Gait & Posture 40 (2014) 1–10

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Review

Effect of light touch on postural sway in individuals with balance problems: A systematic review A.M.S. Baldan a, S.R. Alouche a, I.M.G. Araujo b, S.M.S.F. Freitas a,* a b

Programa de Po´s-Graduac¸a˜o em Fisioterapia, Universidade Cidade de Sa˜o Paulo, Sa˜o Paulo, SP, Brazil Graduac¸a˜o em Fisioterapia, Universidade Cidade de Sa˜o Paulo, Sa˜o Paulo, SP, Brazil

A R T I C L E I N F O

A B S T R A C T

Article history: Received 19 April 2013 Received in revised form 31 October 2013 Accepted 31 December 2013

The aim of the present review was to examine the experimental, case-control studies that investigated the effect of light touch on postural sway in individuals with balance problems due to aging, brain lesion or other motor or sensory deficits. Articles published before the end of March of 2013 were searched in PubMed, Scielo and Lilacs databases using terms related to postural control and sensory information. Twelve studies that assessed the postural sway of individuals with balance problems during quiet standing with the light touch using a force plate were reviewed. Two reviewers rated all selected articles as having good quality. The effect of light touch on postural control was reported by all eligible studies regardless of the cause of the balance problem of the participants. Such effect was more evident when the applied vertical force was greater than 1 N, but if individuals with poor balance took more advantage of the light touch than healthy ones it depended on the source of their balance problems and not the amount of the applied force. These findings suggested that the maintenance of the fingertip lightly touching an external surface could provide additional somatosensory information for individuals with poor balance and then it could be used as a strategy to improve the control of upright standing during intervention programs. ß 2014 Elsevier B.V. All rights reserved.

Keywords: Postural control Center of pressure Equilibrium Sensory feedback

1. Introduction The contact of the index fingertip on an external rigid and fixed surface has been described as helpful in the control of postural sway of healthy young individuals during quiet standing [1–6]. This effect was usually investigated by asking individuals to lightly touch an external rigid and fixed surface with an applied force less than 1 N, which is not enough to provide mechanical support to them. Thus, the effect is attributed to the additional somatosensory information obtained by contacting the glabrous skin of the tip of the index finger with the external surface [1,2,5]. The additional sensory information is afforded by the large density of cutaneous mechanoreceptors in addition to kinesthetic receptors providing information about the arm position [7]. For healthy individuals the postural sway during natural standing is about 1 cm in the anterior-posterior direction and 0.5 cm in the medial-lateral [8]. The light touch studies showed that about 50% of the postural sway is reduced with additional somatosensory information [1]. This reduction was observed regardless of the different experimental

* Corresponding author at: Rua Cesa´rio Galeno, 448/475 – Tatuape´, Sa˜o Paulo, SP 03071-000, Brazil. Tel.: +55 11 2178 1565. E-mail address: [email protected] (S.M.S.F. Freitas). 0966-6362/$ – see front matter ß 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gaitpost.2013.12.028

condition that participants were assessed, such as: the position of the feet (single foot standing [1], natural feet position [9] or tandem position [6]); level of applied force on the external surface (light touch or heavy touch [1–3]); and visual conditions (eyes open or closed [2,10,11]). While the light touch effect is well known on healthy individuals, just few studies investigated it on individuals with balance problems due to aging [12–14] or those with brain lesion [15–17]. Overall, individuals with balance problems demonstrated increased postural sway during quiet standing compared to healthy individuals [12–21]. Based on this fact, the light touch could be even more important in the control of postural sway of those individuals. Therefore, the aim of the present review was to examine the experimental, case-control studies that investigated the effect of light touch on postural sway in individuals with balance problems. Studies that measured the postural sway using a force plate and the light touch paradigm were reviewed. In particular, the main question is whether individuals with balance problems use additional somatosensory information from the light touch to reduce their postural sway. In addition, we were interested in investigating if these individuals take more advantage of the light touch than healthy ones. Better understanding of the light touch effects on different groups of individuals with balance problems would contribute to the comprehension of the

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A.M.S. Baldan et al. / Gait & Posture 40 (2014) 1–10

importance of the somatosensory information to the postural control. Moreover, movement science professionals would benefit of such knowledge to plan appropriate intervention programs for these individuals with poor balance using the light touch strategy as additional source of somatosensory information to improve their upright postural control. 2. Methods 2.1. Search strategy The article searches were carried out using three electronic bibliographic databases: PubMed, Scielo and Lilacs (the last two were used to include possible studies written in Portuguese, native language of the authors of the present study). The following terms were used in the search strategy: ‘postural control’, ‘balance’, ‘body sway’, ‘centre of pressure’ OR ‘centre of pressure’, ‘oscillation’, ‘equilibrium’, AND ‘posture’. These keywords were individually crossed with the terms related to sensory information: ‘light touch’, ‘somatosensory’, ‘haptic’ AND ‘tactile’. The search was limited to papers published until the end of March of 2013.

