Purpose: This study determined the forces acting on a handbike, using strain gauges, in three field test scenarios- accelerating, braking and road irregularities. In addition an initial optimization study was conducted usingthe determined acceleration forces.Methods: Free Body Diagrams and Finite Element Analysis (FEA) was used to determine strain gauge positions.Laboratory calibrations were carried out to transform the measured strains into forces. One healthy male subjectperformed five trials of each field test scenario – all out acceleration for three pedal cycles, braking the handbikefrom a velocity of 41.7±0.3 km/h and riding across wooden list, simulating a cobblestone road (velocity of37.3±1.1 km/h). A FE-model of the handbike, used for optimization, was validated by carrying out a calibrationstudy for each field test scenario. Lastly, an initial optimization study, in regard to frame stiffness, was conductedby applying the acceleration force, calculated with the laboratory calibration, to the FE-model of the handbike.Results: For the acceleration scenario the tangential and radial force peaks were 407.6 N and 380.0 N, respectively,the peak brake force was 1571.1 N and the peak forces caused by road irregularities, were 12952.4 N and21586.7 N, at the front and rear wheel, respectively, calculated with the laboratory calibrations. The tangentialand radial force peaks were 25.2 percent higher and 8.4 percent lower, respectively, while the peak brake androad irregularity forces, at the front wheel, were 96.4 and 1328.3 percent higher, respectively, calculated with thelaboratory calibrations compared to the SW calibrations. The lowest displacement of the crankbox, 0.494mm, wasfound by thickening the front V-tube of the FE-model.Conclusion: The acceleration forces found was considered slightly overestimated and the brake force was consideredvalid, while the road irregularity forces was not. As disagreement between the results of the FE-modeland laboratory calibration were present, the FE-model cannot fully be trusted for FEA, especially in regard tobrake and road irregularity force. The initial optimization study revealed that the highest stiffness by least weightincrease was obtained by thickening the frontal V-tube.