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Journal of Exercise Physiology onli ne

October 2018 Volume 21 Number 5

EditorOfficial- in Research- Chief Journal of JEP online Tommythe American Boone , PhD Society, MBA of ReviewExercise Board Physiologists Cardiorespiratory F itness of V isually I mpaired Todd Astorino, PhD Julien Baker,ISSN 1097 PhD - 9751 F ootballers through D irect and Indirect Methods: Steve Brock, PhD A Pilot Study Lance Dalleck, PhD Eric Goulet, PhD 1 , 2 3 Robert Gotshall, PhD Pablo R. O. Silva Míriam Mainenti , Lilian Felicio , Arthur Alexander Hutchison, PhD Ferreira 1 , Agnaldo Lopes 1 , Marcus Bernhoeft 4 , *Patrícia S. M. Knight - Maloney, PhD Vig ário 1 Len Kravitz, PhD James Laskin, PhD 1 Yit Aun Lim, PhD Postgraduate Program in Rehabilitation Sciences, Centro Lonnie Lowery, PhD Universitário Augusto Motta (UNISUAM), Rio de Janeiro, RJ, Derek Marks, PhD Brazil , 2 Physical Education Colleg e of the Brazilian Army , Rio Cristine Mermier, PhD de Janeiro, RJ, Brazil , 3 Faculty of Physical Education and Robert Robergs, PhD Physiothera py, Federal University of Uberlândia, Minas Chantal Vella, PhD 4 Dale Wagner, PhD Gerais, MG, Brazil , Institute of Pediatrics and Childcare Frank Wyatt, PhD Martagão Gesteira; Federal University of Rio de Jane iro, Rio Ben Zhou, PhD de Janeiro, RJ, Brazil

ABSTRACT

Official Research Journal Silva PRO, Mai nenti, M, Feli cio L, Ferreira A , Lopes A, of the American Society of B ernhoeft M, Vigário PS. Cardiorespiratory F itness of Exerc ise Physiologists V isually I mpaired F ootballers through D irect and I ndirect

M ethods: A P ilot S tudy. JEP online 20 1 8 ; 21 ( 5 ): 170 - 183 . The ISSN 1097 - 9751 purpose of this study was to compare the cardiorespiratory

fitness of visually impaired (VI) footballers with non - blind footballers and to examine the validity of the 20 - m shuttle run test in estimating cardiorespiratory fitness in VI footballers. A cross - sectional study was conducted with 8 VI football 5 - a - side players and 7 age - match ed non - blind futsal players. The groups performed the cardiopulmonary exercise testing (CPE T ) and the 20 - m shuttle run to obtain the maximal oxygen consumption (VO 2 max). The VI footballers presented a lower VO 2 max than the non - blind footballers on both the CPE T ( P = 0.04) and the 20 - m shuttle run ( P < 0.05). The 20 - m shuttle run test underestimated VO 2 max in the VI footballers ( P = 0.02). The agreement between the estimated and measured VO 2 max values were better among non - blind footballers (ICC 2,1 = 0.72) than the VI footballers (ICC 2,1 = 171

0.58), confirmed by Altman and Bland's graphical approach. The VI footballers presented a lower cardiorespiratory fitness than the non - blind footballers , which was observed through direct and indirect methods. The 20 - m shuttle run test underestimate d the VO 2 max and is not a valid method to assess cardiorespiratory fitness in VI footballers .

Key W ords : F ootball, O xygen C onsumption , Visual Impairment

INTRODUCTION

The number of individuals with disability engaging in sports has e xponentially increas ed in recent years. In the Paralympic Summer Games, disabled individuals may compete in 22 sports modalities according to six main impairments types: visual impairment , cerebral palsy , intellectual impairment, limb deficiency or amputat ion, spinal cord - related disability, and les autre s (i.e., it includes those ones who do not fit into these five aforementioned categories) (29). For instance, football 5 - a - side is an adapted sport for people with visual impairments in which each team com prises four players who must have total vision loss ( i .e., a B1 level of visual impairment ) and one goalkeeper who can be either visually impaired or fully sighted. The rules of football 5 - a - side are similar to those of conventional futsal with some modifi cations such as the ball that makes noise when it moves and a guide is placed behind the opponent’s goal to orient the players at the time of the kick (20). This modality involves intermittent efforts that require both aerobic and anaerobic metabolic deman ds (8). Therefore, footballers should have well - developed aerobic and anaerobic fitness to achieve optimal performance in this modality (1).

