Introduction: Local muscle cooling has been shown to reduce symptoms in some neuromuscular diseases.
Purpose: To determine whether lowering body temperature using a cooling vest would result in improvement in muscle strength, subjective perceptions of weakness and fatigue, and pulmonary function in patients with generalized myasthenia gravis (MG).
Methods: Patients (five female, one male) with generalized MG, aged 29–58 yr, were studied when mean body temperature was lowered (34.9 ± 0.62°C) using a cooling vest (CT) and at normal body temperature (35.8 ± 0.58°C) (NT). Isokinetic and isometric muscle strength and isokinetic endurance were measured using upper body muscle groups. The myasthenic muscle score (MMS) was performed to assess muscle impairment specific to MG patients. Pulmonary function measurements included forced vital capacity (FVC), maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP). The fatigue impact scale (FIS) was used to track subjective perceptions of fatigue. Core body and skin temperatures were measured throughout each NT and CT trial.
Results: Mean body temperature (0.65core + 0.35skin) was reduced significantly following 30–45 min of cooling (NT = 35.76 ± 0.58, CT= 34.96 ± 0.62°C). The MMS and MIP increased significantly (NT = 91.9 vs CT = 96.3; and NT = 69.3 vs CT = 79.5 cm/H2O) with cooling. Although all other variables were not statistically different between temperature conditions, individual results for grip strength of the right hand, fatigue ratio for wrist extensors and shoulder internal and external rotators, FVC, and MEP showed improvement for the majority of the subjects.
Conclusion: Cooling in patients with MG shows promise to decrease symptoms of weakness and fatigue, thus allowing increased muscle strength and endurance in some patients.
1Exercise Physiology Laboratories, Division of Physical Performance and Development, University of New Mexico, Albuquerque, NM; and 2Physical Therapy Department, School of Medicine, University of New Mexico, Albuquerque, NM2006
Address for correspondence: Dr. Christine Mermier, Exercise Physiology Laboratories, Johnson Center, University of New Mexico, Albuquerque, NM 87131; E-mail: firstname.lastname@example.org.
Submitted for publication November 2004.
Accepted for publication July 2005.
Supported by NIH NCRR GCRC GRANT 5 MO1 RROO997
The authors wish to acknowledge Lou Stephenson, Ph.D., and Brad Laprise of Natick for their equipment loans and technical assistance, and the nursing staff of the Clinical Research Center at the University of New Mexico Health Sciences Center.