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      The six-minute walk test is an excellent predictor of functional ambulation after total knee arthroplasty

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          Abstract

          Background

          The Six-minute walk (6MW) and Timed-Up-and-Go (TUG) are short walk tests commonly used to evaluate functional recovery after total knee arthroplasty (TKA). However, little is known about walking capacity of TKA recipients over extended periods typical of everyday living and whether these short walk tests actually predict longer, more functional distances. Further, short walk tests only correlate moderately with patient-reported outcomes. The overarching aims of this study were to compare the performance of TKA recipients in an extended walk test to healthy age-matched controls and to determine the utility of this extended walk test as a research tool to evaluate longer term functional mobility in TKA recipients.

          Methods

          The mobility of 32 TKA recipients one year post-surgery and 43 healthy age-matched controls were assessed using the TUG, 6MW and 30-minute walk (30MW) tests. The latter test was repeated one week later. Self-reported function was measured using the WOMAC Index and a physical activity questionnaire.

          Results

          30MW distance was significantly shorter amongst TKA recipients (mean 2108 m [95% CI 1837 to 2381 m]; Controls 3086 m [2981 to 3191 m], P < 0.001). Test-retest repeatability was high (ICC = 0.97, TKA; 0.96, Controls). Amongst TKA recipients, the 30MW distance correlated strongly with the shorter tests (6MW, r = 0.97, P < 0.001; TUG, r = −0.82, P < 0.001). Multiple regression modeling found 6MW distance to be the only significant predictor (P < 0.001) of 30MW distance, explaining 96% of the variability. The TUG test models were moderate predictors of WOMAC function (55%) and physical activity (36%) and were stronger predictors than 6MW and 30 MW tests.

          Conclusions

          Though TKA recipients are able to walk for 30 minutes one year post-surgery, their performance falls significantly short of age-matched norms. The 30MW test is strongly predicted by 6MW test performance, thus providing strong construct validity for the use of the 6MW test in the TKA population. Neither a short nor long walk test is a strong predictor of patient-reported function after TKA.

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          Most cited references29

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          American College of Sports Medicine Position Stand. The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness, and flexibility in healthy adults.

          ACSM Position Stand on The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Adults. Med. Sci. Sports Exerc., Vol. 30, No. 6, pp. 975-991, 1998. The combination of frequency, intensity, and duration of chronic exercise has been found to be effective for producing a training effect. The interaction of these factors provide the overload stimulus. In general, the lower the stimulus the lower the training effect, and the greater the stimulus the greater the effect. As a result of specificity of training and the need for maintaining muscular strength and endurance, and flexibility of the major muscle groups, a well-rounded training program including aerobic and resistance training, and flexibility exercises is recommended. Although age in itself is not a limiting factor to exercise training, a more gradual approach in applying the prescription at older ages seems prudent. It has also been shown that aerobic endurance training of fewer than 2 d.wk-1, at less than 40-50% of VO2R, and for less than 10 min-1 is generally not a sufficient stimulus for developing and maintaining fitness in healthy adults. Even so, many health benefits from physical activity can be achieved at lower intensities of exercise if frequency and duration of training are increased appropriately. In this regard, physical activity can be accumulated through the day in shorter bouts of 10-min durations. In the interpretation of this position stand, it must be recognized that the recommendations should be used in the context of participant's needs, goals, and initial abilities. In this regard, a sliding scale as to the amount of time allotted and intensity of effort should be carefully gauged for the cardiorespiratory, muscular strength and endurance, and flexibility components of the program. An appropriate warm-up and cool-down period, which would include flexibility exercises, is also recommended. The important factor is to design a program for the individual to provide the proper amount of physical activity to attain maximal benefit at the lowest risk. Emphasis should be placed on factors that result in permanent lifestyle change and encourage a lifetime of physical activity.
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            Quadriceps strength and the time course of functional recovery after total knee arthroplasty.

            Prospective study with repeated measures. The overall goal of this investigation was to describe the time course of recovery of impairments and function after total knee arthroplasty (TKA), as well as to provide direction for rehabilitation efforts. We hypothesized that quadriceps strength would be more strongly correlated with functional performance than knee flexion range of motion (ROM) or pain at all time periods studied before and after TKA. TKA is a very common surgery, but very little is known regarding the influence of impairments on functional limitations in this population. Forty subjects who underwent unilateral TKA followed by rehabilitation, including 6 weeks of outpatient physical therapy, were studied. Testing occurred at 5 time periods: preoperatively, and at 1, 2, 3, and 6 months after surgery. Test measures included quadriceps strength, knee ROM, timed up-and-go test, timed stair-climbing test, bodily pain, and general health and knee function questionnaires. Subjects experienced significant worsening of knee ROM, quadriceps strength, and performance on functional tests 1 month after surgery. Quadriceps strength went through the greatest decline of all the physical measures assessed and never matched the strength of the uninvolved limb. All measures underwent significant improvements following the 1-month test. Quadriceps strength was the most highly correlated measure associated with functional performance at all testing sessions. Functional measures underwent an expected decline early after TKA, but recovery was more rapid than anticipated and long-term outcomes were better than previously reported in the literature. The high correlation between quadriceps strength and functional performance suggests that improved postoperative quadriceps strengthening could be important to enhance the potential benefits of TKA.
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              Six minute walking distance in healthy elderly subjects.

              The six minute walking distance (6MWD) test is a commonly used test to estimate functional exercise capacity in patients with chronic diseases including chronic obstructive lung disease. Surprisingly, no attempt has been made to establish normal values for the 6MWD. The aim of this study, therefore, was to evaluate the 6MWD in healthy elderly volunteers and to evaluate its determining factors. Fifty-one healthy subjects aged 50-85 yrs volunteered to participate in the trial. All subjects were free of diseases that could interfere with performance in a walking test. Tests were performed in a quiet 50-m long hospital corridor. Patients were encouraged every 30 s to continue walking as quickly as possible. Walking distance averaged 631+/-93 m and was 84 m greater in the male compared to female subjects (p<0.001). The 6MWD showed significant correlations with age (r=-0.51, p<0.01) and height (r=0.54, p<0.01). Stepwise multiple regression analysis showed that age, height, sex and weight were independent contributors to the 6MWD in healthy subjects, thus explaining 66% of the variability. It is concluded that the six minute walking distance can be predicted adequately using a clinically useful model in healthy elderly subjects. Its variability is explained largely by age, sex, height and weight. Results of the six minute walking distance may be interpreted more adequately if expressed as a percentage of the predicted value.
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                Author and article information

                Journal
                BMC Musculoskelet Disord
                BMC Musculoskelet Disord
                BMC Musculoskeletal Disorders
                BioMed Central
                1471-2474
                2013
                24 April 2013
                : 14
                : 145
                Affiliations
                [1 ]South West Sydney Clinical School, University of New South Wales, Sydney, Australia
                [2 ]Orthopaedics Department, Liverpool Hospital, Sydney, Australia
                [3 ]Whitlam Orthopaedic Research Centre, Sydney, Australia
                [4 ]Ingham Institute Applied Medical Research, Sydney, Australia
                [5 ]School of Science and Health, University of Western Sydney, Sydney, Australia
                Article
                1471-2474-14-145
                10.1186/1471-2474-14-145
                3644243
                23617377
                18d45d0d-c850-400a-a51d-de89782de3ab
                Copyright ©2013 Ko et al.; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 20 August 2012
                : 19 April 2013
                Categories
                Research Article

                Orthopedics
                gait,self-reported outcomes
                Orthopedics
                gait, self-reported outcomes

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