Keywords: Resistance Training - Parkinson Disease - Postural Balance - Rehabilitation - Quality
of Life
Palavras-chave: Treinamento de Resistência - Doença de Parkinson - Equilíbrio Postural - Reabilitação
- Qualidade de Vida
INTRODUCTION
Parkinson’s disease (PD) patients show lack of postural stability and motor coordination[1 ] and impaired ability to keep the center of mass over the base of support during
movement. Maintaining upright stance involves muscle activation and joint integrity
as well as neural responses to external disturbances[2 ],[3 ],[4 ].
Assessing postural control is challenging, but static posturography (SP) provides
quantitative information on postural control. SP measures shifts in the vertical forces
on a force platform that are exerted by body sway during upright stance and these
measurements make it possible to infer the center of pressure (COP). PD patients have
larger COP displacement variability than healthy older adults[5 ],[6 ],[7 ]. Moreover, studies have suggested that there may be an association between mediolateral
sway, increased COP velocity, poor postural control and risk of falls in this population[8 ],[9 ].
It has been reported in the literature that muscle strength[10 ], mobility[11 ] and balance[12 ] may improve with resistance exercise training (RT), with a positive impact on functional
capacity and reduction of the risk of falls in PD[13 ]. However, only a few well-designed controlled studies[14 ],[15 ],[16 ],[17 ] have qualitatively assessed SP in relation to RT programs, RT modalities and postural
control, among PD patients.
Therefore, the aim of this study was primarily to determine the effects of a three-month
RT intervention on SP measurements among PD patients. The secondary objective was
to evaluate the impact of this exercise intervention on motor performance, functional
balance scores, dynamic posturography measurements and perceptions of quality of life
(QoL).
METHODS
Study design and participants
We conducted a three-arm, single-blind randomized controlled trial. Patients were
recruited from the outpatient clinic of the Movement Disorders Clinic, Hospital das
Clinicas HCFMUSP, Department of Neurology, Faculdade de Medicina, Universidade de
São Paulo, and from the Brazil Parkinson Association, São Paulo, between September
2013 and February 2016.
Eligibility criteria
The study inclusion criteria were: idiopathic PD diagnosis based on the United Kingdom
Parkinson’s Disease Society Brain Bank diagnostic criteria[18 ]; age 50-75 years; Hoehn and Yahr (HY) stage scores of 2-3; antiparkinsonian drug
treatment consisting of stable daily doses for at least three months before inclusion;
ability to walk independently without assistance devices; and Mini-Mental State Examination
(MMSE) score of 24 or more. The exclusion criteria were: orthopedic conditions; severe
pain; unstable cardiovascular and/or metabolic disease; vestibular dysfunction; prior
stroke; and attending a physical rehabilitation program at least six months before
inclusion.
This study was approved by the local ethics committee and was registered at ClinicalTrials.gov
(NCT: 02674724).
Randomization and blinding
The participants were randomly assigned to one of three groups: RT by using weightlifting
machines at a gym (gym group); RT by using free weights and elastic bands (freew group);
and a control group. We used a computer random number generator to create 13 blocks
of six-number sequences (expecting a study dropout proportion of 20% or more). Randomly
generated number sequences were placed in sealed opaque envelopes and randomly assigned
to patients after enrollment. A physiotherapist, blinded to intervention assignment,
examined all participants before and after the intervention in their best clinical
condition (ON state). The flow chart shows group allocation ([Figure 1 ]).
Figure 1 The CONSORT flow diagram.
Consolidated Standards of Reporting Trials : patients recruitment and follow-up. Randomized, single-blinded clinical trial with
three groups: Gym: resistance training with gym equipment group; FreeW: resistance
training with free weights group; Control: control group.
Study intervention
The conceptual framework of our intervention was based on the American College of
Sports Medicine guidelines[19 ]. It is recommended that free-weight multiple machines and single-joint exercises
should be used. For older patients, the lifting velocity should be slow to moderate,
with one to three sets per exercise, at 60-80% of a one-repetition maximum (1-RM)
for 8-12 repetitions with 1-3 min of rest between sets[19 ].
