Take Home Points

  1. Isometric training seems to produce increases in strength at the specific angle trained, but not through a joint’s full ROM.

In today’s world, individuals are looking for faster, more efficient methods for improving their physique. There are many products and programs convincing consumers they can get in great shape in a short period of time. Examples of these products include, but are not limited to the Bodyblade six exercises in six minutes routine, Ab Circle Pro 3-minute workout, and Perfect Pushup. Some of these products have been tested and validated such as the Bodyblade. Others continue to remain under speculation and scrutiny. Many times the ads use testimonies rather than proper research and validation beforehand.
Similar to other products, the Shake Weight (SW) claims to “increase muscle tone and create muscle definition through reduction of body fat” (Glenn 2012). The benefits of the SW are based on the concept of “dynamic inertia” reported by the company. Both ends of the modality are spring loaded and allow the weight to forcefully move back and forth and claim to generate greater gains in muscle size and strength than traditional training (Glenn 2012). The company states that the SW increases muscle activity by more than 300% compared to traditional weights, claims based on comparisons of an isometric bicep curl. (Glenn 2012).
Isometric training has been compared to dynamic training through force production and strength through range of motion (ROM). Studies have suggested that isometric training increases isometric contraction when comparing isometric contraction with dynamic training. One of the concerns with isometric training is the lack of training throughout full ROM of each joint (Glenn 2012). Studies have also examined angle-specific training responses to isometric training. Results from these studies suggest that strength was increased for contractions only within 20 degrees of the training angle. Isometric training seems to produce increases in strength at the specific angle trained, but not through a joint’s full ROM.
Glenn (2012) compared the electromyographic (EMG) muscle activity of the SW to a traditional dumbbell (DB) performing the same exercises. Twelve men (22.9 years) and 13 women (23 years) volunteered to participate in this study. Subjects performed the chest shake (CS), biceps shake (BS), and triceps shake (TS) using the SW and DB Maximal voluntary isometric contractions (MVIC) were exhibited for all muscles. EMG activity was recorded for the pectoralis major (PM), triceps brachii (TB), biceps brachii (BB), anterior deltoid (AD), trapezius (TR), and rectus abdominus (RA) and compared to detect differences between modalities. EMG activity for each muscle group was reported as a percentage of each subject’s individual maximum voluntary isometric contraction (MVIC).
During the CS exercise muscle activity was significantly greater for DB in the BB muscle when compared to the SW mode (50.8 ± 28.9%; 35.8 ± 30.8%). The SW did not have any advantage over the DB for any exercise, nor for any muscle group. Further, no muscle group during any of the SW trials exhibited an MVIC over 60%, the level necessary to increase muscular strength. The purpose of this study was to determine if a traditional dumbbell repeated the muscle activation of the SW modality when performing the same exercises. The results of this study showed that the SW had no significant increases from a traditional dumbbell in muscle activation. This study could be done with heavier weights to determine if a heavier load would cause higher levels of activation when performing the same exercises. From a practical standpoint the traditional DB would seem to be more economical when beginning a similarly styled activity program. Data from this study also suggests that completing exercises from this program lacked the ability to generate muscle activation greater than 60% of MVIC for almost every muscle tested (Glenn 2012).
1. Glenn JM, Cook I, Di Brezzo R, Gray M, Vincenzo JL. Comparison of the shake weight(®) modality exercises when compared to traditional dumbbells. J Sports Sci Med. 2012 Dec 1;11(4):703-8.

Written by Chris Barber, CPT

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