during walking as much as — and in some cases more than — varying ankle joint stiffness.

That's a useful reminder: small details in how the body is organised can have outsized effects on movement. Understanding kinematics helps you spot them and design training that targets what actually matters.

Kinetics in sports performance

Kinetics takes you to the forces behind the movement. Lee and Park (2020) used machine learning to estimate three-dimensional lower-limb kinetics during walking from a single inertial measurement unit (IMU) attached to the sacrum — a sign of how accessible force analysis is becoming. Understanding kinetics lets you design programmes that raise performance while keeping injury risk down.

Why it matters for your coaching

Grasp both halves and you can do three things better: optimise training programmes, improve performance, and prevent injury. For a trainer moving into strength and conditioning, that depth is exactly what sets you apart from someone working on movement alone.

References

• Honert, E. C., Bastas, G., & Zelik, K. E. (2018). Effect of toe joint stiffness and toe shape on walking biomechanics. Bioinspiration & Biomimetics, 13(6), 066005.
• Lee, M. H., & Park, S. (2020). Estimation of Three-Dimensional Lower Limb Kinetics Data during Walking Using Machine Learning from a Single IMU Attached to the Sacrum. Sensors, 20(21), 6277.