A group of up to four patients participated in each RT session, consisting of 50 minutes
of training, twice a week for 3 months. The aim of both RT groups was to activate
all postural muscles, especially trunk muscles, that play a role in maintaining balance
during motor performance and in reducing the risk of falls[20 ],[21 ]. Lower-limb muscles were also recruited for stability in performing the exercises.
Each RT session started with a five-minute warm-up, in which the participants were
asked to side-tilt and rotate the trunk with their arms abducted, and to raise and
lower their arms without moving the trunk. They were then instructed to perform hip
flexion, extension and abduction with 10 repetitions of each exercise. At the end
of each session, there was a cool-down period that included upright stretching of
quadriceps, hamstring, triceps brachii and pectoris muscles for 15 seconds each[22 ].
We chose to perform two different RT protocols due to lack of evidence regarding what
the most effective type of exercise might be, for improving postural control in PD.
All three groups were instructed to perform stretching exercises at home.
RT by using weightlifting machines at a gym (gym group)
The participants performed RT using weightlifting machines at a gym (Biodelta®, São
Paulo, Brazil). The initial workload was defined as 60% of a one-repetition maximum
(1-RM) and then they were encouraged to perform three sets of 8 to 12 repetitions
with 60-second rests between sets[19 ]. The workload was progressively increased by 5 to 10% if the patient did not feel
muscle fatigue after the previous training[19 ]. The weightlifting exercises included lateral pulldown, back extension, seated row,
seated chest press, abdominal crunch and leg press ([Figure 2 ]).
Figure 2 Resistance training program.Participants in the gym group performed resistance exercises
using machines, which included lateral pulldown, back extension, seated row, seated
chest press, abdominal crunch and leg press. The main objective was to recruit postural
muscles, especially extensor trunk muscles with lower-limb stabilization to perform
each exercise. Workloads were progressively increased by 5 to 10%. Participants in
the freew group performed exercises aimed at recruiting the same muscle groups as
in the gym group, which were: abdominals, paraspinal, middle trapezius, latissimus
dorsi, rhomboid, quadriceps femoris, gluteal muscles and lower limbs. The training
workload was increased through use of dumbbells, elastic bands and ankle weights.
All participants were instructed not to perform the Valsalva maneuver during the movement
phase, but to activate abdominal muscles during expiration.
RT by using free weights and elastic bands (freew group)
The RT program targeted the same muscle groups as in the gym group, including abdominal,
paraspinal, middle trapezius, latissimus dorsi, rhomboid, quadriceps femoris and gluteal
muscles. The workload was progressively increased, using dumbbells, elastic bands
and ankle weights if the patient did not feel muscle fatigue after the previous training[19 ] ([Figure 2 ]).
Control group
Each participant received a booklet describing sets of stretching exercises to be
performed twice a week during the study period. They were instructed to perform a
variety of seated and standing 15-second stretches involving trunk, hamstring, pectoral,
brachial triceps and quadriceps muscles[23 ]. Their practice frequency was monitored through phone calls. This exercise protocol
is customarily used in rehabilitation programs and has no equivalent workloads in
RT.
Primary endpoint measurements
The study was conducted at the Laboratory of Movement Study, Instituto de Ortopedia
e Traumatologia, Hospital das Clínicas, Faculdade de Medicina, Universidade de São
Paulo, Brazil.
For SP, the participants were placed in a quiet upright stance on the force platform
(AccuSway Plus, Advanced Mechanical Technology Inc., AMTI, Massachusetts, United States).
Postural sway data was analyzed using the Balance Clinic® software. They were instructed
to maintain a comfortable standing position and look fixedly at a spot one meter away
and not to move or speak during the test (unless when performing the dual-task condition).
A baseline support base was drawn on a sheet of paper, for use in subsequent assessments.
The mean measurements for three 60-second trials were recorded for each condition
tested: eyes-open (EO), eyes-closed (EC) and dual-task (DT). For the latter, the participants
were asked to say as many words beginning with the letter F as possible, during the
whole test period, and then to name as many animals and fruits as they could. The
primary outcome measurements included the following COP displacement variables assessed
in SP after the RT intervention:
Mediolateral displacement (ML), representing the standard deviation of the COP on
the mediolateral axis, expressed in centimeters (cm).
