Reduced knee-extensor torque production at low to moderate velocities in postmenopausal women with knee osteoarthritis

TL;DR: In this paper, knee extensor muscle weakness was found in postmenopausal women with knee osteoarthritis (KOA), not only as limited maximal and rapid torque development during isometric contractions, but also dynamically at low to moderate velocities.

Abstract: This study aimed to determine deficits in knee extensor muscle function through the torque-time and torque-velocity relationships and whether these deficits are associated with reduced functional performance in postmenopausal women with knee osteoarthritis (KOA). A clinical sample of postmenopausal women with established KOA (n = 18, ≥55 years) was compared to an age-matched healthy control sample (CON) (n = 26). The deficits in different parameters of the knee extensor torque-time (maximal isometric torque and rate of torque development) and torque-velocity relationship (maximum muscle power, maximal velocity and torque at 0-500°·s-1 ) were assessed through a protocol consisting of isometric, isotonic and isokinetic tests. Functional performance was evaluated with sit-to-stand and stair-climbing tasks using a sensor-based technology (ie, time- and power-based outcomes). Postmenopausal women with KOA showed reduced maximal isometric torque (Hedge's g effect size (g) = 1.05, p = 0.001) and rate of torque development (g = 0.77-1.17, all p ≤ 0.02), combined with impaired torque production at slow to moderate velocities (g = 0.92-1.70, p ≤ 0.004), but not at high or maximal velocities (g = 0.16, p > 0.05). KOA were slower (g = 0.81-0.92, p ≤ 0.011) and less powerful (g = 1.11-1.29, p ≤ 0.001) during functional tasks. Additionally, knee extensor deficits were moderately associated with power deficits in stair climbing (r = 0.492-0.659). To conclude, knee extensor muscle weakness was presented in postmenopausal women with KOA, not only as limited maximal and rapid torque development during isometric contractions, but also dynamically at low to moderate velocities. These deficits were related to impaired functional performance. The assessment of knee extensor muscle weakness through the torque-time and torque-velocity relationships might enable individual targets for tailored exercise interventions in KOA.

Summary

Introduction

• On January 23, 2020, China quarantined Wuhan to contain an emerging coronavirus (COVID-19).
• The low detection rate coupled with an average lag of 10 days between infection and detection (6) suggest that newly infected persons who traveled out of Wuhan just before the quarantine might have remained infectious and undetected in dozens of cities in China for days to weeks.
• By assuming these rates of early epidemic growth, the authors estimate that 130 cities in China have ≥50% chance of having a COVID-19 case imported from Wuhan in the 3 weeks preceding the quarantine .
• Under their lower bound estimate of 6.26 days for the doubling time, 190/369 cities lie above the 50% threshold for importation.
• The authors conclusions are based on several key assumptions.

Data

• The authors analyzed the daily number of passengers traveling between Wuhan and 369 other cities in mainland China.
• Users permit Tencent to collect their real-time location information when they install applications, such as WeChat (≈1.13 billion active users in 2019) and QQ (≈808 million active users in 2019), and Tencent Map.
• By using the geolocation of users over time, Tencent reconstructed anonymized origin–destination mobility matrices by mode of transportation (air, road, and train) between 370 cities in China, including 368 cities in mainland China and the Special Administrative Regions of Hong Kong and Macau.
• The authors estimated daily travel volume during the 7 weeks preceding the Wuhan quarantine, December 1, 2019–January 22, 2020, by aligning the dates of the Lunar New Year, resulting in a 3-day shift.

Epidemiologic Model

• By using epidemiologic evidence from the first 425 cases of COVID-19 confirmed in Wuhan by January 22, 2020 (4 ), the authors made the following assumptions regarding the number of new cases, dIw( t), infected in Wuhan per day, t . ●.
• During this 10-day interval, the authors labeled cases as infected.
• Given the uncertainty in these estimates, the authors also performed the estimates by assuming a shorter delay (D = 6 days) and a longer delay (D = 14 days) between infection and case detection .
• Under these assumptions, the authors calculated the number of infectious cases at time, t, by the following: (t) (u)duIω = ∫ t u = t – D dIω.

Mobility Model

• The authors assume that visitors to Wuhan have the same daily risk for infection as residents of Wuhan and construct a nonhomogeneous Poisson process model (18–20) to estimate the exportation of COVID-19 by residents of and travelers to Wuhan.
• This model assumes that newly infected visitors to Wuhan will return to their home city while still infectious.

Inference of Epidemic Parameters

• The authors applied a likelihood-based method to estimate their model parameters, including the number of initial cases i 0 and the epidemic growth rate λ, from the arrival times of the 19 reported cases transported from Wuhan to 11 cities outside of China, as of January 22, 2020 .
• The authors aggregated all other cities without cases reported by January 22, 2020 into a single location (j = 0).
• Then, the likelihood for all 19 cases reported outside of China by January 22, 2020 is given by .

