Heart rate changes following knee extensor muscles isometric exercise and Russian stimulation

Area of Science:

• Exercise Physiology
• Cardiovascular Health
• Neuromuscular Stimulation

Background:

• Static exercise, particularly isometric exercise, elicits a greater heart rate response than dynamic exercise.
• This distinction is significant for managing cardiovascular disorders.
• Neuromuscular electrical stimulation (NMES) presents a viable alternative to volitional isometric exercise.

Purpose of the Study:

• To compare the heart rate responses between volitional isometric exercise and NMES of the knee extensor muscles.
• To evaluate the impact of these two static exercise modalities on heart rate in healthy individuals.

Main Methods:

• A randomized trial involving 65 healthy volunteers (33 males, 32 females, aged 20-22 years).
• Participants underwent both volitional isometric exercise and NMES protocols, with a 48-hour rest period between sessions.
• Peak contraction forces and heart rate (at rest and post-intervention) were measured.

Main Results:

• Voluntary isometric exercise induced a significantly greater and more prolonged increase in heart rate compared to NMES in both females (52.2 bpm vs. 12.9 bpm) and males (56.9 bpm vs. 9.9 bpm).
• Heart rate elevations post-exercise lasted longer (2-3 minutes) than post-stimulation (immediate, short duration).
• Contraction forces generally decreased over repetitions for both methods, with notable differences in peak forces between volitional and stimulated contractions.

Conclusions:

• Intensive voluntary isometric exercise results in a more substantial and sustained heart rate increase than NMES in young, healthy adults.
• These findings suggest that the intensity and duration of cardiovascular response differ significantly between volitional and electrically induced static muscle contractions.
• The study provides valuable insights for exercise prescription in populations where cardiovascular response to exercise is a key consideration.