2.4. Data extraction The methodological procedures and the outcomes related to the effect of light touch on the postural sway assessed by the COP measures were retrieved from all selected studies. Then the results of the most significant outcome obtained from COP measures from each study were assessed and presented as indicative of balance control. In particular, the effects statistically significant of Group (individuals with or without balance problems), Touch (with or no contact of body segment on the external bar) or the interaction between these two factors, Group vs. Touch, on the postural sway were analyzed and described. The applied forces were also extracted from each study as the amount of these forces could affect the findings. In addition, the values of the most significant outcome from each study were extracted based on the data presented in a figure or table by each selected article. Two reviewers estimated the values and then the average between them were used to compute the overall percentage of reduction between the no touch and light touch conditions for each group. 3. Results

2.2. Selection of articles criteria 3.1. Selection of studies Two independent reviewers evaluated the titles and abstracts of the studies, and when it was not possible to identify if a study was eligible for the present review, the full article was assessed. The two reviewers also evaluated the full text of all eligible studies selected for inclusion. When a disagreement between the two reviewers occurred, a third reviewer helped to determine the eligibility of the study. The name of each author and the list of references of the studies were also searched for other eligible studies. The articles were selected for relevancy using the following criteria: (a) body sway was assessed by having participants standing on a force platform, (b) outcomes computed from COP (center of pressure) were assessed, (c) article published in any language, (d) elderly or individuals with balance problems compared to young or healthy individuals, and (e) articles appeared in a peer-reviewed journal. Articles were excluded if: (a) they were review articles, single-case studies or only if the abstracts was published (not full-text articles), (b) involved any intervention (e.g., induced fatigue), (c) assessed only healthy participants, (d) participants aged less than 18 years-old, and (e) they were a clinical trial or involved learning and training for several days. 2.3. Quality assessment Two reviewers rated the quality of each selected study independently and the divergences between them were discussed with another reviewer. Reviewers were not blinded to the author(s) or which journal was the article published. The quality evaluation was performed to identify the validity of the findings of the selected articles and possible bias that could affect the interpretation of the results. Only the selected articles that were included in the present review were assessed. In the present study, a questionnaire composed by 17 items (Table 1) was used to assess the quality of the quantitative articles adapted from that proposed by Law [22]. Each question was scored as ‘‘1 for yes’’ (when the item description was reported and considered acceptable) or ‘‘0 for no’’ (when the item description was not reported and/or inadequate). The final score (which could range from 0 to 17) was obtained by the sum of the points, in which the higher was the score the greater was the quality of the study. In addition, the total score obtained by the studies in each question was calculated to identify the items less reported and/or inadequate.

Although the searches resulted in 3735 studies, only 400 abstracts were identified by the title for detailed review and 67 full-articles were retrieved for evaluation based on their abstracts. Twelve articles, involving 325 participants where 167 participants were those with balance problems and 158 were healthy individuals, were then included in the present systematic review as they met all the inclusion criteria [12– 21,23,24]. None of these studies was selected based on the reference lists. This search process is summarized in a flowchart presented on Fig. 1. 3.2. Quality assessment The score obtained in each question and the total score across studies are presented in Table 1. The two reviewers disagreed on 35 of the 204 (17.16%) items and the third reviewer helped to solve the disagreements. The median score across articles was 14 out of 17 points. The median score across questions was 10, meaning that 7 studies got full score, but ranged from 2 (question 3d) to 12 (questions 2, 3e, 6–9, 12). Overall, most of the studies clearly informed the purpose of the study, as well as used adequate methods, with reliable and appropriate equipment to investigate their main research questions. For example, the sampling frequency was equal or greater than 20 Hz in all studies, which is considered enough for data acquisition of COP signal during quiet standing [8]. However, the duration of each trial was less than 30 s for five studies [12,17,18,21,23] while one study did not report the time of data acquisition [24]. A trial duration lesser than 30 s can lead to erroneous conclusions due to large variability and non-stationary characteristic of the COP signal [8]. The articles also satisfactorily described and discussed their main findings. Thus, the reported details of the eligible articles were considered enough for further reproducibility of each study. For those questions of the qualitative evaluation all articles were rated with full score. However, the methods used to select the participants and the reasons for the sample size were not stated in all articles. In addition, more details about participants’ characteristics, such as body mass and height of the participants, were missing in most of the articles, thus none of studies were rated with full score.

