Clinical Nephrology, Vol. 75 – No. 3/2011 (218-225)
Assessment of habitual physical activity and
energy expenditure in dialysis patients and
relationships to nutritional parameters
Original
©2011 Dustri-Verlag Dr. K. Feistle
ISSN 0301-0430
DOI 10.5414/CNP75218
A. Cupisti1, A. Capitanini2, G. Betti3, C. D’Alessandro1 and G. Barsotti1
1Division
of Nephrology, Department of Internal Medicine, University of Pisa, Pisa,
and Dialysis, Pescia Hospital, Pescia, and 3Nephrology and Dialysis,
Massa-Carrara Hospital, Massa-Carrara, Italy
2Nephrology
Physical activity in dialysis patients
Key words
physical activity –
energy expenditure –
dialysis – nutrition parameters – exercise –
CKD
Received
May 10, 2010;
accepted in revised from
July 6, 2010
Correspondence to
A. Cupisti, MD, PhD
Division of Nephrology,
Department of Internal
Medicine, University of
Pisa, Via Roma 67,
56126 Pisa, Italy
[email protected]
Abstract. Background and aim: Assessment of physical activity level and of energy
expenditure is important in the clinical and
nutritional care of dialysis patients, but it is
not so easy to accomplish. The SenseWear™
Armband (SWA) is a novel multisensory device that is worn on the upper arm and collects
a variety of physiologic data related to physical activity. Thus, duration and intensity of
physical activity is recorded and expressed as
METs (Metabolic Equivalent Task), and energy expenditure is estimated. The aim of our
study was to assess interdialytic spontaneous
physical activity in stable chronic hemodialysis (HD) patients and the relation to nutritional status and dietary nutrient intake. Patients and methods: In 50 stable patients on
maintenance hemodialysis treatment and 33
normal subjects (control group), level of
spontaneous physical activity and estimated
daily energy expenditure was assessed by
SWA and related to biochemistry and anthropometry data, bioelectric impedance vector
analysis, and energy and nutrient intake information coming from a 3-day food recall. Results: In respect to controls, HD patients
showed lower mean daily METs value (1.3 ±
0.3 vs. 1.5 ± 0.2, p < 0.01), a lower time spent
on activities > 3 METs (89 ± 85 vs. 143 ± 104
min/day, p < 0.05), lower number of steps
per day (5,584 ± 3,734 vs. 11,735 ± 5,130,
p < 0.001), resulting in a lower estimated energy expenditure (2,190 ± 629 vs. 2,462 ± 443
Kcal/day, p < 0.05). 31 out of the 50 HD patients (62%) had a mean daily value < 1.4
METs and hence were defined as sedentary.
They differed from the active patients for
higher age (63 ± 12 vs. 54 ± 12 y, p < 0.01),
lower energy intake (26.1 ± 6.4 vs. 32.4 ±
11.3 Kcal/day, p < 0.05) and lower phase angle (5.5 ± 1.0 vs. 6.3 ± 0.9, p < 0.05). SWAbased estimation of daily energy expenditure
was negatively related to age (r = –0.31, p <
0.05), whereas positive relations were observed with BMI (r = 0.51, p < 0.001), phase
angle (r = 0.40, p < 0.01), serum phosphate
(r = 0.49, p < 0.001) and albumin (r = 0.41, p <
0.01). The mean daily METs values were
strongly related to normalized energy intake
(r = 0.47, p < 0.001) and also to protein intake
(r = 0.33, p < 0.05) and to phase angle (r =
0.38, p < 0.01). Multiple regression analysis
showed that energy intake and dietary protein
intake were independently related to the intensity of physical activity. Conclusion: Our
findings indicate that poor physical activity is
highly prevalent in stable dialysis patients
even when free from physical or neurological
disabilities or severe comorbid conditions.
The level and intensity of physical activity is
positively related to body composition and to
dietary nutrient intake. This confirms the strong
interrelationship between exercise and nutrition, which in turn are associated with survival, rehabilitation and quality of life in dialysis patients.
