Sport is meaningful and important in the lives of many people, including those with mental retardation (MR) (31). MR could be considered a significant subaverage general intellectual functioning existing concurrently with deficits in adapted behavior and manifested during the developmental period. MR begins before age 18 but may not always be of lifelong duration, and it is always associated with other psychological behaviors or neurological problems (1). Regular physical fitness activity throughout life is encouraged as being important for preventing diseases and promoting physical and emotional well-being (4,11,27). Many studies reported that individuals with MR demonstrated poor levels on standard fitness tests, in particular on measures of cardiovascular endurance, body composition, muscular endurance and strength, and motor coordination (5,7,13,17,22,27,31). The low levels on fitness tests could be attributed to 5 potential factors: (a) sedentary lifestyle and fewer opportunities for participation in structured physical activity programs; (b) physical characteristics such as short stature; (c) lack of coordination and efficiency; (d) infrequent opportunities to practice test items; and (e) lack of motivation during testing and tendency to stop when uncomfortable (17). These factors suggest that people with MR are in considerable health risk (7,28). Therefore, improved fitness should promote an active lifestyle, decrease health risks, and increase work capacity, which may further decrease the need for premature institutionalization (7,11,13). The determinants that define health-related physical fitness are body composition, cardiovascular endurance, flexibility, muscular endurance, and muscular strength (7,9). There is a general perception that the prevalence of overweight status/obesity is greater among populations with MR compared with populations without disability. Inactivity and inappropriate eating habits may be a major cause of the high obesity rates of individuals with MR (11,25). It is possible that the prevalence of obesity among persons with MR is influenced by the fact that a substantial percentage of people with MR is composed of individuals with Down syndrome (DS). Anatomical and physiological deviation from the norm is common among people with DS (11). Therefore, people with MR generally demonstrate improved health-related physical fitness parameters when exposed to structured exercise regimens (7).
Moreover, sport through a standard training and competition could be useful for testing personal limits and pursuing athletic dreams and goals (31). Track and field has become one of the most popular individual sports for people with MR, both for recreational reasons and for motor skills and fitness development (31). Moreover, track and field for athletes with MR includes all fundamental movements such as walking, running, jumping, and throwing (9). How to improve athletic performance is a primary concern for coaches and researchers on the International Paralympics Committee (IPC). Athletes' performances may be represented by the official results in a specific championship. To help athletes perform successfully in their competitions, important factors related to a successful performance should be identified. These fundamental factors have not been investigated for athletes with MR in track and field. The relationship between sport performance and fundamental factors was studied in other sports-for example, in wheelchair basketball (32) and in volleyball for athletes without disability (12). Therefore, the aims of this study were to assess the contributions of selected fundamental factors to the athletic performance in adult individuals with MR and to analyze the correlation of each selected fundamental factor with subjects' MR levels. This investigation would show (a) the possibility to determine the contributions of selected factors to the athletic performance, and (b) the opportunity for athletes with mild MR to achieve better performances in track and field than athletes with severe MR.
Experimental Approach to the Problem
The experimental protocol was conducted in 3 different periods. During the period 1 (September), athletes passed an obligatory medical-psychiatric and physical examination. During the period 2 (October-May), track and field training began and improved. The athletes participated in a 7-month specific training program of 3 hours per week. Training programs were designed to allow each athlete to progressively achieve their optimal performance. The training was composed of 2 phases: (a) all athletes performed exercises to improve muscular strength, aerobic power, speed, flexibility, and coordination skills; and (b) each athlete performed a specific training in relation to the selected competitions where they will participated. During the 2008 Regional Track and Field Individual Championships (Lazio, Italy), organized by CIP, the athletes took part in 1 or 2 competitions (running or field events) selected within 1 of the 2 ability levels: Level I (60-m run, 300-m run, 400 m in walking, standing long jump, and vortex throw) or Level II (100-m run, shot put, and long jump). The athletes with fewer physical abilities performed in Level I, which included no agonistic competitions. The athletes with good physical abilities performed in Level II, which included agonistic competitions. The inclusion in 1 of the 2 ability levels depended on the coach's subjective evaluation of the athlete's physical abilities.
To investigate the hypotheses of this study, a transversal research design was applied. Therefore, stepwise regression analysis was computed between performances (dependent variables) and the selected fundamental factors (independent variables) (Table 1).
