by Vincent Metzo, MA, LMT, CSCS

Strengthening the trunk muscles and the body’s core has become a prevalent subject over the last 20 years. When we look at the use of unstable surfaces (physioballs a.k.a. Swedish balls, balance disks/platforms, Bosu balls, etc.) and the use of unstable objects to lift (slosh pipes, slosh balls, weights suspended from bars, etc.) the topics of upper and lower extremity strengthening, and that of stabilizing muscles at the shoulder joint and hip also have been studied. These investigations go way back to the late 1990’s. Additionally, the subject of using specific breathing techniques has been studied. To effectively use any tool (slosh pipes, etc.) or method (anatomical breathing, biomechanical breathing or Valsalva maneuver) one must look at the available research to make appropriate decisions.

Starting with some older studies, research by McCool et al. (1997) concluded that the cross-section of the diaphragm was increased (made stronger) by general (weight lifting) and specific (breathing) exercises. The increased strength of the diaphragm should aid in increasing intra-abdominal pressure and assist in trunk stabilization. Mel Siff, in Facts and Fallacies of Fitness (2002), further states that the holding of the breath and timing of breathing during exercise allows the belly to distend automatically is of greater relevance than trying to pull it in (navel to the spine) during heavy lifting and pushing. He further suggests that reactive transversus abdominis activation is set off by changes in breathing pattern and tension changes in the diaphragm. Similar evidence has been put forth more recently by Stuart McGill who also prefers the “bracing” maneuver to the “drawing in” maneuver for trunk and spine stability.

A full body approach to training the trunk and spinal stabilizers is currently overtaking the specific abdominal crunch and transversus abdominus activation methods. This is in part because the only time the trunk muscles will work independently of the limbs is when the body is suspended in water or air. During activities, the body stabilizes as a whole, which includes contributions from the periphery and the muscles, ligaments, and soft tissues that stabilize the adjacent vertebrae. The speed at which the body must stabilize is very important, and thus a specific internally focused conscious activation of muscles may slow down the automatic processes by which we stabilize. Although we may prepare and be able to stabilize slowly before some activities, many times (during falling, being pushed, etc.) we must stabilize in a dynamic, fast, explosive, or ballistic manner. This recruitment of stabilizing muscles all over the body is under the control of preprogrammed processes (feed forward) and ongoing feedback from the proprioceptive and vestibular systems. The proprioceptive system plays a larger role when the support is stationary and the vestibular system when the support is moving.

RELATED: Effectiveness and Efficacy of Suspension Training

Balance on an unstable surface requires that the feet remain in a fixed position. Typically when a perturbation (destabilizing force) moves our center of gravity (COG) off of our base of support (BOS), we step to widen the base of support to stay balanced. When we do activities on a balance apparatus, we now keep the feet and the space between them fixed; (the base of support), so we must use another strategy to maintain our upright position or balance. These other strategies are different than what we use in life, work, or sport, where we would move the feet and change the base of support. Research has shown that in trained dancers, hip and ankle strategies to maintain balance when the feet are fixed in position on a balance apparatus have had positive effects.

This post however isn’t about balance training, it’s about lifting unstable objects. When we begin to explore the research on lifting stable vs. unstable objects we find studies that compare barbell (stable) to dumbbell (unstable) exercises. Campbell et al. (2014) looked at changes in muscle activation during a barbell (BB) (coupled) and dumbbell (DB) (uncoupled) chest press exercise performed on an unstable surface. The results suggested that demands on the core musculature to provide stability are increased with the use of DBs (uncoupled) as opposed to a BB (coupled).

A similar study states, “many believe that the most effective way to recruit the core stabilizing muscles is to execute traditional exercise movements on unstable surfaces. However, physical activity is rarely performed with a stable load on an unstable surface; usually, the surface is stable, and the external resistance is not” (Kohler et al., 2010). In this study, the results indicated that as the instability of the exercise condition increased, the external load decreased so there was little support for training with a lighter load using unstable loads or unstable surfaces.

Next lets examine two studies that looked specifically at unstable load devices. Glass et al. (2016) examined a bicep curl exercise with a type of slosh pipe or unstable water filled tube. The findings indicated that though bicep activation remained unvaried, compensatory activation of postural muscles contribute to postural stability and thus, the device may be a useful tool for neuromuscular training leading to improved stability and control. Lawrence & Carlson (2015) examined the differences in ground reaction forces and muscle activation in the trunk and leg muscles during an unstable load (weights suspended from the bar by an elastic band) and a stable condition (a normally loaded barbell). The unstable load resulted in a decrease in ground reaction force compared to the normally loaded barbell condition. The unstable load did however produce greater muscle activation in the rectus abdominis, external oblique, and soleus. The authors concluded, “The findings of this study suggest that squatting with an unstable load will increase activation of the stabilizing musculature; and while force decrements were statistically significant, the decrease was so small it may not be relevant to practitioners” (Lawrence & Carlson, 2015).