The maximal oxygen uptake (VO 2 max) during physical effort is the most commonly used measurement to describe an in dividual’s aerobic fitness (5) , and it can be obtained through direct and indirect methods (2,14). Cardiopulmonary exercise testing (CPET) is a noninvasive and direct method that evaluates the integrative response of the cardiovascular and respiratory syst ems during an effort through gas exchange analysis. Although CPET provides a valid and reliable measurement of VO 2 max , it requires specialized professionals and sophisticated equipment that is also a time consuming process (4). Indirect methods of VO 2 max estimation have been developed, which are simple to perform, have low financial cost, and can be applied to large and varied populations in different places. For instance, the Léger Shuttle Run Test , also called the 20 - m shuttle run (22,23) is a maximal m ultistage exercise test largely used to estimate the VO 2 max of different populations, including athletes (9,26). The measurement and estimation of variables, however, are susceptible to some degree of error (24). Therefore, it is very important to determi ne to which extent indirect methods truly provide reliable measures of the phenomenon that is being investigated. Otherwise, daily clinical and practical decisions may be made with potential biases, which in the case of sports may directly influence the pe rformance of athletes.

Despite its popularity among adapted sports, football 5 - a - side has rarely been the object of scientific investigations. To date, little is known about the aerobic fitness parameters of blind footballers (7), and yet this information could be useful for maximizing training program periodization and perfo rmance. Moreover, to the author s ’ knowledge, no previous study has investigated the validity of an indirect test to estimate the VO 2 max of blind footballers. Thus, the aims of this st udy were to investigate the cardiorespiratory fitness of blind footballers 172 comparing them with non - blind footballers, and to examine the validity of the 20 - m shuttle run test in estimating the cardiorespiratory fitness of blind footballers.

METHODS

Stud y and S ample A cross - sectional, pilot study was conducted with 8 football 5 - a - side line players, who were all classified in the B1 visual class and who competed on a second division team in the Brazilian National Championship of Football 5 - a - side. A group of 7 age - matched futsal players (Rio de Janeiro, Brazil, second division) with no visual impairments was also included in the study as the control group. During the study, both groups of footballers were in the specific preparatory phase of their training periodization.

The inclusion criteria were: (a) male aged >18 y rs ; (b) practice of competitive football 5 - a - side or futsal for at least 1 yr ; and (c) regularly trained at least 3 times ·w k - 1 . Goalkeepers, beta - blocker users, smokers, and subjects with any muscle or joint injuries that could limit the test performance were excluded from the study. The study was submitted to and approved by the local ethical committee (CAAE: 17691113.1.0000.5235) , and all subjects gave their written consent before study entry .

Direct M easurement of C ardiorespiratory F itness All subjects were submitted to symptom - limited CPET performed on a treadmill, using the ramp protocol proposed by Silva and Torres (27) in a study conducted on Brazilian Paralympic athletes. The protocol c onsisted of 5 min of warm - up at a velocity of 5.0 km·h - 1 and successive increases of 1.0 km·h - 1 during each minute of testing.

Respiratory gas exchange was sampled from a facemask connected to a flow meter and a metabolic gas analyzer (FitMate PRO, Cosme d, Italy). The ventilation flow and expired oxygen fraction were measured and recorded breath - by - breath during exercise.

A 12 - lead electrocardiogram (WinCardio, Micromed, Brazil) was continuously monitored during exercise and recovery. During every 3 min of the test, the systolic and diastolic blood pressure (SBP and DBP, respectively) values were measured ( using a mercury sphygmomanometer, Narcosul, 1400 - C), and the subjects were questioned about their perception of fatigue using the Borg Scale of Perceiv ed Exertion.

