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PubMed2003

Impaired regulation of stride variability in Parkinson's disease subjects with freezing of gait.

Patients with Parkinson's disease (PD) often experience freezing of gait, a debilitating phenomenon during which the subject suddenly becomes unable to start walking or to continue to move forward. Little is known about the gait of those subjects with PD who experience freezing of gait or the pathophysiology of freezing. One possibility is that freezing of gait is a truly paroxysmal phenomenon and that the usual walking pattern of subjects who experience freezing of gait is not different than that of other patients with PD who do not experience these transient episodes of freezing of gait. On the other hand, a recent study noted gait changes just prior to freezing and concluded that dyscontrol of the cadence of walking contributes to freezing. To address this question, we compared the gait of PD subjects with freezing of gait to PD subjects without freezing of gait. Given the potential importance of the dyscontrol of the cadence of walking in freezing, we focused on two aspects of gait dynamics: the average stride time (the inverse of cadence, a measure of the walking pace or rate) and the variability of the stride time (a measure of "dyscontrol," arrhythmicity and unsteadiness). We found that although the average stride time was similar in subjects with and without freezing, stride-to-stride variability was markedly increased among PD subjects with freezing of gait compared to those without freezing of gait, both while "on" (P<0.020) and "off" (P<0.002) anti-parkinsonian medications. Further, we found that increased gait variability was not related to other measures of motor control (while off medications) and levodopa apparently reduced gait variability, both in subjects with and without freezing. These results suggest that a paradigm shift should take place in our view of freezing of gait. PD subjects with freezing of gait have a continuous gait disturbance: the ability to regulate the stride-to-stride variations in gait timing and maintain a stable walking rhythm is markedly impaired in subjects with freezing of gait. In addition, these findings suggest that the inability to control cadence might play an important role in this debilitating phenomenon and highlight the key role of dopamine-mediated pathways in the stride-to-stride regulation of walking.

Aged↗
PubMedDate not supplied

Exercise training for patients with chronic atrial fibrillation.

BACKGROUND: Patients with atrial fibrillation (AF) referred for exercise rehabilitation exemplify the problem inherent in reliance on pulse rate to prescribe and monitor training intensity. METHODS: Exercise training was accomplished by specifying a training walking pace based on 60% to 80% of the peak oxygen intake (VO2max), as determined by the analysis of expired air (Horizon metabolic cart), and/or the ventilatory threshold (VT), together with a perceived exertion of 12 to 14 on the original Borg scale of perceived exertion. RESULTS: At the end of 1 year, a significant training effect was demonstrated (VO2max average increase 15%, 14.8 +/- 3.6 mL/kg/min to 17.0 +/- 3.6 mL/kg/min, P < .02; VO2 at VT, average increase 14%, 11.2 +/- 2.2 to 12.8 +/- 2.6 mL/kg/min, P < .01; peak power output increase 21%, 92.5 +/- 29.3 Watts to 112 +/- 3.7 Watts, P < .05) in a group of 20 patients (13 men, 7 women) with chronic atrial fibrillation. CONCLUSIONS: Patients with chronic atrial fibrillation can achieve significant functional gains from an exercise rehabilitation program.

Aged↗
PubMed2001

Effects of limb-length discrepancy on gait economy and lower-extremity muscle activity in older adults.

