Introduction
Age-related hyperkyphosis, commonly defined by a thoracic spine Cobb angle curvature of 40 degrees or greater, progresses with age and affects up to 40% of older adults [
1]. Hyperkyphosis in older adults has been associated with impaired physical function, reduced health-related quality of life (HrQol), increased falls and fracture risk and is a predictor of all-cause mortality in women [
1‐
10]. Numerous cross-sectional and longitudinal studies have demonstrated hyperkyphosis is associated with slowed gait speed cross-sectionally and is predictive of worsening chair-stand time and Timed Up and Go (time to rise from chair, walk 10-m turn and return to sit) performance longitudinally in adjusted models [
2‐
6,
11]. Furthermore, hyperkyphosis has been identified as a ‘new’ geriatric syndrome, thus targeting hyperkyphosis as an impairment may contribute to slowing the progression to physical frailty [
12].
It is theorized that hyperkyphosis causes an anterior displacement of the center of gravity, which affects physical function characteristics and balance, and in turn negatively impacts physical function [
13]. Therefore, it has been hypothesized that interventions that reduce kyphosis may also improve physical function; however, few randomized controlled trials targeting improvement of kyphosis have reported a significant increase in physical function despite successfully reducing kyphosis [
14‐
18]. Previous trial results could be explained by a ceiling effect in high functioning cohorts of individuals who were already functioning above age-matched normative values for physical function. Further investigation of the effects of a targeted kyphosis intervention on physical function in older adults with low function and hyperkyphosis may inform future treatment for older adults at risk for physical function decline and frailty.
Since it is unknown if older adults with hyperkyphosis and low physical function who undergo a targeted kyphosis intervention will also improve physical function, we performed a secondary analysis using data from the Specialized Center of Research (SCOR) randomized controlled trial that investigated change in kyphosis, physical function and HrQoL in older adults with hyperkyphosis after a 3-month targeted high-intensity kyphosis exercise and posture training intervention [
14]. We categorized participants post-hoc into low and high physical function groups according to baseline physical function scores. We hypothesized that older adults with hyperkyphosis, low physical function, and who are transitioning to frailty would improve physical function after a targeted kyphosis intervention. Our primary aim was to explore change in physical function in older adults with hyperkyphosis and low physical function, and whether they responded differently than adults with higher function. We also explored change in HrQol, spinal strength and spinal curvature in low versus high function groups. Lastly, we explored the feasibility of conducting a targeted high-intensity kyphosis intervention in older adults with hyperkyphosis and low physical function by comparing adherence to the intervention and safety in both low and high function groups. We used change in physical function scores in the low function group to determine a sample size needed to test the hypothesis in a future, fully powered trial.
Results
There were more men in the LFG versus HFG, 54% vs 36%,
p = 0.110. The LFG was older than the HFG, 72.4 (SD = 6.5) years versus 68.8 (SD = 5.15) years,
p = 0.005, and reported poorer general health,
p = 0.006, and more pain 3.3 (SD = 2.7) points in the HFG and 2.0 (SD = 1.7) in the LFG,
p = 0.060, (Table
1).
