Reading material on improving movement analysis and therapy

Dual-Task Paradigm   

To identify differences in gait conditions with an additional task, the dual-task paradigm is utilized. Its premise involves performing each of the tasks first individually and then simultaneously executing both tasks. Each task should have the same conditions during both single and dual-task performance (McIsaac et al., 2015; Pineda et al., 2023). 

Preparation for the Examination: 

Before starting the examination, it’s essential to inform the person being examined about the purpose of the study, how it will be conducted, and assure them that the examination is non-invasive and painless. 

If markers will be applied directly to the body (skin) during the examination, it’s also important to let the individual know when scheduling the appointment that they should avoid using moisturizing or oily skin products (like lotions or balms) to prevent the markers from coming off. 

Preparation for Gait Analysis in the Dual-Task Paradigm: 

Before conducting gait analysis in the dual-task paradigm, several steps need to be taken: 

• Interview: Collect information about the individual’s age, existing medical conditions, past injuries, occupation, hobbies, and the reason for undergoing the study. 
• Anthropometric Measurements: Gather measurements necessary for the specific gait analysis system in use, such as body height and the length of the lower limbs. 
• Additional Measurements: Include any extra measurements, for example, an assessment of the dominant lower limb (if needed for the study). 
• Attachment of Sensors/Markers: Securely attach the motion analysis system’s sensors or markers to the individual’s body, and calibrate the system to ensure accurate data collection. 

Gait Analysis in Single-Task Conditions (Single Task – ST): 

During gait analysis in both single and dual-task conditions, we utilize gait analysis systems to obtain spatiotemporal gait parameters. Depending on the equipment used, it’s important to consider its limitations, which can arise from measurement accuracy and cultural factors (such as how and where sensors/markers are attached). 

After attaching the sensors/markers of the selected gait analysis system, it is advisable to acclimate the individual to walking in the measurement environment. Our observations suggest that a patient’s awareness of having elements of the system attached to their body or that their gait is being recorded can impact their locomotion. A best practice in our motion analysis laboratories is to allow the individual to walk the measurement path multiple times before the actual data recording. 

Gait Recording:  

Typically, gait analysis is conducted at the participant’s preferred walking speed (Langeard et al., 2021). However, there is also the possibility to perform the study at a slow or fast walking pace (Schättin et al., 2016). 

To prevent measurement errors during the study, it is recommended to: 

• Ensure that only research equipment, and not personal phones or electronic devices, are in use by both the participants and the examiners. 
• Limit the number of people in the room to only the individuals being tested and the examiners. 
• Secure the area to prevent unauthorized individuals from entering the room where the study is conducted. 
• Eliminate external distractions, such as blocking windows, closing doors, and reducing external noises. 

The measurement path should be determined with the following considerations: 

• The path’s length should be suitable for the participant’s physical capabilities. 
• The participant should be able to walk in a straight line (they can turn around, but this stage is not included in the measurements). 
• A measurement path located in a space that is too small can disrupt the results by altering gait parameters due to locomotion initiation or approaching an obstacle like a wall. 
• A path that is too short or too long may hinder or prevent the performance of additional tasks in dual-task conditions. 

According to the dual-task paradigm, it is essential to ensure the same testing conditions and conduct the same number of walking cycles in both single and dual-task conditions (Plummer et al., 2013). This consistency is crucial for reliable and meaningful comparisons in gait analysis when individuals are performing tasks that require their attention simultaneously. 

Researching Additional Tasks in Single-Task Conditions (Single Task – ST) 

Despite the increasing number of scientific reports regarding cognitive task assessment, there is a lack of standards defining the principles of their application. The following tasks are most commonly used in research:     

• Serial counting backward from 50 or 100 (the participant verbally counts numbers, e.g., 100, 99, 98…)  (Beauchet et al., 2007; Beauchet et al., 2008; Yamada et al., 2011). 
• Serial subtraction of 7 or 3 from a specified number (the participant provides the results of subtracting from the given number, e.g., subtracting 7 from 376, the patient should list numbers like 376, 369, 362, 355…) (Maclean et al., 2017). 
• Listing animals or professions without repeating names (the participant lists professions like chef, doctor… or another version involves naming animals starting with a specific letter, e.g., C, then providing names like “cat”, “cow”, “crocodile”) (Freire Júnior et al., 2017). 
• Using a mobile phone, e.g., the participant writes a text message (Ehlers et al., 2017; Krasovskyi et al., 2017; Lin and Huang, 2017). 
• Moving a cup of water (the participant’s task is to transfer a cup of liquid or a tray with cups of water) (McIsaac et al., 2015). 
• DIVA-gait computer test (a computer program created at the Academy of Physical Education in Krakow by the team of A. Kreska-Korus, E. Golec, A. Wojtowicz, based on the DIVA program by Nęcka, 1994) (this task was presented in VIDEO 3). 