BACKGROUND: The amount of limb-length discrepancy necessary to adversely affect gait parameters in older adults is unknown, with information being largely anecdotal. This investigation was conducted to determine the effects of limb-length discrepancy on gait economy and lower-extremity muscle activity in older adults. METHODS: Forty-four men and women ranging in age from fifty-five to eighty-six years with no evidence of limb-length discrepancy of >1 cm participated in the study. Subjects walked on a treadmill at a self-selected normal walking pace with artificial limb-length discrepancies of 0, 2, 3, and 4 cm applied in a randomly selected order. Indirect calorimetry was used to measure oxygen consumption and minute ventilation. Electromyography was used to measure muscle activity of the right and left quadriceps femoris, plantar flexors, gluteus maximus, and gluteus medius. Heart rate, the rating of perceived exertion, and frequency of gait compensation patterns were also measured. RESULTS: There was a significant increase in oxygen consumption and the rating of perceived exertion with 2, 3, and 4-cm artificial limb-length discrepancies; a significant increase in heart rate, minute ventilation, and quadriceps activity in the longer limb with 3 and 4-cm artificial limb-length discrepancies; and a significant increase in plantar flexor activity in the shorter limb with a 4-cm artificial limb-length discrepancy compared with the same parameters with no artificial limb-length discrepancy. CONCLUSIONS: Both oxygen consumption and the rating of perceived exertion were greater with a 2-cm artificial limb-length discrepancy than they were with no artificial limb-length discrepancy. There appears to be a breakpoint between 2 and 3 cm of artificial limb-length discrepancy in older adults with regard to the effects on most other physiological parameters. A 3-cm artificial limb-length discrepancy is likely to induce significant quadriceps fatigue in the longer limb. Elderly patients with substantial pulmonary, cardiac, or neuromuscular disease may have difficulty walking with a limb-length discrepancy as small as 2 cm.

Aged↗
PubMed2006

A prospective study of pregravid physical activity and sedentary behaviors in relation to the risk for gestational diabetes mellitus.

BACKGROUND: Although gestational diabetes mellitus (GDM) has been associated with substantial adverse health outcomes for both mothers and offspring, few modifiable risk factors for GDM have been identified. METHODS: We conducted a prospective cohort study among women in the Nurses' Health Study II to assess whether the amount, type, and intensity of pregravid physical activity and sedentary behaviors are associated with GDM risk. The analysis included 21,765 women who reported at least 1 singleton pregnancy between 1990 and 1998. Physical activity and sedentary behaviors were assessed through validated questionnaire. RESULTS: We documented 1428 incident GDM cases. After controlling for body mass index, dietary factors, and other covariates, there was a significant inverse association between vigorous activity and the risk of GDM. The multivariate relative risk (RR) comparing the highest with the lowest quintile of vigorous activity was 0.77 (95% confidence interval [CI], 0.69-0.94) (P = .002 for trend). Among women who did not perform vigorous activity, brisk walking pace was associated with significantly lower GDM risk (RR, 0.66; 95% CI, 0.46-0.95) compared with an easy pace. Women who spent 20 h/wk or more watching television but did not perform vigorous activity had a significantly higher GDM risk than women who spent less than 2 h/wk watching television and were physically active (multivariate RR, 2.30; 95% CI, 1.06-4.97). CONCLUSION: Our prospective study provides strong evidence that regular physical activity before pregnancy is associated with lower GDM risk.

Activities of Daily Living↗
PubMed2003

The relationship between self-report and performance-related measures: questioning the content validity of timed tests.

OBJECTIVE: To examine the determinants of the modest correlation between self-report and performance-related measures in patients with osteoarthritis of the hip or knee. METHODS: Measures included the Lower Extremity Functional Scale (LEFS), the self paced walk, timed up-and-go, and stair test. Each performance measure consisted of 3 domains: time, pain (visual analog scale), and exertion (Borg scale). Activity specificity was assessed by examining correlations between the LEFS with single activity and multiple activity time scores. Domain specificity was examined by comparing correlations between the LEFS and single and multiple domain scores. The impact of measurement error was considered. RESULTS: Increasing the number of activity time scores had no effect. Forming a composite performance score based on time, pain, and exertion substantially increased the correlation from 0.44 (composite timed score) to 0.59 (pooled domain and activity score) (P = 0.009). CONCLUSION: Performance scores based on time alone appear to inadequately represent the breadth of health concepts associated with functional status.

Activities of Daily Living↗
PubMed2006

Effect of patellar taping on vasti onset timing, knee kinematics, and kinetics in asymptomatic individuals with a delayed onset of vastus medialis oblique.

