Surface EMG Data Collection Summary
Serius Strong® Fitness and Therapy Handle vs. Traditional Handle
by
Barbara J Headley, MSc, PT
Mandy Antinori, MS, ATC
While core stabilization tools are plentiful for the pelvic muscles and trunk, there is a dearth of
such tools for developing greater dynamic scapular stabilization. While any lay person can point
to at least one tool for core training – for who has not seen a large gym ball - they would be lost
to point to a tool for similar dynamic shoulder training. When asked to examine the Serius
Strong handle by Railyard Fitness, I was immediately struck by how this simple tool could make
my arm work so hard to lift such a small weight! Pulling with the Serius Strong handle
demonstrates a simple biomechanical principle, i.e., that by increasing the lever arm an equal
demand moment will produce a greater proximal muscle response. It was obvious with the first
trial that the tool greatly increased the amount of work my proximal muscles were doing, both at
the scapular and shoulder level. I simply put the elastic tubing through the groove in the handle
and then kept the tubing in the handle’s groove as I performed the exercise. My arm had to
work hard as I tried the simple task of shoulder flexion. Removing the Serius Strong handle and
pulling the elastic tubing without it suddenly seemed remarkably easy. It felt as if there was a
much greater need for proximal muscles to control the movement with the Serius Strong handle
and that some of the instability that therapists seek for core stabilization was being offered with
the addition of the Serius Strong handle. This simple test led to the following study to explore
just how the Serius Strong handle changed muscle performance during a simple exercise.
Purpose: A small pilot test was designed to study the difference in recruitment patterns when
equal demand moments were performed with and without the Serius Strong handle incorporated
into a pulley system. It was elected to use the same demand moment for both tasks, rather than to
use the same weight because biomechanical principles tells us that the increase in the lever arm
that occurs by adding the Serius Strong handle will increase the muscle workload performed. To
reduce the expected difference in workload that would be produced by different lever arms, the
study called for equal ‘workloads’ if you will, but under two different conditions. Figure 1 shows
how the Serius Strong handle alters the length of the lever arm. The length from A to B is the
‘Length’ for the standard handle, and the length from A to C (an additional 5 inches) represents
the ‘Length’ using the Serius Strong handle. Each subject’s arm was measured from point A to B
and the Moment for each subject was calculated, using 15# as the default weight used with the
standard handle. The calculated weight for each subject was in the range of 10# using the Serius
Strong handle to equalize the moment for each task.
Subjects: Three subjects were studied. The subjects had met the following inclusion and
exclusion criteria as shown in Table 1.In addition, each subject was tested to make sure they had
pain free full range of motion (ROM) and three repetitions of a maximal grip test were done
using one position of the Jamar device. To insure that there was no subtle muscle dysfunction,
the subject also had to perform rapid pronation/supination with the dominant (test) hand. The
subject read the test protocol and signed an Informed Consent after reviewing the protocol with
the principal examiner, B Headley. The subjects ranged in age from 25 to 45, with a mean age of
36.3.One male and two females participated in the study.
Table 1
Inclusion & Exclusion Criteria
EXCLUSION
History of shoulder, elbow or wrist trauma
Upper extremity pain and no use of pain
medication (including anti-inflammatory) for
upper extremity
History of back injury or limitation in
function
INCLUSION
Full range of motion
Normal rapid rate of pronation-supination
with full ROM
Grip strength (using position #2 Jamar
device) is WNL for individual (standardized
for age, size)
Method: The exercise performed was elbow flexion, a biceps curl well known to every therapist
and athletic trainer. Limiting the exercise to a single joint moving would further limit other
variables. Further constraints were imposed by limiting the ROM to maintain equal demand
moments. To do this, the subject was seated next to the pulley system so that the pulley,
anchored by a floor pulley directly under the wrist when it rested at 90 degrees of elbow flexion
with the humerus perpendicular to the floor, the subject was instructed to pull the standard or
Serius Strong handle through a ROM limited from 100 to 80 degrees of elbow flexion. The speed
would be standardized across all repetitions of all subjects. Each subject was allowed to practice
several un-weighted repetitions before the weight was added to insure that they understood the
limitations to ROM. The starting position limited further elbow extension, and a tester limited
elbow flexion beyond the desired range. A 15# weight was used for the standard handle and the
weight was then reduced based on each subject’s forearm length to equalize the demand
moment. It was consistently about 10# with the Serius Strong handle. Six repetitions were
performed using each handle by each subject with a three minute rest period between the two
handle types. The eight muscles monitored on the dominant hand are listed in Table 2. The data
was collected with a Noraxon T2400 G, an 8-channel sEMG telemetry system.
