Trunk axial and sagittal torques have been studied as important motors for lower limb movements in tasks such as kicking. Trunk torques are potential contributors to lower limb forward displacement during the swing phase of running in the kinetic chain. In the swing phase of running, the lower limb is initially accelerated forward and subsequently decelerated before contact with the ground. The torques produced by the trunk muscles could contribute, together with the muscles of the lower limb joints, to this function, being important to avoid overloading the muscles of these segments during running. However, there are no investigations in the literature about the contributions of trunk torques to lower limb advancement in running.

The aim of the study is to understand the accelerations caused by the axial and sagittal torques of the trunk on the segments of the lower limb, during running, at different speeds.

Three running cycles with the right lower limb at speeds of 2m/s, 3m/s, 4m/s and 5m/s were used to perform the induced acceleration analysis in the OpenSim software. The sample consisted of ten experienced, healthy male runners. Data were collected on an instrumented treadmill at Stanford University's Human Performance Laboratory and are freely available. A model of the musculoskeletal system allowed estimating the accelerations caused by joint torques in body segments. The anteroposterior accelerations of the thigh, shank and foot segments, induced by axial and sagittal torques of the trunk and sagittal torques of the hip, knee and ankle, were computed. For each segment, the movement was divided into acceleration and deceleration phases. The percentage of the total acceleration induced by the torques was determined by means of the positive and negative integral.

Axial trunk torque was the main inducer of thigh acceleration (63% to 67%), while sagittal trunk torque was the main inducer of deceleration (45% to 57%), at all running speeds. For acceleration and leg deceleration, the hip in the sagittal plane was the main inducer torque (67% to 82%), while for the foot, the sagittal ankle torque was the main acceleration inducer (39 to 49%), while the sagittal torque of the knee was the main deceleration inducer (95% to 98%) The contribution pattern remained independent of running speed.

It is concluded that the trunk axial and sagittal torques contribute to the acceleration and deceleration of the thigh, which is the segment with the greatest mass and inertia of the lower limb, regardless of running speed.

The study helps in understanding human movement by exploring the effects of torques on joints and segments distal to them. Thus, trunk torque production deficits could overload hip flexor and extensor muscles to accelerate and decelerate the thigh. The study serves as a basis for intervention studies on the trunk and running performance.