Activity in Cerebral Palsy:How it helps muscles (& brains!) Diane L. Damiano, PhD PT National Institutes of Health Bethesda MD USA
TAKE HOME MESSAGE Activity, Activity, Activity…….
Activity and Cerebral Palsy • Those with CP have one of the most sedentary lifestyles among pediatric disabilities (Longmuir & Bar-Or 2000) • Van den Berg-Emons et al (1995) estimated that ‘average’ child with CP would need to exercise 2.5 hours/day to reach activity levels of peers
Outline • Discuss generalized effects of activity on muscle structure & function and motor outcomes (optimizing physical rehabilitation) • Neurobiology of activity: potential role of activity-based protocols for promoting neural recovery and restoration of function
Muscles now known to be one of the most ‘plastic’ tissues in the body “Muscles respond in a fairly stereotypical manner to the amount and type of activity imposed upon them” Lieber et al, 2004
Muscle Myths • Previously thought that fiber types and # of fibers determined genetically and could not change (marathon runners & sprinters born, not made) • Rehabilitation of those with CP and other CNS disorders failed to include muscle strengthening or other intense training paradigms because it would > spasticity.
How Do Muscles Adapt?(Harridge, Exp Physiol, Review 2007) Two basic mechanisms at the level of the muscle fiber (cell): • Change in mm size • Primarily by increase/decrease in fiber diameter • Mediated by satellite cells that repair or grow muscles (or replace themselves) • Change in size directly related to maximal force output • (In extreme cases (elite bodybuilders) & perhaps normal development (Sjostrom, 1992) the number of fibers may increase) • Change in protein isoform (MHC) composition • affects maximal shortening velocity (faster if > Type II)
How can muscle adaptations be indiced? Decrease mm size Immobilization Decrease activity level (contractile activity) Weightlessness Increase mm size: Placing loads on muscles, e.g. progressive resistance exercise (PRE) Change protein isoform (MHC) composition High or low frequency electrical stimulation or high intensity (speed) voluntary training Denervation
Muscle plasticity in adult & developing skeletal mm : changes in MHC composition induced by inactivity & fast-type activity in Type I fibers Schiaffino et al. Physiology 22: 269-278 2007
What happens to muscles in CP? • From infancy on (& perhaps before) children w/ CP do not move as much as those w/o CP & move differently • Muscles cells are not mature at birth; therefore in CP, muscles may fail to develop properly from outset • If muscles are not used, they become progressively weaker– then it becomes even harder to move • To what extent is this preventable or reversible?
What CP Care Environment Does to Muscles • Many treatments in CP weaken muscles: • Muscle-tendon lengthenings: <force-generation capability (Delp & Zajac, 1992) • Orthoses: can cause atrophy of calf mms • Botulinum toxin: paralyzes one mm at a joint to allow > stretch & enhance opposite mm function • ITB: depresses involuntary & voluntary muscle activity • PT: casting, splinting, restrictive garments, prior emphasis on movement quality vs. quantity, ban on strengthening can limit muscle development
Strength in CP vs. Non-CP: Dominant Side (Wiley & Damiano, DMCN 1998)
Muscle Strengthening • Multiple reviews in CP & other conditions showing that strength is predictably increased (Dodd, Tayl0r & Damiano 2002; Taylor, Dodd & Damiano 2006) • Changes in gait speed & other aspects of functioning noted often but not consistently • Depends on ‘dose’ and ‘duration’. Must be done properly & for sufficient time to achieve benefits • Must be maintained across lifespan
Muscle Fatigue in CP • Fatigue is cited as main cause for decline or cessation in walking in CP(Bottos 2004) • Cardio-respiratory endurance lower in CP • No reports on voluntary muscle fatigue in CP • We hypothesized that those with CP would be more fatigable than age-matched peers, and that endurance would worsen with level of involvement
