The Science of Suspension Exercise

by Tony Nunez, MS and Len Kravitz, PhD on Jun 15, 2015

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

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.

Maté-Muñoz, 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.

IDEA Fitness Journal, Volume 12, Issue 7

Find the Perfect Job

More jobs, more applicants and more visits than any other fitness industry job board.

© 2015 by IDEA Health & Fitness Inc. All rights reserved. Reproduction without permission is strictly prohibited.

About the Authors

Tony Nunez, MS

Tony Nunez, MS IDEA Author/Presenter

My name is Tony Nunez and I am a certified personal trainer through the National Strength and Conditioning Association. I have been working in commercial gyms for over 3 years now and recently graduated with my bachelor's of science degree in kinesiology with an emphasis in fitness. Currently, I am instructing older adult group fitness classes, working as the lead personal trainer for the Student Recreation & Wellness Center at CSULB, doing private personal training at people's homes, and recently became a co-owner of a group fitness business - Time 2 Train Long Beach. We specialize in circuit style training for weight loss and muscle endurance. I am a very personable, outgoing individual and I spend my free time with loved ones and performing some type fo physical activity.

Len Kravitz, PhD

Len Kravitz, PhD IDEA Author/Presenter

Len Kravitz, PhD, is the program coordinator of exercise science and a researcher at the University of New Mexico in Albuquerque, where he recently won the Outstanding Teacher of the Year award. Len was also honored as the 2006 Fitness Educator of the Year by the American Council on Exercise.