Introduction
Previous studies have reported that the
limits of physical capability are largely reduced in hemodialysis (HD) patients when
compared with healthy subjects [1, 2, 3]. Dialysis patients may suffer from cardiovascular disease, diabetes, malnutrition, and depression, which limit their exercise capacity.
Nevertheless, evidence exists that maintenance of regular physical exercise may favor
rehabilitation of patients and correction of
several cardiovascular, metabolic and nutritional abnormalities. Data from the literature
suggest that inactivity is associated with increased mortality risk [4, 5, 6], whereas physical exercise is related to quality of life and
nutrition [7, 8, 9, 10]. Namely, regular physical activity may ameliorate appetite and
219
Physical activity in dialysis patients
maintain muscle mass. In turn, adequate
energy and protein intake are mandatory for
physical performance and good nutritional
status.
Several epidemiological studies showed
that protein and energy intake in dialysis patients is largely lower than recommended [11,
12]. The minimum energy requirement
should be no less than the total energy expenditure that is due to resting energy expenditure (60 – 75%) plus energy consumed during
physical activity (25 – 40%). Therefore, evaluation of physical activity is important to assess nutritional requirements. This indicates
that it would be valuable to determine rest energy expenditure as well as the type, quantity
and intensity of physical activity in order to
plan personalized dietary and rehabilitation
programs and to test the efficacy of specific
interventions in HD patients. Physical activity records and questionnaires provide a single, convenient, low-cost estimation of physical activity and/or energy expenditure, but
they are quite subjective and not very reliable
methods [13, 14, 15]. More reliable quantification of spontaneous physical activity can be
obtained by tri-axial accelerometers, that is,
electronic devices worn on the waist to detect
movements in three planes of motion, namely
mediolateral, anteroposterior, and vertical.
Electric transducers and microprocessors
detect accelerations and convert them into
digital signals [2, 16].
The SenseWear™ Armband is a multisensory device including a two-axis accelerometer, heat flux sensor, skin temperature
sensor, near-body ambient temperature sensor, and galvanic skin response sensor. It is
worn on the upper arm and collects a variety
of physiologic data related to physical activity. Duration and intensity of physical activity
are recorded and daily energy expenditure is
estimated by software based on a proprietary
algorithm [17]. This multiple sensor array
was designed to overcome the limitations of
other objective or subjective energy expenditure assessment tools [18], and it has been validated and used in a number of physiological
and pathological conditions [19, 20, 21, 22].
The aim of our study was to assess interdialytic spontaneous physical activity by
SWA in stable chronic hemodialysis (HD) patients and the relation to nutritional status and
dietary nutrient intake.
Patients and methods
Patients
50 stable patients (32 male, 18 female;
aged 59 ± 13 y) on maintenance HD treatment
(time on dialysis 89 ± 78 months), who had no
major skeletal, muscular or neurological disabilities, or had not reported severe impairment with walking, were qualified for enrollment in the study.
Patients with severe cardiac failure (Stage
IV NYHA), or respiratory insufficiency, cancer, dementia, psychiatric or neurologic diseases, and inflammatory systemic diseases
were excluded. Hospitalization within the last
three months, therapies with steroids and/or
immunosuppressive drugs were also considered as exclusion criteria.
The underlying renal diseases were chronic
glomerulonephritis in 13 cases, diabetic nephropathy in 6 cases, vascular nephropathy in
10 cases, polycystic kidney disease in 8 cases,
chronic interstitial nephropathy in 5 and unknown in 8 cases. All the patients were on a
thrice-weekly HD treatment, for 210 – 240
minutes; 23 patients were on on-line hemodiafiltration, 19 patients on standard bicarbonate dialysis and 8 patients on acetate-free
biofiltration. In all the cases synthetic and
highly biocompatible membranes were used
(low-flux and high flux polysulphone, AN69,
polyammide).
Vascular access was native arteriovenous
fistula in 41 cases, arteriovenous graft in 6 cases
and permanent central vein catheter in 3 cases.
