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Enhancing Strength Following Locomotor Training in Incomplete SCI

Much research is focused on the development of effective therapies directed at enhancing locomotion. Typically, as noted earlier in this chapter, the majority of these investigations focus on individuals with incomplete SCI and also predominately employ ambulation-related outcome measures. However, some investigators have also examined the effect of locomotor training on enhancing lower limb strength as a secondary measure, or in other cases have examined the relationship between changes in lower limb strength and walking ability. For the most part, these therapies include a form of body-weight supported treadmill training. In these therapies, the patient’s limb movements may also be assisted by any (or a combination) of the following: therapist, appropriately timed electrical stimulation (i.e., FES) or a robotically controlled servo-mechanism (Hornby et al., 2005a; Hornby et al., 2005b; Wirz et al., 2005; Field-Fote, 2001; Field-Fote & Roach, 2011; Wernig et al., 1998; Wernig et al., 1995). In other locomotor studies involving strength measures, locomotor training consisted of overground walking assisted by FES (Granat et al., 1993) or a combination of this with treadmill and biofeedback training (Petrofsky, 2001). In the present section, the outcomes associated with the strength benefits of these studies will be presented.

 

Table 4: Locomotor Training Studies Examining Strength Measures

Author Year; Country
Score
Research Design
Sample Size
MethodsOutcomes
Field-Fote & Roach, 2011;

USA

PEDro=8

RCT

Level 1

N=64

 

Population: Patients with chronic SCI at least 1-year post-injury, mean ages between 38 and 45; TM group (14 males, 3 females), TS group (14 males, 4 females), OG group (11 males, 4 females), LR group (12 males, 2 females)

 

Treatment: Training 5 days/week for 12 weeks with: treadmill-based training with manual assistance (TM), treadmill-based training with stimulation (TS), overground training with stimulation (OG), or treadmill-based training with robotic assistance (LR)

 

Outcome Measures: Walking speed (over 10m), distance walked in 2 minutes, lower LEMS

1.   There was a significant time effect of training on the LEMS scores of the right and left leg: LEMS scores of all participants increased 8-13%, with no significant between-group differences.

 

 

Petrofsky 2001

USA
Prospective Controlled Trial

Level 2
N=10

Population: 10 males; age 22-30 yrs; incomplete, T3-T12 lesion level

 

Treatment: The control group (n=5) had 2-hour daily conventional physical therapy, including 30 min biofeedback of more affected gluteus medius for 2 months. Experimental treatment (n=5) had same program and used a portable home biofeedback device.

 

Outcome Measures: Muscle strength (isometric strain gauge transducer) and gait analysis.

1.   Gains in strength (in quadriceps, gluteus medius and hamstring) were seen for both groups but were greater for the experimental group than controls.

2.   After 2 months of therapy the reduction in Trendelenburg gait was greater for the experimental group than for the control group and the experimental group showed almost normal gait.

 

Wernig et al. 1995; Germany
Case Control

Level 3
N=153

Population: 153 participants; locomotor training group: 89 participants (44 chronic, 45 acute); control group: 64 participants (24 chronic, 40 acute)

 

Treatment: BWSTT (Laufband therapy) vs conventional rehabilitation. Specific parameters for each were not described or appeared to vary within and between groups.

 

Outcome Measures: Manual muscle testing, walking function and neurological examination pre and post training.

1.   6 /20 chronic individuals initially “nearly paralysed” gained bilateral muscle strength (increased manual muscle testing)

2.   For acute patients, no differences in strength gains between BWSTT and conventional rehab.

3.   Authors noted that locomotor gains had little correlation with strength gains.

Benito Penalva et al. 2010;

Spain

Case control

Level 3

N=42

 

Population: 29 motor incomplete SCI patients (24 males, 5 females, mean age 47; Group A < 3 months post-injury (n=16), Group B > 3 months post-injury (n = 13)

and 13 healthy volunteers (10 males, 3 females, mean age 32) with pre-test only

 

Treatment: Gait training using either the Lokomat or Gait Trainer GT1 (based on availability of the system), 20-45 minutes per sessions (5 days a week for 8 weeks).

 

Outcome Measures: the LEMS, WISCI II, 10MWT, H reflex modulation by TMS

1.   After gait training, there was a significant improvement in LEMS for both groups

 

 

 

 

Galen et al. 2014

USA
Pre-Post Test

Level 4

N= 18

Population: 18 individuals- 14 males and 4 females; motor incomplete SCI; 5 AIS C, 13 AIS D; mean age= 49.3 ± 11 years

 

Treatment: Each person participated in the study for a total period of eight weeks, including 6 weeks of RAGT using the Lokomat system. Peak torques were recorded in hip flexors, extensors, knee flexors and extensors using torque sensors that are incorporated within the Lokomat.