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Table 1 Summary of quality appraisal for individual studies. Question

Lackner Reginella Dickstein Dickstein Tremblay Bacsi Baccini Gomes Bonfim Cunha Franze´n Rabin Total et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. et al. each (1999) (1999) (2001) (2003) (2004) (2005) (2007) (2007) (2008) (2012) (2012) (2013) question

1. Was the objective of the study clearly stated?

1

1

1

0

1

1

1

1

1

1

1

1

11

2. Was the literature review appropriately presented?

1

1

1

1

1

1

1

1

1

1

1

1

12

0

0

0

0

1

1

1

0

1

0

1

1

6

1

1

1

1

1

0

0

1

1

0

0

0

7

1

1

1

1

1

0

0

1

1

1

1

1

10

1

0

0

0

0

0

0

0

0

0

1

0

2

1

1

1

1

1

1

1

1

1

1

1

1

12

1

1

0

0

1

1

1

1

1

1

1

1

10

4. Do the methods allow reproducibility? [equipment used (type, sample rate and duration), experimental procedures (position of the participants and instructions), data analysis (calculation of dependent variables) and statistical analysis (tests, p value)]

0

1

1

0

1

0

1

1

1

1

1

1

9

5. Do the methods used meet all the objectives proposed? [equipment used (type, sample rate and duration), experimental procedures (position of the participants and instructions), data analysis (calculation of dependent variables) and statistical analysis (tests, p value)]

0

1

1

1

1

0

0

0

1

1

1

0

7

6. Reliability of measuring instruments (Are the measuring instruments valid and reliable?)

1

1

1

1

1

1

1

1

1

1

1

1

12

7. Internal validity of a study (Are the results valid and according to the sample studied?)

1

1

1

1

1

1

1

1

1

1

1

1

12

8. Were the results presented clearly and with statistical significance?

1

1

1

1

1

1

1

1

1

1

1

1

12

9. Was the question of the study adequately answered in the discussion?

1

1

1

1

1

1

1

1

1

1

1

1

12

10. Are there implications for clinical practice in accordance with the results of the study?

1

0

1

1

1

0

1

1

1

1

1

0

9

11. Were the limitations acknowledged and described?

1

1

1

0

1

0

1

0

0

1

0

1

7

12. Were the conclusions appropriate, given the study methods, interpreted in a logical manner, and supported by the references used?

1

1

1

1

1

1

1

1

1

1

1

1

12

14

14

14

11

16

10

13

13

15

14

15

13

3. Was the sample adequately selected and described? (a) Sample size (Was the sample size justified?) (b) Were the methods used to recruit the participants well described? (c) Were the criteria for inclusion and exclusion described? (d) Were the participants’ characteristics described in detail? (lesion, age, gender, height, body mass) (e) Was there a control group? (Were the individuals paired properly with those from the study group?) (f) Was an informed consent obtained? (Were ethical issues considered as conditions to participate?)

Total each article (maximum 17) Scoring criteria: 1 for yes/0 for no.

[(Fig._1)TD$IG]

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Fig. 1. Flowchart for selection of eligible articles.

3.3. Methodological data The main characteristics of the 12 eligible articles included in the systematic review are presented on Table 2 with a complete list of the authors, year of publication, sample size, participants’ characteristics, as well as experimental details, such as feet and upper limb position and type and position of upper limb while using the index finger to touch the external surface. The averaged sampling size across all studies was about 14 in each group, ranging from 5 [21] to 36 [14]. The participants’ age ranged from 21 [23] to 74 [12] years-old, with an average of 52 years-old. This large range was due to three studies that compared elderly participants (sample of 64) with young adults [12–14] (sample of 53). The other 103 participants with balance problems presented lesion in the anterior cruciate ligament [19]; sensory changes such as vestibular loss [21] and peripheral neuropathy from diabetes mellitus [20,24]; neurological lesion such as stroke [15], Down syndrome [23] and Parkinson’s disease [16,17]. Overall, participants were assessed with the feet in a parallel position, separated by a confortable [13–16,23] or reduced [18,20] distance between them. Four other studies investigated the postural sway with the participants in a more unstable position: tandem [17,21], semi-tandem [12] or single leg standing [19]. Only one study did not report the feet position used by the participants [24]. The evaluation in the control condition (no touch with the external surface) was performed while participants maintained the arms parallel to the body as described in 7 studies [14,15,17– 19,21,23]. In other studies participants used similar position to the touch condition [20,24], with the arms at the waist level [12] or crossed in front of the body [16]. One study did not report the arms position during no touch condition [13]. However, during the touch condition, all eligible studies investigated the postural sway while participants touched an external surface with their right index fingertip (only one study did not report which finger touched the bar [17]), with their elbow flexed in a waist [12,17,19,21] or shoulder [13] height, or close to 1658 [23], 908 [15,16,18], 458 [14] or in a position with the bar placed at a height of 90 cm from the floor [20]. All eligible studies randomized the order of the experimental conditions. While most of the studies investigated the effect of light touch with a vertical force applied on the external bar limited to 1 N [12,15,17,19,21,23,24] or 2 N [16], only one study assessed the postural sway when participants were allowed to apply a force

