The Science of Suspension Exercise

Recent studies comparing suspension exercise to traditional resistance methods are uncovering intriguing results.

By
Jun 15, 2015

Suspension exercise combines body weight and anchored, seatbelt-like
straps to provide an alternative to free weights and machines.

The question on a lot of trainers’ minds is whether these strap-based
training systems work as well as more traditional resistance training
tools. Though research into this question has been somewhat sparse,
studies are starting to paint a picture of effective ways to integrate
suspension exercise into a workout program.

A Brief Overview of Suspension Exercise

Suspension straps are usually anchored to a fixed point about 6 feet
above the floor or higher. Research studies often call them “labile”
straps, denoting their unstable nature.

Though suspension exercise looks a bit like the still-rings event in
men’s gymnastics, the similarities are few: With the rings event, the
hands remain in contact with the still rings, the legs are off the
ground, and the body continually performs gymnastics skills below, above
and around the rings. With 
suspension exercise, the arms and legs are
placed interchangeably in the device, and exercises progressively and
specifically challenge the musculoskeletal system.

Perhaps the best-known suspension exercise device is made by TRX®,
founded by former U.S. Navy Seal Randy Hetrick, who developed the
product while on active duty because he needed to stay in shape but had
no access to free weights or machines. Today, a few companies are making
suspension devices, which aim to increase the body’s functional movement
capabilities by improving core muscle activation, posture, coordination,
upper- and lower-body strength, total-body joint flexibility and dynamic
balance.

Emerging research from the peer-reviewed studies summarized below
illustrates some of the physiological benefits of suspension exercise.
We have divided the studies into two broad research categories:

  • suspension exercise and core activation
  • suspension exercise vs. traditional resistance training

Suspension Exercise and Core Activation

Suspension exercise devices are inherently unstable, requiring users to
engage many muscles—particularly the core musculature surrounding,
stabilizing and protecting the spine—to maintain optimal bodily form
during exercise. This poses meaningful questions addressed in research
studies.

Lower-Back Loading and 
Stiffness During Suspended Push-Ups

Beach, Howarth & Callaghan (2008) conducted a study that asked: Do the
advantages outweigh the risks when performing suspended push-ups to
activate the abdominal muscles?

Push-ups are workout mainstays because they can increase upper-body
strength and endurance, while also requiring a great deal of core muscle
activation to maintain proper form and position. Beach and colleagues
chose to investigate whether push-ups performed with a suspension
exercise device require greater abdominal-wall and latissimus dorsi
activation than traditional push-ups.

Eleven recreationally trained men (average age, 27) volunteered for the
study. They all performed both the traditional push-up and the suspended
push-up, completing one set of each—eight to 10 repetitions—with 2
minutes between sets to avoid fatigue. In the suspended push-up,
participants’ feet were stabilized on a solid platform and the hands
were placed in the suspension device. Exercise order was randomized.

Familiarization trials before data collection ensured proper form,
technique and rate of repetitions. Infrared light–emitting diodes were
placed on the subjects to let researchers view kinematics, and
electromyography markers on seven bilateral trunk muscle groups—rectus
abdominis, external obliques, internal obliques, latissimus dorsi and
erector spinae at T9, L3 and L5—provided EMG data.

Results showed that suspended push-ups generated more muscle recruitment
of the abdominal wall and latissimus dorsi than standard push-ups.
Average activation levels of the rectus abdominis, external abdominal
obliques, internal abdominal obliques and latissimus dorsi were,
respectively, 184%, 46%, 54% and 59% greater during suspended push-ups
than they were during standard push-ups.

Suspended push-ups also produced greater compressive forces at L4/L5 of
the lumbar spine than traditional push-ups, but the authors noted that
the forces did not exceed established values for safe loading of the
spine. The authors cautioned that while greater compressive forces can
enhance spinal stability, the bigger loads increase the risk of pain in
people with lower-back issues.