Table 1
Study participant characteristics at baseline in the HFG and LFG
Age (years) | | 72.4 ± 6.6 | 68.8 ± 5.2 | 0.005 | 69.7 ± 5.7 |
Gender | Female | 12 (46) | 48 (64) | 0.110 | 60 (59) |
Vertebral Fracture | none | 22 (85) | 65 (87) | 0.741 | 87 (86) |
1 | 2 (8) | 7 (9) | | 9 (9) |
2 | 2 (8) | 3 (4) | | 5 (4.95) |
Diffuse idiopathic hyperostosis (DISH) present (yes) | | 7 (28) | 15 (21) | 0.461 | 22 (23) |
Body Mass Index(kilograms/meter2) | | 27.7 ± 3.9 | 25.7 ± 4.1 | 0.037 | 26.2 ± 4.1 |
Bone mineral density total hip t-score | | −0.5 ± 1.3 | −0.9 ± 1 | 0.074 | −0.85 ± 1.1 |
Bone mineral density total spine t-score | | 0.7 ± 2.8 | −0.5 ± 1.8 | 0.064 | −0.2 ± 2.2 |
Race | Caucasian | 25 (96) | 69 (92) | 0.472 | 94 (93) |
Education | High school, some College | 2 (8) | 11 (15) | 0.360 | 13 (13) |
College, professional degree | 24 (92) | 64 (85) | 0.360 | 88 (87) |
Pain Score from PROMIS scale 1.0-Global health, 0–10 (points) | | 3.3 ± 2.7 | 2 ± 1.7 | 0.060 | 2.3 ± 2.1 |
Self-rated health from PROMIS scale 1.0-Global Health | Fair | 5 (19) | 3 (4) | 0.006 | 8 (9) |
Good | 12 (46) | 19 (25) | | 31 (31) |
Very Good | 7 (27) | 41 (55) | | 48 (48) |
Excellent | 2 (8) | 12 (16) | | 14 (14) |
Co-morbidities | 2 or more | 10 (38) | 30 (40) | 0.890 | 40 (40) |
Twenty-six percent (
n = 26) adults had low function, mean SPPB score 9.62 (SD = 1.2) points, and 74% (
n = 75) were considered high functioning, mean SPPB score 11.37 (SD = 0.7) points (Table
2). At baseline, all physical function and HrQol scores were lower in the LFG versus the HGF,
p = 0.017, except physical activity was similar in both groups,
p = 0.330. Trunk endurance was worse in the LFG,
p = 0.017. There were no differences in baseline levels of kyphosis,
p = 0.216.
Table 2
Means of measures at baseline stratified by HFG, LFG and entire cohort
Physical Function |
Short Physical Performance Battery (SPPB) (0–12 points) | 9.62 (1.2) | 11.37 (0.7) | < 0.001 | 10.92 (1.1) |
4-m gait speed (meters/second) | 1.14 (0.2) | 1.38 (0.34) | < 0.001 | 1.32 (0.3) |
Modified PPT (0–36 points) | 31.4 (2.7) | 33.8 (1.7) | < 0.001 | 33.2 (2.2) |
Timed Up and Go (seconds) | 8.4 (1.6) | 7.1 (1.5) | < 0.001 | 7.4 (1.7) |
Six Minute Walk Test (meters) | 471.7 (77.2) | 524.9 (95.9) | 0.008 | 511.6 (94.1) |
PROMIS Physical function t-score (0–100) | 44.8 (4.7) | 50.1 (7.6) | < 0.001 | 48.7 (7.3) |
Health-related Quality of Life |
SRS 30 Self-image (0–5 points) | 3.33 (0.49) | 3.69 (0.56) | 0.016 | 3.53 (0.55) |
PROMIS Global Health Scale (0–100) | 35.8 (6.5) | 40.7 (4.7) | 0.001 | 39.5 (5.6) |
PROMIS Global Health Scale, Mental Health t-score (0–100) | 48.8 (8.1) | 54.1 (7.5) | 0.003 | 52.8 (7.9) |
PROMIS Global Health Scale, Physical Health t-score (0–100) | 47.9 (7.5) | 53.6 (5.6) | < 0.001 | 52.2 (6.6) |
PASE activity level (0–793) points | 102.1 (60.5) | 111.0 (53.2) | 0.330 | 108.7 (54.9) |
Pain Score 0–10 from PROMIS Global Health scale (0–10 points) | 3.3 (2.7) | 2.0 (1.68) | 0.060 | 3.4 (2.1) |
Spinal Strength |