The subjects were encouraged to perform using their maximal effort. The CPET was considered maximal when one or more of the following parameters were obtained: a VO 2 plateau, maximum heart rate (HR max ) > 180 beats · min - 1 (bpm), or a rating on the Bor g Scale of Perceived Exertion > 18 (19). The t est interruption criteria were based on the American College of Sports and Medicine recommendations (3).

The following variables were considered for statistical analysis: oxygen uptake ( VO 2 max ; mL · kg - 1 · min - 1 ), minute ventilation (VE; L · min - 1 ), heart rate (HR; b eats·min - 1 ), S BP and D BP (mmHg), velocity (km · h - 1 ), and total test duration (min: sec ).

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Indirect E stimation of C ardiorespiratory F itness Blind and non - blind footballers performed the 20 - m shut tle run test (22) with a mean interval of 1 w k after CPET. Both CPET and the 20 - m shuttle run test were performed at the same time of day.

All subjects continuously ran back and forth betwee n two points that were 20 m apart. The runs were synchronized wit h a “ beep ” sound from a prerecorded compact disc. As the test proceeded, the interval between each “ beep ” decreased, requiring the athletes to increase their speed over the course. Each successful run of 20 m was considered a completed shuttle. The test wa s interrupted when the athlete failed to follow the set pace two consecutive times. VO 2 max was estimated using the equation (22,23): VO 2 max = - 24.4 + 6(stage). H eart - rate was monitored through a heart - rate monitor (RS800CX, Polar, Finland).

For the blin d footballers, a guide was placed on the two extreme points to orient them during the test. All players performed a test familiarization.

Statistical A nalys e s

Descriptive statistics are shown as mean ± standard deviation (SD) and [minimum - maximum]. Betwe en - group comparisons , blind vs. nonblind footballers , were made with the Mann - Whitney U - Test. The Wilcoxon test was used compare the measured and the estimated VO 2 max within - groups, and the maximal CPET and 20 - m shuttle run test HRs.

The validity of the 20 - m shuttle test in estimating VO 2 max was assessed by: ( a) the two - way random - effects intraclass correlation coefficient using an absolute agreement definition for single measurements (ICC 2,1 ) and constructing a regression plot. An ICC lower than 0.6 was considered poor (11); and ( b) Altman and Bland's limits of agreement, based on the differences between the measured VO 2 max values and the estimated VO 2 max (Y - axis), and the mean values between the measured VO 2 max and the estimated VO 2 max (X - axis) (6). The lower limit was calculated as the mean of the differences - 2SD and the upper limit as the mean of the differences +2SD (Microsoft Office Excel 2007).

Statistical analyses were performed using SPSS 13.0 software for Windows (SPSS Inc., Chicago, IL), a nd differences were considered statistically significant at P< 0.05.

RESULTS

General C haracteristics There were no differences between the visually impaired footballers and non - blind footballers with regard to age, body mass, and height (Table 1). Visuall y impaired footballers presented lower number of years of training than non - blind footballers ( P= 0.04), with the same number of training sessions/week and hours of training/week.

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Table 1. General C haracteristics of B lind and N on - B lind F ootballers .

Visually Non - B lind P - value* I mpaired F ootballers F ootballers (n=07) (n=08)

Age (y rs) 25.0 ± 5.3 26.3 ± 5.6 0.62 (17.0 – 30.0) (20.0 – 33.0)

Body M ass (kg) 72.5 ± 14.4 72.1 ± 7.4 0.87 ( 50.0 – 94.8) (60.8 – 83.0)

Height (cm) 170. 7 ± 3.8 173.1 ± 5.4 0.44 (164.0 – 176.0) (165.0 – 183.0)

Years of T raining 8.5 ± 3.3 14.6 ± 5.4 0.04 (6.0 – 15.0) (6.0 – 20.0)

