Neuromuscular activation in conventional therapeutic exercises and heavy resistance exercises: implications for rehabilitation.
OBJECTIVE
Central activation failure and muscular atrophy are common after knee joint injury. Thus, exercises that aim to stimulate muscular hypertrophy and increase neural drive to the muscle fibers should be used during rehabilitation. This study examined the level of knee joint neuromuscular activation during 4 conventional therapeutic exercises (quadriceps femoris muscle setting, manual lateralization of the patella, rhythmic stabilization, and the pelvic bridging exercise) and 4 heavy resistance exercises (free-weight squat with a barbell, horizontal seated leg press, isolated knee extension with a cam mechanism, and isolated hamstring muscle curl) in young, untrained men who were healthy.


METHODS
Thirteen male subjects (mean age=25.3 years, SD=3.0) with no previous history of knee injury participated in the study.


METHODS
Neuromuscular activation during the exercises was defined as the root-mean-square (RMS) electromyographic (EMG) signal normalized to the peak RMS EMG signal of a maximal isometric muscle contraction.


RESULTS
Low levels of neuromuscular activation were found during all conventional exercises (<35%). A limitation may be that only a few of many different conventional exercises were investigated. The highest level of neuromuscular activation (67%-79%) was observed during the open kinetic chain resistance exercises (isolated knee extension and hamstring muscle curl). None of the conventional exercises or heavy resistance exercises were found to preferentially activate the vastus medialis muscle over the vastus lateralis muscle.


CONCLUSIONS
The results indicate that heavy resistance exercises should be included in rehabilitation programs to induce sufficient levels of neuromuscular activation to stimulate muscle growth and strength.
Andersen
Lars L
LL
National Institute of Occupational Health, Lersø Parkalle 105, DK 2100 Copenhagen Ø, Denmark.
Magnusson
S Peter
SP
Nielsen
Michael
M
Haleem
John
J
Poulsen
Kenn
K
Aagaard
Per
P
D000328:Adult; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D005081:Exercise Therapy; D006801:Humans; D007718:Knee Injuries / Q000534:rehabilitation*; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000502:physiology; D026741:Physical Therapy Modalities; D052097:Quadriceps Muscle / Q000502:physiology; D016059:Range of Motion, Articular