Take-home message: Suspended push-ups produce significantly
greater challenge to the trunk muscles, latissimus dorsi and spine than
standard push-ups do. People who are susceptible to lower-back pain
should proceed cautiously if performing suspended push-ups.

Nontraditional Abdominal Exercises

Schoffstall, Titcomb & Kilbourne (2010) asked: Do “advanced” abdominal
exercises elicit greater muscle activation than traditional abdominal
exercises?

Abdominal exercise equipment is immensely popular in the health and
fitness industry, and exercise professionals always want new ways of
challenging the abdominal musculature to improve lumbar-spine
stabilization and prevent lower-
back injury. Schoffstall and colleagues
investigated the use of sliding, suspended and stability-ball crunches
on isometric abdominal activity, and compared them with a traditional
crunching exercise.

Eleven men and 10 women of college age participated in this study. They
were instructed on how to perform each exercise with proper form before
data collection began. The study used six exercises:

  • standard crunch
  • V-up (lifting upper body and legs off floor; reaching toward feet with
    hands)
  • prone V-up with stability ball (in prone position, rolling ball toward
    hands until toes contact ball)
  • prone V-up with slide surface (getting into prone V-up position by
    sliding feet up slide surface)
  • prone V-up with suspension device (starting in prone position with
    arms extended and feet secured in stirrups of suspension device;
    exerciser V-ups to shoulder-hip-knee angle of 90 degrees)
  • prone V-up with wheel device (starting in prone position with arms
    extended and feet secured in stirrups of wheel device; participant V-ups
    to shoulder-hip-knee angle of 90 degrees).

EMG electrodes were placed on the following trunk muscle groups: upper
rectus abdominis, lower rectus abdominis, external oblique, internal
oblique and rectus femoris. For each exercise, participants performed a
5-second maximal voluntary isometric contraction (MVIC), repeating the
move if they thought they did not give their best effort the first time.
There were 1-minute breaks between repeated MVICs and 2-minute breaks
between exercises. Exercise selection was randomized.

EMG results found no difference in muscle activity for any of the six
exercises at the external oblique, rectus femoris, upper rectus
abdominis or lower rectus abdominis.

Take-home message: Although equipment often seems to increase
intensity and perceived exertion during abdominal exercises, EMG
analysis of an MVIC at the specific positions tested in this study found
that all exercises were equally effective. This study also challenges
the belief that specific exercises isolate a particular portion of the
abdominal muscles.

Unstable Plank Variations

Snarr & Esco (2014) asked: How do unstable and stable planks affect
muscle activation?

The plank is a key exercise in most sports and rehabilitation programs
because it increases core muscular strength and endurance, which in turn
enhances stability of the spinal column and transfers power to the
extremities during physical activity and exercise. Doing a plank with an
instability device has not been fully researched, which inspired Snarr
and Esco to dig deeper into the issue.

Twelve men and women in their 20s who were active exercisers with 6
months of resistance training experience volunteered for the study.
Investigators had them perform a plank exercise with different stability
and instability devices in a random order to prevent fatigue. Five
variations of the plank were held for a 5-second isometric contraction
and repeated twice. A 3-minute rest was taken between the following
exercises:

  • regular plank with elbows flexed at 90 degrees
  • incline plank with forearms and elbows on stability ball
  • plank with feet on stability ball and with forearms and elbows on ground
  • plank with elbows in suspension exercise device in horizon- tal position
  • horizontal plank with feet in suspension exercise device

Subjects were prepped for EMG analysis with surface EMG electrodes
placed at the rectus abdominis, external oblique and lumbo-sacral
erector spinae.

Results indicated that plank with elbows in a suspension exercise device
elicited significantly higher muscle activation in the rectus abdominis
than all other variations of the plank exercise. Regular plank elicited
the lowest muscle activity at the rectus abdominis. Plank with feet on a
stability ball elicited the highest activation of the external oblique,
while regular plank produced the lowest activation. The highest
activation in the lumbo-sacral erector spinae occurred in the plank with
elbows in the suspension device. The researchers said the increase in
spinal loading with this variation suggests it should be considered an
advanced exercise. They added that people who have a history of
lower-back musculature injury should be cautious if doing planks with a
suspension device.