Twenty-nine trained athletes with MR (17 males and 12 females) volunteered to participate. Mean age was 32.8 ± 6.1 years. The height, weight, body mass index (BMI), and %body fat of male athletes were 167 ± 8.0 cm, 80.1 ± 14.4 kg, 29 ± 5.6 kg/m2, and 25 ± 5.1, respectively. The height, weight, BMI, and %body fat of female athletes were 160 ± 7.0 cm, 73.6 ± 11.1 kg, 28.8 ± 4.0 kg/m2, and 25.7 ± 5.1, respectively.
All subjects lived at home or in group settings, and none was institutionalized. They were classified as having mild (n = 9), moderate (n = 8), severe (n = 9), and profound (n = 3) MR. All participants took part in regional and national track and field events, and they performed either no agonistic competitions (Level I, n = 20) or agonistic competitions (Level II, n = 9).
All the subjects signed written informed consent forms that were reviewed by the Institutional Review Board for human subjects of the University of Rome “Foro Italico” to ensure the subjects were knowledgeable of the normal risks and procedures involved in the study. The written informed consent form was read aloud to participants if they were unable to read. A caregiver signed the form if a participant was unable to provide their own consent.
The criteria used to select participants were that they qualified for the 2008 Regional Track and Field Individual Championships, organized by the Italian Paralympics Committee (CIP) and that they had at least 3 years of track and field training. All participants underwent a medical-psychiatric examination conducted by a mental health staff to assess their level of MR and a physical examination performed by a specialist in sports medicine for athletic eligibility.
Exercise Testing and Measurements
Prior to performing the anthropometric measures and fitness test battery, participants had a variable number of familiarization sessions depending on how fast they became accustomed to field tests. They were helpful in teaching participants the correct exercise execution model.
The fundamental factors included athletes' anthropometric measurements, physical fitness, and coordinative abilities assessed through modified and validated tests for individuals with MR (4,10,16,24,31).
Anthropometric measurements followed the procedures of Gordon et al. (14) and included measurements of height, body weight, BMI, and sum of 4 skinfold measurements (biceps, triceps, subscapular, and suprailiac locations) that were recorded by a trained trainer using a Harpenden skinfold caliper both in women and men. The sum of the 4 measurements was used to obtain athletes' %body fat scores, using the equation proposed by Durnin and Womersley (8).
Physical fitness and coordinative test battery included:
The step test to assess cardiovascular endurance. Participants were required to ascend and descend 2 steps at a preestablished tempo heard on a metronome. The initial tempo was determined by the participant's age. It was possible to complete 3-minute workloads if the individual's heart rate did not exceed a target level after each workload. When the 3 minutes were up, the participant was instructed to remain motionless. A 10-second postexercise heart rate was recorded. Then the results of the step test were placed into a regression equation provided by Jette et al. (19) and used to predict the maximum oxygen uptake (O2max).
The sit and reach test to assess lower back and hamstring flexibility. Participants were instructed to reach as far as possible with the legs straight while sitting at a sit-and-reach box. The score was recorded to the last whole centimeter. The best of 2 trials was reported.
The standing long jump test (SLJT) to assess explosive leg power. Participants stood at a starting line marked on the ground with feet slightly apart. A 2-foot take-off and landing was used, with swinging of the arms and bending of the knees to provide forward drive. The longest distance jumped was measured in centimeters. The best of 2 trials was reported.
The timed up and go test to assess motor coordination (dynamic balance and gait speed). Participants were asked to rise from an armchair, walk 9 m, and return to the chair (total walking distance of 18 m).
The push-ups (PUT) and sit-ups (SUT) tests to measure muscular strength and endurance. In the push-ups test, participants were instructed to perform consecutively as many push-ups as possible. The score was the number of successfully completed push-ups. In the sit-ups test, participants were instructed to complete as many sit-ups as possible in 1 minute. The score was the number of correctly performed sit-ups.
MR level was assessed by mental health specialists throughout a medical-psychiatric examination.
The athletic performance was assessed using the official results of the 2008 Regional Track and Field Individual Championships (Lazio, Italy), organized by CIP.