33 normal subjects, comparable for age,
sex and body mass index, served as controls.
All patients gave their informed consent
to the study that was approved by the Ethics
Committee of the Pisa University Hospital.
Physical activity and energy
expenditure assessment
The level of physical activity and estimated daily total energy expenditure (TEE)
under free-living conditions were assessed by
SenseWear™ Armband (SWA, BodyMedia,
Pittsburgh, PA, USA). This device is worn on
the upper arm (the nondominant one or that is
free from arteriovenous fistula or graft) over
the triceps muscle, in the middle tract be-
220
Cupisti, Capitanini, Betti et al.
tween acromion and olecranon processes.
Subjects were instructed to maintain their
usual daily life habits while wearing the monitor and to remove it only for showers or water
activities.
The SWA device collects a variety of
physiologic data through multiple sensors (a
two-axis accelerometer, heat flux sensor, skin
temperature sensor, near-body ambient temperature sensor, and galvanic skin response
sensor) that are uploaded and analyzed using
software (InnerView™ Research Software,
Version 6.1).
This multichannel approach, which integrates information from a biaxial accelerometer and heat-related sensors, has shown to
provide additional information that cannot be
obtained solely from movement sensors and it
has high sensitivity in detecting even small
changes in energy expenditure associated
with complex activities. The SWA reports actual wear time, avoiding the considerable
challenge in determining whether a monitor
was worn or not. These features provide several advantages over traditional uniaxial accelerometers for assessing physical activity.
The validity of total energy expenditure
(TEE) estimates from the SWA has been supported in studies using both indirect calorimetry and doubly labeled water [22]. The SWA
has been validated both under laboratory conditions and under free living conditions, and it
has potential advantages in accuracy when
compared with traditional accelerometrybased monitors [17, 18, 19, 20, 21].
One of the easiest ways for quantifying the
intensity of a physical activity is the Metabolic
Equivalent Task (MET) method. Kilocalories
and metabolic equivalent are converted using
the following equation: MET = Kcal/h/Kg b.w.
One MET is the energy expended at rest. Thus,
two METs indicate twice the energy expended
at rest, three METs triple the resting energy expenditure, and so on.
For example, such activities as reading,
listening to music, and knitting correspond
approximately to 1.0 – 1.5 METs. Walking
slowly corresponds to 1.5 – 2 METs; walking
at 3 km/h or cycling at 8 km/h correspond to
2 – 3 METs; playing volleyball, cycling at 10
km/h, and household cleaning correspond to
3 – 4 METs; walking at 6 km/h, cycling at 16
km/h, skating at 15 km/h, or digging correspond approximately to 5 – 6 METs.
Measurements were carried out during a
mid-week interdialytic period of 48 h and
included number of steps and minutes spent
in physical activity with an intensity > 3
MET/min, between 6 and 9 MET/min, or > 9
MET/min.
Mean daily METs values may be considered as a measure of the mean daily activity
level; for example, a daily average value < 1.4
METs defines a sedentary patient, whereas
average values > 1.6 METs are associated
with an active life style.
Total energy expenditure (reported as 24 h
average value) was evaluated by a proprietary
algorithm using information of movement, skin
temperature, heat flow, near-body temperature
and galvanic skin response, together with data
about age, height, weight and gender.
Total energy expenditure was also evaluated using a prediction equation, consisting of
an estimation of resting energy expenditure
multiplied by an activity factor. Namely, resting energy expenditure was calculated using
the Harris-Benedict formula and the activity
factor varied from 1.2 for minimal physical
activity, up to 1.5 for moderate but significant
physical activity and up to 1.8 for high
physical activity [23].