This randomized within-subject study investigated the effects of patellar tape on the onset of electromyographic (EMG) activity of vastus medialis obliquus (VMO) relative to vastus lateralis (VL), knee kinematics, and kinetics in 12 currently asymptomatic individuals with a VMO timing deficit and a history of patellofemoral pain. Participants were required to complete stair stepping and normal-pace and fast-pace walking tasks under three experimental conditions; no tape, control tape and therapeutic tape. EMG onsets of VMO and VL were measured by surface electrodes, stance phase knee flexion by the PEAK movement analysis system and vertical ground reaction force by a force plate. A two-way repeated measures analysis of variance showed that neither therapeutic tape nor control tape had any effect on the EMG VMO-VL onset timing difference. Therapeutic tape, but not control tape, led to significant increases in stance phase knee flexion. The first peak vertical ground reaction force was lowered by both control and therapeutic tape but only during fast walking. The results suggest that tape induced effects on neuromotor control of the vasti seen in other studies are related to reductions in pain rather than the presence of a baseline timing deficit. However, this cannot explain the improvements in stance phase knee flexion observed with tape.

Adolescent↗
PubMed1993

Proprioceptive sensibility in women with normal and osteoarthritic knee joints.

The objective of this study was to quantify the effect of degenerative joint change on the proprioceptive acuity of women with osteoarthritis (OA) of the knee. Middle-aged women with OA of the knee, age-matched healthy women, and younger healthy women were studied. Tests examined the ability of subjects to correctly reproduce knee angles in weightbearing and non-weightbearing situations. The knee angles were photographed and measured in degrees. The absolute error (AE) of each matching test was calculated and the mean AE of two tests was used as the criterion variable in a three-way analysis of variance (ANOVA). The relationship between the reproduction error and the osteoarthritic subjects' self-paced walking speed was also examined. Under both test conditions the AE of the osteoarthritic subjects was greater than that of the healthy subjects (p < .05). There was, however, no significant relationship between the AE measurements of the patients and their walking speed. These data indicate that while women with OA may have poorer proprioception than healthy controls, this impairment may not affect their walking ability.

Adult↗
PubMed2003

Measurement and prediction of energy expenditure in males during household and garden tasks.

Participation in at least 30 min of moderate intensity activity on most days is assumed to confer health benefits. This study accordingly determined whether the more vigorous household and garden tasks (sweeping, window cleaning, vacuuming and lawn mowing) are performed by middle-aged men at a moderate intensity of 3-6 metabolic equivalents (METs) in the laboratory and at home. Measured energy expenditure during self-perceived moderate-paced walking was used as a marker of exercise intensity. Energy expenditure was also predicted via indirect methods. Thirty-six males [ X (SD): 40.0 (3.3) years; 179.5 (6.9) cm; 83.4 (14.0) kg] were measured for resting metabolic rate (RMR) and oxygen consumption ( VO(2)) during the five activities using the Douglas bag method. Heart rate, respiratory frequency, CSA (Computer Science Applications) movement counts, Borg scale ratings of perceived exertion and Quetelet's index were also recorded as potential predictors of exercise intensity. Except for vacuuming in the laboratory, which was not significantly different from 3.0 METs ( P=0.98), the MET means in the laboratory and home were all significantly greater than 3.0 ( P</=0.006). The sweeping and vacuuming MET means were significantly higher ( P<0.001) at home than in the laboratory, whereas the converse applied for window cleaning and lawn mowing. Measured RMR was significantly lower ( P<0.001) than the 1-MET constant. Estimating METs by fitting random intercept regression models to the data resulted in standard deviations for the "leave-one-out" prediction errors (predicted-measured) of 0.4 and 0.5 METs for the laboratory and home equations, respectively. While the means indicate that all the activities were performed at a moderate intensity, there was great inter-individual variability in energy expenditure. The laboratory and home-based equations predicted with correct classification rates of 89% and 88%, respectively, whether energy expenditure was <3.0 or >/=3.0 METs.

Activities of Daily Living↗
PubMed2001

Long-term follow-up of functional outcomes and radiographic changes at adjacent levels following lumbar spine fusion for degenerative disc disease.

