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HFSXXX10.1177/0018720815593184Human FactorsMuscle Activity With Stability Ball Versus Dynamic Chair

Evaluating Abdominal and Lower-Back Muscle Activity While Performing Core Exercises on a Stability Ball and a Dynamic Office Chair Michael W. R. Holmes, University of Ontario Institute of Technology, Oshawa, Canada, Diana E. De Carvalho, Thomas Karakolis, and Jack P. Callaghan, University of Waterloo, Waterloo, Canada Objective: The purpose of this study was to evaluate the ability of a dynamic office chair to activate the core muscles while participants performed exercises sitting on the chair compared to a stability ball. Background: Prolonged sitting has become an accepted part of the modern office. However, epidemiological evidence suggests that sedentary postures are linked to many adverse effects on health. The concept of dynamic or active sitting is intended to promote movement while sitting to reduce the time spent in prolonged, static postures. Methods: Sixteen participants performed four pelvic rotation exercises (front-back, side-side, circular, and leg lift) on both a dynamic office chair and a stability ball. Muscle activity from 12 torso muscles were evaluated with surface electromyography. Results: For all exercises, trunk muscle activity on the chair was comparable to that on a stability ball. The right external oblique was the only muscle to produce greater peak activity (p = .019) when using the ball compared to the chair (21.4 ± 14.0 percent maximal voluntary excitations (%MVE) and 14.7 ± 10.8 %MVE for the ball and chair, respectively). The left thoracic erector spinae produced greater average activity (p = .044) on the chair than on the ball. Conclusion: These findings suggest that this dynamic sitting approach could be an effective tool for core muscle activation while promoting movement and exercise while sitting at work. Application: Muscle activations on the dynamic chair are comparable to those on a stability ball, and dynamic office chairs can promote movement and exercise while sitting at work. Keywords: stability ball, office chair, dynamic sitting, core exercises, trunk electromyography

Address correspondence to Jack P. Callaghan, Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada; e-mail: [email protected]. HUMAN FACTORS Vol. XX, No. X, Month XXXX, pp. 1­–13 DOI: 10.1177/0018720815593184 Copyright © 2015, Human Factors and Ergonomics Society.

Introduction

Prolonged sitting has become routine in today’s society, and most working adults spend up to one third of the workday sitting (Jans, Proper, & Hildebrandt, 2007; Miller & Brown, 2004). In Canada, it is estimated that an average adult spends up to 10 hr per day sitting (Statistics Canada, 2011). There are growing concerns around the health implications associated with prolonged sitting or sedentary exposures. Sedentary behaviors have been reported to promote an increased risk of obesity and countless cardiovascular disorders (Hu, Li, Colditz, Willett, & Manson, 2003; Katzmarzyk, Church, Craig, & Bouchard, 2009; Mummery, Schofield, Steele, Eakin, & Brown, 2005). Additionally, from a biomechanical perspective, sitting has been linked to an increased risk of lower-back pain (Frymoyer et al., 1980; Hales & Bernard 1996; Wilder, Pope, & Frymoyer, 1988), which can lead to pain and disability outside of work, affecting an individual’s quality of life and ability to exercise. One common ergonomic recommendation is for employers to promote rest breaks and to encourage movement (Ontario Ministry of Labour, 2004). Unfortunately, these recommendations are not always enforced, and job demands often make such strategies difficult. It would be beneficial if individuals could perform some low-level physical activity while sitting at work. Therefore an ergonomic solution that provides minimal workplace disruptions and productivity interference might be warranted. Damkot, Pope, Lord, and Frymoyer (1984) suggested that a primary contributor to lower-back pain while sitting is movement restriction, which has led some researchers to encourage the use of dynamic office chairs (chairs that allow for a greater range of motion than a traditional chair) to reduce sitting-induced lower-back pain (Kroemer,