Number of T raining 4.5 ± 0.9 4.6 ± 0.8 1.00 S essions/ W eek (3.0 – 5.0) (3.0 – 5.0)

Hours of T raining/ W eek 120 ± 0.0 137.1 ± 16.0 0.07 (120.0 – 120.0) (120.0 – 150.0) Descriptive analysis are present and mean ± sta ndard - deviation ( minimum – maximum ) ; *Mann - Whitney U - Test; S tatistical significance for P <0.05

Cardiopulmonary E xercise T esting The CPET data are presented in Table 2. Prior to CPET, mean resting SBP and DBP values between groups were not significantly different. Visually impaired footballers showed statistically higher resting HR values. The groups also differed significantly in terms of total exercise duration, maximal velocity achieved at the peak of exercise and VO 2 max (all P< 0.05), with all values being lower in the visually impaired footballers.

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Table 2. Cardiopulmonary E xercise T esting D ata of V isually I mpaired and N on - B lind G ootballers. Visually I mpaired Non - B lind P - F ootballers F ootballers value* (n=08) (n=07) Prior to C ardiopulmonary E xer cise T esting - 1 HR rest (b eats· m in ) 81.0 ± 10.2 65.7 ± 8.4 0.01 (64.0 – 91.0) (53.0 – 77.0) SBP rest (mmHg) 123.8 ± 15.1 124.3 ± 14.0 0.90 (110.0 – 160.0) (110.0 – 150.0) DBP rest (mmHg) 74.3 ± 7.3 85.7 ± 12.7 0 .09 (70.0 – 90.0) (70.0 – 100.0) Peak of E xercise Total E xercise D uration 15:53 ± 2:05 19:47 ± 2:43 0.02 (min:s ec ) (12:31 – 18:50) (14:46 – 22:49) Maximal V elocity (km · h - 1 ) 13.9 ± 1.9 16.1 ± 1.5 0.01 ( 11.0 – 16. 0) (13.0 – 17.0) - 1 - 1 VO 2 m ax (mL· k g · min ) 46.3 ± 6.7 54.0 ± 5.9 0.04 (34.4 – 51.7) (46.0 – 62.1) VE p eak (L ·min - 1 ) 106.3 ± 27.5 137.1 ± 24.5 0.08 (60.9 – 136.0) (107.2 – 157.7) - 1 HR p eak (b eats· m in ) 182.9 ± 6.5 187.2 ± 6.8 0.14 (175.0 – 195.0) (178.0 – 198.2) SBP p eak (mmHg) 150.0 ± 13.1 164.3 ± 19.9 0.12 (140.0 – 170.0) (140.0 – 190.0) DBP p eak (mmHg) 90.0 ± 5.3 92.9 ± 7.6 0.34 ( 80.0 – 100.0 ) (80.0 – 100.0)

HR = H eart R ate; VO 2 = O xygen U ptake; VE = M inute V entilation; SBP = Systolic A rterial B lood P ressure; DBP = D iastoli c B lood P ressure; Descriptive analysis are present and mean ± standard - deviation (minimum – maximum) ; * Mann - Whitney U - Test; S tatistical significance for P <0.05

20 - m Shuttle R un T est The 20 - m shuttle run data are presented in Table 3. Before the 20 - m shutt le run test, the visually impaired footballers presented a higher resting HR in comparison to the non - blind footballers ( P< 0.05). At the end of the test, the visually impaired footballers presented lower values for the maximal speed, total distance, comple ted stage, and VO 2 max than the non - 176 blind footballers (all P< 0.05) . The groups achieved a similar HR at the end of the test. In both groups, no differences between the HR max achieved at the end of the 20 - m shuttle run and the HR max achieved at the end o f the CPET (visually impaired footballers P= 0.24; non - blind footballers P= 0.25), demonstrating that the groups reached the same level of effort on the two tests.