Methods • Subjects: 18 w/ CP; 15 controls (ages 10-23y) • Fatigue Protocol: • Biodex isokinetic dynamometer • Consecutive, maximal, (concentric) reciprocal knee extension/flexion reps • 35 repetitions at 60 deg/s • Instructions: “Push all the way up as hard and fast as possible; pull down….” • Verbal encouragement each repetition
1 0.8 0.6 NPTKE (Nm) 0.4 0.2 0 0 5 10 15 20 25 30 35 REPETITIONS Methods Computed slope of the decline in torque (normalized to peak torque) in the quadriceps & hamstrings mms
1 1 0.8 0.8 0.6 0.6 Normalized Peak Torque CP CP CP 0.4 0.4 Controls 0.2 0.2 0 0 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 35 Repetitions Results for the Quadriceps
1.0 0.8 · n=10 n=10 0.6 Slope KE (N-m) n=5 n=5 N=10 0.4 0.2 n=3 0.0 I I II II III III Correlation of Slope & GMFCS Spearman (r) = -0.50, p = .035
RESULTS • Group w/ CP had greater endurance in their quadriceps than controls; hamstrings not different in CP • Stackhouse et al. 2005 evaluated fatigue with electrically elicited contractions: found quadriceps (but not triceps surae) to be less fatigable in CP • We further found that the less functional (and weaker) they were, the greater their endurance tended to be HOW DO YOU EXPLAIN THIS?
FATIGUE PARADOX • Stronger individuals may fatigue more rapidly (inconsistent) • Muscles in CP have predominance of Type I fibers (Rose 2001) • The subjective complaint of fatigue is likely due to weakness. Individuals with CP are working at higher % of maximum, so this makes them feel more tired during a similar task - same thing happens in elderly • Loss of strength with age increases fatigue even more • Suggests that the most effective long term strategy to avoid fatigue is to maintain/increase strength to lessen relative effort
THIGH CT SCANS IN TWO MATCHED PATIENTS WITH COMPLETE SCI (n=56) TRADTIONAL PTCONTROL 6+ MOS. OF FESCYCLING (Sadowsky, McDonald, Damiano et al)
RF Introduction to Muscle Architecture • Fascicle geometry • Fascicle Length (FL) • Fascicle Angle (FA) FL = MT / sin (FA) (Shortland et al, 2002) • Muscle size • (2D) Muscle thickness (MT) • (3D) Cross-sectional area (CSA) • (3D) Muscle volume • (3D) Muscle length
RECTUS FEMORIS 3D US Longitudinal RF Axial
Relationship of muscle size to strength in CP • Ohata et al (2004, 2006) suggested that muscle thickness could be used as a surrogate measure of strength in CP, especially for those who are too young, too cognitively impaired or lack sufficient motor control.
MUSCLE THICKNESS IN ADULTS WITH CP(Ohata et al, Phys Ther 2006) BY STANDING ABILITY BY GMFCS LEVEL
Muscle Ultrasound (US) GE VOLUSON730 E: linear (2D) & volume (3D) probes PARTICIPANTS:18 w/CP (12 ambulators), 20 Controls; 11 measured before & after intense summer sports camp METHODS: • Muscles • Rectus Femoris (RF) • Vastus lateralis (VL) • Position: Supine with hips & knees in extension • Measurements • RF: 50% of ASIS to Patella • VL: 50% of GT to lateral femoral condyle
Control CP 40 40 30 30 20 r = 0.85** r = 0.70** 20 10 10 0 0 20 40 60 80 100 0 0 50 100 150 200 250 300 Relationship of Muscle Thickness to Peak Torque VL MT (mm) ISOMETRIC PEAK TORQUE (N.m) *p < 0.05 **p < 0.01
Rectus Femoris Cross-Sectional Areain CP by GMFCS Level and vs. Control GMFCS X Normalized Cross-Sectional Area : r = 0.50, p =.05
RECTUS FEMORIS THICKNESS CONTROL (23kg) RFT=20.0 mm GMFCS II (21kg) RFT=13.3 mm GMFCS III (25.6kg) RFT=105 mm GMFCS IV (28.4kg) RFT=10.4 mm
CHANGE IN RECTUS CROSS SECTIONAL AREA (CSA) BY WEEKS IN SPORTS CAMP Does intense and prolonged physical activity > mm size in CP? (new evidence suggesting this is possible in as few as 3 weeks)
NEUROBIOLOGY OF ACTIVITY Over the past 40 years, considerable data have been accumulated on the beneficial physiological effects from physical activity We are now becoming aware what activity does for the brain (e.g. it decreases depression & slows cognitive decline in Alzheimer's)