Spinal flexion strength (percent peak torque/body weight) | 28.8 (11.4) | 32.7 (11.3) | 0.119 | 31.7 (11.4) |
Spinal extensor strength (percent peak torque/body weight) | 64.2 (16.2) | 71.0 (22.0) | 0.238 | 69.2 (20.8) |
Timed Loaded Standing (seconds) | 112.0 (49.9) | 138.4 (49.0) | 0.017 | 131.0 (50.3) |
Spinal Curvature |
Cobb angle of kyphosis (degrees) | 56.8 (13.3) | 55.5 (11.7) | 0.640 | 55.9 (12.2) |
Kyphosis derived from kyphometer (degrees) | 53.6 (6.2) | 51.5 (7.8) | 0.216 | 52.0 (7.4) |
Lordosis derived from kyphometer (degrees) | 25.9 (12.2) | 31.7 (11.4) | 0.028 | 30.2 (11.8) |
Within group change in physical function in low function group
There were no significant within-group changes in SPPB, 4-m gait speed, modified Physical Performance Test, TUG, 6 MW or PROMIS physical function in the LFG in the unadjusted analysis (Table
3). The mean SPPB score changes for the LFG was 0.62 (95%CI: − 0.2 to 1.44) points and 4-m gait speed mean change was 0.04 (95%CI: − 0.02 to 0.10) m/s. TUG mean change was 0.2 (95%CI: − 0.6 to 0.3) seconds and the 6 MW mean change was 1.8 (95%CI: − 14.0 to 17.6) meters. After controlling for age, the LFG (mean SPPB = 9.6) improved 0.77 (95%CI: 0.23 to 1.3) points (Additional file
1). After controlling for age and sex, improvement in SPPB increased to 0.84 (95%CI: 0.31 to 1.38) points (Additional file
2). After controlling for age and age and sex, there were no significant within-group changes in the LFG in 4-m gait speed, modified Physical Performance Test, TUG, 6 MW or PROMIS physical function.
Table 3
Change scores pre/post intervention in outcome measures in the HFG, LFG and overall cohort with confidence intervals (CI)
Physical Function |
Short Physical Performance Battery (SPPB) (0–12 points) | 0.62a (− 0.20 to 1.44) | − 0.04 (− 0.28 to 0.19) | 0.020 | 0.13 (− 0.14 to 0.40) |
4-m gait speed (m/s) | 0.04a (− 0.02 to 0.1) | −0.01 (− 0.06 to 0.04) | 0.406 | 0 (− 0.04 to 0.04) |
Modified PPT (0–36 points) | −0.29 (− 2.7 to 2.1) | −1.3 (− 3.0 to 0.3) | 0.166 | −1.1 (− 2.4 to 0.3) |
Time up and go (seconds) | −0.2 (− 0.6 to 0.3) | 0.04 (− 0.2 to 0.3) | 0.370 | −0.01 (− 0.2 to 02) |
6 Minute walking test (meters) | 1.8 (− 14.0 to 17.6) | 8.8 (− 4.6 to 22.1) | 0.265 | 7.0 (−3.6 to 17.6) |
PROMIS Physical Function t-score (0–100 points) | 0.91 (− 5.5 to 2.3) | 2.0 (0.5 to 3.5) | 0.353 | 1.7 (0.5 to 2.9) |
Health-related Quality of Life |
SRS 30 Self-image (0–5 pts) | 0.19 (0.02 to 0.4) | 0.24 (0.1 to 0.3) | 0.473 | 0.23 (0.1 to 0.3) |
PROMIS Global Health Scale (0–100 points) | 1.0 (− 0.8 to 2.8) | 0.3 (− 0.5 to 1.1) | 0.820 | 0.5 (− 0.2 to 1.2) |
PROMIS Global Health scale, Mental Health t-score (0–100 points) | 1.19 (− 0.8 to 3.2) | 0.3 (− 0.9 to 1.5) | 0.536 | 0.52 (− 0.5 to 1.6) |
PROMIS Global Health scale, Physical Health t-score (0–100 points) | 1.8 (− 0.3 to 3.9) | 0.6 (− 0.5 to 1.8) | 0.194 | 0.9 (− 0.06 to 1.9) |
PASE activity (0–793) points | 6.3 (− 14.0 to 26.6) | 1.7 (− 8.2 to 11.6) | 0.928 | 2.9 (− 5.9 to 11.7) |