Nutritional assessment
Nutritional parameters included biochemistry, bioelectric impedance vector analysis (BIVA), height, and body weight before
and after dialysis. Body mass index (BMI)
was calculated as follows: post-dialysis body
weight (kg)/height2 (m2). Predialysis biochemical determinations included serum albumin, C reactive protein, phosphorus, calcium,
and hematocrit. Serum albumin was measured by the nephelometric method. Decreased albumin levels can be suggestive of
protein malnutrition and/or inflammation
[24] and represent an unfavorable prognostic
sign. Serum urea level was determined before
and after dialysis treatment to calculate a single pool Kt/V.
BIVA was performed at the end of the
hemodialysis session with a bioelectrical impedance analyzer (BIA/STA, Akern, Florence, Italy) with a distal, tetrapolar technique,
delivering an excitation current at 50 kHz
[25]. BIVA parameters were measured in du-
221
Physical activity in dialysis patients
plicate. BIVA gives two bioelectric parameters: body resistance (R) and reactance (Xc),
and the impedance vector (Z) is a combination of R and Xc across tissues. The arc tangent of Xc/R is called phase angle (PA),
which is a derived measure obtained from the
relation between the direct measures of resistance and reactance reflecting hydration status and soft tissue cellular mass. Reduced
phase angle reflects increased extra- to intracellular water ratio as well as a decrease in
body cell mass; it is a predictor of survival in a
number of diseases and also in the dialysis
population, where phase angle values lower
than 4.0° are associated with increased mortality risk [26]. A BIVA-derived parameter
with prognostic value is also the body cell
mass index (BCMI): values < 8.0 kg/m2 are
associated with unfavorable prognosis.
Dietary nutrient intake assessment
All the subjects were seen individually by
registered dieticians to collect a 3-day food
record for energy and nutrient intake assessment. The 3-day recalls were collected by interviews during which the subjects were provided with a color photo atlas of common
foods and their servings in order to help them
in estimating the real amounts of consumed
food. The 3-day dietary recall included a dialysis day, a weekend day and a nondialysis day
as suggested by recent guidelines [23, 27].
Dietary composition was assessed with a
computerized diet software (MetaDieta®,
Meteda, AP, Italy). Total energy and nutrient
intakes and their distribution among meals
were examined. The daily intake for each
studied nutrient was calculated as the average
of the 3-day food records.
Daily energy requirement was estimated
by calculation of daily energy expenditure, by
Harris-Benedict equation multiplied by an activity factor, according to EBPG guideline on
Nutrition [23].
Statistical analysis
A statistical package, StatView 5 release
5.0.1 for personal computer, was used for
processing data. Descriptive statistics are
given as mean ± standard deviation. Statistical analysis was performed by Student’s t-test
for unpaired data. Linear correlation analysis
was performed by Pearson’s test. Stepwise
multiple correlation analysis was used to
study all the significant relationships with
physical activity and energy expenditure. Differences were considered to be statistically significant when p < 0.05.
Results
Patients and controls did not differ as far
as body weight (71 ± 17 vs. 69 ± 13 kg), BMI
(24.8 ± 4.6 vs. 24.5 ± 3.3 kg/m2), and phase
angle (5.79 ± 1.04 vs. 5.74 ± 0.85°) were concerned.
In comparison with controls, HD patients
showed lower daily average METs value (1.3
± 0.3 vs. 1.5 ± 0.2, p < 0.01), a lower time
spent on activities > 3 METs (89 ± 85 vs. 143
± 104 min/d, p < 0.05), lower number of steps
per day (5,584 ± 3,734 vs. 11,735 ± 5,130,
p < 0.001), resulting in a lower estimated total
energy expenditure (2,190 ± 629 vs. 2,462 ±
443 kcal/d, p < 0.05). In HD patients, a trend
to a lower energy expenditure, calculated by
SWA, was observed in dialysis days compared to nondialysis days (2,145 ± 558 vs.
2,388 ± 708 kcal/d, p = 0.07, respectively).
Dietary protein intake was significantly
lower in the HD patients than in control subjects (68.0 ± 18.2 vs. 81.5 ± 29.7 g/d, 1.01 ±
0.35 vs. 1.24 ± 0.32 g/kg/d, p < 0.05), whereas
total energy intake were more similar (2,214
± 618 vs. 2,462 ± 443 kcal/d, 28.5 ± 9.0 vs.
