FOA on Sit to Stand in Individuals Post Stroke

Introduction More than 795,000 people have a stroke in the United States each year, one every 40 seconds, leading to 7.6 million Americans who have had a stroke. Further, stroke remains the leading cause of long term disability, with greater than 50 percent of stroke survivors being chronically disabled. One factor contributing to disability is the difficulty with sit to stand transfers.

Individuals post stroke present with decreased knee moment on the affected side resulting in a less efficient sit to stand transition. In addition, individuals post stroke demonstrate increased trunk displacement in the mediolateral direction towards the unaffected side and weight distribution asymmetry. Cheng et al. found that individuals post stroke who were classified as fallers took more time to stand, had more mediolateral sway, and pushed less force through the affected lower extremity during sit to stand.

Sit to stand training is essential during rehabilitation post stroke to improve the ability to stand with a more normal biomechanical pattern and to positively impact other aspects of mobility. Several studies underline the importance of sit to stand training with a focus on increasing use of the affected lower extremity. Forced use training of the affected lower extremity has led to increased muscle activity in the affected limb, improved balance, gait kinematics, gait symmetry, gait velocity, and quality of life.

In order to make sit to stand training more effective the type of instruction and feedback is key. Based on a number of studies, simply changing two to three words of instruction can lead to more effective outcomes. This impactful change in instruction is based on focus of attention research, exploring the difference between internal and external focus instruction. An internal focus refers to thinking about one's own body movements, while an external focus is focusing on an outcome or impact on the environment. An example of internal focus is thinking about what one's shoulders or arm is doing while shooting a basketball, while an external focus would be thinking about the effect on the ball or the basket. Over 80 studies have supported an external focus being more effective than an internal focus of attention in the healthy adult and sports population.

The research in the stroke population related to focus of attention is sparse and contradictory. Some studies show an external focus being detrimental to movement fluency, while others find that an external focus leads to better outcomes. The remaining studies in the stroke population, however, have found no difference between internal and external foci. Most of these studies examined the effect of attentional focus during practice but did not include retention testing, thus the effects on motor learning have not been assessed. In addition, these studies have not examined the effects of focus of attention on functional movements such as sit to stand.

Individuals post stroke may respond differently to focus of attention compared to healthy adults due to their impairments and cerebral changes. Individuals post stroke can have decreased executive function including information processing. Also, these individuals may lose some motor automaticity leading them to consciously try to control their movement.

Statement of the Problem Impairments following stroke often lead to functional limitations such as difficulty performing a sit to stand transfer, which may affect independence in other activities of daily living. Individuals following stroke often perform sit to stand transfers less efficiently than individuals without stroke. This inefficiency is due in part to asymmetry between the unaffected and affected lower extremity. Training people to use the affected side more may increase efficiency of their movement and decrease fall risk. The type of instruction and feedback, specifically focus of attention instruction, may impact how well people following stroke learn to use the affected side more during sit to stand transfers. At this time, the effect of focus of attention instruction and feedback on the increased use of the affected side during sit to stand in individuals post stroke is unknown.

Purpose The purpose of this study is to fill some of the gaps in the literature by examining the effects of focus of attention on performance and learning of sit to stand in individuals post stroke. This study will investigate whether an internal or external focus of attention can lead to improved use of the affected lower extremity during the sit to stand transition, while maintaining an upright trunk position.

Research Questions

The following research questions will be addressed in this study:

1. Does an internal or external focus enhance motor learning of a sit to stand task in which learning will be evaluated using a retention and transfer test? Retention will refer to the ability to perform the sit to stand task without explicit instruction five minutes and one hour after practice. Transfer of learning will be evaluated by exploring the effects of sit to stand training on gait symmetry.
2. Does an internal or external focus lead to an improved performance of a sit to stand task during training as measured by an increased weight shift towards the affected side and upright trunk alignment?

