Core training

Recently, resistance training while balancing on unstable surfaces such as exercise balls has become popular. Canadian researchers David Behm PhD and colleagues published a comprehensive review and position stand on the use of instability to train the core. Research has shown that exercises performed on unstable surfaces produce higher levels of muscle activation in both the core and extremity muscles compared to stable surfaces. However, force and power outputs are decreased while exercising on unstable surfaces, sometimes up to 70%. Interestingly, increasing levels of core muscle activation can also be achieved with free weight exercises such as squats and Olympic lifts without added instability.

In their article, the authors made several recommendations for both athletes and non-athletic conditioning based on their review of the literature. Dr. Behm et al. noted that athletes should emphasize “higher-intensity ground-based lifts” (such as Olympic lifts, squats and deadlifts) while including resistance exercises with unstable devices, as well as unilateral exercises that provide “transverse stress to the core musculature.” Furthermore, they stated that “unstable exercises should not be used when hypertrophy, absolute strength, or power is the primary training goal.”

Dr. David Behm

Similar recommendations were made for the general population, noting the benefits of both free weight and instability training on promoting spinal stability. It’s important to remember to decrease resistance loads on exercises performed on unstable surfaces.

During rehabilitation, unstable surfaces can be effective at improving muscle reaction time and co-contractions that protect joints. In addition, resistance training on unstable may provide localized muscle endurance training, beneficial for the high proportion of Type I “aerobic, slow-twitch” muscle fibers found in core muscles. Dr. Behm and colleagues recommend core endurance training exercises generally be performed at higher repetitions (greater than 15 per set), while athletes requiring more strength and power perform less than 6 repetitions per set. The authors further noted that unstable surfaces can provide musculoskeletal health benefits such as decreased injury risk and increased spinal stabilization as opposed to using free weights.

In summary, unstable exercise devices such as Thera-Band Exercise Balls and Stability Trainers should be included as part of a well-rounded conditioning program for athletes and non-athletes, but not for increasing primary strength and power. In addition, resistance exercises performed on an unstable surface should be performed at a reduced intensity level because of the reduction in force output.

REFERENCES:
Behm DG, et al. The use of instability to train the core musculature. Appl Physiol Nutr Metab. 2010 Feb;35(1):91-108.

Behm DG, et al. Canadian Society for Exercise Physiology position stand: The use of instability to train the core in athletic and nonathletic conditioning. Appl Physiol Nutr Metab. 2010 Feb;35(1):109-12.

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The 7 studies they reviewed included both wobble board training (3 studies) and multi-intervention including strength training, stretching, balance training, and specific exercises (4 studies). Both balance exercise or multi-intervention exercise programs can reduce specific injuries in young athletes participating in basketball, volleyball, soccer, team handball, hockey and floorball. Specifically, balance training reduced the risk of ankle sprains by 36%, and multi-intervention training programs reduced ankle sprain risk by 50% and reduced acute knee injuries by 54%.

Thera-Band stability products can easily be incorporated in pre-season and in-season balance training programs for teams of young athletes to potentially prevent ankle and knee injuries; however, the best dosage (sets, repetitions, etc) has yet to be determined by researchers.

REFERENCE Hübscher M, et al. Neuromuscular training for sports injury prevention: a systematic review. Med Sci Sports Exerc. 2010 Mar;42(3):413-21.

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After the 6-month season, participants in the exercise group significantly improved their static balance and jumping speed. There was no difference in improvement between groups in their jump height or agility running speed. In addition, the researchers found 66% lowered risk for leg injuries in the exercise group (the authors published a separate article in the British Medical Journal in 2008). These studies show that an in-season neuromuscular training program including Thera-Band stability trainers, wobble boards, and soft weights can prevent injury and improve performance in female athletes.

REFERENCE: Pasanen K, Parkkari J, Pasanen M, Kannus P. Effect of a neuromuscular warm-up programme on muscle power, balance, speed and agility: a randomised controlled study. Br J Sports Med. 2009 Dec;43(13):1073-8. Epub 2009 Jul 20.

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Researchers at the University of Toledo performed a systematic review of functional exercise interventions for their effectiveness. They identified 6 studies that met their criteria for the review, including 4 that used balance boards and elastic resistance strengthening. The researchers concluded that functional rehabilitation improves dynamic balance and self-reported function in patients with chronic ankle sprains. The exercise programs from the reviewed studies generally lasted 4 to 6 weeks and were performed 3 to 5 times a week. Finally, they pointed out that wobble board training in rehabilitation programs is “supported by the literature”; therefore, Thera-Band balance boards should be a standard component of chronic ankle instability rehabilitation program.

REFERENCE Webster KA, Gribble PA. Functional rehabilitation interventions for chronic ankle instability: a systematic review. J Sport Rehabil. 2010 Feb;19(1):98-114.

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In a paper published in the Journal of Strength and Conditioning Research, researchers performed a 7 week study of resistance training exercises in 2 groups: one using unstable surfaces and the other on stable surfaces. The researchers hypothesized that the instability resistance training group would demonstrate significantly greater gains in functional testing after the program.

Forty, college-aged, healthy untrained subjects volunteered for the study. Subjects performed squats and vertical jumps, as well as 3 machine-resisted upper body exercises:  lat pull down, butterfly, and bench press. Both groups performed upper body exercises at 70% of 1RM. The stable surface training group performed squats at 75% 1RM, and the instability group performed squats at 50% 1RM while balancing on wobble boards, stability discs, or a BOSU ball. The instability group also performed 4 trunk stabilization exercises on an exercise ball. Subjects were tested for leg extension strength, static and dynamic balance, sit-ups, long jump, hop test for time, shuttle run, and sprint.

After the 7 week training program, both groups improved in strength, balance, and function. There was no significant difference between the groups with the exception that the instability group had better performance on sit-up and hop tests.

While this study found that instability training was as effective as traditional stable training, it was interesting that the instability group had similar results even while training the lower extremities at 1/3 less resistance compared to the stable group. The authors suggested that resistance training on unstable surfaces keeps muscle activation high, even at reduced loads, because the muscles have greater stabilizing functions. The authors also noted that opponents of resistance training on unstable surfaces argue that instability devices are not necessary because balance challenges in daily life are sufficient; therefore, additional challenge is not needed. The authors also pointed out that experienced resistance-trained individuals may not experience the same benefits as the untrained subjects in this study.

In conclusion, the authors noted that resistance training on both stable and unstable surfaces can benefit inexperienced exercisers. To get the benefits of both types of training, Thera-Band® stability trainers, stability discs, exercise balls, and balance boards should be incorporated in resistance training programs.  The authors also suggest reducing the resistance and increasing the repetitions compared to stable surface exercises when performing training on unstable surfaces.

REFERENCE: Kibele A, Behm DG.Seven weeks of instability and traditional resistance training effects on strength, balance and functional performance. J Strength Cond Res. 2009 Dec;23(9):2443-50.

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