Physical function and body composition in kidney transplant recipients over time with physiotherapy intervention

Abstract

Introduction:

The long-term usage of immunosuppressants post-kidney transplantation often results in adverse effects such as weight gain, osteoporosis and an increased risk of cardiovascular diseases. Physical activity has been shown to have a protective effect against these adverse effects. This paper aims to investigate the changes over time in physical function and body composition in kidney transplant recipients with a home exercise regimen prescribed by a physiotherapist.

Methods:

Forty-two kidney transplant recipients aged 45 ± 12 years were recruited before transplant and reviewed at fixed time points after transplant. Body composition, hand grip strength and functional exercise capacity were measured at every session. A home exercise regimen was prescribed and modified when appropriate.

Results:

There was an observed trend towards an improvement in functional exercise capacity in terms of six-minute walk distance. There was no change in body weight, fat mass and skeletal muscle mass.

Conclusion:

There may be a need to provide supervised exercise training programmes for kidney transplant recipients in bringing about positive changes in body composition as well as ensure compliance to exercise training after transplant. Further research is needed for more conclusive results.

Introduction

While organ transplant gives one a new lease of life, long-term usage of immunosuppressants and corticosteroids post-transplantation in maintenance regimens can cause alteration of weight, fat distribution and muscle mass. ¹ A significant increase in fat mass and decrease in muscle mass within a year after kidney transplantation have been reported in several studies.^1–4 Exercise training in kidney transplant recipients has been shown to be essential in the amelioration of the adverse effects of corticosteroids and deconditioning attributed to the years of dialysis therapy. ⁵ However, there is a lack of literature on the impact of a home exercise regimen on body composition and physical function in kidney transplant recipients (KTRs).

Physiotherapy intervention for KTRs usually includes education, aerobic exercise and/or strength training to improve physical function. ⁶ As part of the multidisciplinary Renal Transplant Team in Singapore General Hospital, physiotherapists provide detailed assessment and individualised prescription of suitable home exercises to KTRs before and after transplant.

This study aims to evaluate the changes in body composition and physical function in KTRs over time with physiotherapy intervention. These measures are:

• Body fat mass and skeletal muscle mass;

• Hand grip strength;

• Measured and self-reported functional exercise capacity.

Methods

In the period between December 2013 and April 2015, 42 KTRs who were over 18 years old and under the care of the Renal Transplant Team in Singapore General Hospital received prescription of suitable home exercises from a physiotherapist before and after transplant. Verbal consent was obtained prior to physiotherapy referral and those who declined to attend physiotherapy sessions continued with the usual care from the rest of the Renal Transplant Team. No ethics approval was required as the physiotherapy sessions were part of the clinical services provided at the transplant clinic.

The KTRs were seen after the final doctor review before transplant, within two weeks post-transplant as well as at one, three and six months after transplant. Body composition, hand grip strength and functional exercise capacity were assessed by the physiotherapist at each visit. All data were obtained prospectively.

Procedure

Demographic and clinical data (age, gender, height and transplant information) were retrieved from the KTRs’ medical records.

Body composition

Non-fasted body composition was measured using bioelectrical impedance analysis (BIA) through the InBody R20 device (Biospace Co. Ltd, Seoul, Korea) connected to the Lookin’Body software (Version LBM.1.2.0.8, Biospace Co. Ltd, Seoul, Korea). BIA is based on the capacity of hydrated tissues to conduct electrical energy and has been validated against dual-energy X-ray absorptiometry (DEXA) if body mass index (BMI) falls in the range 16–34 kg/m². ⁷

The portable InBody R20 device consists of a body scale with four contact reusable electrodes under the feet and digital electrodes for finger contact to assess the limbs and trunk. Each KTR stood quietly on the device until analysis was completed. The values of the body weight, skeletal muscle mass, body fat mass, body water and basal metabolic rate were displayed via the software.

