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Stimulated Muscle Force Measurements in Neuromuscular Diseases

Muscle strength assessment is necessary for determining distribution of weakness, disease progression, and/or treatment efficacy for patients with neuromuscular diseases or those with long-term critical illnesses. Manual testing is the standard method used to assess muscle strength, yet it relies on subjective assessment by the clinician and is thus inadequate to quantify small changes in muscle strength. Devices to quantify force objectively (i.e., hand-held dynamometry and isokinetic devices) have been developed and used clinically, however they still rely on voluntary effort. Additionally, neurologically impaired or critically ill patients generally have difficulty with voluntary force assessment tasks.

Our lab has designed and tested a noninvasive muscle force assessment device to objectively quantify muscle strength for clinical use (Figure 1). Specifically, we have investigated the following areas related to the muscle force assessment system:

Figure 1. Muscle force assessment system (ankle dorsiflexors)

Figure 2. Muscle force assessment system modified for thumb adductors muscle group

Figure. 3. Muscle force assessment system adapted for arm flexor muscle

Figure 4. Muscle force assessment system adapted to measure the sternocleidomastoid muscle


Figure 5. Muscle force assessment system modified for use on critically ill patients in the ICU


  1. Brass TJ, Loushin MK, Day JW, Iaizzo PA: An improved method for muscle force assessment in neuromuscular disease. Journal of Medical Engineering and Technology 20: 67-74, 1996.
  2. Day JW, Sakamoto C, Parry GJ, Lehmann-Horn F, Iaizzo PA: Force assessment in periodic paralysis after electrical muscle stimulation. Mayo Clinic Proceedings 77: 232-240, 2002.
  3. Hong J, Iaizzo PA: Force assessment of the stimulated arm flexors: quantification of contractile propoerties. Journal of Medical Engineering & Technology 26:28-35, 2002.
  4. Hong J, Falkenberg JH, Iaizzo PA: Stimulated muscle force assessment of the sternocleidomastoid muscle in humans. Journal of Medical Engineering & Technology 29: 82-89, 2005.
  5. Ginz HF, Iaizzo PA, Girard T, Urwyler A, Pargger H: Decreased isometric skeletal muscle force in critically ill patients. Swiss Medical Weekly 135:555-561, 2005.
  6. Ginz HF, Iaizzo PA, Urwyler A, Pargger H: Use of non-invasive stimulation muscle force assessment in long-term critically ill patients: a future standard in the intensive care unit? Acta Anaesthesiologica Scandinavica (in press) 2007.

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