# Are Torque-Driven Simulation Models of Human Movement Limited by an Assumption of Monoarticularity?
## 3 Results
### Squat Jump  
The matching SJ simulation had a 25 cm (10%) smaller jump height than the measured squat jump performance, whilst the matching TJ simulation was 9 cm (6%) smaller than the measured performance. The SJ squat jump simulation achieved a jump height 16 cm smaller (1.28 m) than that of the TJ simulation (1.44 m), where these differences were the sum of smaller vertical displacement both for the contact and flight phases (Table 7). The optimised activation parameters revealed different activation profiles between the torque generators of the SJ and TJ models (Table 4). In general, the SJ simulation adopted uniform activations throughout the simulation by selecting parameters that did not create a ramp in activation. In contrast, the TJ simulation included both ramped activations and sequential activation of the biaarticular and monoarticular extensors. Typically, the monoarticular activations would ramp up to full activation much later in the simulation than the biaarticular components. The knee flexor activations of the SJ and TJ simulations differed most. The knee flexors and knee extensors of the SJ simulation were relatively submaximal (less than 50%) throughout the simulation, whereas for the TJ simulation there was a ramp to near full activation of the biaarticular knee flexor and a uniform full activation of the biaarticular knee extensor. There was little difference between the model performances with respect to contact phase duration, orientation at take-off, angular momentum and horizontal velocity. The squat jump simulation models differed more from the measured performance and between each other with respect to joint kinematics and take-off velocity. The TJ model was better than the SJ model at matching the joint kinematics of the participant with differences from measured kinematics of 13.4\({}^{\circ}\) and 17.0\({}^{\circ}\), respectively (Table 7, Figures 3 and 4). Considering the kinematics of joints which differed in the representation of the torques between the SJ and TJ simulations, the ankle joints differed most obviously from the measured performance. In both simulations, the ankle plantar flexed until approximately 0.1 s prior to take-off, which coincided with the largest joint angle changes at the knee and hip and appeared to be required to manage the large proximal joint torques by placing the ankle joint in a stronger position (Figures 3 and 4). For the knee and hip joints, the TJ model performed better by more closely matching the larger velocities of the measured performance, but most importantly, in achieving greater joint extension. At the ankle, the SJ model had 10\({}^{\circ}\) less extension at take-off than the measured performance, whilst this was 1\({}^{\circ}\) for the TJ model. At the knee, the SJ model had 49\({}^{\circ}\) less extension at take-off than the measured performance, whilst this was 20\({}^{\circ}\) for the TJ model. At the hip, the SJ model had 46\({}^{\circ}\) less extension at take-off than the measured performance, whilst this was 24\({}^{\circ}\) for the TJ model (Figures 3 and 4).  
Figure 3: Graphical comparison of the squat jump simulations at equal time intervals from initial conditions to take-off; (**a**) TJ, (**b**) SJ and (**c**) measured performance.