 

Outcome Measures: peak torque, peak voluntary isometric torque at the knee and hip

1.     All the tested lower limb muscle groups showed statistically significant (p < 0.001) increases in peak torques in the acute participants.

2.     Comparison between the change in peak torque generated by a muscle and its motor score over time showed a non-linear relationship.

Jayaraman et al. 2008;

USA

Pre-Post

Level 4

N = 5

Population: 5 participants with chronic SCI, age 21-58, level of injury C4-T4.

 

Treatment: 45 30-min sessions of locomotor training (LT) with partial BWS spread over 9-11 weeks.

 

Outcome Measures: Voluntary contractile torque; voluntary activation deficits (using twitch interpolation), muscle cross-sectional area (CSA) using MRI.

1.   All participants demonstrated improved ability to generate peak isometric torque, especially in the more involved plantar flexor (PF, +43.9 + 20.0%) and knee extensor (KE,+21.1+12.3%) muscles

2.   Significant improvements of activation deficit in both KE and PF muscles

3.   All participants demonstrated increased muscle CSA ranging from 6.8% –21.8%

Gregory et al. 2007;

USA

Case series

Level 4

N=3

 

Population: 3 males; all participants were diagnosed as AIS D; 17-27 mos post-injury.

 

Treatment: 12 weeks, 2-3 sessions/week of lower extremity resistance training combined with plyometric training (RPT). Resistance exercises included unilateral leg press, knee extension/flexion, hip extension/flexion and ankle plantar flexion exercises on adjustable load weight machines. Participants performed 2-3 sets of 6-12 repetitions at an intensity of ~70-85% of predicted 1 RM. Unilateral plyometric jump-training exercises were performed in both limbs on a ballistic jump-training device (ShuttlePro MVP ®). Participants completed a total of 20 unilateral ground contacts with each limb at a resistance of ~25% of body mass. Upon successful completion of at least 20 ground contacts, resistance was increased in increments of 10 lbs.

 

Outcome Measures: Maximal cross-sectional area of muscle groups, dynamometry, maximum and self-selected overground gait speed.

1.   RPT resulted in an improved peak torque production in the knee extensors (KE) and ankle plantar flexors (PF).

2.   Time to peak tension decreased from mean (SD) 470.8(82.2) ms to 312.0(65.7) ms in the PF and from 324.5(35.4) ms to 254.2(34.5) ms in the KE.

3.   Average rate of torque development and the absolute amount of torque generated during the initial 220 ms during a maximal voluntary contraction improved; more pronounced improvements in the PF than the KE.

4.   On average, training resulted in a mean (SD) 14.2(3.8) and 8.3(1.9)% increase in max-CSA for the PF and KE, respectively.

5.   RPT resulted in reductions in activation deficits in both the PF and KE muscle groups.

6.   Average 36.1% increase in maximum gait speed and 34.7% increase in self-selected gait speed after training.

Hornby et al. 2005b;

USA
Pre-post

Level 4
N=3

Population: 2 males, 1 female; AIS C; 5 weeks/ 6 weeks/ 18 months post-injury.

 

Treatment: Therapist and Robotic-assisted, body-weight-supported treadmill training (parameters varied between participants).

 

Outcome Measures: LEMS, functional mobility outcomes.

1.   No group statistics

2.   Increase in AIS lower limb motor scores in 2/3 participants in acute phase (5 & 6 weeks) which cannot be separated from natural recovery. No changes seen in 3rd person initiated at 18 months.

Field-Fote 2001;

USA
Pre-post

Level 4

N=19

Population: 13 males and 6 females; mean age 31.7 yrs; all participants were diagnosed as AIS C; >1 yr post-injury.

 

Treatment: Body weight-supported treadmill walking with peroneal nerve FES of the weaker limb for 1.5 hours, 3X/week, 3 months.

 

Outcome Measures: LEMS, Gait outcomes.

1.   LEMS had median increases of 3 points in both the FES-assisted leg and the non-stimulated leg

2.   Increase in AIS lower limb motor scores in 15 of 19 incomplete SCI (AIS C).

Wernig et al. 1998; Germany
Pre-post

 

Level 4
N=76

Population: Strength data reported for 25 chronic participants only

 

Treatment: BWSTT (Laufband therapy). 1-2X/day for 30 minutes, 5 days/week for 8-20 weeks.

 

Outcome Measures: Voluntary muscle scores and walking function.

1.    No group statistics.

2.    All participants showed increases in cumulative muscle scores (i.e. 8 muscles summed) indicative of increased strength.

