Research and News
Posts tagged EMG
Abduction exercise after hip replacement: is there an optimal progression?
Aug 23rd
Patients undergoing total hip replacement often have weak hip abductor muscles before and after surgery. One of the most common hip exercises is sidelying hip abduction using an ankle weight. While this may be an effective exercise to activate the gluteus medius muscle, open-chain, non-weight bearing hip abduction is not specific to the function of the gluteus medius as a pelvic stabilizer in single-leg stance. Resisted lateral walking with a Thera-Band® Band Loop or Tubing with Cuffs is an example of such a closed-chain exercise as the patient steps away from the involved leg.
Researchers at the University of Kentucky evaluated electromyographic (EMG) levels of 4 exercises in total hip patients between 7 and 32 weeks post-operative. Dr. Cale Jacobs and colleagues were interested to see if there was a progression of muscle activation to guide clinical decisions about hip abduction exercise prescription. They published their findings in the Journal of Arthroplasty. The 4 exercises included 2 non-weight bearing and 2 weight-bearing exercises:
- Standing hip abduction with cuff weight at 1% of bodyweight, lifted to 30 degrees
- Sidelying hip abduction with cuff weight at 0.5% of bodyweight, lifted to 50% of leg length
- Standing hip abduction with uninvolved leg to 30 degrees
- Lateral walk with Thera-Band resistance band attached with More >
Exercise Ball Core Muscle Activation: Which exercises are best?
Jul 15th
Thera-Band® exercise balls are used by therapists and trainers around the world for therapy and fitness training. Despite its widespread use, the exercise ball has lacked in research to support its clinical application. Some studies have shown that abdominal exercises performed on exercise balls produce more muscle activation than the same exercise performed on a stable surface (Vera Garcia et al. 2000). In addition to traditional abdominal crunches, the exercise ball offers a variety of exercises aimed at activating the core muscles. With the variety of exercises being performed on exercise balls, more research is needed to prove or disprove the efficacy of specific exercises.
Roll Out
Physical therapy researchers quantified the electromyographic (EMG) activity of the abdominals, latissimus dorsi, lower back, and quadriceps muscles during eight “core” exercises on the exercise ball in 18 healthy subjects. They reported their findings in the Journal of Orthopedic and Sports Physical Therapy.
They found that the upper and lower rectus abdominus muscle were most activated during the roll-out (63% and 53% of maximum, respectively), and pike exercises (47% and 55%), while the internal and external obliques were most active during the pike (84% and 56% respectively) and skier exercises (73% and 47%). Not surprisingly, the lumbar paravertebral More >
Does the exercise ball enhance EMG activity during resistance training?
Jun 24th
When exercise balls became popular in the United States in the 1980s, it was thought that their instability promoted higher activation of the back and abdominal muscles for core stabilization. Several studies have shown that the exercise ball does increase muscle activation of the abdominal muscles compared to a stable surface.
As the exercise ball increased in popularity, trainers and therapists began performing traditional resistance training exercises such as the bench press with dumbbells on an exercise ball. Theoretically, the unstable surface would increase activation of both trunk and shoulder muscles. In addition to the increased risk of injuries associated with traditional resistance training on an exercise ball, researchers began to show that using an exercise ball for extremity exercises was not as effective as once thought.
Canadian researchers (Andersen & Behm 2002) were among the first to show that performing a chest press on an exercise ball significantly decreased force output by 60%. Interestingly, the muscle activation levels remained the same between surface types despite a decrease in force output, suggesting resistance training on an unstable surface may produce less efficient muscle contractions. Subsequently, other researchers (Marshall & Murphy 2006) reported an increase in EMG levels of the deltoid and abdominals More >
Progression of closed-chain gluteus medius exercises
Jun 10th
The gluteus medius muscle is an important frontal plane stabilizer of the pelvis. Although its primary function is pelvic stabilization in singe leg stance (closed-chain), many therapists and trainers continue to strengthen the gluteus medius in an open chain using hip abduction. The addition of an unstable surface such as a Thera-Band® Stability Trainer is thought to increase muscle activation due to the increased challenge of stabilizing the pelvis in the frontal plane while balancing on a labile surface.
Researchers at the Mayo clinic in Rochester Minnesota performed a descriptive electromyographic (EMG) study to quantify the activation of the gluteus medius during different closed-chain weight-bearing exercises. Young, healthy subjects performed 5 exercises: bilateral stance, unilateral stance, unilateral stance on foam, single leg squat, and single leg squat on foam.
The researchers found that single leg stance exercises produced significantly greater EMG activity compared to bilateral stance. In addition, single leg squats produced significantly more EMG activity than single leg stance. While not statistically significant, performing single-leg exercises on a foam pad did produce more EMG activity of the gluteus medius than a stable surface.
Below are the estimated peak muscle activation levels for each exercise. Unfortunately, the authors did not provide the actual % maximal contraction values (MVICs) of More >
Stable vs. Unstable: Using Exercise Balls with the Overhead Press Exercise
Apr 29th
“Functional Training” has become increasingly popular in both rehabilitation and fitness. “Core training” has often been considered a component of functional training because of the transfer of force through the trunk to the extremities. Unstable surfaces such as Thera-Band® Exercise Balls and Stability Trainers are often used with traditional exercise movements to integrate training of the trunk and extremities.
Canadian researchers Anderson and Behm have shown that instability training can provide similar muscle activation levels at lower resistance levels compared to training on stable surfaces. Unfortunately, however, unstable surface training also results in a decrease force output of prime movers. California State University researchers set out to evaluate the electromyographic (EMG) activity of prime movers and core stabilizers during a seated overhead press exercise. 30 healthy, resistance-trained subjects performed an overhead press with dumbbells and barbells while sitting on a stable surface and on an exercise ball. The investigators were interested in looking for differences in EMG levels between the stable load (barbell) and unstable load (dumbbell), on both stable (bench) and unstable surfaces (exercise ball). Subjects used a 10RM resistance (maximum amount of weight lifted for 10 repetitions) for each of the 4 conditions; thus, each condition had a slightly different absolute load.
As expected, More >