Pain Score 0–10 from PROMIS Global Health scale (0–10 points) | − 0.2 (− 0.9 to 0.5) | −0.3 (− 0.6 to 0.06) | 0.54 | −0.26 (− 0. 5 to 0.03) |
Spinal Strength |
Spinal Flexion (percent peak torque/bodyweight) | −0.09 (− 3.4 to 3.2) | 1.5 (− 0.1 to 3.2) | 0.515 | 1.12 (− 0.4 to 2.6) |
Spinal extensor (percent peak torque/bodyweight) | −6.8 (− 16.1 to 2.6) | 6.0 (1.0 to 11.0) | 0.018 | 2.7 (− 1.8 to 7.2) |
Time loaded standing (seconds) | −8.8 (− 23.3 to 5.7) | 5.2 (− 1.6 to 12) | 0.080 | 1.6 (− 4.7 to 7.8) |
Spinal Curvature |
Cobb Angle (degrees) | −0.6 (− 2.0 to 0.9) | − 1.6 (− 2.7 to − 0.4) | 0.390 | − 1.3 (− 2.2 to − 0.4) |
Kyphosis (degrees) | −3.1a (− 5.2 to − 0.9) | −3.7a (− 5.0 to − 2.4) | 0.409 | −3.5 (− 4.6 to − 2.4) |
Lordosis (degrees) | 0.4 (−2.0 to 2.9) | − 1.5 (− 3.0 to 0.03) | 0.229 | −1.0 (− 2.3 to 0.3) |
Within group change in HrQol, spinal strength and spinal curvature
Self-image, a measure of HrQol, improved within both groups 0.19 (95%CI: 0.02 to 0.4) points in the LFG and 0.24 (95%CI: 0.1 to 0.3) points in the HFG (Table
3). Spinal extensor strength had a mean change score of - 6.8 (95%CI: − 16.12 to 2.56) percent in LFG and improved 6.0 (95%CI: 1.0 to 11.0) percent in the HFG. Spinal endurance measured by the Timed Loaded Standing mean change was − 8.8 (95%CI: − 23.3 to 5.7) seconds in the LFG and 5.2 (95%CI: − 1.6 to 12) seconds in the HFG. Kyphometer measured kyphosis improved − 3.1 (95%CI: − 5.2 to − 0.9) degrees and − 3.7 (95%CI: − 5.0 to − 2.4) degrees in the LFG and HFG respectively. PROMIS Global health, physical health scale improved 2.3 (95%CI: 0.25 to 4.39) points in the age and sex adjusted model in the LFG and 2.2 (95%CI: 0.15 to 4.21) points in the age adjusted model in the LFG (Additional files
1 and
2).
Between group change in physical function in low function versus high function
Comparing change pre/post intervention in the LFG and HFG, the LFG improved SPPB more than the HFG,
p = 0.020 (Table
3). The mean SPPB score changes for the LFG was 0.62 (95%CI: − 0.2 to 1.44) points and − 0.04 (95%CI: -0.02 to 0.10) m/s in the LFG and -0.01 (95%CI: -0.06 to 0.04) m/s in the HFG,
p=0.406), TUG, (0.2 (95%CI: -0.6 to 0.3) seconds in the LFG and 0.04 (95%CI: -0.2 to 0.3) seconds in the HFG,
p=0.370), or 6MW, (1.8 (95%CI: -14.0 to 17.6) meters in the LFG and 8.8 (95%CI: − 4.6 to 22.1) meters in the HFG,
p = 0.265) in the unadjusted analysis (Table
3). Comparing change pre/post intervention in the LFG and HFG, the LFG improved SPPB more than the HFG in the age-adjusted model,
p = 0.008 and the age and sex adjusted model,
p = 0.003 (Additional files
1 and
2). After controlling for age, the LFG (mean SPPB = 9.6) improved 0.77 (95%CI: 0.23 to 1.3) points while the HFG (mean SPPB = 11.4 points) changed - 0.093 (95%CI: − 0.04 to 0.22) points (Additional file
1). After controlling for age and sex, improvement in SPPB increased further to 0.84 (95%CI: 0.31 to 1.38) points and changed − 0.12 (95%CI: − 0.43 to 0.19) points in the HFG (Additional file
2).
