The biomechanical demands of standing yoga poses in seniors: The Yoga empowers seniors study (YESS)

Background

The number of older adults participating in yoga has increased dramatically in recent years; yet, the physical demands associated with yoga performance have not been reported. The primary aim of the Yoga Empowers Seniors Study (YESS) was to use biomechanical methods to quantify the physical demands associated with the performance of 7 commonly-practiced standing yoga poses in older adults.

Methods

20 ambulatory older adults (70.7 + − 3.8 yrs) attended 2 weekly 60-minute Hatha yoga classes for 32 weeks. The lower-extremity net joint moments of force (JMOFs), were obtained during the performance of the following poses: Chair, Wall Plank, Tree, Warrior II, Side Stretch, Crescent, and One-Legged Balance. Repeated-measure ANOVA and Tukey’s post-hoc tests were used to identify differences in JMOFs among the poses. Electromyographic analysis was used to support the JMOF findings.

Results

There was a significant main effect for pose, at the ankle, knee and hip, in the frontal and sagittal planes (p = 0.00 – 0.03). The Crescent, Chair, Warrior II, and One-legged Balance poses generated the greatest average support moments. Side Stretch generated the greatest average hip extensor and knee flexor JMOFs. Crescent placed the highest demands on the hip flexors and knee extensors. All of the poses produced ankle plantar-flexor JMOFs. In the frontal plane, the Tree generated the greatest average hip and knee abductor JMOFs; whereas Warrior II generated the greatest average hip and knee adductor JMOFs. Warrior II and One-legged Balance induced the largest average ankle evertor and invertor JMOFs, respectively. The electromyographic findings were consistent with the JMOF results.

Conclusions

Musculoskeletal demand varied significantly across the different poses. These findings may be used to guide the design of evidence-based yoga interventions that address individual-specific training and rehabilitation goals in seniors.

Clinical trial registration

This study is registered with NIH Clinicaltrials.gov #NCT 01411059

Strategies used during a challenging weighted walking task in healthy adults and individuals with knee osteoarthritis

Knee osteoarthritis (OA) is a disease that affects millions of people. While numerous gait differences have been identified between healthy adults and adults with knee OA under normal and challenging conditions, adults with knee OA have not been studied during a challenging weighted walking task. Investigation of the effect of weighted walking on the initial contact and loading response phases of gait was undertaken in 20 healthy and 20 knee OA subjects ages 40-85 years old walking at 1.0m/s while unweighted and weighted with 1/6th of their body weight in a weight vest. Subjects were grouped according to their Kellgren and Lawrence radiographic score and healthy subjects were age-matched to those with knee OA. ANOVA revealed significant effects for hip flexion angle at initial contact, step length, initial double support percent, and load rate. Post hoc t-tests revealed that subjects with knee OA had a larger initial double support percent and hip flexion angle at initial contact and a decreased load rate compared to unweighted, healthy adults. Also, both groups increased their initial double support percent in response to the challenging weighted walking task, but only the healthy adults increased their hip flexion angle at initial contact and decreased their load rate. During the weighted condition, the knee OA group had a shorter step length compared to the healthy group. Because the knee OA group only made minor compensations to their gait strategy, it appears that they may be unable or prefer not to adjust their gait mechanics due to underlying issues.

Relationships among body weight, joint moments generated during functional activities, and hip bone mass in older adults

OBJECTIVE

To investigate the relationships among hip joint moments produced during functional activities and hip bone mass in sedentary older adults.

METHODS

Eight male and eight female older adults (70-85 yr) performed functional activities including walking, chair sit-stand-sit, and stair stepping at a self-selected pace while instrumented for biomechanical analysis. Bone mass at proximal femur, femoral neck, and greater trochanter were measured by dual-energy X-ray absorptiometry. Three-dimensional hip moments were obtained using a six-camera motion analysis system, force platforms, and inverse dynamics techniques. Pearson's correlation coefficients were employed to assess the relationships among hip bone mass, height, weight, age, and joint moments. Stepwise regression analyses were performed to determine the factors that significantly predicted bone mass using all significant variables identified in the correlation analysis.

FINDINGS

Hip bone mass was not significantly correlated with moments during activities in men. Conversely, in women bone mass at all sites were significantly correlated with weight, moments generated with stepping, and moments generated with walking (p<0.05 to p<0.001). Regression analysis results further indicated that the overall moments during stepping independently predicted up to 93% of the variability in bone mass at femoral neck and proximal femur; whereas weight independently predicted up to 92% of the variability in bone mass at greater trochanter.

INTERPRETATION

Submaximal loading events produced during functional activities were highly correlated with hip bone mass in sedentary older women, but not men. The findings may ultimately be used to modify exercise prescription for the preservation of bone mass.

The effect of weighted vest walking on metabolic responses and ground reaction forces

PURPOSE

This study examined how oxygen consumption, relative exercise intensity, vertical ground reaction forces (VGRF), and loading rate (LR) were affected while using a weighted vest (WV) during treadmill walking.