up to 10 N [13] (Table 3). Two studies did not report the amount of applied force on the bar although they asked the participants to lightly touch [14,18]. In addition, six studies [12,16,17,20,21,24] also investigated the postural sway during a condition of heavy touch, that is, participants could exert as much force as they desired to maintain the postural stability. All touch conditions were compared to that with no touch. The bar for most of the studies was fixed and rigid (n = 10) [12,15–21,24]. More details about the experimental conditions can be seen in Table 3. Regarding to the visual information, 66.7% of the studies compared the postural sway of the participants with eyes open versus closed [12,14,15,17,18,20,21,23]. The other studies asked participants to stay only with eyes closed [16,19,24] or to use darkened googles [13] during the evaluation. The assessment of the COP data as indicative the postural sway was done by six studies using a AMTI (models OR6-5 [12,14], OR67 [15,19,23] or AccuSwayPLUS16, or was uninformed [17]) force plate with a median sample rate of 100 Hz [13,15,16,19,23], but a range of 20 [14] to 240 Hz [20,24] (Table 3) among the studies was observed. 3.4. Results and overall conclusion of selected studies A summary of the effects obtained by each study is reported in Table 4. In the present review, the purpose was to examine the effects of Group (individuals with or without balance problems), Touch (with or no contact of body segment on the external bar) or the interaction between these two factors, Group vs. Touch, on the postural sway. In particular, the interaction should be able to identify if the light touch effect was greater for one of the groups. Because there was not a standard outcome across articles, the effects are discussed based on root mean square [13,16,18,20,21], mean sway amplitude [14,15,17,19,23] or velocity of COP [12,24] for different studies. Thus it was not possible to execute a pooled analysis with the data. Then, the Group, Touch or interaction statistically significant effects reported in each selected article were summarized in the present study. Ten of the eligible studies reported that individuals with balance problems (case group) showed greater postural sway compared to healthy individuals (control group) [12–15,17– 21,23]. The study that investigated the effect of light touch in Parkinson’s disease [16] found such result only if participants were assessed during the ON-period. All eligible studies reported the

Table 2 Characteristics of selected studies listed in chronological order, from earliest to latest. Study

Population (patients/control)

Mean age (years)

Feet position

Arm position No touch condition

Touch condition

1

Lackner et al. (1999)

- 5 Bilateral vestibular loss patients (BVL) - 5 Healthy adults (controls)

59 (BVL) 58.8 (controls)

Tandem position (right foot behind left)

Participant’s arms hung passively by sides

2

Reginella et al. (1999)

- 8 Healthy older adults - 8 Healthy young adults

68.5 (older) 23.6 (young)

Feet positioned shoulder width apart

Uninformed

3

Dickstein et al. (2001)

59.7 (DM-PN) 60.6 (controls)

Feet 5 cm apart between the medial malleoli

4

Dickstein et al. (2003)

59.7 (DM-PN) 61.1 (controls)

Standing

5

Tremblay et al. (2004)

- 8 Subjects with profound sensory peripheral neuropathy from diabetes mellitus (DM-PN) - 8 Healthy adults (controls) - 8 Subjects with diabetes mellitus with profound sensory peripheral neuropathy (DM-PN) - 10 Healthy adults (controls) - 36 Healthy older adults - 25 Healthy young adults

70 (older) 23 (young)

Normal standing position, head facing forward, feet comfortably apart and weight evenly distributed

The touch plate was positioned at the subjects’ right side, 90 cm height from the floor, immediately anterior to the right foot but with no touch The right hand was held above the touch bar surface, keeping a distance of at least 10 cm between the plate and the index finger Participant’s arms hung passively by sides

6

Bacsi et al. (2005)

- 10 Patients with orthostatic tremor (OT) - 10 Controls age-matched

63.1 (OT) 63 (controls)

Participant’s arms hung passively by sides

7

Baccini et al. (2007) Gomes et al. (2007)

-

74.3 (older) 23.9 (young) 21 (DS) 21.2 (CS)

Stance width (feet 20 cm apart or together with less than 4 cm apart) Semi-tandem position

The touch bar was adjusted to a comfortable height (approximately waist level) and lateral distance for the subject The touch plate was located on the inside wall of the EquiTest and aligned with the right shoulder for each subject The touch plate was positioned at the subjects’ right side, 90 cm height from the floor, immediately anterior to the right foot The touch plate was positioned at the subjects’ right side at 90 cm height from the floor, immediately anterior to the right foot Subjects were instructed to bring the right arm at 458 in front so that the tip of the index could maintain contact with either one of the designated texture surfaces on the touch-plate placed slightly lateral and anterior to the participant’s right side The touch plate was placed directly in front of the subject’s left arm at elbow height

Stand upright with the feet parallel at shoulder width

Participants’ arms hung passively by sides

9

Bonfim et al. (2008)

- 28 Individuals with unilateral anterior cruciate ligament (ACL) injury - 28 Healthy young individuals (controls)

23.6 (ACL) 22.1 (controls)

Participant’s arms hung passively by side

10

Cunha et al. (2012)

- 8 Chronic hemiparetic post Stroke - 8 Healthy subjects (controls)