Table 3. 20 - m S huttle R un T est D ata of V isually I mpaired and N on - B lind F ootballers . Visuall y Non - B lind P - value* I mpaired F ootballers F ootballers (n=07) (n=08)

HR rest (beats·min - 1 ) 101.9 ± 15.2 87.1 ± 5.6 0.01 ( 76.0 – 123.0) (75.0 – 92.0)

- 1 HR max end of the test (beats·min ) 186.8 ± 6.8 190.9 ± 2 .6 0.27 ( 178.0 – 196.0) ( 187.0 – 194.0)

Completed S tage 6.2 ± 1.3 10.8 ± 1.9 (4.3 – 8.1) (9.1 – 14.2) <0.05

Maximal S peed (km·h - 1 ) 11.0 ± 0.7 13.1 ± 1.0 <0.05 ( 10.0 – 12.0] (12.5 – 15.0)

Total D istance (m) 845.7 ± 263.0 1773.3 ± 459.9 <0.05 (520.0 – 1200.0) ( 1400.0 – 2540.0)

VO max (mL·kg - 1 ·min - 1 ) 41.6 ± 4.2 54.5 ± 5.9 2 estimated <0.05 (35.6 – 47.6) (50.6 – 65.6)

HR = H eart R ate; VO 2 = O xygen U ptake; Descriptive analysis are present and mean ± standard - deviation (minimum – maximum); * Mann - Whitney U - Test; S tatistical significance for P <0.05

Validity In the non - blind footballers, there was no statistical evidence of difference between the estimated and the measured VO 2 max ( P = 0.61), whereas i n visually impaired footballers the 177

VO 2 max estimated though the 20 - m shuttle run test was lower than the VO 2 max measured through the CPET ( P = 0.02). The agreement between the estimated and measured VO 2 max values was better in nonblind footballers (ICC 2 ,1 = 0.72) than in visually impaired footballers (ICC 2,1 = 0.58), as shown in Figure 1.

Figure 1. Regression P lot between M easured and E stimated VO 2 max of V isually I mpaired and N on - B lind F ootballers.

Altman and Bland's graphical approach pointed out m ore clearly that in the group of visually impaired footballers there was a trend o f higher values in the measured VO 2 max , although the differences were within the limits of agreement. This is due to the fact that seven of the eight players have presented positive differences between the measured and the estimated VO 2 max (above the X axis), suggesting the presence of fixed bias (Figure 2).

Figure 2. Altman and Bland’s G raphical A pproach for V alidity between M easured and E stimated VO 2 max in V isually I mpaired F ootballers. 178

For the verification of the possible presence of pr oportional bias, the correlation between the difference between the measured VO 2 max and the estimated VO 2 max (X and Y axis) was calculated. As there was no statistically significant correlation (r = 0.67, P = 0.07), it appeared not to have proportional b ias. Among the non - blind footballers, 4 of the 7 players presented a negative difference, that is, higher values of estimated VO 2 max . The correlation between the difference between the measured VO 2 max and the measured VO 2 max measurements (X and Y axis ) showed that there was no trend of proportional bias (r = 0.004; P = 0.992) (Figure 3). As noted among visually impaired footballers, all differences were within the calculated limits of agreement.

Figure 3. Altman and Bland’s G raphical A ppr oach for V alidity between M easured and E stimated VO 2 max in N on - B lind F ootballers.

DISCUSSION

The purpose of this study was to compare the cardiorespiratory fitness of blind footballers with non - blind footballers, and to examine the validity of the 20 - m shuttle run test in estimating the cardiorespiratory fitness of blind footballers. Assessment of cardiorespiratory fitness is of great importance in sports to achieve better planning, monitoring, and periodization of training. Concerning football 5 - a - side, it is particularly important because the sport involves intermittent efforts that require both aerobic and anaerobic demands (8). To our knowledge, this is the first study that has investigated the cardiorespiratory fitness of visually impaired footballer s through direct and indirect methods, making comparisons with non - blind footballers. The main findings of this study were that visually impaired footballers presented a lower cardiorespiratory fitness than non - blind footballers and that the 20 - m shuttle r un test significantly underestimated the VO 2 max in visually impaired footballers in comparison to CPET.

