Substantiating Appropriate Motion Capture Techniques for the Assessment of Nordic Walking Gait and Posture in Older Adults

The overall goal of this experiment is to determine the effects that Nordic Walking Poles have on both gait patterns and postural alignment, specifically in older adults. This method can help answer key questions in the field of biomechanics, such as how can arctic walking be used to aid in improving gait and posture in older adults. And what are optimum methods of assessing such gait and postural variables.

The main advantage of this technique is that it demonstrates two efficient methods for assessing gait and posture as they pertain to Nordic Walking. The implication of this technique may extend towards therapy settings. Specifically As a use of Nordic poles, may aid with various gait and conditions.

Demonstrating this procedure will be Zach Bonsegen, one of my graduate students. To begin, provide each participant with a set of poles and instruct them to stand tall. Then, have the participant place the poles'tips in front of their toes and place their elbows next to their body.

Instruct the participants to lengthen the poles until their elbows form an approximate 90 degree angle next to the body, ensure the adjustment corresponds to approximately 65%of the participant's body height. Then, securely tighten the poles and angle the boot tips backwards. Before securing the wrist straps, instruct the participant in correct body posture by having them place their poles behind the lower back, and stand tall.

Also ask the participants to stand with their chest tall and the shoulders relaxed. Then, have each participant secure their wrist straps, place the pole tips behind them, and relax their arms at their sides. While keeping their hands open, instruct the subject to begin walking with minimal arm swings for approximately 100 meters.

While still keeping the hands open, and dragging the poles behind them, instruct the participant to begin walking faster and with larger arm movements. Then, ask the participants to visualize bringing their hand up, as if they are about to shake someone's hand. Finally, as the arm swings forward, have the participant gently grasp the handle and apply a force against the ground.

With each arm swing, instruct the individual to slightly lift the poles off the ground and firmly plant them with each subsequent stride. The tip of the pole should be aligned with the foot midline. Learning and understanding the technique is critical to ensure consistency with this protocol.

To ensure this to happen, we've broken the instructions into four succinct statements to simplify things, and ensure optimal performance from all participants. Begin data collection by collecting each participant's anthropometric measurements. Start by using a tape measure to measure each leg's length as the distance from the anterior superior iliac spine to the center of the medial malleolus.

Then, measure the distance between the left and right osseous, known as the interosseous distance, as well as the shoulder offsets. Using calipers, measure the widths of each joint, by finding the distance between the bony prominences of each joint. Do this to measure their knee widths, ankle widths, elbow widths, wrist widths and also measure hand thicknesses.

Lastly, use the standard weight scale to measure the participant's weight and the tape measure to measure the participant's height. In order to assess gait patterns and postural alignment over a long period of time, use an accelerometry system for data collection during the six-minute walk test. Ensure that the accelerometry system is comprised of at least six sensors, each with accelerometers and gyroscopes incorporated into them, in order to measure both the acceleration and angular velocity of each specific body segment.

Prior to their placement on the participant, ensure that all of the sensors are securely docked to the system's docking station, in order to synchronize them and calibrate the system. Next, use adjustable hook and loop straps to attach the senors to the wrists posteriorly, to the ankle anteriorly, to the L5 vertebrae of the lumbar spine and to the trunk atop the sternum. Set the sampling rate to a minimum of 100 Hertz.

Then, ask the participant to perform two trials of the six-minute walk test, one with poles and one without. Randomly assign the two trials to control for order effect. Instruct the participant to walk back and forth along the 25 meter walkway at a self-selected speed for six minutes.

Before the participant begins, be sure to click start to begin data collection with the accelerometry system. When both trials of the six-minute walk test have been completed, assess short-duration gait events using a three-dimensional motion capture system with two force plates embedded in the pathway. Synchronize the force plates to the motion capture system by first connecting them to the computer via the wires provided from the company.

Then, in the motion capture system software, add the force plates to the capture volume by entering the dimensions, position, orientation, sensitivities and any other required information for the system. Ensure that the force platforms are zeroed to prevent noise in the data, and ensure they are collecting at a sufficient sampling rate of 1, 000 Hertz. Next, complete a dynamic calibration of the system by first waving a 3-marker wand in a controlled manner through the capture space.

Then, perform a static calibration to set the global xyz coordinate system by placing a four marker L-frame at that specified reference point and select set volume within the computer software. Calibration of the motion capture system is critical to ensure accuracy of collected data and is done before all else. To ensure accurate results, the image error is assessed and, if necessary, calibrations are repeated until optimal values are obtained.

With the software calibrated, fit the participant with the 39 reflective markers, attaching them using double-sided tape, and placing them on the specific anatomical landmarks shown here and described in the accompanying text protocol. Finally, instruct the participant to perform six trials of a 5 meter walk, through the system's capture volume, three with poles and three without. Randomly assign these trials to control for order effect.

This graph represents a typical hip power profile over one single gait cycle and compares a participant's gait with poles to the gait without poles. The arrows at H1, H2 and H3 indicate the changes in power generation and absorption in comparing these phases with and without poles. When using poles, significantly smaller hip power generation is seen at heel contact as well as at pre-swing and initial swing, compared to walking without poles.

Shown here is a typical knee power profile over one single gait cycle comparing with poles to without poles. When using poles, significantly smaller knee power absorption is seen at heel contact, at pre-swing and at terminal swing compared to walking without poles. Once mastered, this technique can be done in 45 to 60 minutes per participant, if it's performed properly.

While performing the procedure, it's important to ensure that the participants walk naturally both with and without the poles. Therefore, they should not be made aware of where the force plates are. Following this procedure, other methods like EMG can be performed in order to answer additional questions such as activation patterns of the muscles, especially muscles of the upper body.

After watching this video, you should have a good understanding of how to assess Nordic Walking gait and posture, using at least one of the two different motion capture systems. This protocol allows researchers in the field of biomechanics to explore the effect of Nordic Walking on gait and posture in older adults but also in other populations with gait and posture disorders such as individual with Parkinson's disease. Don't forget that introducing a new implement, such as the poles, could increase the level of attention needed to perform the motor task, and therefore, participants should be made aware to start training in a safe environment.