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Reduced knee extensor torque production at low to moderate velocities in postmenopausal women with knee osteoarthritis" ?

In this paper, the authors explored the relationship between knee extensor muscle strength and knee velocity during sitting-to-stand transitions and stair climbing in postmenopausal women. 

Q2. What are the future works mentioned in the paper "Reduced knee extensor torque production at low to moderate velocities in postmenopausal women with knee osteoarthritis" ?

Due to limited sample size, the authors were not able to cluster participants by structural KOA and/or pain severity, which should be considered in further studies. 

Q3. What corrections were applied when the sphericity assumption was violated?

Feldt corrections were applied when the sphericity assumption was violated and pairwise comparisons were carried out applying Bonferroni corrections. 

Q4. What are the advantages of instrumented measurements of functional movements?

10,11 Instrumented measurements offunctional movements (eg, sit- to- stand from a chair), in which body- fixed sensors are used to automatically detect sub- durations, allow for a more detailed quantification of the movement strategy14 and appear to have greater clinical relevance than manual recordings. 

Q5. how much time did KOA need to complete the STS task?

In particular, KOA needed more time to complete the STS task (+25%, p = 0.011), mainly attributed to a slower sitto- stand transition phase (ie, concentric phase) (+17%, p  =  0.017) in addition to a slower stand- to- sit transition phase (ie, eccentric phase) (+18%, p = 0.061). 

Q6. What is the role of the trunk kinematics in the evaluation of functional movements?

In addition, sensors can use trunk kinematics to accurately measure power production during sit- tostand transitions and stair climbing,16 which appears more clinically relevant than time- based assessments to evaluate functional trajectories among older adults or mobility- limited populations. 

Q7. What are the main contributors to the loss of maximal torque capabilities?

the loss of muscle mass, and especially the atrophy of type II fibers, seem to be major contributors to the loss of maximal torque capabilities. 

Q8. What was the rate of torque development calculated from the isometric contractions?

From the explosive isometric contractions, the rate of torque development (RTD) was calculated as the linear slope of the torque- time curve from the onset of torque production (set at 7.5 Nm) in different time intervals of 100 ms (RTD0– 100, RTD0– 200 and RTD100– 200). 

Q9. What is the relationship between the torque deficits observed at low and moderate velocities?

The torque deficits observed at low and moderate velocities provoked a flattening of the high- torque portion of the torque- velocity relationship, resulting in a lower T0. 

Q10. What is the benefit of plotting the full torque velocity profile instead of using all points as single?

Even more, the benefit of plotting the full torque- velocity profile instead of using all points as “single measurement points” allows excluding trials that deviate from the torque- velocity relationship (ie, those trials where participants failed to reach their maximal performance), further improving the reliability of the method.45 

Q11. What is the effect of the longer STS time in KOA?

As previously outlined by Sonoo et al,43 the longer STS time in KOA appeared to be related to changes in movement strategy, to pain and to knee muscle weakness. 

Q12. What was the corresponding torque and velocity for the isokinetic and isokinetic contractions?

From the isotonic and isokinetic contractions, instantaneous knee extensor power (W) was calculated as the product of torque (Nm) and angular velocity (rad·s−1) signals. 

Q13. What are the x- and y axis intercepts?

The x- and y axis intercepts correspond to the theorical maximal isometric torque (T0) and maximal shortening velocity (V0, white circle), respectively. 

Q14. What are the common outcomes of physical function in KOA?

physical function outcomes have primarily been obtained from either self- reported questionnaires11,12 or from manually recorded time required to perform the task. 

Q15. What were the parameters used to determine the torque- velocity relationship?

To ensure that the torque- velocity relationship was obtained from trials performed maximally, those trials indicated to be limited by pain and/or deviating from the estimated relationship were excluded. 

Q16. What was the highest value of the torque- time curve?

From the maximal voluntary isometric contractions, Tmax (Nm) was defined as the highest value of the torque- time curve (Figure 2A). 

Q17. What is the relationship between the knee extensor muscle weakness and functional performance?

The authors clearly observed that sensor- based power production measured during functional tasks was more closely related to knee extensor muscle weakness than time- based outcomes, even when sub- phase duration was analyzed (Table  2). 

Q18. What is the reason why the weakness was more evident in explosive conditions?

This weakness was largely due to limited high force production capabilities and was more evident in explosive conditions and at low to moderate contraction velocities (ie, at high force demands). 

Q19. Why did the authors not perform a multiple regression analysis?

Due to the limited sample size, the authors could not perform a multiple regression analysis to address whether different components of knee extensor muscle weakness could explain more of the variance in physical function compared to one specific component, but as the authors have pointed above, muscle power seems to be a determinant factor.