Fatigue due to motorcycle riding is an important field of study as it is one of the key parameters through which the end user rates the motorcycle. The fatigue due to riding can be broadly divided into two major activities the body performs: 1. Maintain the body posture, absorbing road shocks and 2. Generate the required forces to control the motorcycle. The current methods of estimating fatigue are limited to subjective feel and objective measurements of parameters like steering torque; shock levels at seat, etc. during riding. These parameters estimate the inputs to the vehicle irrespective of the rider posture and hence predict same fatigue for all postures, but it is well known that the riding posture significantly affects the fatigue of rider. In this study the authors propose a direct way of measuring fatigue using Electromyography (EMG). The objective of this study is to determine physical fatigue due to motorcycle riding using surface EMG. Two motorcycles similar in all the specifications except the riding posture are taken up for this study; one has an erect/straight posture while the other has a leaning forward posture. Experiments are conducted using these motorcycles on two road conditions one involving high number of road shocks and the other involving maneuvering through heavy traffic. Surface EMG measurements are carried out on four muscle groups identified as the most common areas of fatigue in motorcycle riding. Fatigue in these muscle groups is estimated using the features extracted from EMG signal such as mean power frequency (MPF) and RMS amplitude for each of the experiments. The subjective rating of the rider is also captured after each experiment. Results show that the leaning forward posture causes lower fatigue when exposed to road shocks and body fatigue caused due to control of motorcycle in traffic is similar for both the postures. The subjective rating also agrees with results of EMG measurements. Copyright © 2010 SAE International and Copyright © 2010 SAE Japan.