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It is important to notice that although visually impaired footballers had lower cardiorespiratory fitness than non - blind footballers, all visually imp aired participants presented VO 2 max values within the predicted range associated with good cardiorespiratory health for their age and sex (15). A study revealed that visually impaired goalball players had better physical fitness, including body compositio n, aerobic and musculoskeletal function than less active adolescents with visual impairments (21). Similarly, visually impaired students benefited from 10 w ks of rope jumping exercise training in terms of their aerobic capacity and flexibility (10). These and our findings have important clinical and practical meanings because there is a high prevalence of sedentary behavior in people with disabilities , which may increase the risk of cardiovascular diseases (30,16) . Thus, individuals with visual impairments should be encouraged to include physical activity in their daily routines to maintain a healthier lifestyle.

Concerning the cardiorespiratory fitness of visually impaired and non - blind footballers, we have s ome hypotheses that could explain the difference s observed in the present study. First, already in the 1980s it was argued that people with visual impairment have a slower walking pattern when performed independently compared to what is presented when accompanied by a guide (12). Recent studies added mo re differences in gait pattern, such as shorter stride length, prolonged stance phase, earlier heel strike, increased step width, and slower speed (18,19,28). Regarding specifically the sport’s modality, although football 5 - a - side has rules and technical c haracteristics adapted from conventional futsal (20), we suppose that the absence of vision could influence game dynamics, including speed and intensity. Magno e Silva et al. (25) reported that the players generally have an adapted running pattern characte rized by an anterior position of the trunk, with the head and arms in front of the body. Together, these adaptations could slow the players’ movement. Consequently, the intensity of the game and training could be lower than that for conventional futsal, le ading to cardiorespiratory differences.

In addition, in football 5 - a - side, footballers must say the word “go” or “ voy ” when moving toward the player that is with the ball (20) , h owever, this rule does not completely prevent collisions between the athlete s. In Brazilians visually impaired footballers, for example, a study revealed that 84.6% had some kind of football - related injury. The main cause was traumatic contact, principally of the lower limbs and head (25). In the Rio 2016 Summer Paralympic Games, football 5 - a - side was the sport that presented the highest injury incidence rate (13), as ever seen in London 2012 (29). Therefore, some players may be afraid of hitting othe r players or even being injured and , consequently , may move more slowly during the game and in training when compared with non - blind footballers.

In the reviewed literature, we found only one study that evaluated the cardiorespiratory fitness of visually impaired footballers (7). Six players of the Brazilian 5 - a - side football team perf ormed the 20 - m shuttle run test and showed slightly higher mean oxygen consumption (44.7 ± 4.7 mL·kg - 1 ·min - 1 ) than observed in the present study ( 41.6 ± 4.2 mL · kg - 1 · min - 1 ). Th is differences may be influenced by the players’ competitive levels and training routine.

With respect to the estimation of the VO 2 max, our results showed that although blind footballers reached the same intensity of effort on both tests (HR were similar for both CPET and 20 - m shuttle run), their VO 2 max values were systematically l ower on the 20 - m shuttle run test compared to the CPET, except for one player. In the agreement analysis, we observed that the ICC was below the proposed cut - off point for useful measures, indicating 180 poor agreement between the two methods (11), which was a lso confirmed by Altman and Bland's graphical approach.

To date, little is known about the overall validity of physical tests for individuals with visual impairments. We found no studies that evaluated the validity of the 20 - m shuttle run test in this po pulation. However, we have some hypotheses that may be useful in explaining the differences observed between the measured and the estimated VO 2 max. The first is related to the test design, which seems to have an important visual component. In the 20 - m shu ttle run test, the participants r a n back and forth between two points. In our study, although a guide was placed on the two extreme points to orient the players during the test, the guide cannot assure that the players will run a straight course. Another p oint that should be taken into account is that the players performed the course without a sight partner and some of them may have felt insecure when performing the test, mainly in the stages involving high speeds.

