• Manual Muscle Testing Score [ Time Frame: 2 years ]
  This scale reflects on muscle strength. It is based on Medical Research Council scale for muscle power, where muscle strength can have a score of 0-5 (0 means no strength and 5 means full strength).Several muscles are examined in Manual Muscle Testing (MMT) and the total strength is reported as the sum of the Medical Research Council (MRC) muscles scale score of each muscles. Total MMT score for this study can range from 0-160, where 0 means no strength in any muscles and 160 means full strength in all the muscles examined.
• IBM-Functional rating scale (IBM-FRS) [ Time Frame: 2 years ]
  This scale measure the limitations in daily life from IBM. It ask 10 questions regarding the activities of daily life and each question is scored between 0-4 (Where 4 means no difficulty and 0 means maximum difficulty). Total score can vary from 0-40, and 40 means no limitations in daily life from IBM.
• Grip test [ Time Frame: 2 years ]
  A change in grip strength using a Jamar hand dynamometer to assess the grip strength in every participant. Best of three attempts will be used.
• Get up and go test [ Time Frame: 2 years ]
  Time will be measured for a participant to stand up from a chair (using arms if necessary), walk 3 meters, turn around, return to the chair, and sit down. The better of two trials will be used.
• Six minute walk [ Time Frame: 2 years ]
  Distance walked in 6 minutes will be measured. This has been used as a primary and secondary outcome measures in several clinical trials in various neuromuscular disorders.
• Quality of Health and Well Being [ Time Frame: 2 years ]
  Short Form-36 (SF-36) is a measure of the global quality of health and well-being. The SF-36 is an eight-scaled score, which are the weighted sums of the questions in their corresponding section. Each scale can be transformed into a 0-100 scale. Lower score means more disability. SF-36 will be scored utilizing a standardized scoring manual. We will obtain a physical component summary scale and a mental component summary scale.
• Myositis Intention to Treat Activities Index (MITAX) [ Time Frame: 2 years ]
  MITAX is a scale assessing the extra-muscular disease severity of myositis. It contains 24 questions covering 7 extra muscular organ systems. Each question is scored between 0-4, where 0 = not present, 1= improving, 2= same, 3= worse, and 4= new. This score is then converted to a final score ranging from A-E for each system based on a predefined scoring schema. Total MITAX score can range between 0 to 54.
• Physician Global Assessment Score [ Time Frame: 2 years ]
  This is recorded on a 10-cm visual analog scale (VAS) by the physician at the time of evaluation. The score should reflect on the individual's appearance, medical history, physical examination, laboratory testing, and prescribed medical therapy. In this scale 0 means no evidence of disease related damage and 10 means extremely severe damage.

• Manual Muscle Testing Score [ Time Frame: 2 years ]
  An increase in MMT score on a Medical Research Council Muscle Scale (MRC) scale from baseline
• IBM-Functional rating scale (IBM-FRS) [ Time Frame: 2 years ]
  An increase in inclusion body myositis functional rating scale from baseline
• Grip test [ Time Frame: 2 years ]
  A change in grip strength using a Jamar hand dynamometer to assess the grip strength in every participant. Best of three attempts will be used.
• Get up and go test [ Time Frame: 2 years ]
  Time will be measured for a participant to stand up from a chair (using arms if necessary), walk 3 meters, turn around, return to the chair, and sit down. The better of two trials will be used.
• Six minute walk [ Time Frame: 2 years ]
  Distance walked in 6 minutes will be measured. This has been used as a primary and secondary outcome measures in several clinical trials in various neuromuscular disorders.
• Quality of Health and Well Being [ Time Frame: 2 years ]
  SF-36 is a measure of the global quality of health and well-being. Usually, the physical functioning domain of the SF-36 correlates highly with the Health Assessment Questionnaire (HAQ) disability index. SF-36 will be scored utilizing a standardized scoring manual. We will obtain a physical component summary scale and a mental component summary scale.
• Myositis Intention to Treat Activities Index (MITAX) [ Time Frame: 2 years ]
  MITAX is a scale assessing the extra-muscular disease severity of myositis. It contains 24 questions covering 7 extra muscular organ systems. Each question is scored between 0-4, where 0 = not present, 1= improving, 2= same, 3= worse, and 4= new. This score is then converted to a final score ranging from A-E for each system based on a predefined scoring schema. Total MITAX score can range between 0 to 54.
• Physician Global Assessment Score [ Time Frame: 2 years ]
  This is recorded on a 10-cm visual analog scale (VAS) by the physician at the time of evaluation. The score should reflect on the individual's appearance, medical history, physical examination, laboratory testing, and prescribed medical therapy