30.6 ± 5.8 kcal/kg/d, respectively).
BIVA analysis showed similar phase angle
values in patients and controls (5.8 ± 1.0 vs.
5.7 ± 0.8°), but BCMI was lower in HD patients (8.5 ± 2.0 vs. 9.5 ± 2.0 kg/m2, p < 0.05).
Twelve of the 50 studied HD patients
showed daily mean values of energy expenditure between 1.4 and 1.6 METs, and 7 patients
over 1.6 METs; of consequence, 31 out of the
50 studied patients (62%) had a mean daily
value < 1.4 METs, and thus they were defined
as sedentary. The prevalence of a sedentary
condition was significantly lower in the control group (18%, p < 0.01). Table 1 shows
some clinical data of the sedentary and
non-sedentary dialysis patients. Data about
physical activity parameters derived by SWA
elaboration analysis in the two groups are reported in Table 2.
222
Cupisti, Capitanini, Betti et al.
Table 1. Clinical and biochemical data of the study subjects, divided by sedentary (< 1.4 METs) and active (³ 1.4 METs).
Active
n = 19
Sedentary
n = 31
p
Age, y
53.6 ± 11.8
63.3 ± 12.5
< 0.010
Dialysis age, months
123 ± 105
68 ± 48
< 0.02
Kt/V
1.4 ± 0.2
1.4 ± 0.2
ns
23.8 ± 4.0
25.4 ± 4.9
ns
Phase angle, °
6.3 ± 0.9
5.5 ± 1.0
< 0.01
S. Albumin, g/dl
3.9 ± 0.3
3.9 ± 0.4
ns
nPNA, g/kg/d
1.16 ± 0.23
1.06 ± 0.24
ns
Hemoglobin, g/dl
12.0 ± 1.6
12.0 ± 1.3
ns
Hematocrit, %
37.3 ± 4.5
37.1 ± 4.1
ns
0.5 ± 0.6
0.5 ± 0.4
ns
ns
BMI, kg/m2
CRP, mg/dl
319 ± 289
267 ± 209
Ca ´P, mg2/dl2
49.4 ± 12.3
43,5 ± 12,5
HCO3–, mmol/l
19.6 ± 2.1
20.9 ± 1.8
= 0.03
EPO dose, IU/w
7210 ± 9420
7621 ± 7984
ns
EPO res I
10.5 ± 13.9
9.1 ± 8.8
ns
Table 2. Data from Sense-Wear Arm-band (SWA), and comparison of Total
Energy Expenditure (TEE) with data from prediction equation and dietary recalls.
Active
n = 19
Sedentary
n = 31
p-value
1.7 ± 0.2
1.1 ± 0.1
< 0.001
165 ± 80
34 ± 26
< 0.001
Data from SWA
Time on 3 – 6 METs, min/d
Time on > 6 METs, min/d
10 ± 10
0±0
< 0.001
8681 ± 3833
3173 ± 1890
< 0.001
Activity energy expenditure, kcal /d
799 ± 490
135 ± 132
< 0.001
SWA TEE, kcal/kg/d
35.0 ± 6.4
29.1 ± 6.0
0.002
32.4 ± 3.5
32.3 ± 5.2
ns
Dietary energy intake, kcal/kg/d
32.4 ± 7.3
26.1 ± 6.4
< 0.05
Dietary protein intake, g/kg/d
1.04 ± 0.36
0.93 ± 0.25
ns
Steps, n./d
Data from prediction equation
Equation TEE, kcal/kg/d
Using the SWA-derived calculations,
daily TEE negatively correlated with age (r =
–0.33, p < 0.05), whereas positive correlations were observed with BMI (r = 0.51, p <
0.001), phase angle (r = 0.404, p < 0.01) phosphate (r = 0.49, p < 0.001), serum PTH (r =
0.32, p < 0.05) and albumin (r = 0.38, p < 0.01).