57 (stroke) 58 (controls)

Participant’s arms hung passively by side

Participants kept their elbow flexed to 908 to touch the bar

Right and left index fingertip

11

Franze´n et al. (2012)

- 14 Male adults with ‘‘idiopathic’’ Parkinson disease (PD) - 14 Healthy control subjects

64 (PD) 64 (controls)

Single-leg stance, with the contralateral leg knee flexed to approximately 908, the hip in a neutral position Bipedal standing with their heels separated by a distance about of 16 cm Bipedal standing on a platform that slowly (18/s) rotated left and right (about 108)

The touch plate was positioned at the subject’s waist level The touch plate was positioned at the right side, at a distance so that the participant could comfortably touch the center of its metal plate with his or her fingertip with elbow flexed to approximately 1658 The touch plate was positioned waistheight on the participant’s right side

Arms crossed over their chest

Light touch: both index fingers/heavy touch: palmar grasping the bar with both hands

12

Rabin et al. (2013)

- 13 Adults with Parkinson disease (PD) - 13 Healthy control subjects

72.2 (PD) 72.1 (controls)

Arm was positioned at waist height in front of the subject at a comfortable distance from the body midline for touching with elbows flexed at approximately 908 The touch bar was adjusted to waist height

Romberg stance (a tandem stance widened by a 10 cm medial-lateral gap)

With both arms at the waist

Participant’s arms hung passively by sides

Right index fingertip

Right index fingertip

Right index fingertip

Right index fingertip

Right index fingertip

Left index fingertip

Right index fingertip Right index fingertip

A.M.S. Baldan et al. / Gait & Posture 40 (2014) 1–10

8

20 Older adults 20 Young adults 9 Adults with Down syndrome (DS) 9 Control subjects (CS)

Type of touch/touch position

Right index fingertip

Touch with more versus the less-affected hand

5

6

Table 3 Experimental conditions and equipments used to investigate the postural sway. Total trials (N Trial*condition)

Experimental conditions

Force applied

Trials order/duration

Equipment/acquisition frequency

1

Lackner et al. (1999)

24 Trials (4 Trials*2 Vision*3 Touch)

- LT: limited to 1 N - HT: as much force as desired

Randomized 25 s

Force platform (Kistler 9261A)/60 Hz

2

Reginella et al. (1999)

- Less than 10 N

3

Dickstein et al. (2001)

18 Trials (3 Trials*2 Floor*3 Touch) 24 Trials (2 Trials*2 Vision*3 Touch *2 Surface)

- LT: limited to 1 N - HT: as much force as desired

Randomized 40 s Randomized 40 s

EquiTest – NeuroCom/ 100 Hz Dual force platforms/ 240 Hz

4

Dickstein et al. (2003)

45 Trials (5 Trials*3 Touch*3 Velocities)

- LT: limited to 1 N - HT: as much force as desired

Randomized Uninformed

Dual force platforms/ 240 Hz

5

Tremblay et al. (2004)

24 Trials (2 Trials*2 Vision*3 Touch *2 Feet)

- Visual (NV: no vision vs. V: vision) - Touch (NT: no touch, LT: light touch, HT: heavy touch) - Floor (fixed vs. sway) - Touch (NT: no touch, fixed, sway-referenced)a - Visual (NV: no vision vs. V: vision) - Touch (NT: no touch, LT: light touch, HT: heavy touch) - Surface (firm and foam) - Touch (NT: no touch, LT: light touch, HT: heavy touch) - Backward translation velocities of the support surface at 10, 20, and 30 cm/sb - Visual (NV: no vision vs. V: vision) - Touch (NT: no touch, Smooth touch and Rough touch) - Support surface (firm and foam)

Bacsi et al. (2005)

8 Trials (1 Trial*2 Vision*2 Touch *2 Feet)

Randomized between vision and touch conditions; alternated for support surface blocks 60 s Randomized 26 s

Dual force platforms (AMTI OR6-5)/20 Hz

6

Participants were told that the touch-plate was not designed to support heavy forces and therefore could not be used as a cane or other walking aid Forceful grip was not permitted

7

Baccini et al. (2007)

6 Trials (1 Trial*2 Vision*3 Touch)

- LT: limited to 1 N - HT: as much force as desired

Randomized 20 s

Force platform (AMTI OR6-5)/50 Hz

8

Gomes et al. (2007)

- LT: limited to 2 N

9

Bonfim et al. (2008)

10

Cunha et al. (2012)

8 Trials (2 Trial*2 Vision*2 Touch) 12 Trials (3Trials*2Touch*2Legs) 12 Trials (2 Trials*2 Vision*3 Touch)

Randomized 20 s Randomized 30 s Randomized 35 s

Force platform (AMTI OR6)/100 Hz Force platform (AMTIOR6-7-1000)/100 Hz Force platform (AMTI OR6-7-1000)/100 Hz

11

Franze´n et al. (2012)

3 Trials (1 Trial*3 Touch)

- LT: not exceeding 2 N - HT: uninformed

Randomized 30 s

Force platform (AMTI AccuSwayPLUS)/100 Hz

12

Rabin et al. (2013)

8 Trials (1 Trial*2 Vision*3 Touch*2 Legs)

- LT: limited to 1 N - Unrestricted manual contact

Randomized 25 s

Dual force platforms (AMTI)/120 Hz

a b

Participants worn darkened goggles. Eyes closed only.

