Isometric hip and knee torque measurements as an outcome measure in robot assisted gait training
Summary (3 min read)
Introduction
- The primary sensory and motor consequences of spinal cord injury (SCI) are well known, and vary according to the level and extent of lesion.
- This degree of muscle atrophy and the related loss of force generating capacity can contribute to functional impairment and can compromise progression of rehabilitation in SCI subjects.
- In recent years the use of robotic assistance during BWSTT has emerged as an alternative to therapist assisted(Adams et al., 2006; Hicks et al., 2005) or FES assisted BWSTT(Postans et al., 2004) and may provide a more resource efficient method of delivering intensive and progressive gait training (Hornby, Zemon, & Campbell, 2005).
- Recently it has been shown that the peak torques, recorded using the torque sensors integrated within the DGO exoskeleton, provides data with good inter and intra-rater reliability in both healthy subjects and subjects with neuromuscular disorder.
Methodology
- Eighteen subjects with ISCI participated in this study (Age range: 26-63 years mean age = 49.3 + 11 years) of which five were classified as sub acute/chronic subjects (> 6 months from time of injury) and thirteen were classified as acute subjects (<6 months from the time of injury).
- Subjects were recruited if they were Acute or Chronic ISCI subjects graded as AIS classification C/D.(Marino et al., 2003) Between the ages of 18-65 years.
- Subjects were not recruited if they had Complications requiring immobilization such as fractures and pressure sores.
- Osteoporosis or contractures limiting range of motion.
- Ethics approval was obtained from the National Health Service (NHS) regional ethics committee and subjects were recruited from the Queen Elizabeth National Spinal Injuries Unit, Glasgow.
Insert Table 1 here.
- Informed and signed consent was obtained from all subjects prior to the start of the study.
- A repeated measures study design was used.
- When RAGT began, subjects walked on the Lokomat at a speed of 1-1.2 km/h with body weight support between 80-70% of their body weight.
- This protocol was adopted in order to prevent any effects including muscle fatigue that subjects may experience following training, which may influence the subject’s ability to perform a peak isometric contraction.
- If the Friedman’s test indicated that there were significant differences in the generated peak torques over the six weeks of training, a Wilcoxon signed rank test was used to identify the between week differences in the generated peak torque.
Insert Figure 1 here.
- The peak torque generated as a result of isometric contraction of the muscle was successfully recorded in the hip flexors and extensors and knee flexors and extensors in all subjects.
- Examples of the peak torques recorded in two acute subjects (P15 and P10) are presented in Figures 2a and 2b respectively.
- Both subjects (P15 and P10) were classified as AIS D on the ASIA scale.
- Subject P15 was unable able to walk prior to the RAGT but following six weeks of Lokomat training the subject was able to walk with the assistance of single elbow crutch and without any braces, hence progressing from a score of 0 to a score of 19 on the WISCI II scale.
- In contrast, P10 who remained non-ambulant showed little or no change in the peak torque generated by the lower limb muscles tested over the six weeks of RAGT.
Insert Figure 2 (2a& 2b) here.
- The normalized values of the peak torques generated in the hip flexor and extensors and knee flexors and extensors were analyzed separately for acute and subacute/chronic subjects.
- In the subacute/chronic subjects the pooled data showed no significant change in the peak torque generated throughout the six weeks of RAGT .
- This contrasts with data from acute subjects who show a gradual increase in their peak torque over the six weeks of RAGT .
Insert Figures 3(3a, 3b) & 4(4a,4b) here.
- Friedman’s test performed on the pooled data from subacute/chronic subjects showed that the change in peak torque over the 6 weeks were not significant in all four muscle groups (hip flexor p=0.656, hip extensor p=0.608, knee flexor p=0.192 and knee extensor p=0.156).
- Friedman’s test performed on the pooled data from acute subjects showed that the change in peak torque over the 6 weeks in acute subjects were highly significant in all four muscle groups (p<0.001 in all four muscle groups).
- Therefore a Wilcoxon signed rank test was used to compare the peak torques recorded between the training weeks in acute subjects.
- The results of these tests along with their p value are presented in Table 2.
Insert Table 2 here.
- An increase in the lower limb motor score corresponded to an increase in the peak torque generated by the muscles that were tested.
- However this correlation between the motor score and peak torque was not a linear relationship .
- When the subject had the ability to perform full ROM against gravity in both lower limbs i.e. having a lower limb motor score >6, the between subject variability of the peak torque measure increased.
- This observation was valid for both acute and sub-acute/chronic subjects who had participated in this study.
