Evaluation of Functional Exercise Capacity of Apparently Healthy Nigerians using Six-Minute Walk Test (A Preliminary Study).

Ajiboye OA¹; Anigbogu CN²; Jaja SI²; Ajuluchukwu JN³; Olawale OA¹; Tella BA¹;

¹Department of Physiotherapy, Lagos University Teaching Hospital/College of Medicine, University of Lagos

²Department of Physiology, College of Medicine, University of Lagos.

³Department of Medicine, College of Medicine, University of Lagos.

Address correspondence to: Ajiboye OA, e-mail: oaajiboye@yahoo.com

Background / Objective:

Six Minute Walk Test (6-MWT) is a popular and widely accepted modality of objective evaluation of functional exercise capacity as it is inexpensive and easy to perform. Despite the popularity of the 6MWT in the clinical setting, there is a paucity of 6MWD reference values for healthy subjects. Studies have established regression equations to predict the six minute walking distance (6-MWD) in healthy Caucasians, Asians and North Africans; but such regression equations have not been established for the Nigerians. The main aims of this study were to determine 6-MWD in apparently healthy Nigerians, determine their cardiorespiratory response to 6MWD test, and compare measured 6MWD with predicted 6MWD from existing reference equations derived from other populations.

Materials and Methods:

68 apparently healthy subjects (43males, 25 females) with no history of
cardiovascular or musculoskeletal disorders participated in the study. American Thoracic Society (ATS) standardized 6-MWT method was used; cardiorespiratory parameters (systolic, diastolic blood pressures, heart rate and respiratory rate) were taken before and after the test. Data were analyzed using SPSS (version 17.0) Data were summarized using mean and standard deviation. Independent t-tests were used to determine the level of significance of the 6MWD covered by Nigerians and other populations and to compare the means of the cardiorespiratory variables between male and female subjects and regression analysis was used to establish the equations. Level of significance was p<0.05.

Results:

The mean age of the subjects was 39±11.4years and 41± 8.7 years respectively for males and females. The mean height, weight and BMI of males were 1.71±0.08m, 70±12.5kg, 23.7±3.4kg/m² and that of females were 1.62±0.05m, 74±13.5kg, 28± 4.8kg/m². The male subjects had a 13.8% increase in heart rate while the female subjects had a 19.8% increase. The male subjects had 17.3% and 15.6% increase in SBP and DBP respectively while the female subjects had 15% and 11% increase in SBP and DBP. The male and female subjects had a 28.3% and 29.5% increase in respiratory rate respectively. The distance covered in six minutes by the subjects was 528±58.5m and 499.9±53.2m (p= 0.047) for males and females respectively. There was no significant difference between the distance covered in both male and female participants so the mean distance covered by both was 518±57.9m. The 6MWD measured in Nigerian subjects was significantly lower than predicted values from Caucasians (581±71.4m, p=0.004), Brazilians (587±37m, p=0.003) and Tunisians (754±12m, p=0.001) and significantly higher than the Arabian population (475±21m, P=0.012).

The resulting gender-specific regression equations in the distance walked for healthy adults are:

• 6MWD_male (m) = (324.6 × height_m) - (0.322 × age_yrs) – (1.65 × weight_kg) + 99.8. R= 0.406
• 6MWD_female (m) = (779×height_m) + (0.136 × age_yrs)-(1.88×weight_kg)- 632.438. R= 0.691
• 6MWD_both (m) = 74 + (333.8 × height_m) – (0.414× age_yrs) – (1.41 × weight_kg). R=0.514

Conclusion:

6MWD in healthy Nigerians cannot be predicted by established reference equations from other populations. There is a need to establish appropriate regression equations for Nigerians.

Key words: 6-minute walk test, predicted equations, 6-minute walk distance.