This study will examine the role of temperature in changing energy metabolism in human muscle. In order to do this, researchers will use magnetic resonance imaging (MRI) to provide information about how parts of muscle operate during exercise.

Magnetic resonance imaging (MRI) is a diagnostic tool that creates high quality images of the human body without the use of X-ray (radiation). In this study, MRI will be used to measure the temperature and energy level of specific muscles during rest and exercise. In addition, the muscles being tested will be heated and cooled to see if temperature directly affects levels of energy in muscle.

This study will examine the role of temperature in modulating aspects of energy metabolism in human skeletal muscle. Tests will be conducted at rest and during concentric dorsiflexion exercise of the Tibialis anterior (TA) muscle using an existing custom-designed dynamometer in conjunction with mild local heating and cooling. Magnetic resonance spectroscopy (MRS), performed in a 4-tesla whole-body NMR system, will be used to non-invasively measure muscle temperature and energy-state. Specifically these tests will assess the extent to which temperature changes occur during aerobic exercise and how small temperature changes affect mitochondrial function in-vivo.

Ages 18 to 50.

Male and female subjects.

Capable of giving informed consent.

Healthy normal volunteers.

No cardiac pacemaker of implantable defibrillator.

No aneurysm clip.

No neural stimulator (e.g. TENS-unit).

No ear implant of any type.

No metal in the eye (e.g. from machining).

No implanted device (e.g. insulin pump, drug infusion device).

No metallic foreign body, shrapnel, or bullet.