Hand grip strength

Bilateral hand grip strength was determined via a hydraulic hand dynamometer (Model J00105, Lafayette Instrument, Indiana, USA). Each KTR performed a maximal voluntary isometric contraction for 5 s. Two trials were repeated with a rest interval of 10 s to avoid the effects of fatigue. The mean measurements (force in kg) for each hand were then recorded manually. Previous studies reported that reduced hand grip strength resulted in more postoperative complications,^8–10 longer length of stay^11,12 and poorer functional status. ¹³

Functional exercise capacity

Each KTR performed the Six-Minute Walk Test (6MWT) along a quiet 20-m walkway, with the procedure described by the American Thoracic Society. ¹⁴ The self-paced 6MWT is a reliable and simple field test which allows an objective evaluation of a person’s submaximal level of functional exercise capacity. ¹⁴ Distance was recorded to the nearest 10th of a metre.

In addition to the 6MWT, each KTR also completed the Duke Activity Status Index (DASI), which is a 12-item questionnaire that utilises self-reported physical work capacity to estimate peak metabolic equivalents (METs). It has been shown to be a valid measurement of functional capacity. ¹⁵

Educational intervention by the physiotherapist

Upon completion of the assessment, the physiotherapist explained the results and prescribed an individualised unsupervised home exercise regimen to the KTR which comprised: i) aerobic exercise at 60% VO_2peak for 30 m over 5 days per week, ii) resistance exercises with less than 5 kg load for one to two sets of 10 repetitions over three days per week, and iii) stretching exercises three days per week for three to five repetitions with 30 s hold each. ¹⁶

Statistical analysis

All data were analysed using SPSS software (IBM SPSS Statistics Version 21.0, New York, USA). Descriptive and frequency statistics were employed to determine baseline demographics before transplant. Descriptive statistics were used to observe trend for body weight, BMI, skeletal muscle mass, body fat mass, DASI functional METs, right and left hand grip strength, and six-minute walk distance (6MWD) measured at each time point. The t-test was employed to compare the differences between baseline and post-transplant data at each time point, by using only complete data points for each variable stated above.

Results

Baseline demographics

Forty-two KTRs (18 females) completed the study, of whom 33 (78.6%) completed haemodialysis prior to transplant and 30 (71.4%) underwent living donor renal transplant. No adverse events happened during the physiotherapy sessions. Baseline characteristics of the sample are summarised in Table 1. At baseline, the KTRs were not overweight and their grip strength did not differ between left and right. Their self-reported functional exercise capacity was moderate at about 6.9 ± 2.1 METs.

Table 1.

Baseline demographics of the kidney transplant recipients (n=42).

Variable	Mean ± SD	95% CI
Age, years	45 ± 12	(41, 48)
Weight, kg	59.7 ± 16.1	(54.6, 64.8)
BMI, kg/m2	22.2 ± 4.2	(20.9, 23.5)
Skeletal muscle mass, kg	25.3 ± 7.4	(22.8, 27.9)
Body fat mass, kg	13.9 ± 8.3	(11.1, 16.7)
DASI functional METs	6.9 ± 2.1	(6.2, 7.6)
Left hand grip strength, kg	21.2 ± 15.4	(16.5, 25.8)
Right hand grip strength, kg	22.1 ± 16.5	(17.1, 27.1)
6MWD, m	419.1 ± 138.1	(373.3, 464.8)

SD: standard deviation; CI: confidence interval; kg: kilogram; BMI: body mass index; m: metre; DASI: Duke Activity Status Index; MET: metabolic equivalent; 6MWD: six-minute walk distance.

Change in weight and body composition

The body weight and body composition pre- and post-transplant are shown in Figure 1 and Figure 2 respectively.

Figure 1.

Body weight (and standard deviation) at different time points.

Figure 2.

Body composition (mean muscle mass and mean fat mass) at different time points.

Changes in hand grip strength

Baseline right and left hand grip strength was about 65.4 ± 23.9% and 68.2 ± 22.3% predicted of normative values, respectively. ¹⁷ Bilateral hand grip strength pre- and post-transplant is shown in Figure 3. There was a mean drop of −0.2 ± 4.0 kg (n = 13; p = 0.837) in left hand grip strength immediately post-transplant. However, it improved by 1.8 ± 2.7 kg (n = 16; p = 0.018) and 2.1 ± 2.3 kg (n = 15; p = 0.003) at one and three months post-transplant respectively.