Course of the Study:  

1. Explain the additional task to the participant, detailing what it entails. If the study requires it, conduct sessions in which the participant learns how to perform the task.    
2. Record the progression of the additional task study, and document the results     

During the additional task study, the most commonly measured indicators are reaction time and the quantity of correct tasks or the number of errors. 

When selecting the type of additional task, remember that it must be achievable under the same conditions as during the dual-task gait analysis. You can find more information on this topic in the section about cross-cultural communication. 

Gait Analysis in Dual-Task Conditions (Dual Task – DT): 

 According to the dual-task paradigm, the final stage involves simultaneously performing both tasks (walking and the additional task) under the same conditions in which the single tasks were conducted. The same indicators are recorded for this dual-task performance. 

Development of Gait Indicators: 

To conduct gait analysis with an additional task, it’s necessary to develop indicators for each part of the study. 

For gait analysis, these indicators will mainly involve spatiotemporal measurements. However, it’s important to select a consistent sample for both the single and dual-task conditions. In the analysis, one cycle of gait for each limb from each pass along the path should be considered. To do this, appropriate actions need to be taken within the operating system of the measurement device to identify and include only the chosen gait cycles, recorded in the middle section of the path/measurement (Schättin et al., 2016). 

For selected indicators, calculate their average values and standard deviations. 

Further analysis may involve considerations such as the dominant and non-dominant limb, limbs affected by pathological processes either directly or indirectly, and so on. 

Development of Additional Task Indicators: 

The most commonly used indicators for additional tasks are: 

• Reaction time, 
• Quantity of correct responses, 
• Number of errors. 

To obtain these indicators, you can count correct events (correct counting results, named animals or professions), errors, and determine reaction times. This can be done in three ways: 

1/ The least demanding but most error-prone method is counting correct reactions during the study and measuring the study time using a stopwatch. By dividing the study time by the number of correct responses, you can calculate the reaction time. 

2/ Recording the study on a Dictaphone and later calculating the number of correct responses and reaction times from the recording. The recorded study can be listened to for error elimination. 

3/ Using a computer program that automatically records study results. The DIVA-gait test, for instance, records: 

• Detection time (only considering correct reaction time), 
• Number of detections, 
• Number of errors, including the following error types: 
• No alarm: the participant did not activate the reaction button when the signal letter was displayed. 
• Double alarm: the participant pressed the reaction button a second time when the signal letter was displayed. 
• False alarm: the participant activated the reaction button when the signal letter was not displayed (see VIDEO 3). 

Gait Indicators with an Additional Task: 

Distinctive indicators for gait analysis with an additional task include: 

Variability: 

For each of the individuals being studied, you can calculate: 

• The variability of gait cycle time/step time (depending on the available data in the gait analysis system). 
• The variability of gait cycle length/step length. 

To calculate this variability, you can use the following: 

V – variability, SD – standard deviation, m – mean. 

It is essential to pay special attention to the precision of measurements, which is particularly important for the reliability of variability. Regarding the dual-task paradigm, it’s crucial to replicate the testing conditions during both single and dual-task gait analysis. The repeatability of the sample size and obtaining unaltered gait indicators unaffected by other events, such as the initiation of gait or the presence of external individuals, is key. 

The Dual-Task Effect 

The Dual-Task Effect is calculated for each of the indicators according to the following formula (Plummer-D’Amato et al., 2012):   

α DTE- Dual-Task Effect for indicator α  

α ST – the value of the indicator under single-task conditions,  

α DT – the value of the indicator under dual-task conditions.  

The α indicator can be any of the indicators studied in walking or in the additional task (e.g., Dual-Task Effect on walking speed or Dual-Task Effect on reaction time). 

When interpreting the indicator’s values, it’s important to be particularly attentive: for speed, an increase in the indicator will signify greater task efficiency, but in the case of reaction time, it will indicate decreased task efficiency. 

Mean Dual-Task Effect  

Mean Dual-Task Effect is calculated according to the following formula: 

  

m DTE – Mean Dual-Task Effect,  

α DTE – Dual-Task Effect for indicator α (gait indicator)  

β DTE – Dual-Task Effect for indicator β (additional task indicator)  

The Average Dual-Task Effect is most commonly calculated for gait speed and reaction time. It can also be applied to other indicators, but it’s essential to note that one must relate to walking, and the other to the additional task. 

In cases where an increase in one indicator represents improvement while a decrease in the other signifies a decline in task efficiency, applying this formula indiscriminately can lead to a misrepresentation of the result. In such a situation, for the second indicator, you should place a minus sign (-) before conducting the operation. This scenario occurs when the Average Dual-Task Effect is calculated for gait speed and reaction time. 