- In addition, subacute/chronic subjects had higher lower limb motor score in both hip and knee joints compared to the acute subjects.
Discussion
- This study has succeeded in objectively recording changes in muscle strength in both acute and subacute/chronic subjects with ISCI during their participation in a 6 week intensive Lokomat RAGT programme.
- An increase in the recorded peak torque in the lower limb muscles was generally accompanied by a better ambulatory function in acute subjects as illustrated in the example shown in Figure 2a.
- From the evidence presented in this study, it is clear that for those subjects that respond to the RAGT that significant gains in the force generating capacity of the lower limb muscles can be observed by the third week of training (Table 2) in acute ISCI subjects.
- This is likely to be due to the fact that these subacute/chronic subjects were ambulant; therefore a better ambulatory capacity following ISCI seems to stabilize muscle strength.
- At these grades the lack of precision in the manual muscle test scoring system makes it difficult to account for improvement in the force generating capacity of the muscle.
Conclusion
- This study has recorded in ISCI subjects patterns of change in isometric peak torque in lower limb muscles over a 6 week programme of RAGT.
- Peak torque seems to increase most in those subjects who achieve the greatest change in locomotor function at the end of the 6 week training period.
- The measurement of isometric peak torque and its use as an outcome measure provides a more objective method for longitudinal monitoring of the force generating capacity of the muscle in subjects post injury, compared to the use of manual muscle testing.
- The differential effects of Lokomat training on muscle strength seen in acute verses subacute/chronic ISCI subjects also merits further investigation using a larger sample of subjects.
- Similarly, regular monitoring for change in the force generating capacity of the lower limb muscles can provide a useful yet simple method for personalizing the rehabilitation programme and in identifying responding subjects.
Did you find this useful? Give us your feedback
Citations
62 citations
25 citations
Cites background from "Isometric hip and knee torque measu..."
..., 2014 [228] Robotic-assisted BWSTT 5 days/wk, 6 wk ASIA C&D 14 M/4 F Percent peak torque increased 68% for hip flexion, 54% for hip extension, 93% for knee flexion and 71% for knee extension....
[...]
16 citations
15 citations
Cites methods from "Isometric hip and knee torque measu..."
...The amplitude (mVrms) value for the EMG signal was calculated as the average of the completed bursts from 10-second epochs during the last 10seconds of each power output until participants reached voluntary fatigue.(22) The EMG signals were bandpass filtered (fourth-order Butterworth) at 10–500 HZ....
[...]
11 citations
Cites methods from "Isometric hip and knee torque measu..."
...The amplitude (microvolts root mean square, mVrms) value for the EMG signal was calculated as the average of the completed kick thrusts from 10s epochs during the last 10 s of each power output until the participants reached voluntary fatigue.(21) The EMG amplitude from the MVIC was calculated for a 2-s time period corresponding to seconds 2–4 of the 6-s isometric muscle contraction....
[...]
References
262 citations
"Isometric hip and knee torque measu..." refers background in this paper
...Although preliminary studies have shown that Lokomat training improves gait in both acute (Hornby et al., 2005), and chronic ISCI subjects (Wirz et al., 2005) there have been no studies documenting the associated changes in the force generating capacity of the lower limb muscles, in subjects as…...
[...]
...4 training improves gait in both acute (Hornby et al., 2005), and chronic ISCI subjects (Wirz et al....
[...]
210 citations
"Isometric hip and knee torque measu..." refers background or methods or result in this paper
...Although preliminary studies have shown that Lokomat training improves gait in both acute (Hornby et al., 2005), and chronic ISCI subjects (Wirz et al., 2005) there have been no studies documenting the associated changes in the force generating capacity of the lower limb muscles, in subjects as they progress through RAGT using BWSTT Strength changes in lower limb muscles following locomotor training have been previously documented in ISCI subjects using objective outcome measures such as peak torque recorded using a Biodex dynamometer....
[...]
...In recent years the use of robotic assistance during BWSTT has emerged as an alternative to therapist assisted(Adams et al., 2006; Hicks et al., 2005) or FES assisted BWSTT(Postans et al., 2004) and may provide a more resource efficient method of delivering intensive and progressive gait training (Hornby, Zemon, & Campbell, 2005)....
[...]
...For acute subjects BWSTT also serves as a method for early lower limb mobilization and exercise....
[...]
...In recent years the use of robotic assistance during BWSTT has emerged as an alternative to therapist assisted(Adams et al., 2006; Hicks et al., 2005) or FES assisted BWSTT(Postans et al., 2004) and may provide a more resource efficient method of delivering intensive and progressive gait training…...
[...]