Nairn et al. (2015) compared holding a slosh-pipe-like device to lifting while lying on a Swiss ball. A standard bench press on a stable bench was performed as a control. The effects of the location of instability (under the shoulders vs. in the hands) on kinematic and electromyographical patterns during the bench press exercise were examined. The results found trunk muscle activation was greatest during the bench press with the slosh-pipe-like tube and smallest during the standard stable bench press. Range of elbow flexion was decreased with the slosh-pipe-like tube and the pipe itself showed increased medial-lateral movement. The authors concluded “the results further support the notion that instability devices may be more beneficial for trunk muscles rather than prime movers” (Nairn et al., 2015).

RELATED: Foundations of Steel Mace Training

Behm et al. (2010) suggests using instability exercises (whether balance like exercises or lifting unstable objects) can be part of a program, but should not take the place of other traditional exercises as the results of the different types of training tools and methods are different.


Unstable objects such as the slosh pipe can be an addition to an exercise program, but should be utilized with other stable traditional exercises. The slosh pipe can be a relatively cost effective exercise tool that can be used for one-on-one or group training. The video below showcases a variety of exercises from a park group exercise class.

Vincent is the Dean of Advanced Personal Training at the Swedish Institute and the Director of Education for Kettlebell Concepts in New York City. After a few years working in corporate fitness and receiving his Diploma and License as a Massage Therapist, he began teaching at the Swedish Institute where he developed and runs the Advanced Personal Training Program, the first personal training degree program in Manhattan. In addition to maintaining a private massage therapy practice and personal training business where he works with track and field athletes, Broadway dancers and fitness clients, Vincent is the creator of the FCES (Flexibility and Corrective Exercise Specialist), Focus on Flexibility and Periodization of Sports Massage workshops, As the director of education for Kettlebell Concepts, he authored the KBC Level 2 course called The KBC Metabolic and Neurologic Specialist Certificate (KBCMNS.)


Kohler, J.M., Flanagan, S.P., & Whiting, W.C. (2010). Muscle activation patterns while lifting stable and unstable loads on stable and unstable surfaces. J Strength Cond Res 24(2): 313-321.

Behm, D.g., Drinkwater, E. J., Willardson, J. M., & Cowley, P. M. (2010). Canadian Society for Exercise Physiology position stand: The use of instability to train the core in athletic and nonathletic conditioning. Applied Physiology, Nutrition, and Metabolism. 35(1): 109-112.

Behm, D.g., Drinkwater, E. J., Willardson, J. M., & Cowley, P. M. (2010). The use of instability to train the core musculature. Applied Physiology, Nutrition, and Metabolism, 35(1): 91-108.

Saeterbakken, A. H. & Fimland, M. S. (2011). Muscle activity of the core during bilateral, unilateral, seated and standing resistance exercise. European Journal of Applied Physiology. 112(5): 1671–1678.

De Serres, S. J., & Milner, T. E. (1991). Wrist muscle activation patterns and stiffness associated with stable and unstable mechanical loads. Experimental Brain Research, 86(2): 451–458.

Burdet, E., Osu, R., Franklin, D. W., Milner, T. E., & Kawato, M. (2001). The central nervous system stabilizes unstable dynamics by learning optimal impedance. Nature, 414, 446–449.

Goodman, C., A., Pearce, A., J., Nicholes, C., J., Gatt, B., M., & Fairweather, I., H. (2008). No difference in 1RM strength and muscle activation during the barbell chest press on a stable and unstable surface. Journal of Strength and Conditioning Research, 22(1): 88-94.

Wahl, M. J., & Behm, D. G. (2008). Not all instability training devices enhance muscle activation in highly resistance-trained individuals. Journal of Strength and Conditioning Research, 22(4): 1360-1370.

Campbell, B. M., Kutz, M., R., Morgan, A., L., Fullenkamp, A., M., & Ballenger, R. (2014). An evaluation of upper-body muscle activation during coupled and uncoupled instability resistance training. Journal of Strength and Conditioning Research, 28(7): 1833–1838.

Glass, S., C., Blanchette, T., W., Karwan, L., A., Pearson, S., S., O’Neil, A., P., & Karlik, D., A. (2016). Core muscle activation during unstable bicep curl using a water-filled instability training tube. Journal of Strength & Conditioning Research, 30(11): 3212–3219.

Nairn, B., C., Sutherland, C., A., & Drake, J. D. M. (2015). Location of Instability During a Bench Press Alters Movement Patterns and Electromyographical Activity. Journal of Strength & Conditioning Research, 29(11): 3162–3170.

Lawrence, M., A., & Carlson, L., A. (2015). Effects of an unstable load on force and muscle activation during a parallel back squat. , 29(10): 2949–2953.

Byrne, J., M., Bishop, N., S., Caines, A., M., Crane, K., A., Feaver, A., M., & Pearcey, G.,E.,P. (2014). Effect of using a suspension training system on muscle activation during the performance of a front plank exercise. Journal of Strength and Conditioning Research, 28(11), 3049–3055.

Youdas, J. W., Keith, J., M., Nonn, D., E., Squires, A., C., & Hollman, J., H. (2016). Activation of spinal stabilizers and shoulder complex muscles during an inverted row using a portable pull-up device and body weight resistance. Journal of Strength & Conditioning Research, 30(7), 1933-1941.