Limitations in this Study

One limitation of this study is the sample size. However, football 5 - a - side players are a population with specifics characteristics that make them different from nonathletic individuals with visual impairments. Other studies of this population have also had small sample s sizes (7,25). Another data characteristic that co uld have influenced our results was the lower values for years of training presented by th e visually impaired footballers when compar ed to non - blind athletes. However, considering that even lower it was a high mean value for “years of training” (8 .5 y rs for the visually impaired group), the bias was minimized. Furthermore, to our knowledge, this is the first study that has investigated cardiorespiratory fitness in blind footballers. We used the CPET as the gold standard method and compared the results to those of an indirect method that is commonly used to estimate the cardiorespiratory fitness of footballers.

CONCLUSIONS

Visually impaired footballers had lower cardiorespiratory fitness than non - blind foo tballers, and the 20 m - shuttle run test was not a valid method to estimate VO 2 max in this population. The findings here observed and discussed suggest that visually impaired individuals, even athletes, compose a population in which strategies for achievin g the real maximum physical development should be developed and applied considering the deficiency - related limitations.

ACKNOWLEDG MENTS FAPERJ - Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro

Address for correspondence: Patrícia dos Santo s Vigário, Postgraduate Program in Rehabilitation Sciences, Augusto Motta University (UNISUAM), Praça das Nações 34, Bonsucesso, Rio de Janeiro, RJ, Brazil, ZIP code 21041 - 010, E mail: patriciavigario@ yahoo.com.br

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REFERENCES

1. Alvarez JC, D’Ottavio S, Ve ra JG, Castagna C. Aerobic fitness in futsal players of different competitive level. J Strength Cond Res . 2009;23(7): 2163 - 2166.

2. Al - Rahamned H, Eston R. Estimation of peak oxygen uptake fro m peak power output in able - bodied and paraplegic individuals. J Exerc Sci Fit . 2012;10(2): 78 - 82.

3. American College of Sports Medicine. ACSM's G uidelines for E xercise T esting and Prescription. (8th Edition ). Philadelphia , PA: Lippincott Williams & Wilkins , 2009.

4. Balady GJ, Arena R, Sietsema K, Myers J, Coke L, Fletcher GF, Forman D, Franklin B, Guazzi M, Gulati M, Keteyian SJ, Lavie CJ, Macko R, Mancini D, Milani RV. Clinician's Guide to cardiopulmonary exercise testing in a dults : A scientific statement from the American Heart Association. Circ . 2010;122(2): 191 - 225.

5. Bassett Junior DR, Howley ET. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med Sci Sports Exerc . 2000;32(1): 70 - 84.

6. Bland JM, Altman DG. Measuring agreement in method comparison Studies. Stat Methods Med Res . 1999; 8(2):135 - 160.

7. Campos LFCC, Silva AAC, Santos LGTF, C osta LT, Montagner PC, Borin JP, Araujo PF, Gorla JI. Effects of training in physical fitness and body composition of the Brazilian 5 - a - side football team. Revista Andaluza de Medicina del Deporte . 2013; 6(3): 91 - 95 .

8. Castagna C, D’Ottavio S, Granda VJ, Barbero AJC. Match demands of professional Futsal : a case study. J Sci Med Sport . 2009;12(4): 490 - 494.

9. Castagna C, Manzi V, Impellizzeri F, Weston M, Barbero AJC. Relationship between endurance field tests and match p erformance in young soccer players. J Strength Cond Res . 2010;24(12): 3227 - 3233.

10. Chen CC, Lin SY. The impact of rope jumping exercise on physical fitness of visually impaired students . Res Develop Disab. 2011;32(1): 25 - 29.

11. Chinn S. Repeatability and method comparison . Thorax . 1991;46(6): 454 - 456.

12. Clark - Carter DD, Heyes AD, Howarth CI. The Efficiency and walking speed of visually impaired people. Ergonomics . 1986;29(6): 779 - 789.