The means and standard deviations of the selected fundamental factors (anthropometric measurements [height, weight, BMI, %body fat], cardiovascular endurance [predicted O2max]), lower back and hamstring flexibility, explosive leg power, motor coordination, muscular strength and endurance] were calculated (Table 2). Stepwise regression analysis was computed between performance (dependent variables) and the selected fundamental variables (independent variables). The criteria used for all of the stepwise regression analyses were that the probability for variables entering p ≤ 0.05 and the probability for variables removing p ≥ 0.1. Spearman's correlations were calculated between the selected fundamental factors and MR level. The standard error of the estimate (SEE) was also calculated to assess the accuracy of predictions made with the regression line.
The power of a statistical test of a null hypothesis is the probability that it will lead to the rejection of the null hypothesis. Moreover, an unpaired T-test was used to assess the gender effect for each dependent variable. Statistical analysis was performed with the SPSS statistical package (Version 15.0 for Windows; SPSS Inc., Chicago, IL, USA). Statistical significance was assumed at the conventional level of p ≤ 0.05.
The study of gender effect for each performance showed only a significant difference between sex and 300-m run (p < 0.01).
The result of the stepwise regression analyses between the 60-m run and the selected fundamental factors showed that 2 factors-motor coordination and body weight-had significant contributions to the 60 m with adjusted R2 = 0.99, F = 266.296, SEE = 0.118, power = 1, p = 0.004. This result indicated that approximately 99% of the variance of the 60-m run can be accounted for by the motor coordination and body weight.
The result of the stepwise regression analyses between the 300-m run and the selected fundamental factors showed that only the %body fat data had significant contribution to the 300-m run with adjusted R2 = 0.76, F = 13.399, SEE = 8.572, power = 0.85, p = 0.035. This result indicated that 76% of the variance of the 300-m run can be accounted for by the %body fat data.
The result of the stepwise regression analyses between the 400 m in walking and the selected fundamental factors did not show significant results.
The result of the stepwise regression analyses between the vortex throw and the selected fundamental factors showed that only the explosive leg power had a significant contribution to the vortex throw with adjusted R2 = 0.28, F = 4.858, SEE = 2.685, power = 0.46, p = 0.05. This result indicated that 28% of the variance of the vortex throw can be accounted for by the explosive leg power.
The result of the stepwise regression analyses between the standing long jump and the selected fundamental factors showed that only the explosive leg power had significant contribution to the standing long jump with adjusted R2 = 0.56, F = 8.541, SEE = 0.126, power = 0.67, p = 0.033. This result indicated that 56% of the variance of the standing long jump can be accounted for by the explosive leg power.
The result of the stepwise regression analyses between the 100-m run and the selected fundamental factors showed that only %body fat had a significant contribution to the 100-m run with adjusted R2 = 0.50, F = 7.009, SEE = 1.082, power = 0.57, p < 0.05. This result indicated that 50% of the variance of 100-m run can be accounted for by %body fat data.
The result of the stepwise regression analyses between the shot put and the selected fundamental factors showed that only the PUT had significant contribution to the shot put with adjusted R2 = 0.83, F = 20.637, SEE = 0.604, power = 0.89, p = 0.02. This result indicated that 83% of the variance of the shot put can be accounted for by the PUT.
The result of the stepwise regression analyses between the long jump and the selected fundamental factors showed that only the body weight had significant contribution to the long jump with adjusted R2 = 0.99, F = 570.449, SEE = 0.049, power = 1, p = 0.027. This result indicated that 99% of the variance of the long jump can be accounted for by the body weight.
Correlation Between Athletes' Selected Fundamental Factors and MR Level
MR level was positively correlated to motor coordination (p = 0.012; R = 0.463) and negatively correlated to SUT (p = 0.035; R = −0.393), indicating that athletes with lower MR obtained higher performance scores in motor coordination and SUT tests.
The first purpose of this study was to determine the contributions of selected fundamental factors to the athletic performance in adult individuals with MR. The results of this study provided support for the possibility to predict the performance efficiency of athletes with MR, confirming the first hypothesis of this investigation. Although few studies investigated the relationship between sport performance and fundamental factors (12,32), there is a paucity of information about the relation between selected fundamental factors and track and field for athletes with MR.
