**3.1.2 The 6MWT in the hallway**

For each individual, the 6MWT was performed along a corridor 22 m in length, according to Lipkin protocol (Lipkin et al., 1986). The participants were told to walk the distance of 22 m back and forth, at their own speed, in such a way that they would cover the longest possible distance within 6 minutes. The volunteers were allowed to slow down or stop, but at the end of the test they were expected to have the impression that they could not walk any further within 6 minutes.

#### **3.1.3 The 6MWT on the treadmill**

The software adjusting the ERT-100 treadmill belt speed to the patient's walking speed in the range of 1÷10 km per hour was applied for the six-minute walk test. The treadmill was

The guidelines approved by the American Thoracic Society (ATS) in 2002 definitely recognize the six-minute walk test (6MWT) as a useful tool for the evaluation of physical efficiency in individuals with at least moderate chronic obstructive pulmonary disease, heart failure and intermittent dysbasia (ATS, 2002). In order to compare the results obtained in various research centres, the guidelines recommend that the test be performed in a hallway 30 m in length and at least 3 m in width. As a result, some centres without hallways of this

The authors of the ATS report appreciate the advantages of the 6MWT on a treadmill as it

So far, ATS has not approved the use of a treadmill to determine the six-minute walking distance (6MWD) because patients are unable to pace themselves on a treadmill. The divergence between the distances covered on the treadmill and in the hallway was pointed out. To support this point of view, a study of patients with severe lung disease was presented where the mean distance walked on the treadmill was shorter by 14% when compared with the standard 6MWD using a 30 m hallway (Stevens et al, 1999). In particular, doubts were expressed regarding the wide range of differences, with patients walking

The popularity of the 6MWT in clinical practice (Montogomery & Gardnem, 1998; Roul et al., 1998; Zugck et al., 2000; Rostagno et al., 2003; Lipkin et al., 1986; Redelmeier et al., 1997), problems with the performance of the test on the treadmill and our first positive results with the use of a modified treadmill adapting to the pace of the patient's walk, encouraged us to check if our version of the algorithm enables healthy volunteers to cover a similar walking

29 healthy volunteers, full-time and extramural students of the Academy of Physical Education in Katowice, took part in a test. The volunteers were 28 years old (21÷48) on average. The order of taking the 6MWT on the treadmill and in the hallway was established at random. The tests with the use of both methods were performed at a 7-day interval.

For each individual, the 6MWT was performed along a corridor 22 m in length, according to Lipkin protocol (Lipkin et al., 1986). The participants were told to walk the distance of 22 m back and forth, at their own speed, in such a way that they would cover the longest possible distance within 6 minutes. The volunteers were allowed to slow down or stop, but at the end of the test they were expected to have the impression that they could not walk any

The software adjusting the ERT-100 treadmill belt speed to the patient's walking speed in the range of 1÷10 km per hour was applied for the six-minute walk test. The treadmill was

**3. A six-minute walk test on a special treadmill: Primary results in healthy** 

area have a limited possibility of carrying out this simple test.

saves space and allows constant monitoring during the exercise.

between 120÷390 m on the treadmill and 360 m in the hallway.

distance both on the treadmill and in the hallway.

**volunteers** 

**3.1 Methods** 

**3.1.1 The population tested** 

**3.1.2 The 6MWT in the hallway** 

**3.1.3 The 6MWT on the treadmill** 

further within 6 minutes.

in a horizontal position and the belt speed was controlled by constant measurement of the patient's position on the treadmill.

After 6 minutes from the start of the test, the program ended the test and displayed the distance covered by the patient.

The test on the treadmill was preceded by a training session lasting a few minutes on the day before the actual test. During the training session the participant learned how the treadmill worked and walked a distance of 100 meters at a changeable pace, as well as practiced stopping and restarting the walk.

The participants were informed about the treadmill test in an identical way as about the hallway test.

### **3.1.4 Analyzed parameters**

The comfort of the test and the distance covered in metres were subject to evaluation in both cases. The evaluation scale for comfort included the question of which type of test was less problematic during performance or whether the comfort of both tests was so similar that the differences were negligent. The number of indications to a given type of test was calculated. The treadmill was also monitored from the point of view of smooth speed adjustment to the individual's sudden slowdown without affecting his or her balance.

The pulse and blood pressure were measured before and after each test in order to assess the hemodynamic impact of both 6MWT varieties.