Table 2 Surface EMG Monitoring
Wrist Extensor group
Biceps
Pectoralis Major
Anterior Deltoid
Infraspinatus
Middle Trapezius
Lower Trapezius
Brachioradialis
Analysis of Data: The data were analyzed through the Noraxon software, Master Research
Edition 1.06.26, in addition to manual analysis performed by the primary consultant, B Headley.
The peak microvolt value was calculated for all repetitions using each handle. To better
understand the relative contribution of each muscle group for comparison of the two handles, the
highest peak value for each muscle was then used as the maximum value for that muscle and
each of the other peak values was compared to that value to determine the percent participation
of each muscle in each repetition with each of the two handles. The average percent values for
the 6 repetition set that was greatest are also included in Table 3. Figure 2 shows an example of
one repetition using each handle, both performed by the same subject.
In Appendix A the tracings of all repetitions can be found, as well as the peak values for each
repetition for all three subjects and both handles. Appendix B contains the percent workloads of
each repetition for each subject and the variance of each set of six trials per task. Appendix C
plots the peaks in Excel to show the difference in motor control strategies.
Table 3
Maximum Peak Microvolt & Average Percent Workloads for Each Subject
Wrist Extensor
group
Biceps
Pectoralis Major
Anterior Deltoid
Infraspinatus
Middle Trapezius
ower Trapezius
Brachioradialis
#1 Peak
1596
#2 Peak
2071.3
#3 Peak
592.2
326
286.2
1015.8
555.8
436.2
303.4
829.1
1095.7
455.3
NA
437
500.4
550.1
1609.1
682.2^
152.4
439.3
322.4
163.7
174.9
747.2
#1 %
#2 %
#3 %
0.881
0.870
0.891
0.735
0.654
0.862
0.791
0.831
0.860
0.827
0.783
0.886
0.839
0.954
0.780
0.860
0.861
0.866*
0.833
0.830
0.894
0.905
0.891
0.861
^This is the only maximum peak that was greater using Traditional handle
*This is the sole average that was greater using Traditional handle than Serius Strong handle
Figure 1 Surface EMG: Biceps Curl with Two Handle Grips
Results: The data present some intriguing trends. Despite the fact that less weight was lifted
using the Serius Strong handle – to equalize the demand moment – there was unanimous
agreement that using the Serius Strong handle required greater effort. All of the maximum peak
values for all subjects were collected using the Serius Strong handle with the exception of one
muscle for Subject #3 in a case where the biceps muscle demonstrated partial inhibition with the
Serius Strong handle due to the increased effort it required. When the percent workload was
calculated for each muscle, each repetition compared to the maximum peak effort, an average
was calculated for the six repetitions using the Traditional handle and the six repetitions using
the Serius Strong handle. The highest average percent workload was greater using the Serius
Strong handle in all subjects with the sole exception that the biceps muscle for Subject #3 was
greater with the Traditional handle. This again represents in ability of this muscle to increase in
response to the increased demand, with less overall amplitude achieved in this muscle, by this
subject, when challenged by the Serius Strong handle even though the demand moment was
equal.
In looking at the data of each subject, comparing the two handles, there are some consistent
patterns:
1. All subjects clearly felt there was greater perceived exertion with the Serius Strong handle
even though the demand moments were equal.
2. The forearm extensor muscle group generated greater force with the Serius Strong handle as
did the brachioradialis.
3. Subjects used different motor control strategies. Subject #2 used greater trunk and most
proximal core muscle to stabilize. When Subject #3 had some inhibition of the biceps with the
Serius Strong handle, there was an increased use of the anterior deltoid, a more distal muscle,
with less help from the more proximal pectoral group. Subject #1 had small increases in the
proximal scapular stabilizers, using more distal muscles at greater force with the Serius Strong
handle, i.e., forearm extensors, brachioradialis and anterior deltoid.