Anteroposterior displacement (AP), representing the standard deviation of the COP
on the anteroposterior axis, expressed in cm.
Velocity, as the mean velocity of COP displacement in all directions, measured in
centimeters per second (cm/s).
Area of the ellipsis that covers 95% of the COP trajectory, expressed in square centimeters
(cm2 ).
Secondary endpoint measurements
The secondary outcome measurements of the study included: Unified Parkinson's Disease
Rating Scale, Part III (motor examination) (UPDRS-III); Berg Balance Scale (BBS);
Mini-Balance Evaluation Systems Test (Mini-Best); Timed Up and Go (TUG) test to assess
functional balance; 39-item Parkinson's Disease Questionnaire (PDQ-39) to assess how
often people affected by Parkinson's disease experience difficulties across eight
dimensions of daily living: mobility, impact on activities of daily living, bodily
discomfort, emotional wellbeing, stigma, social support, cognition and communication
domains; and dynamic posturography (Balance Master platform, NeuroCom® International
Inc., Oregon, United States) to assess the following tasks: a) stepping up and over
an obstacle: first stepping with the left leg then swinging the opposite leg onto
a 10-cm-high box and then landing the left leg on the force plate. The leg lift-up
index quantifies the maximal lifting force exerted by the leading leg and is expressed
as a percentage of the individual’s body weight; b) movement time (MovTime) quantifies
the number of seconds required to complete the task of stepping up and over an obstacle;
and c) tandem speed is the velocity at which tandem walking is performed, expressed
as cm/s. The score recorded was the mean value of three trials for each task.
All measurements were collected at baseline, at one week after completing the intervention
period (at three months) and at the six-month follow-up.
Statistical analysis
The sample size was calculated after a pilot study. The number of participants required
to detect a change of at least one standard deviation in SP measurements was 21 for
each group (power=0.8; alpha=0.05).
Differences in baseline characteristics among groups were assessed by means of univariate
analysis of variance (ANOVA) for age, MMSE scores and disease duration. We also tested
for the equality-of-proportion hypothesis, for HY stage, gender and race/ethnic group.
To determine the effect of treatment, two-way ANOVA (group versus time) was used to
compare posturography measurements and functional balance scores. Whenever an interaction
was noted, Tukey’s multiple-comparison post-hoc test was used to compare each pair of groups for each outcome.
All analyses were conducted on an intention-to-treat basis using the Statistica software
package v. 13.3 (TIBCO, United States) and Excel Office 2010. An α level of significance
was set at p<0.05 and all tests were two-sided.
RESULTS
Out of 316 patients screened for eligibility, 74 met the inclusion criteria and were
enrolled in the study. Six patients did not complete the training protocol ([Figure 1 ]).
Baseline characteristics
[Table 1 ] shows the demographic and clinical characteristics of the participants. There were
no significant differences among the groups at baseline with regard to MMSE, UPDRS-III,
Mini-Best and BBS, TUG, PDQ-39 domains scores or posturography variables (p>0.05).
Table 1
Demographic and clinical characteristics of the participants.