There are very few studies with more than 20 years' follow-up of lumbar spine fusions for disc degeneration. Currently, there is a lot of interest in the subject of degenerative changes above the level of fusion; this study is concerned with such changes in the very long term (30 years). Twenty-eight patients showing sound fusion on radiographs following posterior midline spinal fusion performed by a single surgeon between 1968 and 1970 were compared with an age- and gender-matched group of 28 patients who had undergone surgery for degenerative disc disease without fusion during the same period, by the same surgeon and using similar criteria for evaluation (Short Form 36 and Oswestry Disability Index; functional testing using self-paced walk and timed up-and-go; flexion and extension lateral radiographs of the lumbar spine). In this study, the incidence of radiographic changes at levels above the level of previous involvement was twice as high in the fusion group as in the non-fusion group. However, there was no statistically significant difference between the two groups in the outcomes measured using validated scales and functional testing. The study emphasises the importance of complete evaluation of these patients using validated outcome measurement instruments against the background of radiographic changes and subjective assessment of back pain. It also shows that radiographic changes do not necessarily mean functional impairment in all patients following lumbar spine fusion for degenerative disc disease.

Case-Control Studies↗
PubMed2004

A case-control study of maternal recreational physical activity and risk of gestational diabetes mellitus.

Despite the maternal and infant morbidity associated with gestational diabetes mellitus (GDM), few modifiable risk factors have been identified. We explored the relation between recreational physical activity performed during the year before and during the first 20 weeks of pregnancy and the risk of GDM. 155 GDM cases and 386 normotensive, non-diabetic pregnant controls provided information about the type, intensity, frequency, and duration of physical activity performed during these time periods. Women who participated in any recreational physical activity during the first 20 weeks of pregnancy, as compared with inactive women, experienced a 48% reduction in risk of GDM (odds ratio [OR] = 0.52; 95% confidence interval [CI] 0.33-0.80). The number of hours spent performing recreational activities and the energy expended were related to a decrease in GDM risk. No clear patterns related to distance walked and pace of walking emerged. Daily stair climbing, when compared with no stair climbing, was associated with a 49-78% reduction in GDM risk (P for trend <0.011). Recreational physical activity performed during the year before the index pregnancy was also associated with statistically significant reductions in GDM risk, but women who engaged in physical activity during both time periods experienced the greatest reduction in risk (OR = 0.40; 95% CI 0.23-0.68). These data suggest that recreational physical activity performed before and/or during pregnancy is associated with a reduced risk of GDM.

Adult↗
PubMed2007

Strategies used by older adults to change travel direction.

INTRODUCTION: A distinct body reorientation strategy during steering tasks has been reported in young adults. As challenges to whole-body stability in older adults occur when navigating complex environments, this study was designed to examine control strategies used by older adults to initiate a voluntary change in travel direction. METHODS: Thirteen older adults, recruited from an independent living division of a local retirement residence, were instrumented with reflective markers and whole-body kinematic data were monitored using a video camera (30 Hz). Participants executed self-paced walking trials 3-m along a straight path and were instructed prior to the trial to continue either straight ahead or randomly turn 40 degrees left or right and continue walking for an additional 2-m. Timing of changes with respect to when the trunk crossed the turning point were calculated for deviations in head and trunk position and foot rotation in the medial-lateral plane. RESULTS: Older adults reoriented themselves into the new travel direction in a top-down, segmental sequence, beginning with head reorientation followed by trunk reorientation, foot rotation and foot displacement into the new travel direction. These changes were initiated over two or more steps 69% of the time and over one step 31% of the time. A significant relationship between turning strategy used and balance confidence was observed; the frequency of using a turning strategy involving two or more steps to initiate a change in travel direction increased as balance confidence decreased. DISCUSSION AND CONCLUSION: Older adults made segmental changes to voluntarily reorient themselves in a new travel direction in a similar sequence to that observed in young adults. Older adults chose primarily to initiate these changes two or more steps prior to the turn; the selection of this strategy was related to balance confidence.

Adaptation, Physiological↗
PubMed2005

Performance measures were necessary to obtain a complete picture of osteoarthritic patients.

