Understanding Rotational Overload Effects of Thigh Wearable Resistance on Kinematic and Kinetic Properties of Sprint Running
by Paul Macadam
Figure 1. Thigh attached wearable resistance
This article covers a specific research review of the EXOGEN Shorts in speed and sprint training. Exogen SHORTS along with the CALF sleeves are key products for overall leg speed and power development across sport.
New advancements in materials and training technology have enabled more organic load/weights to be attached directly to the human body, via specialised base garments creating the innovation in wearable resistance (WR). Athletes can now wear comfortable and relevant resistance during sport-specific movements, such as sprint-running for athletics and team sports. Measurements of sprint-running mechanics are often linear in quantification, despite being the result of joint rotations. Therefore, quantifying rotational movement, especially with the emergence of WR limb loading is important and potentially ground breaking.
The placement of WR attached to the thighs enables the rotational movement of lower limbs to be overloaded in a sprint-specific manner (Figure 1). Therefore, a more direct overload to the sprint action is achieved through thigh WR, as greater changes to the rotational action of the thigh have been found compared to linear findings. From acute changes to sprint performance, thigh attached WR increases the rotational inertia of the leg with a concomitant decrease in angular velocity of the lower limbs and hence affects swing mechanics by reducing step frequency.
These findings suggest that for athletes seeking to overload step frequency and develop vertical stiffness and anterior-posterior impulse during accelerated sprinting, WR enables the application of a sprint-specific form of rotational overloaded resistance training.
While progressive overload is often achieved through greater load increases, WR also enables progressive overload via changing the position of the load. For example, Figure 2 shows that by moving the load further away from the hip, a greater amount of thigh rotation inertia will be required to overcome during the swing phase of sprint-running.
Figure 2. Progressive overload via changes in position, i.e. more distal from the axis of rotation results in a greater amount of rotational inertia to overcome.
Following a 5-week training program with thigh WR, increases were found in the angular velocity of the lower limbs over similar angular displacement ranges, emphasising the direct rotational overload and adaptation from the thigh WR. Moreover, linear changes in kinematics and kinetics resulted in reduced contact times, and increased vertical stiffness, horizontal force and power contributing to substantially faster velocity. Therefore, WR provides a sprint-specific method for rotational overload and subsequent speed-specific adaptation.
Practitioners may wish to utilise this form of placement for athletes needing to overload the acceleration and early maximal velocity phase of sprint-running. Some key points are:
- Thigh WR enables the rotational action of the thigh to be directly overloaded resulting in significant changes to rotational kinematics and linear kinematics and kinetics. By utilising wearable sensor technology (i.e. IMUs) to quantify movement specific loading through WR, practitioners can assess sprint performance during sprint-specific resistance training.
- Sprint-specific resistance training should be used to develop speed using thigh positioned WR. This form of resistance enables a relevant load to be applied directly to the body that will directly stress specific sprint movements under the specific demands of an actual sport and competitive environment, without compromising the speed of motion, range of motion and specific skill.
- WR offers athletes a means to target angular velocity of the thighs, step frequency, net anterior-posterior impulses, and vertical stiffness, during sprint-specific form training, whilst minimally affecting step length. Given the importance of these variables in attaining sprinting speeds, and that the thigh moment inertia increases with WR, this form of loading could be a suitable training tool to overload the hip musculature to improve sprint mechanics.
- Substantial increases in maximal horizontal force and power suggest this form of loading may be suitable to improve acceleration and early maximal velocity phase of sprint-running. Moreover, WR attached to the thighs can be used in a training plan to improve sprint times by increasing sprint mechanical properties, reducing contact times and increasing in vertical stiffness.
Paul Macadam (https://www.aut.ac.nz/student-profiles/paul-macadam) is a Research and Development Manager and Public Health Directorate at Isle of Man, and a PhD Candidate AUT. His research includes Understanding Rotational Overload Effects of Thigh Wearable Resistance on Kinematic and Kinetic Properties of Sprint-Running.
He is involved in research for advancements in technology that enable loads to be attached to the body, creating wearable resistance (WR) which athletes can wear during sport-specific movements, such as sprint-running, measurements of sprint-running mechanics are often linear in quantification, despite being the result of joint rotations. He works on quantifying rotational movement, especially with the emergence of WR limb loading.
His research is aimed to assess the kinematic and kinetic effects of a sprint-specific rotational form of resistance through thigh attached WR and sought to determine whether IMUs could quantify rotational kinematics of sprint-running.