Take-home message: Performing a plank with different instability
devices increases activation of core muscle groups such as the rectus
abdominis, external obliques and lumbo-sacral erector spinae. Caution is
advised if clients have a history of lower-back weakness or impairment.

Suspension Exercise vs.
Traditional Resistance Training

We have not seen a lot of peer-reviewed research comparing suspension
exercise and traditional resistance training. The studies reviewed below
compare specific markers of muscular performance using specific
suspended exercises vs. similar traditional resistance training.

Torso Muscle Activation 
During Suspended Rowing Exercise

Fenwick, Brown & McGill (2009) asked: What are the differences in torso
and hip muscle activation, as well as spinal load and stiffness, during
three rowing exercise variations?

Many types of rowing exercises emphasize the upper-body posterior chain.
Rowing works the lower, middle and upper trapezius and the rhomboids,
posterior deltoids and biceps brachii. Choosing the correct exercise for
a client could depend on training goals and injury status, not only in
the muscles described, but also in the torso and spine. Fenwick and
colleagues investigated lower erector spinae muscle activation and
spinal loading in three specific rowing exercises.

Seven healthy, recreationally active men (average age, 27) participated
in the study. Proper performance of each rowing exercise was taught and
monitored. The three exercises were an inverted row on a suspension
device, a bent-over barbell row and a standing single-arm cable row.

The inverted row on a suspension device challenges exercisers to apply
enough force to pull their body weight up toward a fixed anchor.
Participants lie supine on the ground (with knees bent and feet on the
floor) and grasp a suspension device handle in each hand. The length of
this device is established to allow participants to pull their upper
body toward the ceiling in a rowing action until the upper body is
horizontal (or parallel) to the ground.

In this study, muscle activity was monitored using a 16-lead
electromyography system, placed bilaterally over eight muscle groups:
rectus abdominis (right, left), external obliques (right, left),
internal obliques (right, left), latissimus dorsi (right, left), upper
(thoracic) erector spinae (right, left), lumbar erector spinae (right,
left), gluteus medius (right), gluteus maximus (right), rectus femoris
(right) and biceps femoris (right).

Fenwick et al. determined that the inverted row exercise (see Figure 1)
on the suspension device required less spinal load and shear force than
the other two rowing exercises, while still stimulating trunk muscle
activation. Greater muscle activity in the latissimus dorsi and upper
erector spinae occurred during the inverted row than did during the
other two exercises. The bent-over row exercise had the largest muscle
activation symmetrically across the back, but this option also inflicted
the largest load on the lumbar spine. The researchers noted that the
inverted row exercise would be most fitting for people with compromised
trunk musculature. The single-arm cable pulley row was determined to be
highly effective for challenging the rotational capabilities of the
trunk musculature.

Figure 1

Take-home message: Rowing exercises are great for
upper-posterior-chain muscle activation, but spinal load should be taken
into account when selecting the proper rowing exercise. In this study,
the inverted row on the suspension device resulted in meaningful
thoracic and upper-back muscle activation with modest load on the lumbar
spine. For clients unconcerned about loading, the standing bent-over row
is a very good option as long as they focus on maintaining a neutral
spine during the exercise.

Muscle Activation and Spinal 
Load With Suspended Pushing Exercises

McGill, Cannon & Andersen (2014) asked: How do muscle activity and
spinal load differ for suspension push-up exercises versus traditional
push-up exercises?