Figure 3.

Bilateral mean hand grip strength at different time points.

There was a mean gain of 1.6 ± 3.0 kg (n = 13; p = 0.072) in right hand grip strength immediately post-transplant. However, it improved by 2.5 ± 2.8 kg (n = 15; p = 0.004) and 3.8 ± 4.3 kg (n = 15; p = 0.004) at one and three months post-transplant respectively.

Changes in functional exercise capacity

Self-reported functional METs measured via DASI decreased to 5.9 ± 1.0 a month after transplant. At three and six months post-transplant, the self-reported functional METs increased to 7.3 ± 1.8 and 8.2 ± 1.3 respectively.

6MWD improved gradually over time as shown in Figure 4. There was no analysis done at six months post-transplant as only two KTRs agreed to do the test at this time point. There was a mean drop in 6MWD of −5.0 ± 228.8 m (n = 14; p = 0.936) immediately post-transplant. However, 6MWD improved by 76.9 ± 83.6 m (n = 16; p = 0.002) and 119.8 ± 151.8 m (n = 11; p = 0.026), at one and three months post-transplant respectively.

Figure 4.

The Six-Minute Walk Test distance at different time points.

Discussion

This is a novel study that investigated the changes in physical function and body composition in kidney transplant recipients over six months with a home exercise regimen. Functional exercise capacity appeared to improve over time, which is in agreement with the results from a randomised controlled trial (RCT) where VO_2peak and the percentage age-predicted VO_2peak increased from baseline to 12 months for the subjects in the exercise group. ⁶ The improvement in exercise capacity could be attributed to the physiotherapy intervention before and after transplant, which focused on engaging the KTRs to participate in regular physical activity after transplant. However, given that there was no control group, the improvement in exercise capacity could also be attributed to the additional attention given by the physiotherapist through the scheduled visits and the regular emphasis on lifestyle changes by the transplant coordinator.

There was no change in body weight and fat mass of the KTRs in this study. This is in contrast to the results shown by Han et al. ² where the 50 KTRs gained approximately 3 kg within one year of kidney transplantation and fat mass increased continuously after transplantation. This difference could be attributed to the lack of physiotherapy intervention, hence resulting in a greater increase in body weight and fat mass. However, Painter et al. ⁶ demonstrated that a 12-month unsupervised exercise programme with regular phone follow-up did not significantly improve body composition when compared with usual care. In this RCT, the 52 KTRs within the exercise group gained approximately 8 kg within one year of kidney transplantation and fat mass also increased continuously after transplantation. ⁶ This may imply that a supervised moderate-intensity exercise regimen post kidney transplant could be more effective in bringing about positive changes in body composition.

Study limitations

The main limitation of this study was the missing data at various time points due to the KTRs not keeping their regular appointments, as these KTRs were re-hospitalised due to acute rejection or graft failure, infection and other medical reasons. Systemic or surgical wound infections, renal dysfunction, post-surgical complications (e.g. systemic thrombosis, uncontrolled pain), rejection and volume overload or depletion are known to be leading causes of unplanned re-hospitalisations related to kidney transplantation.^18,19

Another limitation is the convenience sampling, which might have led to selection bias. A control group of KTRs who did not receive physiotherapy intervention would be ideal for fair comparison through a RCT.

Conclusion

Although functional exercise capacity improved over time with a home exercise regimen prescribed by a physiotherapist, there was no corresponding improvement in body composition. Due to the small sample size, these results must be interpreted with caution. Nevertheless, the improvement observed in physical function with prescribed home exercise is encouraging. There appears to be a need for supervised resistance training programmes for KTRs to ensure compliance to an exercise regimen that includes both aerobic and resistance training, in order to significantly increase exercise capacity and skeletal muscle mass while preventing gains in weight and fat mass after transplantation.