- Visual (NV: no vision vs. V: vision) - External support (with or without) - Stance width (feet apart or together) - Visual (NV: no vision vs. V: vision) - Touch (NT: no touch, LT: light touch, HT: heavy touch) - Visual (NV: no vision vs. V: vision) - Touch (NT: no touch, LT: light touch) - Touch (NT: no touch, LT: light touch) - 2 Legs (right and left)b - Visual (NV: no vision vs. V: vision) - Touch (NT: no touch, LT: light touch right and light touch left) - Touch (NT: no touch, LT: light touch, HT: heavy touch) on a horizontal platform that slowly (18/s) rotated four cycles to left and right (about 108)b - Touch with eyes closed (NT: no touch, unrestricted manual contact, LT: light touch) - Touch with eyes open (NT: no touch)

- LT: limited to 1 N - LT: limited to 1 N

Force platform (Kistler 9286A)/200Hz

A.M.S. Baldan et al. / Gait & Posture 40 (2014) 1–10

Study

Table 4 Dependent variables, results and overall conclusion of selected studies. Study

Outcome measures

Results

Conclusions

Group

Touch

Interaction

Forces (N)

BVL NV, LT  controls NV, NT n.s.

BVL: 0.3–0.6 and 0.8/controls: 0.3–0.6 and 3.5–4 Older: 2.5–5/controls: 1.5–3

Touch is more efficient in BVL

n.s.

DM-PN: 0.27 and 12.3/controls: 0.26 and 6.5 Not reported

Touch effect is similar between groupsa

Lackner et al. (1999)

RMS COP-ML and Head mean displacement

BVL > controls

NV, LT  V, NT

2

Reginella et al. (1999)

RMS COP-AP, velocity and peak-to-peak displacement

Older > young adults

3

Dickstein et al. (2001)

RMS COP-ML and AP, RMS trunk velocity

DM-PN > controls (COP-ML)

Fixed, touch < NT < sway, touch HT < LT < NT

4

Dickstein et al. (2003)

DM-PN = controls

HT < LT < NT

n.s.

5

Tremblay et al. (2004)

Older > young adults

LT < NT

n.s.

6

Bacsi et al. (2005)

EMG response latencies of the two medial gastrocnemius muscles; total body COP response latencies; and first 75 ms of velocity of COP-AP and ML MSA COP-AP displacement, perceived stability RMS COP-AP and ML, energy at 14–18 Hz

OT > controls

7

Baccini et al. (2007)

Length, area, velocity of COP-AP and ML

Older > young adults

LT  NT (COP-AP only) HT < LT < NT

8

Gomes et al. (2007)

Speed and MSA of COP-ML and AP

DS  CS

LT < NT

Controls, LT  OT, LT Older NT & LT  young NT & LT DS, LT (only ML)  control, LT

9

Bonfim et al. (2008)

ACL > controls

LT < NT

10

Cunha et al. (2012)

Stroke  controls

LT  NT

ACL, LT  controls, LT n.s.

11

Franze´n et al. (2012)

PD-off = controls/PD-on > controls

HT = LT < NT

n.s.

12

Rabin et al. (2013)

MSA COP-AP and ML and peak frequency of COP-AP and ML COP area, mean velocity and mean sway of COP-AP and ML and velocity RMS COP-AP and ML and velocity of COPAP and ML and hip resistive torque MSA COP-AP and ML and body sway at the shoulder

PD > Controls

HT < LT

n.s.

Older: >1/controls: 0.09). 4. Discussion The present systematic review of 12 studies provided evidences of the light touch effect on the postural sway of individuals with balance problems. Although only few studies were performed (considering our inclusion criteria and the number of findings from