In the stepwise regression model of the 60-m run, 2 dimensional variables-motor coordination and body weight-had high significant contributions to athletes' performance. Moreover, the results of SEE and power showed that motor coordination and body weight were good predictors of 60-m performance. The motor coordination had a positive contribution to 60-m run performance, confirming as this fundamental factor is included in track and field activity (30). However, athletes with MR present problems in motor coordination in relation to MR level (2,5). Several studies showed that the MR degree has an effect on performance (22). In fact, persons with MR have shown poor gross motor control, which can affect performance on physical fitness tests, resulting in lower measures of fitness (29). Moreover, the high body weight had a negative contribution to 60-m run performance. In general, studies reported that individuals with MR demonstrate poor fitness level related to measures of body composition (7,17,31).
In the stepwise regression model of the 100-m run and 300-m run and the selected fundamental factors, only %body fat had a significant contribution to athletes' performance. In fact, a lower %body fat had a positive contribution to performance. The incidence of obesity among individuals with MR is high and increases in adulthood (7,11,17). Therefore, it is necessary to point out that the training should decrease athletes' %body fat to improve running performance. Moreover, the results of SEE and power showed that %body fat was a good predictor of 300-m performance. The unpaired T-test results showed that gender had a significant effect on 300 because the %body fat of the female athletes was significantly greater than that of the male athletes (20).
In the stepwise regression model of 400 m in walking and the selected fundamental factors, all potential predictors were removed from the model as insignificant (p > 0.05). This result could be explained by the fact that the 400 m in walking was a new proposal by CIP to facilitate the athletes with reduced physical abilities. Therefore, it was possible that the athletes were not specifically trained for this new competition. In fact, the athletes who performed in 400 m in walking showed O2max values lower than all other athletes (22.1 ± 3.2 ml/kg min and 25.9 ± 5.2 ml/kg min, respectively). However, the mean of O2max of all group was very low (25.3 ± 5.0 ml/kg min), confirming that individuals with MR exhibited much lower levels of performance on cardiovascular fitness test when compared to persons without disability (18,21,26,27).
In the stepwise regression model of the vortex throw, only the explosive leg power had a significant contribution to athletes' performance, probably because the athletes flexed the legs before the throw. The explosive leg power also had significant contribution to athletes' performance in standing long jump. This result could be justified by the similarity of SLJT and competition.
In the stepwise regression model of the shot put and the selected fundamental factors, the PUT had a significant positive contribution to athletes' performance. PUT is fundamental in the final movement of shot put performance during the extension of athlete's arm (6). However, individuals with MR could show poor fitness performance on muscular endurance (17). Moreover, the results of SEE and power showed that PUT was a good predictor of shot put performance.
In the stepwise regression model of the long jump and the selected fundamental factors, only body weight had a high significant contribution to athletes' performance indicating that a lower body weight had a positive contribution to this performance. Moreover, the results of SEE and power showed that body weight was a good predictor of shot put performance.
The second purpose of this study was to analyze the correlation of each selected fundamental factor with subjects' MR levels. The results of the present study confirmed the second hypothesis of this study and showed that athletes with lower MR obtained higher performance scores in motor coordination test and in SUT, confirming that an individual with a higher intelligence quotient obtain better performance results (2,22,29). In fact, some studies showed that individuals with MR, with a reduction of adaptability provoked by a permanent loss of certain capacities, present some difficulties in motor abilities such as writing, handling objects, running, jumping, hopping, throwing, balance, space and time orientation, side movements, sports, and even daily activities (15,23). Therefore, individuals with MR present lack of coordinated movements (17) because they have problems with processing information and lack of ability (3).
Through a standard training and competition, track and field could be useful for testing personal limits and pursuing athletic dreams and goals (31). Our findings suggest the possibility to determine the contributions of selected factors in relation to athletes' regional and national performances in track and field. This should be addressed by coaches in athletics training to help adult athletes with MR to perform successfully in their no agonistic and agonistic competitions and eventually to allow them to access at an international level. In fact, athletes who performed in Level II could access at international sports competition, organized by the International Sports Federation for Persons with Intellectual Disability (INAS-FID). INAS-FID provides opportunities for high-performance athletes with MR, primarily at the international level. To access these opportunities, athletes must meet established qualification or performance standards that request intense training (31).
The authors acknowledge all athletes who participated in experimental trails. They also acknowledge Giorgio Pes, Regional Coordinator in C.I.P. Track and Field Individual Championships, for his precious involvement in the planning and intervention. Any grant support for this project was obtained. The authors have no declared conflicts of interest.
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