OBJECTIVES: Self-report questionnaires and performance measures represent two methods for assessing physical function. A recurring theme is that self-report measures are superior to performance measures. This study investigated the association between three performance test outcomes of four activities (pain, exertion, and time or distance; for self-paced walk, stair test, timed up-and-go, 6-minute walk) with self-reports of physical function (WOMAC Physical Function subscale and LEFS) and the association between the change scores of the performance tests and those of the self-report measures. STUDY DESIGN AND SETTING: Performance and self-report measures were administered three times (presurgery and at approximately 1 week and approximately 8 weeks post arthroplasty) to 85 patients who underwent total hip or knee arthroplasty. Components of the performance tests were pooled within each domain across the four measures. Multiple regression analyses were applied. Independent variables were performance tests components; dependent variables were self-report measures. Standardized regression coefficients described the cross-sectional and longitudinal associations. RESULTS: Pain was the principal determinant of WOMAC Physical Function subscale scores. Pain, exertion, and time or distance were strongly associated with the LEFS at the first, second, and third assessments, respectively. Change in pain was most strongly associated with change in self-reported physical function. CONCLUSION: Our findings caution against the isolated use of self-report assessments of physical function.

Aged↗
PubMed2006

Biomechanical evaluation of different fixation plates in medial opening upper tibial osteotomy.

In this biomechanical study, 25 in vitro calf tibial models were used in order to compare the stability of the plates under axial compression loading. A 10-mm medial opening gap was stabilized in each of the five calf tibial models either with four or two-holed rectangular shaped plates with wedges, with four-holed reversed L-shaped plates with wedges, with the combination of these two types of plates, or with six-holed anatomical T-plates. The compression behavior of the model was tested by using a universal mechanical testing system. The specimens fixed with the combination of plates with the four-holed reversed L-shaped and with two-holed rectangular shaped; or with six-holed anatomical T-plates, showed significantly better stability than those of others. Four different kinds of failure (slippage of wedge, lateral cortex fracture, damage and/or loosening of screws, and bending of plates) were observed on the models. When the average value of force loading on the plates that were designed by the first author was considered, the plates were stable and the average force values at these points were higher than the loading force on a knee during the normal paced walking or running conditions.

Animals↗
PubMed2000

Genetic identification of neurons controlling a sexually dimorphic behaviour.

In the fruit fly Drosophila melanogaster, locomotor activity is sexually dimorphic: female flies constantly modulate their activity pattern whereas males show a steadier, stereotyped walking pace [1]. Here, we mapped the area of the brain controlling this behavioural dimorphism. Adult male Drosophila expressing a dominant feminising transgene in a small cluster of neurons in the pars intercerebralis exhibited a female-like pattern of locomotor activity. Genetic ablation of these neurons prevented the feminisation of the locomotor activity of transgenic males. The results suggest that this cluster of neurons modulates sex-specific activity, but is not involved in initiating fly locomotion. Nor does it control male courtship behaviour, because feminisation of courtship was not correlated with the feminisation of locomotor activity.

Animals↗
PubMed1985

Arterial oxygen desaturation during treadmill and bicycle exercise in patients with chronic obstructive airways disease.

Nine men with severe chronic obstructive airways disease (COAD), known to desaturate on exercise, performed a 6 min self-paced walk on a treadmill, followed by a bicycle exercise with workloads adjusted to mimic the oxygen consumption achieved on the treadmill. During both exercises, ventilation, oxygen consumption, carbon dioxide production, PaO2, PaCO2, pH and arterial lactate were measured and subjective breathlessness recorded. A reasonable match of oxygen consumption between the two exercises was achieved. In all subjects PaO2 fell to a lower level during treadmill compared with bicycle exercise. Ventilation, carbon dioxide production and arterial lactate were higher during bicycle exercise. Subjective breathlessness was greater during bicycle exercise, in proportion to the higher ventilation on the bicycle. The greater anaerobiosis occurring on the bicycle led to acidosis and an increased ventilation, minimizing the exercise fall in PaO2. Bicycle testing may seriously underestimate exercise desaturation occurring during level walking in patients with severe COAD.

Aged↗
PubMed1987

Arterial oxygen saturation and breathlessness in patients with chronic obstructive airways disease.