•Gym group
•(n=23)
•Freew group
•(n=26)
•Control
•(n=25)
•Gym group vs. control
•p-value
•Freew group vs. control
•p-value
•Gym group vs. Freew group
•p-value
p-value
Gender, n (%)
Male
17 (73.9)
18 (69.2)
18 (72)
0.882a
0.828a
0.717a
_
Female
6 (26.1)
8 (30.8)
7 (28)
Race/ethnic group, n (%)
White
16 (69.6)
17 (65.4)
13 (52)
0.214a
0.332a
0.755a
_
Black
1 (4.3)
0
2 (8)
0.602a
0.141a
0.283a
Mixed
5 (21.7)
7 (26.9)
8 (32)
0.424a
0.691a
0.674a
Asian
1 (4.3)
2 (7.7)
2 (8)
0.602a
0.967a
0.626a
HY stage, n (%)
2
6 (26.1)
3 (11.5)
6 (24)
0.868a
0.243a
0.189a
_
2.5
14 (60.9)
20 (76.9)
16 (64)
0.823a
0.311a
0.224a
3
3 (13)
3 (11.5)
3 (12)
0.913a
0.959a
0.873a
Education level, years
Mean (SD)
7.3 (5.1)
9.4 (4.4)
8.5 (3.8)
_
_
_
0.255b
Range
2-19
2-16
3-15
BMI
Mean (SD)
25.6 (3.1)
25.9 (3.6)
25.7 (4.3)
_
_
_
0.972b
Range
18.5-33.6
19.4-32.5
18.3-36.5
Age, years
Mean (SD)
63.4 (6.9)
63.2 (6.4)
63.6 (7)
_
_
_
0.977b
Range
50-75
50-74
52-75
Disease duration, years
Mean (SD)
7.6 (6)
8.4 (5.9)
9.6 (4.8)
_
_
_
0.462b
Range
2-30
2-25
2-18
MMSE scores
Mean (SD)
27.4 (1.9)
26.9 (2.4)
27.5 (2.1)
_
_
_
0.527b
Range
24-30
24-30
24-30
Data presented as mean (standard deviation, SD) or (%). %: percentage; N: number;
HY stage: Hoehn and Yahr stage; BMI: body mass index; MMSE: Mini-Mental State Examination;
a: test for equality of proportions, b: ANOVA.
Effects of intervention
ANOVA did not show any significant group versus time interactions in SP measurements
(primary outcome), in relation to the eyes-open condition for ML (F4,142 =2.232; p=0.068), AP (F4,142 =2.125; p=0.080), velocity (F4,142 =0.615; p=0.666) or area (F4,142 =2.021; p=0.094). Similarly, there was no significant main effect regarding group
in SP measurements, in relation to the eyes-closed condition for ML (F4,142 =0.747; p=0.561), AP (F4,142 =1.582; p=0.182), velocity (F4,142 =0.386; p=0.817) or area (F4,142 =0.758; p=0.553). There was also no significant effect regarding the dual-task condition
for ML (F4,142 =1.652; p=0.164), AP (F4,142 =0.640; p=0.634), velocity (F4,142 =0.192; p=0.941) or area (F4,142 =0.755; p=0.556) ([Figure 3 ]).
Figure 3 Static posturography measurements under eyes-open, eyes-closed and dual-task conditions
ANOVA showed that there was a group-versus-time interaction for UPDRS-III scores (F4,142 =3.396; p=0.010). Tukey’s post-hoc tests showed a reduction in UPDRS-III score at the three-month follow-up, compared
with baseline (26.46 vs. 29.58; p=0.028), in the freew group and at the three-month
follow-up, compared with baseline (25.61 vs. 29.13; p=0.014), in the gym group ([Table 2 ]).
Table 2
Functional clinical tests, dynamic posturography and quality of life.
