The relationship between lower limb muscle strength and lower limb function in hiv positive patients on highly active antiretroviral therapy
Mhariwa, Peter, Clever.
The Human Immunodeficiency Virus (HIV) has been found to cause muscle weakness, wasting and peripheral neuropathies. The specific relationship between lower limb muscle strength and lower limb function in HIV positive patients on Highly Active Antiretroviral Therapy (HAART) has not been examined. The aims of the current study were to establish lower limb muscle strength in HIV positive patients on HAART, establish lower limb muscle strength in HIV negative people, compare lower limb muscle strength between patients who are HIV positive on HAART and HIV negative people, establish lower limb function in patients who are HIV positive on HAART and to establish the relationship between lower limb muscle strength and lower limb function in patients who are HIV positive on HAART. A cross-sectional, descriptive study design was used. Dynamometry was used to measure lower limb muscle strength. The lower Extremity Functional Scale (LEFS) was used to determine lower limb function. A pilot study was done to establish the feasibility and proficiency required to perform hand held dynamometry. Intra and inter-rater reliability were also determined during the pilot phase. Intra and inter-rater reliability were high for the raters' measurement of lower limb muscle strength using a dynamometer with 'r' values of 0.97. For HIV positive patients on HAART, 19% (n=22) were in the age band 45-49years, whereas 33% (n=10) of HIV negative subjects were in age interval 25-29 years. Those over 45 years who were HIV positive on HAART constituted 57% (n=64) of the sample. The mean muscle strength obtained ranged from 9.30kg/m2 in ankle dorsiflexors to 15.80kg/m2 in hip extensors in HIV positive people on HAART for an average of 4 years while knee flexors generated 11.81 kg/m2 and knee extensors generated 15.36kg/m2 in this cohort.Jn the HIV negative matched group, the mean muscle strength ranged from 11.20 kg/m2 in ankle dorsiflexors to 17.70 kg/m2 in hip extensors while knee flexors generated 12.65kg/m2 and knee extensors generated 17.07kg/m2. The majority 78% (n=88) of HIV positive patients on HAART had no difficulty with lower limb function while 22% (n=17) had difficulty. Only 2% (n=2) of HIV positive patients on HAART had quite a bit of difficulty with lower limb functional activities after measurements using the Lower Extremity Functional scale (LEFS). A multiple linear regression showed that there was a positive correlation coefficient of r=0.71 (p-value= 0.00) between lower limb muscle strength and lower limb function. The coefficient of determination 0.50 means that 50% of the changes in lower limb function are attributable to lower limb muscle strength. Gender, employment status and mode of transport also positively affected lower limb function. A detailed regression model showed that lower limb ankle plantar flexors contributed the most to lower limb function in this cohort. This is contrary to International literature which states that hip and trunk muscles are the most active in HIV negative people during lower limb functional activities. That plantar flexors contribute the most in lower limb functional activities instead of hip and trunk muscles confirms the existence of proximal weakness in this cohort which was established by other researchers. This study highlighted that 50% of lower limb function is a result of lower limb muscle strength in HIV positive people on HAART attending an outpatient clinic in Mutare, Zimbabwe. Ankle plantar flexors instead of hip flexors were the most active muscle group in lower limb functional activities in this cohort. It therefore means exercise prescription to activate/strengthen hip flexors and other proximal muscles will improve this population's lower limb functional activities since progressive resisted aerobic exercises have been proved to strengthen muscles.
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree of Master of Science in Physiotherapy. Johannesburg, 2015
HIV, Antiretroviral therapy, Muscle strength, Lower limb, Highly active antiretroviral therapy (HAART)