The scientists investigated this question by quantifying muscle
activation levels and spinal loads during suspension strap push-ups and
similar push-ups done on stable surfaces. Fourteen resistance-trained
men (average age, 21) with no back-related injuries/pain were recruited
for the study, which acquired data via EMG analysis. Eighteen reflective
body markers placed on each subject allowed a 3D analysis of kinematics.
The men performed eight standard and suspended push-up position
variations to a 60-beats-per-minute metronome for three repetitions.
Suspended push-ups were performed at three angles: upright, slight
forward lean angle (~60 degrees) and forward long angle (~45-degree
angle).

Results indicated that suspended push-ups performed at three different
angles elicited less shear force on the spine than traditional push-ups.
Each suspended push-up angle resulted in greater spinal compression
owing to the spine’s proximity to the ground. Suspended push-ups also
elicited greater abdominal activation for mid-torso bracing than the
standard push-up.

Take-home message: Suspension strap push-up exercises require
greater torso muscle activity than push-ups performed on stable
surfaces. Suspended push-ups can be an effective way of increasing or
decreasing push-up intensity depending on the angle of the push-up in
relation to the ground.


Components of Fitness

Janot et al. (2013) asked: How do the effects of suspension exercise on
strength, core endurance, flexibility, balance and body composition
compare with those of traditional resistance training?

Suspension exercise provides a body weight resistance system for
exercises involving multiple movement planes, muscle groups and joints.
However, very little research has compared the musculoskeletal and
functional training effectiveness of suspension exercise with that of
traditional resistance training. In one of the most well-rounded studies
to date, Janot et al. (2013) compared the effects of suspension exercise
and traditional resistance training on upper- and lower-body strength,
core endurance, flexibility, balance and body composition in younger and
middle-aged adults.

Fifty-four physically active men and women were divided into two groups
based on age: 19–25 and 44–64. Within the two age categories, subjects
were randomly assigned to either the suspension exercise group or the
traditional resistance training group. A third subgroup of younger
adults was created as a control group ( n = 10). Eight older
adults were placed in the suspension exercise group and seven in the
traditional group. Fifteen younger adults were placed in the suspension
exercise group and 14 in the traditional group. Prior to the 7-week
training program, the researchers measured participants’ body
composition, balance, flexibility, core endurance and muscular strength.
Both intervention groups trained 3 days per week on nonconsecutive days.

The suspension exercise group performed chest press, suspended lunge,
two-arm row, squat, YTW, single-stiff-leg dead lift, triceps extension,
hamstring curl, plank, and isometric side hold with the Pallof press.
The traditional training group performed bench press, lunge (both legs),
seated row, squat, YTW, single-stiff-leg dead lift (both legs), triceps
extension, plank, and isometric side hold in a Roman chair. Both groups
completed two sets of 10 repetitions for all moves except core
exercises, where time intervals were used instead of repetitions. For
both suspension and traditional training, a rating of perceived exertion
between 5 and 7 (on a 0–10 scale) was maintained for each workout
throughout the 7-week training program. Progressions for each exercise
were given to the suspension exercise group, and loads increased 5% and
10% for upper- and lower-body exercises, respectively, for the
traditional group, to maintain RPE.

Overall results showed that suspension exercise and traditional
resistance training were equally effective at improving balance,
flexibility, core endurance and lower-body muscular strength in younger
adults. Lower-body strength did improve more with traditional resistance
training (26.5%) than with suspension exercise (13.1%). Suspension
exercise produced significantly more improvement in abdominal flexor
(80.5% versus 52.9%) and back extensor (31.1% versus 9.4%) endurance in
younger subjects. Middle-aged exercisers showed similar improvements in
both modalities for most musculoskeletal variables of interest.

Take-home message: With a 7-week training program, suspension
exercise provides similar muscular fitness benefits to traditional
training in middle-aged and younger adults.

Muscular Strength and Power, 
Velocity and Jumping Ability

Maté-Muñoz et al. (2014) asked: What are the differences in muscle
actions after instability and traditional resistance circuit training?