Gym group
Freew group
Control group
P value
Baseline
3 months
6 months
Baseline
3 months
6 months
Baseline
3 months
6 months
UPDRS-III (0-108)
29.13 (10.06)
25.61 (10.03)
27.65 (9.92)
29.58 (12.06)
26.46 (11.17)
28.38 (10.05)
26.44 (9.95)
27.48 (7.99)
27.60 (8.12)
0.010*
TUG (sec)
8.70 (3.39)
8.04 (3.27)
7.91 (2.89)
8.5 (2.10)
7.88 (1.88)
7.96 (1.93)
8.56 (1.73)
8.20 (1.87)
8.12 (1.88)
0.894
BBS (0-56)
52.09 (4.5)
53.17 (3.17)
52.96 (2.93)
51.00 (4.74)
52.62 (3.02)
52.96 (2.82)
52.28 (2.79)
52.28 (3.41)
52.24 (3.07)
0.043*
Mini-Best (0-32)
24.48 (4.24)
25.87 (4.97)
25.70 (4.24)
23.69 (4.71)
25.35 (4.04)
25.69 (3.92)
24.92 (4.14)
24.52 (3.97)
25.04 (3.66)
0.014*
Stepping up
Lift-up index left (%)
16.65 (5.25)
19.74 (5.75)
19.04 (3.96)
16.35 (5.59)
19.00 (6.89)
18.65 (7.53)
19.48 (8.28)
19.08 (6.32)
20.84 (6.84)
0.253
Lift-up index right (%)
18.48 (7.48)
20.48 (7.48)
20.17 (6.04)
16.69 (7.00)
19.77 (8.65)
18.88 (8.38)
18.00 (6.81)
19.04 (7.04)
20.76 (7.22)
0.583
MovTime left (sec)
2.02 (0.71)
1.81 (0.65)
1.69 (0.55)
2.09 (0.73)
1.92 (0.78)
1.96 (0.73)
1.82 (0.40)
1.82 (0.38)
1.70 (0.30)
0.232
MovTime right (sec)
1.93 (0.70)
1.69 (0.64)
1.76 (0.77)
1.95 (0.07)
1.80 (0.68)
1.85 (0.77)
1.71 (0.39)
1.68 (0.30)
1.63 (0.35)
0.613
Tandem speed (cm/s)
19.40 (11.4)
20.93 (10.37)
22.58 (11.63)
19.80 (5.96)
22.65 (7.16)
22.00 (7.91)
19.38 (5.73)
19.25 (6.20)
19.82 (5.54)
0.132
PDQ-39
Mobility
34.72 (24.10)
21.46 (21.04)
25.80 (25.16)
30.52 (22.02)
23.94 (19.34)
24.63 (20.63)
23.12 (19.51)
24.94 (17.64)
23.52 (17.97)
0.019*
Daily living
37.58 (23.70)
25.21 (19.53)
29.21 (19.61)
36.53 (25.99)
28.21 (21.14)
29.02 (22.18)
24.24 (21.44)
24.03 (16.41)
20.18 (16.55)
0.247
Emotional wellbeing
30.79 (22.68)
21.04 (16.54)
22.45 (17.73)
28.54 (23.44)
22.61 (15.08)
27.43 (16.35)
22.36 (16.65)
22.68 (15.42)
23.70 (17.41)
0.304
Stigma
20.90 (21.62)
19.03 (22.65)
14.10 (17.21)
25.03 (18.38)
19.73 (18.17)
18.78 (16.79)
12.78 (15.89)
13.49 (18.46)
11.52 (15.71)
0.749
Social Support
15.78 (16.84)
9.06 (13.68)
10.14 (15.26)
15.88 (22.87)
11.54 (22.74)
11.22 (19.14)
8.19 (13.95)
9.33 (15.07)
12.14 (18.85)
0.373
Cognition
26.50 (20.87)
25.30 (17.55)
24.25 (19.03)
27.44 (20.36)
27.39 (19.60)
26.46 (20.23)
19.52 (19.30)
18.78 (15.62)
17.00 (18.84)
0.997
Communication
26.19 (20.64)
22.49 (19.56)
21.69 (18.11)
26.28 (26.22)
23.65 (19.49)
20.86 (15.54)
27.49 (17.99)
23.97 (16.36)
25.02 (21.37)
0.954
Bodily discomfort
42.43 (24.66)
26.78 (22.02)
32.16 (20.35)
25.96 (26.01)
25.47 (14.05)
25.92 (20.19)
34.97 (21.89)
32.32 (20.87)
32.35 (17.70)
0.078
Data presented as mean (standard deviation), sec: seconds; %: percentage; cm/s: centimeters
per second; UPDRS-III: Unified Parkinson’s Disease Rating Scale, part III; TUG: timed
up & go; MovTime: movement time; PDQ-39: quality of life perception; BBS: Berg balance
scale; Mini-Best: Mini-Balance Evaluation Systems Test; lift-up index: maximal lifting
force; Tandem speed: tandem walk speed; *: difference among groups (p<0.05).