In situations where both Dual-Task Effects show the same directional change (e.g., gait speed and the number of correct task completions), it’s necessary to consider whether this alteration represents an improvement or a decline in task performance efficiency. 

Interpreting Results: 

To interpret the results of gait analysis with a dual task, you should consider the following aspects: 

1. Assessment of Spatiotemporal Gait Indicators in Relation to Normative Values: 

Norms for specific gait indicators are available in the literature concerning gait analysis in single-task conditions. If the person being examined experiences disruptions in their gait pattern due to changes in range of motion, muscle strength, etc., these factors will influence gait indicators, both in single-task and dual-task conditions. The application of the dual-task paradigm allows for the evaluation of gait under the additional cognitive load, helping identify disruptions that may not be detected in traditional gait assessments. Assessing gait with a dual task reflects locomotion as it occurs in everyday life. 

Walking speed is considered a fundamental gait indicator. It holds significant clinical importance due to its simplicity. Schmid (2012) and colleagues have indicated that a minimum walking speed necessary for societal functioning is around 0.8 m/s. When analyzing gait, it’s also essential to consider factors such as stride frequency and stride length, as these indicators have a profound impact on walking speed. 

2. Analysis of Additional Task Indicators: 

In gait analysis with a dual task, the most commonly analyzed indicator is the average reaction time. In our own studies conducted using the DIVA-gait test, this indicator has proven to be the most sensitive measure of the additional task. Our experiences suggest that in cases of outlier results, it’s advisable to consult with a psychologist for further interpretation and insights.  

3. Analysis of Gait Indicators with an Additional Task: 

The Dual-Task Effect and Average Dual-Task Effect are referred to as absolute indicators (expressed in percentages). In addition to these, the variability of the gait cycle is also analyzed. 

 
Dual-Task Effect (DTE): 

The Dual-Task Effect allows the assessment of the magnitude of change in a specific indicator, expressed as a percentage. It enables the evaluation of a chosen variable between different assessments and a comparison to identify where the most significant changes occur. 

For example, if an individual exhibits a reduction in stride length by 0.1 meters and a decrease in speed by 0.1 m/s when an additional task is introduced, it can be challenging to determine which change is more substantial. However, if we calculate the Dual-Task Effect for stride length and find it to be 16%, and the Dual-Task Effect for gait speed is 10%, we can conclude that the greater changes have occurred in stride length. 

Comparing the Dual-Task Effects for gait performance indicators (e.g., gait speed) and the additional task (e.g., reaction time), we can determine the attention-sharing strategy employed by the nervous system and which task experienced more significant changes. 

Average Dual-Task Effect: 

The Average Dual-Task Effect is an indicator that assesses the efficiency of performing both tasks simultaneously in comparison to performing them in single-task conditions. It informs us whether the nervous system possesses sufficient resources to control the simultaneous execution of both tasks. A worsening of this indicator indicates that operational capacities have been exceeded, resulting in a decreased efficiency in task performance. 

Plummer and Eskes (2013) emphasize the importance of distinguishing attention allocation strategies. They provide an example that interpreting the Average Dual-Task Effect with the same value can indicate different types of attention allocation. It may reflect changes in both tasks concurrently, but it can also signify situations where there is only a reduction in the efficiency of either gait or the additional task. 

The Average Dual-Task Effect allows for comparisons of walking abilities under dual-task conditions across different study groups. It can be utilized to identify conditions where the most significant changes occur and to assess the effectiveness of therapeutic interventions. 

Variability: 

Variability in stride length and stride time indicates the extent to which these indicators change during locomotion, expressed as a percentage. Larger changes suggest poorer motor control of gait. Although this area requires further research, it appears that measures of variability in stride length and stride time can be considered sensitive risk indicators for falls during walking (Herman et al., 2020; Maki, 1997). Gabell and Nayauk (1984) found that variability in stride length and stride time did not exceed 6% in healthy individuals. 

A specific interpretation of the results in gait with an additional task involves considering the following aspects: 

1. The Average Dual-Task Effect indicates whether the individual has the neural resources to perform both tasks simultaneously. 
2. Analyzing the Dual-Task Effects for both tasks allows for the determination of the strategy being employed (whether gait and/or the additional task is affected). 
3. Variability indicators determine if there has been a deterioration in motor control. If the magnitude of variability exceeds the norm, it is associated with an increased risk of falling. 
4. A gait speed below 0.8 m/s can identify individuals with limited societal functioning (Schmid et al., 2007). 
5. Analyzing gait and additional task indicators can help understand the mechanism of motor control during gait with an additional task.