the three databases), based on the qualitative analysis, they were all considered to have good quality, with adequate methodological procedures and satisfactory description of the experimental tasks used to investigate their research questions. These descriptions increase the possibility of reproducibility of the studies by other researchers as well as professional could use similar methods for evaluation or intervention programs having the light touch as a strategy for balance control. Thus, it can be assumed that the bias in the performance of the present review was minimized and the findings reported by the eligible studies are reliable. However, in according to the assessment by the two independent reviewers, most of the articles failed in presenting more details about the characteristics of the participants, in particular, from the case groups of individuals with balance problems. Differences between groups in some of these not reported anthropometric characteristics (e.g., body mass and height) could affect the interpretation of the obtained results of the studies and the question if groups had similar characteristics in these studies is still open. Overall, the well-known effect on healthy individuals was observed in individuals with deficits in the central nervous system (such as Parkinson’s disease [16,17], stroke [15] and orthostatic tremor [18]) or in a specific sensory channel (individuals with peripheral neuropathy due to diabetes mellitus [20,24] and with vestibular loss [21], in individuals with lesion in the anterior cruciate ligament, and in older adults [12–14]). Although these individuals presented greater postural sway than healthy ones, they were also able to use the additional somatosensory information provided by the light touch to control the postural sway similarly as healthy individuals. In addition, the postural sway was more reduced with the light touch for elderly [12], bilateral vestibular loss patients [21] and individuals with unilateral anterior cruciate ligament [19] or Down syndrome [23] compared to healthy individuals. Specifically, these individuals take more advantage of the light touch effect compared to healthy individuals. The first aim of this review was to investigate if individuals with balance problems take advantage of the information provided by the use of light touch on an external surface to reduce the postural sway during the maintenance of the upright stance. All eligible studies reported that individuals with balance problems use the additional somatosensory information of the light touch (compared to no touch condition) to reduce their postural sway. These effects were observed independent of the visual condition (vision vs. no vision), support surface (firm vs. foam) and base of support assumed by the participants during the different experimental conditions investigated by the studies. These findings corroborate those from other studies of healthy individuals [1–3,5,11].

Table 5 Quantitative analysis of the most significant outcome for individual studies and percentage of its reduction with the use of light touch.

1 2 3 4 5 6 7 8 9 10 11 12 a

Study

Outcome measures

Lackner et al. (1999) Reginella et al. (1999) Dickstein et al. (2001) Dickstein et al. (2003) Tremblay et al. (2004) Bacsi et al. (2005) Baccini et al. (2007) Gomes et al. (2007) Bonfim et al. (2008) Cunha et al. (2012) Franze´n et al. (2012) Rabin et al. (2012)

RMS COP-ML RMS COP-AP RMS COP-ML COP-ML initial rate of changea MSA COP-AP RMS COP-AP Velocity of COP-AP MSA COP-ML MSA COP-AP MSA COP-AP RMS COP-AP MSA COP-AP

Control group

Case group

No touch (CE)

Touch (CE)

0.40 0.39 0.38 1.61 0.37 2.81 1.58 0.26 1.03 0.34 0.71 3.87 Control group

0.23 0.13 0.26 3.96 0.23 1.62 0.96 0.17 0.67 0.19 0.32 1.75

% Reduction 41.77 66.67 31.58 145.96 37.84 42.35 39.56 35.29 34.95 44.12 55.08 54.78 44.00

No Touch (CE)

Touch (CE)

0.85 0.51 0.45 0.60 0.41 5.08 2.59 0.25 1.52 0.46 0.76 5.80 Case group

0.46 0.25 0.37 1.72 0.20 3.92 1.27 0.16 0.83 0.31 0.32 4.27

The initial rate of change at velocity of 20 cm/s increased with light touch and it was not included in the overall reduction.

% Reduction 46.47 50.98 17.78 186.67 51.22 22.93 51.16 38.00 45.39 32.61 58.21 26.40 40.10

A.M.S. Baldan et al. / Gait & Posture 40 (2014) 1–10

In addition, similar to the findings from healthy individuals, four reviewed studies [12,17,20,24] reported that the reduction of postural sway is related to the amount of force applied on the external surface. That is, the comparison of the amount of postural sway in two conditions of force applied on the bar (LT vs. HT) indicated a more stable position as more vertical force was applied. For example, Dickstein and collaborators [20] observed that individuals with peripheral neuropathy (case group) and healthy individuals (control group) reduced the postural sway in the heavy touch condition. However, because the averaged vertical force exerted on the bar in that condition was 12.3 and 6.5 N for the case and control groups, respectively, it was considered that the touch offered some mechanical support in addition to somatosensory information. In fact, studies reported that a force greater than 4 N could provide some mechanical support [1]. Baccini and collaborators [12] also indicated that older adults took more advantage of the heavy touch as greater reduction of their postural sway was observed. However, the authors did not measure the force applied on the bar and it is not possible to conclude that the effect was due only to the amount of exerted force. In contrast, Franze´n and collaborators [16] reported similar attenuation of postural sway between the LT and HT conditions in Parkinson’s disease; but, once again, they did not report the amount of vertical forces in each condition. Thus, it is possible that the reduction of postural sway is associated to the amount of vertical force, but more studies should be done to support such hypothesis and to describe the relationship between the amount of postural sway and vertical force of the touch, in particular, because in the studies that mentioned this possible relationship the applied forces were not reported or measured [12,16,24]. Overall, most of the studies that investigated the trajectory of COP during the quiet standing in individuals with balance problems observed increased postural sway when compared to healthy (or young in the case of older adults) individuals [12– 15,17–21]. This finding could be attributed to different factors such as the changes in the motor, sensory or central nervous systems leading to more unstable upright position. Because these groups of individuals present greater postural sway due to different balance problems, it could be hypothesized that they would take more advantage of the light effect compared to healthy individuals to attenuate their postural sway. In fact, this hypothesis was confirmed by some studies of the present review [12,19,21,23]; but seven [13–17,20,24] selected studies reported similar effect between the investigated groups. It is clear from these results that the healthy individuals are not the only ones to take benefit of the additional somatosensory information provided by the fingertip touch to control their balance. In fact, the overall reduction of the most significant outcome of each study with the light touch (40% and 44% for control and case groups, respectively, in Table 5) suggested that control and case groups were able to use the additional somatosensory information in a similar way. However, two factors excluded a more precise analysis and conclusion about this question. First, the heterogeneity of the groups of participants in the studies, in which individuals with balance problems from different causes could present different responses to their disabilities. The second factor is related to the use of different dependent measures of COP assessment, which not allowed a more complex statistical comparison of the effects of the use of light touch across studies. Thus only a limited quantitative analysis was performed due to the absence of standardization across postural control studies. Another factor that distinguished the participants of the studies was the magnitude of the applied force on the external surface. Overall, the individuals with balance problems exerted more vertical force than healthy individuals during the light touch

