1. Robert Albert, and Stephen Glass Ph.D.FACSM (Sponsor S. Glass FACSM)
 Core Muscle Activation During Unstable Overhead Squat Using a Water-Filled Training Tube
Robert Albert, and Stephen Glass Ph.D.FACSM (Sponsor S. Glass FACSM)
Department of Movement Science Grand Valley State University, Allendale MI
This project has been approved by Grand Valley State University’s HRRC , {approval number H}, {expiration date: November 2015}
Abstract
PURPOSE: Stability and balance are essential components for functional movement. While these components are often developed by exercising on unstable surfaces, another alternative is to use an instable implement. The purpose of this study was to use a novel water-filled implement (“slosh tube”) to assess the degree of muscle instability created during an overhead squat. METHODS: Eleven men (age= 20.1 ± 1.0y, ht=179.8 ± 4.8cm, mass= 89.2 ± 6.9kg) completed three 30s trials of an overhead squat using an 11.4 kg tube that was partially filled with water. A central valve allowed three conditions of water movement: 50% open, 100% open, and a stable(S), closed valve setting. Subjects completed 8-10 repetitions within each condition using a counter-balanced design. Muscle activation was assessed on the right side, with passive EMG electrodes placed over the belly of the vastus lateralis (VLAT), deltoid, rectus abdominus (AB), and paraspinal muscles. Integrated EMG was measured for each repetition and converted to a %MVC for each muscle. Instability was determined using the natural log of the coefficient of variation across repetitions. A two way repeated measures ANOVA across (contraction, condition) was used to examine concentric and eccentric contractions in each muscle. %MVC was also assessed. RESULTS: Significant compensatory muscle activation denoted by increased activation variability was seen in the deltoid muscle during eccentric contractions between the stable lift and the 100% open lift (Stable LogCV= 3.06 ±0.45, 100% open = 3.60 ± 0.50). Additionally, paraspinal muscle activity was significantly more variable during the eccentric phases of the 50% open lift (LogCv= 3.28 ± 0.26) compared to the stable lift (2.77 ± 0.67). No significant differences were seen in any other muscles or lift conditions.
CONCLUSION: We conclude that the water-filled training tube induces compensatory muscle activation in the deltoid and paraspinal muscles during the eccentric phase of the overhead squat. The central control valve of the training tube allows for either turbulent or laminar water movement, which activates either the paraspinal muscles (turbulent flow) or the deltoid(laminar flow). This device may serve as an effective training tool to train compensatory muscle activation.
Methods
Subjects: 11 Men with powerlifting/ Cross Fit™ experience recruited
Day 1: Orientation, Practice and 1RM
Height, Weight, Resting BP, HHQ
Informed Consent
Standing Shoulder Press 1RM assessed using barbell
Practice with device at all settings, at prescribed pace (20 reps/min)
Day 2: Experimental Treatment
Bipolar, surface electrodes placed on the participant’s right side, and on the muscle belly of the: Deltoid, Rectus Abdominus, Paraspinal Muscles, and Vastus Lateralis. Ground electrodes were placed on boney prominences. Before electrodes were placed on subject, the specific area of skin was shaved, given an abrasion, and scrubbed with alcohol to reduce the amount of external disturbances from the muscle activity to the electrode. Skin impedance was kept below 2KΩ.
Following electrode placement:
Researchers positioned the device over the subject’s head
Subject stood in a natural overhead squat position
A metronome cadence was set at 20 repetitions/minute
Subject completed 8-10 repetitions across a 30 second time-span (Figure 1)
Concentric and eccentric transitions were marked
EMG (bipolar, 20mm interelectrode distance) was recorded at 1,000Hz (Biopac Systems Tel 100)
Three trials were completed in a counterbalanced order
Stable (valve closed)
50% (valve half opened)
100% (valve open)
Post trials: Subject performed a Maximum Voluntary Contraction (MVC) for each of the 4 muscles.
EMG data were:
High pass filtered (Blackman ~67db)
Rectified. Each concentric (CON) and eccentric (ECC) contraction were integrated
Integrals were converted to % MVC and adjusted for any sample size differences
Due to the uneven distribution and variances, the Natural Log of the Coefficient of Variation (LnCV) was computed across repetitions for each muscle to determine compensatory muscle activity (variability).
One Way ANOVA was used to determine differences across lift conditions for each muscle and for CON and ECC. Tukey post hoc tests were used for paired comparisons.
Image 5: Sample EMG data on deltoid data
Figure 1. Overhead Squat using Water-Filled Training Tube
Integral of contraction
Repetitions
50% valve open
100% valve open
Figure 2. Deltoid Muscle Activation
Discussion
The training tube in this study allows the distribution of load to be in flux throughout the overhead squat movement. This varying distribution increases the variability of muscle activation throughout completion of the lift (Glass et al.). Previous work by Glass et al using the same device showed increased compensatory activation of the paraspinal muscles during bicep curls at 50% open position. Similarly, the overhead squat at 50% open valve required significant compensatory activation of the paraspinal muscles. This is due to the turbulent flow created by the valve setting, which required continual torso stabilization from rotation. This results not only in forces pushing left and right, but also anterior and posterior within the tube. Paraspinal muscles are used during sagittal plane movements as well as rotational movements (Colado et al.), therefore significantly variable activation while experiencing turbulent flow are not surprising.