Strength, power and movement velocity are important markers for training
competitive and recreational athletes. Traditional resistance training
has proven effective at improving these markers, and circuit training
has been found to produce even greater benefits in untrained
individuals. Maté-Muñoz and colleagues investigated the improvements in
upper- and lower-body strength, power, movement velocity and jumping
ability during training with two unstable devices versus traditional
resistance training.

Thirty-six men (average age, 23) were randomly placed in one of three
groups: control, traditional resistance and instability resistance. The
two resistance training groups exercised 3 days per week for 7 weeks.
Both groups completed circuit-style workouts; however, the instability
resistance group performed similar resistance training exercises
with two instability devices: a TRX Suspension Trainer™ and a BOSU®
Balance Trainer. All three groups performed a pretest so that changes in
upper- and lower-body strength, power, movement velocity and jumping
ability could be determined after the training.

No subjects had any experience with the unstable devices used, but all
participants had been physically active at least 2–3 days per week
before the study began. To limit a learning effect, subjects completed a
1-week practice period of three sessions, separated by 1 day. Two
different circuit-style workouts (see the sidebar for photos of the
instability resistance circuit group exercises) were created for the
traditional and instability resistance groups. The workouts alternated
throughout the study, with each one consisting of three 15-rep sets of
eight exercises. The Borg scale of perceived exertion was used to
determine and maintain exercise intensity throughout the training
program. Body position was regularly changed on the suspension device
(to create more instability) to increase intensity and add progressive
overload.

Strength (one-repetition maximum), power, movement velocity and jumping
ability improved significantly in both the instability group and the
traditional resistance training group compared with the control group.
Findings indicated that training with unstable devices under lighter
loads produced strength and power increases similar to those gained
through traditional resistance training. The researchers suggested that
the increases in strength and power from unstable training resulted from
greater activation of the trunk muscles and sympathetic transmission of
motor neurons (or greater neural drive).

Take-home message: Unstable training modes and traditional
resistance training programs provide similar benefits to muscular
strength, power, movement velocity and jumping ability in untrained,
college-aged males. Both training modes can follow similar principles of
progressive overload.


Literature Review Summary

Suspension exercise is a new, versatile exercise for younger and older
adults. It requires core activation and stabilization, while increasing
upper- and lower-body muscular strength, power and endurance. The
physiological mechanisms involved in acute and chronic exercise are not
yet explained, but preliminary research describes responses similar to
those elicited by resistance training. Research into the use of
suspension exercise devices shows promise, but further study is needed
to learn more about the benefits for clinical and sports populations.


References

Beach, T.A.C., Howarth, S.J., & Callaghan, J.P. 2008. Muscular contribution to low-back loading and stiffness during standard and suspended push-ups. Human Movement Science, 27 (3), 457-72.
Fenwick, C.M.J., Brown, S.H.M., & McGill, S.M. 2009. Comparison of different rowing exercises: Trunk muscle activation and lumbar spine motion, load and stiffness. Journal of Strength and Conditioning Research, 23 (5), 1408-17.
Janot, J., et al. 2013. Effects of TRX versus traditional resistance training programs on measures of muscular performance in adults. Journal of Fitness Research, 2 (2), 23-38.
Mat├®-Mu├▒oz, J.L., et al. 2014. Effects of instability versus traditional resistance training on strength, power and velocity in untrained men. Journal of Sports Science and Medicine, 13 (3), 460-68.
McGill, S.M., Cannon, J., & Andersen, J.T. 2014. Analysis of pushing exercises: Muscle activity and spine load while contrasting techniques on stable surfaces with a labile suspension strap training system. Journal of Strength and Conditioning Research, 28 (1), 105-16.
Schoffstall, J.E., Titcomb, D.A., & Kilbourne, B.F. 2010. Electromyography response of the abdominal musculature to varying abdominal exercises. Journal of Strength and Conditioning Research, 24 (12), 3422-26.
Snarr, R L., & Esco, M.R. 2014. Electromyographical comparison of plank variations performed with and without instability devices. Journal of Strength and Conditioning Research, 28 (11), 3298-3305.

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