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condition [13–15,18,20]. However, this difference in the magnitude of applied force does not seem to be related to greater reduction of postural sway as some studies [13,15,20] revealed similar effect between groups or even greater effect for healthy individuals [18] with less force applied. Therefore, it could be assumed that the size of the effect of the light touch is not related only to the amount of postural sway in the no-touch condition and the magnitude of the force applied, but to the source of their balance problems. The fact that the amount of applied force during the touch is not the key factor for the improvement in postural control suggests that any contact with an external surface could help individuals with balance problems to reduce their postural sway, for example. This is an important strategy to be recommended for individuals with poor balance. In summary, the results of the present review allowed to conclude that individuals with balance problems are able to use the additional somatosensory information provided by the light touch of the fingertip in contact with the bar to reduce their postural sway. The findings from the present review indicate that this additional somatosensory information is very important to the postural control, in particular when other sensory systems are not available or fully functional (e.g., closed eyes or vestibular loss). Therefore, the instruction to maintain the fingertip lightly touching an external surface could be a strategy to improve the control of upright standing, not only the healthy individuals [1–3,5,11], but also those with balance problems. Thus, movement science professionals could use such strategy during the balance evaluation or in intervention programs for individuals that have greater postural sway during standing. Acknowledgments This work was supported by a FAPESP/Brazil grant (#2010/ 15360-4) to Freitas, S.M.S.F. Araujo is thankful to CNPq/Brazil (#121521/2010-9) and FAPESP/Brazil (#2010/15360-4) for her scholarships. Conflict of interest None declared. References [1] Holden M, Ventura J, Lackner JR. Stabilization of posture by precision contact of the index finger. J Vestib Res 1994;4(4):285–301. [2] Jeka JJ, Lackner JR. Fingertip contact influences human postural control. Exp Brain Res 1994;100(3):495–502. [3] Jeka JJ, Lackner JR. The role of haptic cues from rough and slippery surfaces in human postural control. Exp Brain Res 1995;103(2):267–76. [4] Kouzaki M, Masani K. Reduced postural sway during quiet standing by light touch is due to finger tactile feedback but not mechanical support. Exp Brain Res 2008;188(1):153–8. [5] Lackner JR, Rabin E, DiZio P. Stabilization of posture by precision touch of the index finger with rigid and flexible filaments. Exp Brain Res 2001;139(4): 454–64. [6] Rabin E, DiZio P, Ventura J, Lackner JR. Influences of arm proprioception and degrees of freedom on postural control with light touch feedback. J Neurophysiol 2008;99(2):595–604. [7] Jeka JJ, Easton RD, Bentzen BL, Lackner JR. Haptic cues for orientation and postural control in sighted and blind individuals. Percept Psychophys 1996;58(3):409–23. [8] Duarte M, Freitas SM. Revision of posturography based on force plate for balance evaluation. Rev Bras Fisioter 2010;14(3):183–92. [9] Dickstein R. Stance stability with unilateral and bilateral light touch of an external stationary object. Somatosens Mot Res 2005;22(4):319–25. [10] Freitas SM, Prado JM, Duarte M. The use of a safety harness does not affect body sway during quiet standing. Clin Biomech (Bristol Avon) 2005;20(3):336–9. [11] Krishnamoorthy V, Slijper H, Latash ML. Effects of different types of light touch on postural sway. Exp Brain Res 2002;147(1):71–9. [12] Baccini M, Rinaldi LA, Federighi G, Vannucchi L, Paci M, Masotti G. Effectiveness of fingertip light contact in reducing postural sway in older people. Age Ageing 2007;36(1):30–5.

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