Between group change in HrQol, spinal strength and spinal curvature
Comparing change pre/post intervention in the LFG and HFG, there no significant between-group changes in self-image,
p = 0.473 (Table
3). There were significant between-group changes in spinal extensor strength,
p = 0.018. There were no significant between-group changes in Timed Loaded standing,
p = 0.800. Both groups improved equally in kyphometer measured kyphosis,
p = 0.409. There was significant between-group changes in spinal extensor strength in the age-adjusted model,
p = 0.036 and borderline between-group change in the age and sex adjusted models,
p = 0.050.
Feasibility
Adherence during the 3 month intervention was 83% in the LFG and 79% in the HFG (Table
4). There were no adverse events in either group. 69% (18/26) of the low function participants and 68% (51/76) of the high function participants had non-reportable events including including pain and stiffness several hours to days after exercise, often from a pre-existing musculoskeletal complaint, which resolved within an expected period of time [
44]. The LFG reported an average 2.83 events per person and the HFG reported 2.35 events per person.
Table 4
Adherence and safety/adverse events in the LFG and HFG
Mean adherence to sessions (percent) | 20 (83) | 19 (79) |
Number of people reporting non-reportable eventsa (percent) | 18 (69) | 51 (68) |
Number non-reportable events | 51 | 120 |
Range of non-reportable events per person | 1 to 8 | 1 to 8 |
Mean number of non-reportable events per person | 2.8 | 2.4 |
Number of people reporting adverse eventsb | 0 | 0 |
Sample size calculation
Based on a 2-by-2 repeated measures design a sample size of
n = 138 (69 in invervention, 69 in control group) achieves 80% power to detect a difference in mean change of 0.6 points on the SPPB at a 0.050 significance level (alpha) using a two-sided, two-sample t-test (Additional file
3).
Discussion
The primary purpose of this secondary data analysis was to explore the hypothesis that targeting kyphosis will improve physical function in a low functioning cohort of older adults with hyperkyphosis who are transitioning to physical frailty. While there were no statistically significant changes in physical function in the participants with low physical function in the unadjusted analysis, there were significant improvements in SPPB in the adjusted models, and there were clinically significant improvements for the mean SPPB score and gait speed after the targeted kyphosis intervention in the LFG in both unadjusted and adjusted models. There were small improvements in self-image in both groups. Kyphosis improved across both LFG and HFG, even though spinal extensor strength and Time Loaded Standing had relative, negative changes the LFG and relative positive changes in the HFG. Adherence to the intervention, adverse events and non-reportable events were similar in both groups suggesting the intervention is acceptable and safe in a low functioning cohort.