For Mini-Best scores, a significant group-versus-time interaction was observed (F4,142 =3.231; p=0.014). Tukey’s post-hoc tests showed improved scores at the three-month (25.35 vs. 23.69; p=0.015) and six-month
follow-ups, compared with baseline (25.69 vs. 23.69; p=0.001), in the freew group
only.
Similarly, a significant group-versus-time interaction was observed for BBS scores
(F4,142 =2.529; p=0.043). Tukey’s post-hoc tests showed score improvements at the three-month (52.62 vs. 51.00; p=0.020) and
six-month follow-ups, compared with baseline (52.96 vs. 51.00; p=0.001), in the freew
group.
For PDQ-39 domains, group-versus-time interaction was seen for the mobility domain
(F4,142 =3.021; p=0.019). Tukey’s post-hoc test showed score improvement at the three-month follow-up, compared with baseline
(21.46 vs. 34.72; p=0.001) in the gym group. Interactions were not significant for
other domains: activities of daily living (F4,142 =1.368; p=0.247); bodily discomfort (F4,142 =2.144; p=0.078); emotional well-being (F4,142 =1.220; p=0.304); stigma (F4,142 =0.637; p=0.636); social support (F4,142 =1.070; p=0.373); cognition (F4,142 =0.346; p=0.997); and communication (F4,142 =0.166; p=0.954) ([Table 2 ]).
For TUG, no group-versus-time interaction was seen in any group (F4,142 =0.273; p=0.894) ([Table 2 ]).
For dynamic posturography, no significant group-versus-time interaction was seen for
tandem walking speed task (F4,142 =1.800; p=0.132). Similarly, for the task of stepping up and over an obstacle, there
was no significant interaction for lift-up index starting with the left leg (F4,142 =1.351; p=0.253) or the right leg (F4,142 =0.798; p=0.528). Likewise, no interaction for movement time was seen for the left
leg (F4,142 =1.414; p=0.232) or the right leg (F4,142 =0.670; p=0.613) ([Table 2 ]).
There were no serious adverse events in our study. The events reported during training
sessions for the freew group included a fall episode (one participant), mild transient
joint pain (three participants) and orthostatic hypotension (three participants),
with no serious injury. For the gym group, there were reports of an outdoor fall (one
participant), mild transient muscle pain (three participants) and orthostatic hypotension
(two participants). For the control group, only one participant reported joint pain.
DISCUSSION
Our study found that there were no statistically significant changes in SP measurements
following a three-month RT intervention among PD patients. However, there is no consensus
on SP measurements and how they correlate with postural control in PD patients.
Some authors have suggested that larger COP displacement is likely to be a predictor
of postural instability[8 ],[24 ], but few have investigated SP measurement after RT in PD. Santos et al.[25 ] assessed the effects of two months of RT using gym weightlifting equipment, starting
at a workload of 40% of 1-RM. In addition to improved gait speed, they found only
a reduction in COP sway path length measurements after the training[25 ]. Similarly, a ten-week high-intensity RT intervention resulted in a 29% increase
in the posterior COP sway and 11% increase in COP velocity[26 ]. According to those authors, larger posterior COP sway could increase arm movement
by shifting the center of gravity forward and helping gait initiation, which suggests
that lower-limb training may interfere with anticipatory postural adjustments[26 ]. However, the sample size was small and these findings should be interpreted with
caution. In contrast, another three-month RT protocol including trunk and lower limb
exercises did not show any changes in COP sway, in comparison with balance exercises[27 ]. Although this balance program gave rise to improvements in clinical balance tests,
these were insufficient to show on SP measurements[27 ].
Although the dual-task condition has been shown to influence postural control in PD[5 ], we did not see this effect in our patients. Despite methodological differences
between the RT intervention evaluated in our study and those of the other studies
mentioned above, it is important to point out that the question remains whether one
or two COP variable changes after a RT program can be inferred to represent a functional
gain in PD patients. SP is considered to be the gold standard for the evaluation of
postural control, but postural instability is multifactorial in PD and muscle strengthening
alone may be insufficient to improve postural adjustments so as to maintain an upright
stance.