METHODS

A sample of 10 (aged 23.4 +/- 1.7 yr) subjects performed a standardized walking test (4-min stages at 0.89, 1.12, 1.34, 1.56, and 1.79 m x s(-1)) on a treadmill under four weighted vest conditions (0, 10, 15, and 20% of body mass (BM)). Dependent variables included oxygen consumption (VO2), relative exercise intensity, first (F1) and second (F2) peaks of the VGRF curve, and LR.

RESULTS

Repeated-measures ANOVA revealed significant vest versus speed interaction for V O2 and relative exercise intensity. Follow-up contrasts showed significant vest effect differences between 0% BM and all other WV conditions, and between 10 and 20% BM at all speeds for V O2. Follow-up analysis of relative exercise intensity demonstrated no significant vest effect difference at slower speeds, but significant differences at higher speeds. A significant main effect for WV condition was found for F1, F2, and LR. Follow-up testing revealed F1 and F2 at 0% BM were significantly different than at 10, 15, and 20% BM. F1 and F2 at 10% BM were significantly different than 20% BM, whereas F1 at 15% BM was significantly different than at 20% BM. LR at 0% BM was significantly different than at 15 and 20% BM.

CONCLUSION

Using a weighted vest can increase the metabolic costs, relative exercise intensity, and loading of the skeletal system during walking.

Biomechanics of the heel-raise exercise

The purpose of this investigation was to determine whether increases in internal (muscular) demand would be proportional to increases in the external demand during heel-raise exercise. Seven male (mean age 74.9 +/- 4.8 years) and 9 female (mean age 74.4 +/- 5.1 years) older adults performed both double-leg heel raises and single-leg heel raises under 3 loading conditions (no external resistance and +5% and +10% of each participant's body weight). Kinematic and kinetic dependent variables were calculated using standard inverse-dynamics techniques. The results suggest that although the single-heel raise led to increases in peak net joint moments, power, and mechanical-energy expenditure (MEE), it did so at the expense of range of motion and angular velocity. In addition, increasing the external resistance by 5% of participants' body weight did not elicit significant changes in either the power or the MEE of the ankle joint. These effects should be considered when prescribing these exercises to older adults.

Lower-Extremity Kinetic Response to Weighted-Vest Resistance during Stepping Exercise in Older Adults

Stepping activities when wearing a weighted vest may enhance physical function in older persons. Using 3 weighted-vest resistance dosages, this study characterized the lower-extremity joint biomechanics associated with stepping activities in elders. Twenty healthy community-dwelling older adults, ages 74.5 ± 4.5 yrs, performed 3 trials of forward step-up and lateral step-up exercises while wearing a weighted vest which added 0% body weight (BW), 5% BW, or 10% BW. They performed these activities on a force platform while instrumented for biomechanical analysis. Repeated-measures ANOVA was used to evaluate the differences in ankle, knee, and hip maximum joint angles, peak net joint moments, joint powers, and impulses among both steping activities and the 3 loading conditions. Findings indicated that the 5% BW vest increased the kinetic output associated with the exercise activities at all three lower-extremity joints. These increases ranged from 5.9% for peak hip power to 12.5% for knee extensor impulse. The application of an additional 5% BW resistance did not affect peak joint moments or powers, but it did increase the joint impulses by 4–11%. Comparisons between exercise activities, across the 3 loading conditions, indicated that forward stepping preferentially targeted the hip extensors while lateral stepping targeted the plantar flexors; both activities equally targeted the knee extensors. Weighted-vest loads of 5% and 10% BW substantially increased the mechanical demand on the knee extensors, hip extensors (forward stepping), and ankle plantar flexors (lateral stepping).

Squatting exercises in older adults: kinematic and kinetic comparisons

PURPOSES

Squatting activities may be used, within exercise programs, to preserve physical function in older adults. This study characterized the lower-extremity peak joint angles, peak moments, powers, work, impulse, and muscle recruitment patterns (electromyographic; EMG) associated with two types of squatting activities in elders.

METHODS

Twenty-two healthy, older adults (ages 70-85) performed three trials each of: 1) a squat to a self-selected depth (normal squat; SQ) and 2) a squat onto a chair with a standardized height of 43.8 cm (chair squat; CSQ). Descending and ascending phase joint kinematics and kinetics were obtained using a motion analysis system and inverse dynamics techniques. Results were averaged across the three trials. A 2 x 2 (activity x phase) ANOVA with repeated measures was used to examine the biomechanical differences among the two activities and phases. EMG temporal characteristics were qualitatively examined.

RESULTS

CSQ generated greater hip flexion angles, peak moments, power, and work, whereas SQ generated greater knee and ankle flexion angles, peak moments, power, and work. SQ generated a greater knee extensor impulse, a greater plantar flexor impulse and a greater total support impulse. The EMG temporal patterns were consistent with the kinetic data.

CONCLUSIONS

The results suggest that, with older adults, CSQ places greater demand on the hip extensors, whereas SQ places greater demand on the knee extensors and ankle plantar flexors. Clinicians may use these discriminate findings to more effectively target specific lower-extremity muscle groups when prescribing exercise for older adults.