13. Derman W , Runciman P , Schwellnus M , Jordaan E , Blauwet C , Webborn N , Lexell J , van de Vliet P , Tuakli - Wosornu Y , Kis sick J , Stomphorst J . High precompetition injury rate dominates the injury profile at the Rio 2016 Summer Paralympic Games: A prospectiv e cohort study of 51 198 athlete days. Brit J Sports Med . 2018; 52(1):24 - 31.

182

14. Evans HJ, Ferrar KE, Smith AE, Parfitt G, Eston RG. A systematic review of m ethods to predict maximal oxygen uptake from submaximal, open circuit spirometry in healthy adults. J Sci Med Sport . 2015; 18(2):183 - 188.

15. Fletcher GF, Balady GJ, Amsterdam EA, Chaitman B, Eckel R, Fleg J, Froelicher VF, Leon AS, Piña IL, Rodney R, Simons - Morton DA, Williams MA, Bazzarre T. Exercise standards for testing and training : A statement for healthcare professionals from the American Heart Association. Circ . 2001;104(14): 1694 - 1740.

16. Greguol M, Gobbi E, Carraro A. Physical activity practice , body i mage and visual impairment : A comparison between Brazilian and Italian children and adolescents. Res Develop Disab. 2014;35(1): 21 - 26.

17. Hallemans A, Ortibus E, Meire F, Aerts P. Low vision affects dynamic stability of gait. Gait Post . 2010;32(4): 547 - 551.

18. Hallemans A, Ortibus E, Truijen S, Meire F. Development of independent locomotion in children with a severe visual impairment. Res Develop Disab. 2011;32(6): 2069 - 2074.

19. Howley ET , Bassett Junior DR, Welch HG. Criteria for maximal oxygen uptake : R eview and commentary . Med Sci Sports Exerc . 1995;27(9): 1292 - 1301.

20. International Blind Sports Federation (IBSA). Futsal laws of the game 2009 - 2013 B1 & B2/B3 categories adopted by the IBSA Futsal Subcommittee 2009. Retrieved 02/04/2014 (Online) . http://www.handisport.be/documents/Document%20sport/5aside %20Rules%202009 - 2013.pdf

21. Karakaya IC, Aki E, Ergun N. Physical fitness of visually im paired adolescent goalball players . Percept Motor Skills . 2009; 108 (1): 129 - 133.

22. Leger LA, Lambert J. A maximal multistage 20 - m shuttle run test to predict VO 2 max. Eur J Appl Physiol . 1982:49(1): 129 - 133.

23. Leger LA, Mercier D, Gadoury C, Lambert J. The multistage 20 metre shuttle run test for aerobic fitness . J Sport Sci . 1988;6: 93 - 101.

24. Luiz RR, Costa AJ, Kale PL, Werneck GL. Assessment of agreement of a quantitative variable: a new graphical approach. J Clin Epidemiol . 2003; 56(10):963 - 967.

25. Magno e Silva MP, Morato MP, Bilzon JL, Duarte E. Sports injuries in Brazilian blind footballers. Inter J Sports Med . 2013;34(3): 239 - 243.

26. Nassis GP, Geladas ND, Soldatos Y, Sotiropoulos A, Bekris V, Souglis A. Relationship between the 20 - m multistage shuttle run test and 2 soccer - specific field tests for the assess ment of aerobic fitness in adult semi - professional soccer players. J Strength Cond Res . 2010;24(10): 2693 - 2697.

183

27. Silva AC, Torres FC. Ergoespirometria em atletas paraolímpicos brasileiros. Revista Brasileira de Medicina do Esporte . 2002;8(3): 107 - 116.

28. Tomomitsu MS, Alonso AC, Morimoto E, Bobbio TG, Greve JM. Static and dynamic postural control in low - vision and normal - vision adults . Clinics (São Paulo) . 2013; 68 (4): 517 - 521.

29. Webborn N , Cushman D , Blauwet CA, Emery C , Derman W . The Epidemiology of injuries in football at the London 2012 Paralympic Games. PM&R . 2016; 8(6):545 - 5 52.

30. Webborn N, Van de Vliet P. Paralympic medicine . Lancet . 2012; 380 (9836) : 65 - 71.

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