Our RT protocol did not have any impact on dynamic posturography measurements and
the same question can be raised as in relation to SP. Although the PD patients were
25% weaker and slower in lifting their leg over a box, compared with healthy controls[28 ], studies have found no improvement in postural parameters after three[29 ] or six-month RT interventions[23 ], and the intervention was insufficient to optimize strategies for gains in functional
independence[12 ].
In our study, significant improvement in motor symptoms was seen in both RT groups,
with reductions in UPDRS-III scores (-3.52 for the gym group; -3.12 for the freew
group). In contrast, these scores increased in the control group (+1.04). Previous
studies showed that a score reduction of 2.3 to 2.7 is clinically relevant[30 ]. One study reported that a reduction in UPDRS-III score was maintained up to a 24-month
follow-up[13 ] and another demonstrated a score reduction of 5.07 after a six-month RT intervention[23 ]. However, there was no change in UPDRS scores after a two-month RT intervention;
its short duration and/or training design were insufficient to promote neuromuscular
adaptations[25 ].
The impact of RT on functional mobility is not yet clear. TUG time was reduced after
three-month[31 ] and six-month RT programs[23 ]. In contrast, our findings concur with the results from a meta-analysis that reported
that RT was not superior to other training interventions regarding TUG time[32 ]. Likewise, another three-month RT intervention increased muscle strength, but was
insufficient to increase TUG time[10 ]. None of the studies mentioned above reported any reduction close to 3.5 seconds,
which is considered to be the minimal clinically significant difference[33 ]. It is noteworthy that the three groups in our study showed good time performance
at baseline (less than 9 seconds), so it is possible that a ceiling effect may have
occurred.
The freew group performed better in the BBS and Mini-Best tests. Although BBS is a
widely used scale, ceiling effects are likely to occur. Thus the Mini-Best scale is
more sensitive for detecting postural instability than BBS[34 ]. Bearing in mind that a three-month high-intensity RT intervention had a positive
impact on BBS scores[35 ] and another three-month RT protocol did not improve on BESTest scores[27 ], we chose to use both scales in order to broaden our functional assessment. The
freew group was asked to perform more coordinated specific sequences of movements
against different external loads and, even though they trained at a lower workload
than the gym group, this practice may have been more demanding in terms of motor control
and may have resulted in better postural control.
In our study, we found better perceived QoL for the mobility domain (PDQ-39) in the
gym group after RT intervention. Our findings are in accordance with those of other
studies reporting better perceived QoL following a two-month high-intensity training
program[25 ] and a six-month program[13 ].
Our study had some limitations. We cannot rule out the existence of a placebo effect
since the control group could have expected to participate in RT intervention; the
isokinetic machine for muscle strengthening was not available for our study; the participants
in our sample were not stratified for the presence of dyskinesia, and involuntary
movements may have influenced posturographic measurements and may have had a confounding
effect or produced outliers; and our training protocol did not include exercises for
plantar flexion and dorsiflexion or for hip abduction or adduction, which may have
influenced our balance measurements, especially static balance. However, the strengths
of this study were the single-blind randomized design with a supervised training protocol
and the three-month follow-up after the intervention.
Although SP allows quantitative measurements of body sway, our findings suggest that
it was not an appropriate tool for discriminating postural control changes after RT
intervention and it may have limited value in assessing patients in clinical practice.
SP is considered to be the golden standard assessment for postural control measurements,
but in our study the functional scales provided better assessments on the functional
capacity of our sample of patients. Therefore, further studies with more comprehensive
assessments of the impact of RT and posturography measurements are needed.
The study intervention helped to improve motor ability and perceived QoL in the gym
group. It helped to improve motor and balance scores with moderately positive effects
in the freew group, possibly because training with free weights required greater postural
motor control. Both protocols were well accepted and could easily be implemented in
centers for physical activities. Overall, there was good adherence to training among
the participants and they showed no serious adverse events during the exercise sessions,
which suggests that this training was safe.
In conclusion, after this three-month training intervention, there were no changes
in SP measurements. However, both intervention groups showed improved motor performance
(UPDRS-III motor scores) with better perceived QoL in the gym group and moderate effects
on functional balance in the freew group.