Discussion: The Serius Strong handle is a tool that fits into rehabilitation or fitness venues
easily. It is simple to use, cost effective and adds a dimension to exercise of the shoulder girdle
that provides unprecedented opportunity to enhance the proximal stabilization of upper quarter
muscles with greater rapid oscillation of agonists and antagonists. The demand moment may be
equal, but the alteration in the set-up has shown that the increase in lever arm that occurs
increases the stabilizing effort that is required. The need to control the handle’s movement in
the hand requires rapid alternating or co-contraction efforts of the proximal muscles, increasing
their response to changes in posture. The demand at the wrist is increased, and by Janda’s
theory, that increases the proprioceptive feedback to the central nervous system, facilitating
greater motor output [1]. Janda has reported that there are alterations in afferent input and arthrokinetic reflexes after injury which in term have been shown to reduce activation thresholds of
neurons within the spinal cord. There have been multiple factors implicated in reflex inhibition
of muscles after injury [2].These central nervous system changes after injury result alter motor
strategies, frequently with inhibition of the prime movers. Other muscle dysfunction includes
delayed activation, hyperirritability, delayed relaxation, reduction in endurance and changes in
the motor units activated. The primary author has also indicated that there are multiple types of
dysfunction found by sEMG at the motor unit that effect how well the muscle can respond to the
motor unit action potential it receives [3].
All these factors are just as true for the upper extremity as the lower extremity, yet rehabilitation
tools for the upper extremity have been lacking in direct facilitation to enhance proprioceptive
feedback that are simple, can be done easily by the patient without direct therapist time, and can
be done at home. The upper extremity tools available on the market are generally not easily
tolerated by patients at the early stages of rehabilitation, immediately post surgery, or in the case
of chronic pain. The Serius Strong handle can be suited for all client populations from those who
have very limited motion and muscle strength to those seeking a high-demand workout. While
therapists and trainers often instruct patients in what hand position to perform their home
exercise program, i.e., thumb up, palm down, the client has many things to remember and hand
positions, if given, do not seem highly relevant to the client. The Serius Strong handle builds the
hand position in as a ‘default’ position so that as long as the tubing is threaded through the
channel, keeping the tubing in the channel is obvious to any user. The need to maintain this
position can also help provide constraints on the exercise that can reduce compensatory motor
plans being used.
Note: It should be noted that due to the marked increase in activation of the forearm muscles,
particularly the wrist extensor muscle group, patients with ‘tennis elbow’ or lateral epicondylitis
should use the tool only under careful supervision from a health care provider.
REFERENCES
[1] Bullock-Saxton, J.E., V. Janda, and M.I. Bullock, The influence of ankle sprain injury on
muscle activation during hip extension. Int. J. Sports Med, 1994. 15: p. 330-334.
[2] Richardson, C., et al., Therapeutic Exercise for Spinal Segmental Stabilization in Low Back
Pain. 1999, New York: Churchill Livingstone.
[3] Headley, B.J. and K. McLaughlin, Low Back Pain. Outcomes Still Lag.New Neural-Kinetic
model may provide answers with sEMG. Advance for Physical Therapists & PTAssistants, 2005:
p. 37-40.
About the Authors
Barbara J Headley, MSc, PT received her bachelor and master degrees in physical therapy and
has been practicing for 38 years. Headley has dedicated the last 23 years to the study of
movement and soft tissue dysfunction using surface electromyography (sEMG). A pioneer in this
field, Headley has studied the effect pain and trigger points have on motor unit action potentials.
She has developed a neural-kinetic system for evaluating and treating movement dysfunction.
The author of several books, international lecturer and involved in clinical research, Headley has
used sEMG to evaluate and treat patients for over two decades. Self-employed, Headley has been
a consultant at Boulder Center for Sports Medicine in Boulder CO for two years.
Mandy Antinori, MS, ATC, CSCS earned her bachelor’s degree in Kinesiology-Athletic
Training with extensive training in Proprioceptive Neuromuscular Facilitation (PNF).Antinori
went on to earn a master’s degree in Kinesiology-Sports Medicine and has become a competent
clinician, educator and researcher.Antinori has completed a mentorship with Headley, studying
sEMG. She has been active in integrating sEMG into the sports medicine arena while working
full-time at Boulder Center for Sports Medicine in Boulder CO.