As we hypothesized, SPPB improved a clinically significant amount in the LFG. SPPB changed 0.62 (95%CI: − 0.2 to 1.44) points in the unadjusted model and improved 0.77 (95%CI: 0.23 to 1.3) and 0.84 (95%CI: 0.31 to 1.38) points in the age and age and sex adjusted models in the LFG. This is similar to 2 previous randomized studies that included lower functioning adults [
17,
18]. Benedetti et al. [
17] performed a targeted exercise program among older adults with hyperkyphosis, and both active and control groups improved SPPB while only the control group improvement was significant (
p = 0.03). Baseline score for SPPB in the active group was 10.33 (SD = 1.17) points and improved 0.74 points after the intervention, and the control group baseline score was 9.38 (SD = 1.04) points and improved 1.08 points, consistent with the 0.62 (SD = 2.00) point change in our LFG. However, both groups in the Benedetti trial received an exercise program. The active group received targeted spinal strengthening while the control group received a global posture training program, which may explain why both groups improved. Jang et al. [
18] tested the efficacy of an 8-week kyphosis correction exercise program in a frailer group than our current LFG. The experimental and control group baseline SPPB scores were 8.7 points and 8.9 points, respectively. The control group received written instructions on the intervention exercises and performed them independently, and the experimental group received in-clinic training and feedback on the exercises. After the intervention period, SPPB scores improved 1.4 points in the experimental group and did not change in the control group. These results support our hypothesis that a combined kyphosis exercise and posture training program in a low functioning cohort may improve physical function, but a larger study powered to detect a significant change in physical function is needed.
It is possible targeting kyphosis in older adults with low physical function and hyperkyphosis may slow expected age-related decline in physical function. The minimum clinically important difference (MCID) has been reported to be between 0.3 to 0.8 points on the SPPB using a combination of both distribution and anchor-based methods in two different studies evaluating cohorts similar to the current cohort (age range 70–89) of mildly frail older adults. This suggests the 0.62 (95%CI: − 0.2 to 1.44) point improvement on the SPPB in the LFG may be clinically relevant [
45,
46]. Furthermore older adults in LFG improved from a baseline SPPB of 9.62 (1.2) to a score greater than the cut-off score of 10 suggesting targeting kyphosis may mitigate risk of future disability [
22]. The LFG improved gait-speed 0.04 (95%CI: − 0.02 to 0.11) m/s which may be clinically relevant given MCID has been reported to be between 0.03 to 0.06 m/s utilizing both distribution and anchor-based methods [
45,
46]. In fact, on average 3 years after the SCOR intervention, kyphosis was maintained and gait speed improved an additional 0.08 m/s, highlighting the potential long-term benefits of a short-term kyphosis intervention [
47]. Moreover, Merchant et al. [
48] concluded trunk adaptations including flexed posture precede declines in gait speed in a cross-sectional gait kinematics study of older Chinese men who were mildly frail when compared to fit older men. Our LFG may have been transitioning to frailty and improving kyphosis may have associated with a small improvement in gait speed, possibly slowing the progression to frailty.
We investigated change in self-image, which is central to psychological well-being and a measure of HRQoL and has been linked to kyphosis [
1,
49]. Self-image, a subdomain of self-esteem, is related to exercise self-efficacy, one’s belief in one’s ability participate in regular exercise [
50]. We observed a small within group improvement in self-image for both the LFG 0.19 (95%CI: 0.02 to 0.37) points and the HFG 0.24 (95%CI: 0.14 to 0.34) points after receiving the intervention and both groups responded simarly,
p = 0.473. These changes are less than the 0.43 (95% CI: 0.24 to 0.61) point change reported after a 6-month targeted kyphosis intervention delivered 3 times a week [
15]. Improving self-image through a targeted kyphosis intervention may be useful in facilitating maintence of physical activity in older adults; however, neither LFG or HFG group improved physical activity significantly after the intervention and it is possible that a 3-month intervention was not adequate to facilitate a change. Sinaki et al. conducted a 2 year home-based progressive back strengthening exercise intervention randomized trial in post-menopausal women and found physical activity improved significantly more in the intervention group,
p = 0.009, at the 2 year mark suggesting a longer exposure to kyphosis targeted intervention may lead to improved physical activity [
51].