Additionally, significant compensatory activation was seen in the deltoid muscle during eccentric contractions between the stable lift and the 100% open lift. Interestingly, the increased activation compensation for both muscles was seen only during the eccentric phase of the movement, most likely due to the highest turbulence in water movement being generated during the lowering phase. Functional training devices such as the water slosh tube used in this study could demonstrate many applications in the exercise field. Instability created by the tube could prove useful in training settings as well as recovery settings when used by an individual needing to utilize proper form for the sake of learning or protection from re-injury. A 25 pound tube is light and easy to use, yet can create ample instability that forces adjustments in balance in order to complete the task. For individuals who suffer low pack pain, often there is a loss of compensatory activation in paraspinal muscles, leading to further injury (Jacobs et al.). This device may serve as an effective tool to enhance the compensatory activation ability of core and support muscles. We conclude that the partially water-filled instability device used in this study is an effective piece of equipment to invoke compensatory muscle activation of core and support muscles during an overhead squat.
References:
Anderson K & Behm D. Trunk muscle activity increases with unstable squat movements. Can J. Appl. Phyiol. 30(1):
Beach T., Howarth S., Callaghan J. Muscular contributions to low-back loading and stiffness during standard and suspended push-ups. Human Movement Science. 27(3):
Behm D. and Colado, C. The effectiveness of resistance training using unstable surfaces and devices for rehabilitation. The International Journal of Sports Physical Therapy 7(2):
Colado J, Pablos C, Chulvi-Medrano I, Garcia-Masso X, Flandez J, Behm D. The progression of paraspinal muscle recruitment intensity in localized and global strength training exercise is not based on instability alone. Arch Phys Med Rehabil 92(11): , 2011.
Glass SC, Blanchette TW, Karwan LA, Pearson SS, O’Neil AP, Karlik DA. Core Muscle Activation During Unstable Bicep Curl Using A Water-Filled Instability Training Tube. Journal of Strength and Conditioning Research PAP doi: /JSC
Jacobs J, Henry S, Nagle K. Low back pain associates with altered activity of the cerebral cortex prior to arm movements that require postural adjustment. Clin Neurophysiol. 121(3): 121: , 2010.
Lehman, G., MacMillan, B., MacIntyre,I., Chivers C., Fluter M. Shoulder muscle EMG activity during push up variations on and off a Swiss ball. Dynamic Medicine. 5(7):
Introduction
Strength training serves a variety of roles in the overall conditioning program of athletes as well as clinical patients. Improving strength, mobility, balance and coordinated movement require not only minimal levels of strength, but also the ability to quickly activate muscles necessary for function. Often injuries arise as a result of an individual’s inability to make rapid adjustments in muscle activation during movement in order to maintain posture and balance. Currently, a popular form of training called “Functional Training seeks to use strength and agility training outside the standard model. Mobility, agility and instability conditions are created in order to challenge the musculosketal system to rapidly adjust by compensatory muscle activation. Often functional training is done using common resistance exercises with the subject standing on either a stable surface, or an unstable surface (i.e stable ground vs foam, soft surface, wobble board etc.) A number of studies utilizing unstable surfaces have shown that compared to a stable surface, maximal activation of primary muscles decreases, typically because a lighter weight must be used in order to safely lift a load on the unstable surface (Anderson & Behm 2005; Lehman et al. 2006, Beach et al. 2008). A review by Behm and Colado (2012) cited 11 studies that demonstrated a combined reduction of 29% in force output for primary muscle when the exercise was performed on an unstable surface. However this is not surprising, given the fact that core musculature must be activated to a much greater extent in order to continually balance the load, and therefore lighter loads are necessary. A new approach to creating conditions for compensatory muscle activation is to use a water-filled lifting implement. Water creates turbulence during the movement, theoretically creating rapid and varied compensatory activation of core and support muscles. If the intent is to train the ability of the muscle to rapidly adjust to movement, this device may serve as effective training tool. The intent of the present study was to examine the effectiveness of the training tube to cause compensatory muscle activation of core and support muscles during an overhead squat.
100% open > Stable
Figure 3. Paraspinal Muscle Activation
50% open > Stable
Figure 4. Abdominal Muscle Activation
Table 1. Subject Characteristics
Variable
Mean ±SD
Age (y)
20.10 ± 0.99
Height (cm)
± 1.88
Weight(kg)
89.17 ± 6.88
RSBP
± 5.40
RDBP
85.43 ± 3.41
Overhead Press 1RM(kg)
79.26 ± 12.41
Implement at % 1RM
14.64 ± 2.23
Figure 5. Vastus Lateralis Muscle Activation
Purpose
The purpose of this study was to examine the compensatory muscle activation patterns of the shoulder, leg and core muscles while using a water-filled training device during an overhead squat.