MSK consequences of SCI and other neuro diagnoses

what happens to bones?

• bone loss

mechanism of bone loss

• imbalance in bone formation

• loss of loading and normal pull of muscles with endocrine, neural, and vascular changes

  • kidneys reasborb Ca2 → renal stones and failure

• bone/fat relationship can contribute → increase in bone marrow adiposity

bone loss in SCI

• rapid decline in first 2 years with the first 6 mo being the greatest

  • cortical thinning and greatest decrease in trabecular (spongy) bone

• chronic slow loss after

where does the greatest BMD occcur in SCI?

distal femur and femoral neck; spine not really affected

fractures in SCI

• 46% fracture risk

• occurs during nontraumatic activities increased complications and hospital stays

complications of fractures

• Pressure ulcers
• Altered positioning in wheelchair
• Respiratory illness
• Urinary tract infections
• Autonomic dysreflexia
• Spasticity
• Delirium
• Nonunion
• Mortality
• Decreased functional mobility
• Decreased independence

relationship between bone and muscle

• muscle pulls on bone to help form shape of bone

• muscle functions as an endocrine tissue regulating glucose metabolism

influencers of muscle mass

• genetics

• activity

• neurologic factors/motor unit health

• inflammation/chronic disease

• endocrine function

• metabolic factors

• age

pathway of muscle

① muscle central denervation, neuromuscular junction degeneration;

② decreased sex hormone secretion;

③ fat deposition;

④ protein degradation;

⑤ macrophage phenotype switch, from M2 to M1 type transition;

⑥ insulin resistance;

⑦ muscle fiber type transition, from slow oxidation type to fast glycolysis type;

⑧ muscle cell apoptosis.

how does muscle change with SCI

• fibers change from slow to fast fibers

• faster contractile properties

• becomes more fatigable

energy balance

increased adiposity in intramuscular and visceral due to reduced energy expenditure and same energy consumption

Assessing obesity in SCI

• Fat mass over 20% is gold standard
• BMI and waist circumference both underestimate obesity in SCI

how does muscle impact hormonally

• metabolic syndrome and cardiovascular disease

• • 70% higher risk of CAD in paraplegia
  • Five-fold higher risk of cardiovascular disease in tetraplegia
  • Primary cause of death in chronic SCI!

how to mitigate MSK impacts of SCI

• electrical stim

e-stim

• electrical stim for strengthening

• functional e-stim (FES)

potential benefits of e-stim

• body comp

  • muscle

  • fat

• bone

• cardiovascular

  • metabolism

CONTRAINDICATIONS/PRECAUTIONS of e-stim for SCI

• Bone density/fracture history
• Pacemaker
• Uncontrolled autonomic dysreflexia (AD)
• Uncontrolled hyper/hypotension
• Open skin
• Thrombosis
• Pregnancy
• Cancer
• ROM limits that impact activity

FES rowing

• muslce

  • increase in lean mass

• fat

  • mixed results

• bone

• cardiovascular & metabolism

  • not reported

FES cycling

• muscle

  • increase in muscle size

• fat

  • modest changes

• bone

  • 2.5-5 hrs/wk over 3-5 sessions

  • slowed rate of bone loss

• cardiovascular & metabolism

  • increase in plasma glucose and muscle glucose uptake

  • decreased intramuscular fat

NMES resistance training

• muscle

  • increases in muscle size

• fat

  • modest changes

• bone

  • 30 min, 3-5 days per week, for 12 months

  • increases trabecular bone

• cardiovascular & metabolism

  • activates glucose uptake pathways

  • decreased intra-muscular fat

bone

Bone requires more time to change to a point where we can measure it (6-12 months)
• Dosing is critical to improve bone

what is needed for bone density increases

• Strong visible contractions
• Resistance
• At least 1 year of intervention

measures of intensity

• RPE
• VO2
• HR with caution
• Power output
• Loading

NMES Recommendations

• 4 sets of 8-10 reps with 3-5-minute recovery 2x/wk
• Add resistance (1 kg/wk) once achieved
• Parameters: 30 Hz, 350-450μs, up to 200mA
• At least 8-16 wks for muscle and health benefits, at least 6 months for bone changes
• increase sets, reps, resistance, parameters to increase intensity to increases muscle/lean mass
• Key Point: A strong contraction must be elicited!

FES Cycling Recommendations

• 20-60 mins, 20-50 rpm, 2-7x/wk
• Add resistance (0.5-1 Nm) once achieved
• Parameters: 30-50 Hz, 350-450μs, up to 140 mA
• At least 8-16 wks for health benefits, at least 6 months for bone changes
• Key Point: A strong visible contraction must be elicited!

FES Rowing Recommendations

• 30 mins, 3-5 x/wk, 60-80% VO2 peak
• Resistance by effort
• Parameters: 20-50Hz, 400-450μs, up to 150 mA
• Study durations ranged 5 wks to 1 year
• increases VO2 seen after 5 weeks
• increases UE strength & some body comp (fat & lean tissue) after 6 wks
• increases Bone 9-12 months

Stroke

Muscle
• Preferential atrophy of type II fibers
• Hypertrophy of type I fibers
Bone
• Risk of osteoporosis 1.82-fold higher in a study with 1537 people post stroke (compared to 5830 without stroke)

Multiple Sclerosis

Muscle
• Animal study showed increased fast twitch fibers
Bone
• Decreased BMD secondary to immobility and/or medications

Parkinson's Disease

Muscle
• Type I fiber hypertrophy
• Type II fiber atrophy in some cases
Bone
• Higher incidence of osteoporosis compared to similar aged peers
• Mechanisms not well understood

Traumatic Brain Injury

Muscle
• Animal study showed differential atrophy across muscles (mechanism unclear)
Bone
• Pituitary and hypothalamic nuclei play a role in regulation of bone remodeling
• Decreased BMD and heterotopic ossification (HO, extra bone)