1. To assess changes in impedance parameters in Idiopathic Inflammatory Myopathies (IIMs).
2. To assess whether EIM parameters are reflective of disease severity, based on clinical outcome measures of IIMs.

1. To assess changes in impedance parameters in Idiopathic Inflammatory Myopathies (IIMs) There are structural and compositional changes in muscles, such as edema, adipose infiltration, and/or atrophy, in IIMs. Electrical impedance myography (EIM) is sensitive to such changes. EIM parameters will be different when compared to healthy controls in IIMs.
2. To assess whether EIM parameters are reflective of disease severity, based on clinical outcome measures of IIMs.

Clinical outcome measures reflect on disease severity which is an indirect measure of muscle involvement in IIMs. If EIM parameters correlate with clinical outcome measure, it would indirectly prove that EIM can reflect disease severity in IIMs

• Device: electrical impedance myography
  Electrical impedance myography (EIM) is a new electrodiagnostic method of quantitative muscle evaluation. It utilizes concepts of bio impedance, the ability of biological tissue to impede externally applied electrical current.
• Other: healthy control group
  healthy control

• Experimental: Inclusion Body Myositis patients
  Subjects with clinically or clinico-pathologically defined IBM will be included in this study. Patients with consistent clinical and laboratory features including ages 18 to 80 years, duration of symptoms> 12 months, serum creatine kinases (CK) no greater than 15 times upper limit of normal, prominent weakness of quadriceps and/or finger flexor weakness>shoulder abduction weakness along with some characteristic histopathological findings of endomysial inflammatory infiltrate, rimmed vacuoles and protein accumulation or 15-18 nm filaments will be considered as clinically or clinicopathologically defined IBM as proposed by the European Neuromuscular Center (ENMC IBM working group, 2013).
  Intervention: Device: electrical impedance myography
• Experimental: Idiopathic Inflammatory Myopathies patients
  Subjects with more than 2 of the following criteria, symmetric proximal weakness, elevated CK, electromyography (EMG) suggesting myositis, muscles biopsy showing inflammatory changes, and typical skin rashes of dermatomyositis (DM) will be recruited as dermatomyositis and polymyositis (DM/PM) based on Bohan and Peter criteria.
  Intervention: Device: electrical impedance myography
• Placebo Comparator: control
  Healthy controls without any known neuromuscular disorders and no family history of Amyotrophic lateral sclerosis (ALS) will be recruited for the study.
  Intervention: Other: healthy control group

Inclusion Criteria:

• duration of weakness >12 months.
• ages 18 to 80 years old.
• serum CK level no greater than 15 times the upper limit of normal.
• quadriceps weakness >hip flexor weakness and/or finger flexor weakness >shoulder abduction weakness.
• one or more of the following pathological findings:
• endomysial inflammatory infiltrate.
• rimmed vacuoles.
• protein accumulation or 15-18 mm filaments.

DM/PM inclusion criteria:

• ages 18 to 80
• Symmetric proximal weakness
• Elevated CK
• EMG suggestive of myopathy with evidence of muscle membrane irritation
• Muscle biopsy suggestive of inflammatory myositis (degeneration, regeneration, necrosis, and interstitial mononuclear infiltrates)
• Typical skin rashes of DM (Heliotrope rash or Gottron sign)

Key inclusion criteria for the control group:

• no active neuromuscular disorders or known history of neuromuscular disorders.
• no sign or symptoms of muscle weakness.
• no family history of muscular dystrophies or ALS.
• ages 18 to 80

Exclusion Criteria:

• Patients with decompensated congestive heart failure
• Patients with chronic kidney disease on hemodialysis
• Patients with active cancer on chemotherapy or radiotherapy
• Patients with severe disease who are already wheel chair bound