#### **3.1.5 Statistical analysis**

The aim of the statistical analysis was to compare the values of the distance covered, obtained in both 6MWT varieties. Also the heart rate and blood pressure before and after the test were compared using the Student's test for matched pairs for independent trials.

Multidimensional statistical research was conducted, as well the T2 test was applied for vectors of the expected values for both varieties in order to verify whether the compared research leads to similar hemodynamic consequences.

#### **3.2 Results**

The comfort of the treadmill test was indicated as better by 18/29 of the participants, the hallway test was indicated as better by 4/29 of the participants and both tests were evaluated as identical in terms of comfort by 7/29 of the participants.

During the test, healthy volunteers were walking most frequently with the speed of 7 km/hour (4÷10). The average distance covered on the treadmill was 683**.**0 m and was usually 57**.**1 m longer on average than in the hallway (Table 1). This difference turned out to be statistically significant. The participants covered 29 laps on average during the hallway test (19÷36).

No considerable difference could be seen in the heart rate before the tests. Also, the resulting accelerated heart rate after both types of tests did not show any marked difference (Table 2), just like blood pressure (Table 2).

The Six-Minute Walk Test on the Treadmill 227

ATS guidelines approved in 2002, which specify the length and width of the hallway, will certainly make it possible to compare the 6MWT results obtained in various centres. Another way of comparing the results obtained in various places is the proposed return to

In our study most, i.e. 86% of the healthy volunteers who had participated in the test, evaluated the comfort of a treadmill test as better than or the same as the hallway test. Hence, the applied design solutions and algorithm may be regarded as appropriate and flexible in terms of adjusting the speed of the treadmill belt to the walking speed of

In the paper by Stevens et al., the participants could put in motion, speed up and slow down the treadmill by means of a special switch (Stevens et al., 1999). Although Stevens et al. enabled the participants to adjust the treadmill to their walking speed "by hand", the distance covered on the treadmill turned out to be shorter indeed than the distance walked in the hallway because the participant could hardly adjust to the speed of the treadmill belt. We applied a treadmill which adjusts its speed to the walking capacity of the individual. As a result, the persons taking part in the test covered a distance 57**.**1 meters longer on average than in the hallway. The distance covered on the treadmill is longer than that walked in the hallway both due to flexible adjustment of the treadmill belt to the walking speed and due to avoiding multiple turnarounds and hence the need to speed up and slow down in the

The multi-aspect analysis of the results including the distance covered, blood pressure and pulse measured before and after the 6MWT, shows similar hemodynamic consequences for both methods. Thus, it can be inferred that in the future it will be possible to determine the conversion rate, at least for healthy subjects, facilitating the comparison of the results

As opposed to conditions in the hallway, the 6MWT on a moving treadmill creates possibilities of easy monitoring of heart rate and arterial blood pressure. This enables the hemodynamic surveillance that is necessary for the safe test performance in patients with

The attempt by Stevens at al. to use the treadmill for a 6MWT in patients with respiratory failure did not meet the expectations as it shortened the distance in comparison with a hallway test. Our results show the expected elongation of the distance compared with the hallway test, although they cannot be currently referred to patients with intermittent dysbasia, heart failure or severe lung disease. Patients suffering from such diseases are less fit, which may affect their ability to perform the 6MWT on a modified adjustable treadmill. We are aware of the fact that the decision whether our modified treadmill meets the expectations of physicians who use the 6MWT in their medical practice and research can only be made after performing the tests in these groups of patients. In finished, but yet not published trial we assumed that the quality of the algorithm version adjusting the speed of the treadmill belt to the pace of the patient's walk during the six-minute walk test (6MWT) on a moving treadmill, checked for healthy volunteers, makes it possible to perform the test

obtained during a test in a 30-m hallway with the results on an adjustable treadmill.

safely in patients with heart failure (Szczurek et al., 2006; Prochaczek et al., 2007).

The work was intended to compare the distance covered, the level of exertion and hemodynamic effects in a hallway test and in a test on a modified treadmill for patients with

the idea of using the treadmill.

a healthy individual.

hallway test.

cardiac insufficiency.


Table 1. The distance covered during the six-minute walk test on the treadmill and in the hallway


Table 2. The heart rate and blood pressure before and after the test performed on the treadmill and in the hallway

The Hotteling T2 test was used to assess the equality of vectors of the expected values for seven analyzed parameters of the 6MWT.

The obtained result: T2=11**.**7 and F=7**.**3<<53 (where 53 stands for the threshold of the hypothesis at significance level <0**.**05) gives a clear evidence about the identical hemodynamic effects of both testing methods.