PROMOTING ACTIVITY Activity should be done ‘early and often’; parents can have the largest effect on this in infancy In addition to physical changes, personality, cognitive & social development may also be affected by early activity (or lack thereof)
Activty-Based Exercise Programs • Catch-22:Those with CP need intense exercise to improve motor function, but they lack the motor function to exercise intensely. • Therapeutic approach: Use of devices that force or enable person to exercise beyond their voluntary capabilities • Body-weight supported treadmill training • Lokomat and other motor driven gait devices • FES and motor-assisted cycles
RANDOMIZED TRIAL OF TREADMILL TRAINING IN INFANTS WITH DOWN SYNDROME(Ulrich DA, Ulrich BD, Angulo-Kinzler RM, Yun J 2001) Description: 30 infants with DS assigned to control or home treadmill training beginning at independent sitting. Followed until onset of independent walking.
Review of BWSTT in Pediatric Rehabilitation(Damiano & DeJong, 2008 in press) • Shown to be efficacious (RCT) in Down Syndrome to accelerate motor milestone acquisition; more intense training seems to increase activity levels at 2 years • Pediatric SCI – prolonged training in a few individual cases with impressive anecdotal results in most (children can be taught to step even if they cannot move voluntarily) • CNS impairments: 17 studies (no RCT) suggesting that this improves gait speed and GMFM D&E. No comparison to alternatives (e.g. over ground training)
Potential Benefits of Treadmill Training in CP Strengthen anti-gravity muscles (by adjusting BWS or adding weights) Increase gait speed (> belt speed) Improve gait symmetry (e.g. elongating shorter strides) Improve interlimb coordination (through appropriate sensory inputs + practice) Increase endurance aerobic training) Combinations of above
Motor-Assisted Cycling • BWS treadmill training labor & cost intensive, difficult for therapist/ family • External assistance needed for those who cannot cycle on their own due to paresis or lack of motor control (FES-cycles or new motor assist devices) • Cycling can be performed in home with little or no assistance, trunk balance or WS • Form of locomotion similar in phasing & frequency to walking (Ting, 2002) • Evidence of shared neural circuitry & similar reflex modulation in walking & cycling (Brooke 1997)
Current Cycling Trial • PARTICIPANTS: 10 children w/ CP, ages 5-17, GMFCS III/IV • PROTOCOL: All perform 50RPM passive or active-assisted cycling 30 min/day for 5 days/week X 3 mos • GOAL: improve lower extremity coordination • PRIMARY OUTCOMES: Changes in ‘comfortable’ & ‘as fast as possible’ cadence, variability in cadence, EMG reciprocation vs. synchronization • SECONDARY OUTCOMES: 1) changes in spasticity; 2) Changes in cortical activation in response to a sensory stimulation using fMRI – none able to be still enough
Case study from motor-assisted cycling study 5 ½ yo boy with spastic diplegia GMFCS III – ambulates w/ post walker Ashworth 3 (0-4) in quadriceps & hamstrings (strong catch in first half of motion) Had adapted cycle, but needed assist from parents to ride He was able to cycle with the device part of the time (no resistance)
Cortical Plasticity The brain is also use-dependent Dramatic changes in the PNS produce dramatic changes in brain (e.g. SCI; amputation) Spinal circuits can be accessed and trained – effects may be specific and localized Spinal circuits may be used to drive cortical changes that may be more generalized How do we help the brain recover?
What type of activity does brain like? Intense (amount, speed, mm activation) Some imposed rhythm but variable (more neural control) Complex or interesting; solving problems Electrical stimulation (other sensory stimulation) Locomotor training (loading/ proprioceptive input)