...The observation that acute subjects who positively responded to RAGT had significant increase in peak torques within the first 3 weeks of training, suggests that this type of quantitative monitoring could also be considered as a useful marker in identifying subjects who are positively responding to RAGT using BWSTT....
[...]
165 citations
"Isometric hip and knee torque measu..." refers background in this paper
...Following injury, the onset of muscle atrophy can be rapid and is evident soon after injury(Dudley-Javoroski & Shields, 2008)....
[...]
147 citations
"Isometric hip and knee torque measu..." refers background in this paper
...For the acute subjects, the functional gains in gait and muscle power are likely to reflect the combination of the natural recovery process post injury (Basso, 2000) supplemented by the impact of the intensive RAGT programme (Dietz, 2008)....
[...]
107 citations
"Isometric hip and knee torque measu..." refers background in this paper
...For the acute subjects, the functional gains in gait and muscle power are likely to reflect the combination of the natural recovery process post injury (Basso, 2000) supplemented by the impact of the intensive RAGT programme (Dietz, 2008)....
[...]
Related Papers (5)
Frequently Asked Questions (13)
Q2. What are the future works in "Isometric hip and knee torque measurements as an outcome measure in robot assisted gait training" ?
A further option is that in the chronic subjects the threshold level of activity to induce new muscle hypertrophy is elevated compared with that in acute subjects ( i. e. loss of muscle plasticity ) and further research will be required to explain these findings. RAGT, in addition to having the potential to improve the force generating capacity of the lower limb muscles and gait function in responding ISCI subjects has also been reported to have an exercise impact on cardiovascular fitness and so contributes to improvements in the overall health and wellbeing of subjects irrespective of time post injury. This suggests that when designing new pharmaceutical or regenerative treatments careful consideration should be given to the level and intensity of any concomitant rehabilitation programme.
Q3. What is the effect of RAGT on the body?
in addition to having the potential to improve the force generating capacity of the lower limb muscles and gait function in responding ISCI subjects has also been reported to have an exercise impact on cardiovascular fitness and so contributes to improvements in the overall health and wellbeing of subjects irrespective of time post injury.
Q4. What is the significance of the change in peak torques?
a change in peak torques generated by the lower limb muscles that exceeds the baseline measures, has the potential to be used as an indicator that helps the clinician to decide whether to continue training or to alter the rehabilitation strategy.
Q5. What is the effect of the RAGT programme on the body?
For the acute subjects, the functional gains in gait and muscle power are likely to reflect the combination of the natural recovery process post injury (Basso, 2000) supplemented by the impact of the intensive RAGT programme (Dietz, 2008).
Q6. What is the significance of manual muscle testing?
Manual muscle testing is an important component of the standard neurological classification of spinal cord injury (ASIA) scoring system.
Q7. What was the peak torque generated in the hip flexors and extensors?
The peak torque generated as a result of isometric contraction of the muscle was successfully recorded in the hip flexors and extensors and knee flexors and extensors in all subjects.
Q8. What was the test used to determine the difference in the generated peak torque?
If the Friedman’s test indicated that there were significant differences in the generated peak torques over the six weeks of training, a Wilcoxon signed rank test was used to identify the between week differences in the generated peak torque.
Q9. What is the advantage of RAGT in a clinical trial?
Use of interventions such as RAGT may offer advantages in such trials as both the dose and intensity of the rehabilitation programme can be easily monitored and standardized and that the integrated dynamometry provides for simple longitudinal collection of a set of important outcome measures.
Q10. What is the main reason for the loss of muscle?
This degree of muscle atrophy and the related loss of force generating capacity can contribute to functional impairment and can compromise progression of rehabilitation in SCI subjects.
Q11. What is the significance of the observation that RAGT is used to identify the subjects who are?
The observation that acute subjects who positively responded to RAGT had significant increase in peak torques within the first 3 weeks of training, suggests that this type of quantitative monitoring could also be considered as a useful marker in identifying subjects who are positively responding to RAGT using BWSTT.
Q12. Why did the subjects who participated in this study have a better ambulatory capacity?
This is likely to be due to the fact that these subacute/chronic subjects were ambulant; therefore a better ambulatory capacity (Figure 2) following ISCI seems to stabilize muscle strength.
Q13. What is the difference between therapist assisted and BWSTT?
In recent years the use of robotic assistance during BWSTT has emerged as an alternative to therapist assisted(Adams et al., 2006; Hicks et al., 2005) or FES assisted BWSTT(Postans et al., 2004) and may provide a more resource efficient method of delivering intensive and progressive gait training (Hornby, Zemon, & Campbell, 2005).