In addition, significant correlations were also
found between daily total energy expenditure
and energy intake (r = 0.37, p < 0.01) and in
particular with complex carbohydrates dietary intake (r = 0.48, p < 0.001).
Similarly, the mean daily METs values
were directly related to normalized protein
(r = 0.36, p < 0.01) and energy intake (r = 0.42,
p < 0.01) (Figure 1).
iPTH, pg/ml
METs, 24 h mean
5 patients were able to perform a physical activity over 6 METs beyond 5 minutes.
Data from dietary recalls
Evaluating the duration and intensity of
physical activity, we observed that 11 patients
had a physical expenditure greater than 3
METs for 30 – 60 minutes, 8 patients for
60 – 120 minutes and 15 patients for over 120
minutes, while 16 patients spent fewer than
30 minutes on 3 METs activities. Finally, only
In our series, the minutes spent on a physical activity over 3 METs correlated positively
with dialysis vintage (r = 0.41, p < 0.01),
phase angle (r = 0.36, p < 0.01) and BCMI
(r = 0.41, p < 0,01), and also to normalized energy (r = 0.51, p < 0.001) (Figure 2) and protein (r = 0.37, p < 0.01) dietary intake.
No relationship was observed between
parameters of physical activity and CRP,
Kt/V, hemoglobin or hematocrit.
Multiple regression analysis showed that
energy intake and dietary protein intake were
independently related to TEE evaluated by
SWA and to the time of mild to moderate
physical activity. As a whole, the estimated
daily energy expenditure was similar when
using SWA or the prediction equation (31.4 ±
7.2 vs. 32.4 ± 4.7 kcal/Kg/b.w., respectively).
However, differences exist where sedentary
or active dialysis patients are concerned. Table 2 shows that when using SWA, as expected, sedentary patients had a lower energy
expenditure than non-sedentary patients;
however, no difference resulted when using
the prediction equation. The conclusion is
that daily energy expenditure estimated by
the prediction equation is higher than that recorded by SWA in sedentary patients, while a
trend to underestimate occurs in active
patients (Table 2).
The analysis of 3-day dietary recalls
showed that sedentary ate less than active
patients (Table 2), and as a whole, reported
energy intake is lower than estimated energy
expenditure by SWA and also by the predic-
Physical activity in dialysis patients
Figure 1. Relationship between mean daily METs
values (as a measure of the mean daily activity
level) and the dietary energy intake in the hemodialysis studied patients.
Figure 2. Relationship between minutes spent at
physical activity > 3 METs (as a measure of intensity
of physical performance) and the dietary energy intake in the hemodialysis studied patients.
tion equation, both in patients and in controls
(Table 2).
Discussion
The results of the study indicate that the
level of exercise is quite low in dialysis patients and that it is related to age, body composition and dietary nutrient intake. They
confirm that levels of physical activity were
associated with phase angle [2], as an indicator of body composition and nutritional intake [32] among patients with ESRD and that
223
these patients were less active than sedentary
controls. These similar conclusions were obtained using different methods for both physical activity measurement (namely SWA or
tri-axis accelerometers) and dietary nutrient
intake assessment (3-day food recall or food
frequency questionnaires). In addition, we
also observed an association between phase
angle and minutes spent in activities greater
than 3 METs, that is, with the intensity of the
physical exercise
The level of habitual physical activity
measured with a simple method, SWA, in stable HD patients is directly correlated with
phase angle and BCMI, which are markers of
nutritional status and predictors of survival in
dialysis patients. Namely, the lower the physical activity, the lower the phase angle, energy
intake and protein intake.
Implementation of regular physical activity is important to ameliorate quality of life,
rehabilitation and even survival [28, 29], but
exercise capacity in chronic HD patients is
generally reduced because of the high prevalence of physical disabilities, social and psychological problems, and relevant comorbid
conditions. Physical exercise is not for everyone, but it requires individual prescription.