Spinal extensor strength and endurance decreased in the LFG, but increased in the HFG after the intervention (− 6.0% vs + 6.8%,
p = 0.018) and (− 8.8 s vs + 5.2 s,
p = 0.080), respectively. Weakness in the spinal extensors increases risk of kyphosis progression and more recently trunk muscle composition has been linked to increased risk of kyphosis progression and decline in physical function [
52‐
55]. The LFG had lower baseline spinal endurance (112 s vs 138 s) and higher baseline pain scores (3.3 vs 2.0 points) which may have affected their ability to improve during the intervention, and they may have benefited from more time to accommodate to the strengthening intervention provided in the 3 month intervention. There is a dose-response relationship to strength training in older adults and while 12-weeks leads to improved strength, longer durations up to 53 weeks leads to greater improvements in muscular strength [
56]. While trunk muscle composition may be an important biologic factor in decline in physical function in older adults, it is unknown if improved trunk muscle composition has a mediating effect on improved physical function. Future trials targeting older adults with hyperkyphosis and low physical function should consider assessing trunk muscle composition in future trials to investigate it as a mediating factor for change in physical function.
Several factors indicate the intervention was well-tolerated in both the low- and high-functioning groups. Adherence to the intervention was similar in both groups. The LFG attended an average of 1 more class than the HFG participants (20 versus 19 of the possible 24 classes) and a similar number of people had non-reportable complaints in the LFG and HFG (69% vs 68%). The LFG started the intervention with higher resting pain scores (3.3 vs 2.0 points); however, both groups had small non-significant reductions in pain over the 3 month intervention period (− 0.3 points in HFG, − 0.2 points in LFG). There were no reportable adverse events in either group. The adherence rates, non-reportable events and reportable adverse events are consistent with findings reported in a meta analysis (
n = 13 studies) evaluating the impact of exercise on hyperkyphotic posture in post-menopausal women and men [
57]. These results suggest testing this intervention in a larger cohort of older adults who have low physical function is feasible and safe. Specific drop-out data within the HFG and LFG is unavailable which could have artificially influenced adherence and safety in either group. However, 9 participants dropped out in the first week due to lack of interest or time and 2 did not have analyzable baseline radiographs which reflects favorably on the integrity of the cohorts.
This analysis suggests that lower functioning older adults who are transitioning to frailty with hyperkyphosis may improve physical function after a targeted kyphosis intervention; however, there were several limitations. This was a post-hoc exploratory analysis of previously reported data from a randomized controlled trial. Causal relationships cannot be established because the number of older adults in the low functioning group was small, and the analysis was not powered to detect significant changes in physical function. Furthermore, we did not adjust for covariates due to the small sample size in our analyses, although we did perform age and sex-adjusted sensitivity analyses, and it is possible the changes in physical function were attributable to other covariates. There were differences in baseline characteristics of BMI, self-reported health, physical function and HrQol in the LFG and HFG that may have influenced results. The results in our LFG are not generalizable to a frail cohort of older adults given participants needed to be able to rise from a chair without their hands and walk a block without an assistive device to meet recruitment criteria. However we can generalize to a cohort of older adults who are transitioning to physical frailty based on a SPPB score of 10 or less. The difference in baseline SPPB scores were small (9.6 vs 11.4) which could limit generalizability to all older adults; however, there was a significant difference between change in SPPB score after controlling for age, thus this intervention may be generalizable to older adults transitioning to frailty regardless of age. Furthermore, for each unit increase in SPPB score, the odds of incident disability risk decrease by approximately 25%, suggesting the small magnitude of difference between the LFG and HFG baseline SPPB scores is clinically relevant [
20]. Despite the limitations, the magnitude and direction of changes in SPPB and gait speed suggest further study is warranted to test the hypothesis that lower functioning older adults who are transitioning to frailty with hyperkyphosis who participate in a targeted kyphosis intervention will improve physical function. The strength of this study is that no prior published studies have specifically targeted lower functioning older adults with hyperkyphosis to determine the effects of a kyphosis intervention on physical function. However, our results are consistent with other studies that included a range of physical functioning, including lower functioning older adults with hyperkyphosis [
17,
18].
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