Participant demographics and clinical information will be collected, including age, gender, weight, height, location of stroke, how long ago the stroke occurred, and fall history. All participants will consent to participation in this study. The Star Cancellation Test and Montreal Cognitive Assessment (MOCA) will be used to determine eligibility. Gait speed and the Fugl Meyer for the lower extremity, excluding reflexes, will also be completed to help describe the sample. Blood pressure, heart rate, and oxygen saturation, via a pulse oximeter, will be taken and a gait belt will be placed on the participant prior to the start of baseline measures. Temporospatial gait parameters will be collected using the GAITRite mat at baseline, 5 minutes after training, and 1 hour after training. Temporospatial gait parameters will be averaged across four passes over the GAITRite mat at each measurement session. Participants will be instructed to 'walk past the end of the mat at your normal comfortable pace'. Gait speed will be recorded at baseline as part of the individuals' baseline measurements.

Participants will then be seated on a hi-lo table with their feet on the HR pressure mat for baseline assessment of sit to stand. Initial mat height will be determined by raising or lowering the mat table until the femur is parallel to the floor. This initial mat position will be the height used during each reassessment at baseline, 5 minutes after training, and 1 hour post training. This height will also be used to decide the mat positions needed during training. After the initial mat height is achieved and recorded, an IMU marker will be placed on the superior third of the sternum directly inferior to the sternal notch.

Next, participants will be asked to stand up and sit down to determine comfortable foot placement in relation to their knees. Tape marks will be placed in front of the toes and on the lateral edges of both feet as well as around the buttocks to allow for a standardized starting position for all assessment timepoints. For all data collection during baseline, 5 minutes post, and 1 hour post training, participants will be instructed to "please stand up three times at your normal speed without your arms if possible". The average force under the affected foot and the average overall force beneath both feet during the sit to stand transition will be captured by the HR pressure mat. The maximal lateral trunk position will be captured throughout this transition by the IMU marker. If individuals need to use their upper extremities this will be recorded.

After baseline data collection, participants will be randomized into either the internal or external focus condition. Initial group allocation will be determined by a random number generator, blocks of 6 with a 1:1 ratio. Group allocation envelops will be opened directly prior to acquisition trials so baseline assessors will be blinded to group assignment of participants. Participants will be blinded to initial group assignment throughout the entirety of the sessions.

Training Prior to training, a demonstration of the task will be provided to the participants. Those in the external focus condition will be told, "as you stand up and as you sit down try to bring the targets together like this". Those in the internal focus condition will be told, "as you stand up and as you sit down bring your right/left (R/L) shoulder and R/L hip as far to the R/L as possible." Participants will be asked to perform one repetition with the question "can you show me?". The demonstration is only provided before the first set but these same instructions will be given prior to the start of each successive set during training.

During training trials, individuals will perform four sets of ten sit to stand repetitions. During the external focus condition, foam circles will be taped to the participant's lateral shoulder and lateral hip. In order to define this distance, participant girth will be measured in a seated position, by measuring the distance between bilateral outer thighs, using greater trochanters as landmarks. When the individual is standing in midline targets will be placed half of this girth measurement plus 10 centimeters away from the lateral tip of their acromion and another target placed the same distance away from their greater trochanter.

During training, participants will perform four sets of sit to stand transitions with the mat at progressively lower seat heights to increasingly challenge the participants, with instruction and feedback consistent with their condition allocation. The four sets will occur in the following sequences: 130 percent of the initial mat height determined at baseline assessment, 120 percent, 110 percent and 100 percent. Each set will end after the tenth repetition or when the participant reports a RPE rating of >15/20. If participants are unable to complete 10 repetitions, the number completed will be recorded for each trial. Two minute rest breaks will occur between each set or until the participant reports a rate of perceived exertion (RPE) of <12/20 on the Borg RPE scale. During training, one verbal correction will be given during each set after the 2nd, 4th, and 7th trials, based on patient performance and condition allocation. The feedback provided will be recorded.

Immediately after the training, participants will take a 5 minute break followed by the post-5 minute retention test in which instrumented sit to stand and gait will be administered. Following the retention test, individuals will complete a general health questionnaire. Approximately one hour after the training ends, 1-hour retention testing will be administered consisting of 3 instrumented sit to stands and gait over the GAITRite. After the immediate long term data collection, the participants will complete the post manipulation questionnaire to determine what the participants were focusing on during training.

One week later participants will return and complete the same protocol in the opposite attentional condition to which they were initially randomized.