Nine patients with chronic obstructive airways disease performed a 6 min self-paced walk (breathing air) on a treadmill and then identical (but operator-controlled) treadmill walks breathing either air or supplemental oxygen sufficient to just prevent arterial oxygen desaturation during the exercise. During the exercises, ventilation was recorded and patients recorded their sensation of breathlessness on a visual analogue scale (VAS) every 30 s. Breathing supplemental oxygen produced a small fall in mean exercise ventilation and a large and consistent reduction in mean exercise breathlessness. In seven patients the VAS scores were higher on air than with supplemental oxygen, at similar levels of ventilation. An analysis of covariance, to control for reduction in ventilation, showed a decrease in mean breathlessness when breathing supplemental oxygen, significant at the 8% level. The reduction in breathlessness produced by preventing exercise desaturation cannot be explained by the decrease in ventilation. This suggests that hypoxia may be a stimulus for breathlessness. The mechanism is unknown.

Aged↗
PubMed1996

Effects of hormone replacement therapy on muscle performance and balance in post-menopausal women.

1. A randomized controlled trial of the effect of oral hormone replacement therapy plus calcium compared with calcium alone on balance, muscle performance and falls was conducted over 48 weeks in 116 post-menopausal women (aged 45-70 years), all of whom had suffered a distal radial fracture during the previous 3 months. Treatment was with Prempak C or Premarin 0.625 mg in the test group with 1 g calcium daily (Sandocal) in both groups. Measurements were made of balance, assessed as sway, leg extensor power and self-paced walking speed, at 12-week intervals over 24 weeks. Hand grip strength was measured every 12 weeks for 48 weeks, and falls in the preceding 12 weeks were recorded at each visit. 2. There was no relation between initial levels of oestradiol and any other variable assessed, except body mass. Levels of follicle-stimulating hormone in the test group were in the premenopausal range. There was no significant change attributable to hormone replacement therapy at any time point in any of the outcome variables. The only significant difference was an increase of 4.2% (95% confidence interval 0.7-7.6%) in leg extensor power in the control group (calcium alone) compared with the group treated with hormone replacement therapy. 3. Of the total group, 37% fell again during the year, with three patients suffering a further fracture. Frequent fallers swayed significantly more often than the others, but there was no evidence that their muscle strength was poorer or that the group treated with hormone replacement therapy fell less frequently. 4. Hormone replacement therapy did not increase muscle performance, improve balance or reduce falls over a year in middle-aged women.

Accidental Falls↗
PubMed2001

Velocity training induces power-specific adaptations in highly functioning older adults.

OBJECTIVE: To test the efficacy of high-velocity training in healthy older persons. DESIGN: A 12-week randomized trial, with subjects blocked for gender and residence, comparing high-velocity resistance training with a self-paced walking program. SETTING: Retirement community. PARTICIPANTS: Forty-three volunteers over the age of 70 years. INTERVENTION: Power group: high-velocity leg exercises 3 times weekly with weekly increases in resistance combined with 45 minutes of moderate, nonresistance exercise weekly. Walking group: moderate intensity exercise 30 minutes daily, 6 days weekly. MAIN OUTCOME MEASURES: Variables measured included leg press peak power and leg extensor strength. Functional performance outcomes included: 6-minute walk distance, Short Physical Performance Battery, Physical Performance Test, and Medical Outcomes Study Short-Form Health Survey. RESULTS: Peak power improved 22% (p =.004) in the power group (3.7 +/- 1.0 W/kg to 4.5 +/- 1.4 W/kg) but did not change in the walking group (3.99 +/-.76 W/kg to 3.65 +/-.94 W/kg). Leg extensor power at resistance of 50%, 60%, and 70% of body weight increased 50%, 77%, and 141%, respectively, in the power group (p <.0001, repeated-measures analysis of variance). Strength improved 22% in the power-trained individuals and 12% in the walkers (p <.0001). Training did not improve functional task performance in either group. One subject developed a radiculopathy during training. CONCLUSIONS: Resistance training focusing on speed of movement improved leg power and maximal strength substantially, but did not improve functional performance in healthy high-functioning older volunteers.

Adaptation, Physiological↗