Dialysis staff commitment is important for
the safety and success of physical activity
programs, whereas dedicated exercise professionals may be needed depending on the
type of the exercise training [30].
Assessment of habitual activity is not easy.
Baecke self-administered habitual physical activity questionnaire or the Five-City Project
7-day recall physical activity questionnaire can
be used, but they give only indirect measurements and are highly dependent on a patient’s
mental skill and collaboration. Pedometers
are very useful devices, but they count steps
in a similar way during walking or running
and, therefore, they do not give any information about the timing and intensity of physical
activity. In addition, pedometers may not record physical activity in types of exercise different from walking or running, and so estimation of energy expenditure is far from
accurate.
Meanwhile, several studies have shown
that SWA can give an accurate assessment of
daily physical activity in general population
[13]. This method is simple, noninvasive and
low-cost. The major advantage of using SWA
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Cupisti, Capitanini, Betti et al.
in ambulatory settings is that it can record
spontaneous physical activity for long periods of time and so evaluate daily energy expenditure, the timing, duration and intensity
of physical exercise, and time spent during
resting and sleeping. Our experience confirms that the SWA was user-friendly in terms
of easy attachment/detachment, minimal discomfort, and little or no interference in daily
life activities.
Although the use of SWA has been validated in healthy individuals or athletes, there
are not enough data to establish the reference
values for SWA-determined physical activity
in different groups of chronically ill patients.
Phase angle was the only nutritional parameter that showed direct relationship with physical activity parameters, such as the daily
mean METs values, the minutes spent in activities > 3 METs, or the daily TEE. It means
that lower phase angle values, which are associated with higher mortality rate in dialysis
patients, are associated with a sedentary condition, and poor physical performance capacity. Moreover, low physical activity is also associated with low energy and protein intake
and contributes to decreased muscle tone and
mass; in other words, poor physical activity is
strongly associated with malnutrition and to
changes predictive of poor prognosis. On the
other hand, good physical activity increases
lean body mass, increases food intake and
contributes to the maintenance of good nutritional status. It may ameliorate a patient’s prognosis, quality of life, and rehabilitation.
It must be underlined that our series included stable HD patients, without pathologies
preventing them from performing physical activity. Hemoglobin levels reached target levels
in most of the patients, so no relationship was
expected with physical activity parameters.
Similarly, no relationship was observed with
dialysis dose and with inflammation markers
as already reported in the literature [31, 32].
Spontaneous physical activity tended to be
lower on dialysis days. This was already observed by Majchrzak et al. using a tri-axial accelerometer: physical activity was lower on
dialysis days when compared with nondialysis days, and this decrease was attributed
to the lack of movements during the 4-hour
HD procedure [16].
Information from the 3-day recall indicated that daily energy intake was lower than
total energy expenditure estimated by SWA in
both in patients and controls (Table 2). This
probably reflects the tendency to underestimation of the food dietary recall method. Obviously there could be a potential underestimation of energy and nutrients intake through
dietary interviews, which could represent a
limitation of this kind of investigation. Even
if the food record analysis represents the most
valid and simple tool for nutrient and calorie
estimation, the occurrence of a conscious or
unconscious underreporting is largely known
and recently confirmed in healthy adults [33]
as well as in renal failure patients [34, 35].
Furthermore, dietary intake may differ
among a dialysis day, a weekend day and a
nondialysis day. This is the reason we used
the average values of these 3 days, according
to Kidney Disease Outcomes Quality Initiative (K/DOQI) Recommendation for Nutritional Management [23, 27]. This method
provides a closer insight into dietary habits,
and it is preferred by patients who do not always comply with accurate recordings for a
longer period.
In conclusion, our findings indicate that
poor physical activity is highly prevalent in
dialysis patients even when free from physical
or neurological disabilities or severe comorbid
conditions. The level and intensity of physical activity is positively related to body composition and to dietary nutrient intake. This
confirms the strong interrelationship between
exercise and nutrition, which in turn are associated with survival, rehabilitation and quality of life of dialysis patients.
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