Granat et al. 1993;

UK
Pre-post

Level 4
N=6

Population: 3 males and 3 females; age 20-40 yrs; all participants were diagnosed as Frankel C or D; C4-L1 lesion level; 2-18 yrs post-injury.

 

Treatment: FES-assisted locomotor training to quadriceps, hip abductors, hamstrings, erector spinae, common peroneal nerve, minimum 30 min, 5 days/week.

 

Outcome Measures: Manual muscle tests, maximum voluntary contraction (MVC), upright motor control, spasticity, balance and gait outcomes.

1.   Significant increase in strength (increase in hip flexors and knee extensor manual muscle test).

2.   Increased strength as indicated by increased quadriceps torque with MVC.

Tester et al. 2011;

USA

Observational

Level 5

N=30

 

Population: 22 males, 8 females; mean(SD) age 40(14), 23(18) months post-injury; AIS score C or D

 

Treatment: 21 participants underwent a 9-week manual-assisted locomotor training (LT) with 5 sessions/week; each session entailed 20-30 minutes of partial BWS treadmill stepping with manual assistance as needed

 

Outcome Measures: presence of arm swing in relation to LEMS, WISCI II presence of arm swing

 

1.   Arm swing was absent during treadmill stepping for 18/30 (60%) of individuals

2.   There was no significant difference between arm-swing vs. no arm-swing groups in the level of injury or UEMS but there was a significant difference in LEMS

 

 

Discussion

In general, investigators have noted significant increases of lower limb strength following locomotor training – despite variations between training protocols and specific methods employed. Outcome measures have included manual muscle testing of individual lower limb muscles in incomplete SCI or summated scores of several muscles (Hornby et al., 2005; Wirz et al., 2005; Field-Fote, 2001; Wernig et al., 1998; Wernig et al., 1995; Granat et al., 1993). Most recent studies have adhered to AIS international guidelines for manual muscle testing (Hornby et al., 2005a; Hornby et al., 2005b; Wirz et al., 2005; Field-Fote, 2001; Field-Fote & Roach, 2011; Tester et al., 2011; Benito-Penalva et al., 2010). Others have employed muscle torque measurements by employing strain gauge transducers (Petrofsky, 2001; Granat et al., 1993), a dynamometer, or twitch interpolation technique (Jayaraman et al., 2008).

All investigators have reported increases in lower limb muscle strength in individuals with chronic SCI. One study (Benito-Penalva et al., 2010) also found similar increases in a group with subacute SCI (< 3 months post-injury). However, several investigators have noted that enhanced walking capability was not necessarily associated with parallel increases in strength (Wirz et al. 2005; Field-Fote, 2001; Field-Fote & Roach, 2011; Wernig et al., 1998; Wernig et al., 1995). Furthermore, the clinical relevance of the small strength gains following locomotor training is questionable when considering the duration and complexity of the intervention (Field-Fote, 2001). However, there is weak evidence (from 1 study, n = 3) that significant improvements in muscle strength may be realized when locomotor training is combined with conventional therapy (Hornby et al., 2005b). In a more recent study that examined the effects of a 12-week resistance and plyometric training program, improvements in knee extensor and ankle plantarflexor torque production were accompanied by >30% improvement in gait speed (Gregory et al., 2007).

Detecting group differences in strength gains during the acute phase may be more challenging given the natural recovery. Wernig et al. (1995) found no differences between those provided locomotor training versus those treated conventionally in muscle strength gains. However, specific subject characteristics were inadequately described other than stating that body-weight supported treadmill training was initiated within a few weeks (i.e., 2-20 weeks, median 7 weeks) following injury. There was also a lack of standardized assessment, further confounding the findings.

Conclusion

There is level 1b evidence (Field-Fote & Roach 2011) that most forms of locomotor training (i.e., including body weight supported treadmill training with various assists and FES-assisted overland training) increase lower limb muscle strength in chronic SCI as indicated by overall increases in total lower extremity motor scores.

There is level 3 evidence (Wernig et al. 1995) that body weight supported treadmill training is not significantly different than conventional rehabilitation therapy in enhancing lower limb muscle strength in acute SCI, although these studies are confounded by the natural recovery that may take place in the acute period.

There is level 4 evidence (Gregory et al. 2007) that a resistance and plyometrics training program can enable improvements in overground gait speed in chronic incomplete SCI.

  • Locomotor training programs are beneficial in improving lower limb muscle strength although in acute SCI similar strength increases may be obtained with conventional rehabilitation.

    The real benefit of locomotor training on muscle strength may be realized when it is combined with conventional therapy. This should be further explored in acute, incomplete SCI where better functional outcomes may be realized with the combination of therapies.