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1994; van Dieen, de Looze, & Hermans, 2001). Additionally, core strength training programs have been shown to reduce lower-back pain in patients (Bentsen, Lindgärde, & Manthorpe, 1997) and can also promote increased physical activity. Sitting-induced lower-back pain can stem from lowlevel static loading of the back muscles, which is associated with an increased risk of muscular disorders (Visser & van Dieen, 2006), disc degeneration (Videman & Battié, 1999), and spine stiffness (Beach, Parkinson, Stothart, & Callaghan, 2005). Encouraging spine movement while sitting could help prevent static loads on the spine (Callaghan & McGill, 2001) and, thus, subsequent spine problems that may develop as a result of such exposures. Based on these results, it has been suggested that stability balls might be a good replacement for office chairs. Gregory, Dunk, and Callaghan (2006) suggested that the unstable nature of a stability ball induces movement, which might promote increases in muscle activity and, potentially, strength. Additionally, Jackson, Banerjee-Guenette, Gregory, and Callaghan (2013) found that performing clerical work on a stability ball resulted in increased energy expenditure as compared to performing the same duties on a traditional office chair. Despite these benefits, for stability balls to be a viable replacement to traditional office chairs, there are some fundamental problems that need to be addressed. For instance, stability balls introduce postural stability challenges, can hinder workspace reaching activities, and have limited adjustability to accommodate a range of the working population. Interestingly, it has been shown that during prolonged sitting, individuals sit on a stability ball the same as an office chair, with no significant differences in muscle activity (Gregory et al., 2006; Kingma & van Dieen, 2009), spine posture, spine loads, or overall spine stability (McGill, Kavcic, & Harvey, 2006). In addition, participants often report increased lower-back discomfort when sitting on a stability ball as compared to an office chair (Gregory et al., 2006; Kingma & van Dieen, 2009). However, significant variation in sitting strategies and spine postures have also been demonstrated, with some individuals adopting multiple postures, thus suggesting a reduction in prolonged, static loading (Callaghan & McGill, 2001).

The approach of dynamic (also referred to as active) sitting in the workplace has recently gained further attention (Grooten, Conradsson, Ang, & Franzen, 2013; O’Sullivan, McCarthy, White, O’Sullivan, & Dankaerts, 2012; O’Sullivan, O’Sullivan, O’Keeffe, O’Sullivan, & Dankaerts, 2013). Such a solution could promote movements, like those often endorsed by stability ball advocates, but without some of the noted challenges. Most studies that focus on prolonged sitting evaluate stability balls as the dynamic sitting solution in comparison to traditional office chairs (Gregory et al., 2006; McGill et al., 2006; van Dieen et al., 2001). These studies suggest that dynamic sitting results in only minimal changes in trunk posture and muscle activity when compared to sitting on a traditional office chair (Gregory et al., 2006; Kingma & van Dieen, 2009; McGill et al., 2006; van Dieen et al., 2001). A recent systematic review by O’Sullivan et al. (2012) suggested that dynamic sitting approaches are not effective for reducing lower-back pain. Schult et al. (2013) performed a detailed investigation of stability balls and stability ball chairs as alternatives for regular office chairs in the workplace. The authors reported that the use of stability balls was associated with workers’ improved perception of posture and energy levels and improved balance while using the stability ball chair. However, participants also reported pain when using the stability ball and stability ball chair, which is in agreement with previous discomfort findings (Gregory et al., 2006; Kingma & van Dieen, 2009). Schult et al. concluded that a risk-benefit assessment should be explored prior to incorporating these changes in the workplace. From an exercise perspective, Vera-Garcia, Grenier, and McGill (2000) demonstrated greater trunk muscle activity and co-contraction when performing abdominal curl-ups on a stability ball compared to traditional curl-ups. Additionally, Marshall and Murphy (2005) evaluated core stability exercises on and off of a stability ball. Although the findings appear to be both muscle and exercise specific, overall, the authors concluded that the stability ball can lead to greater muscle activations than performing the same exercises on a stable surface. Interestingly, Drake, Fischer, Brown, and Callaghan (2006)

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failed to see a training advantage to performing trunk extensor exercises on a ball versus a mat. Despite the large number of studies that advocate the use of stability balls for increasing trunk muscle activity and strength, there have been no studies to evaluate a dynamic office chair that can replicate stability ball exercise motions. Such a device could encourage motion while sitting and also promote safe exercise in the workplace. The purpose of this study was to evaluate a dynamic office chair (compared to a stability ball) as a tool to activate the core muscles while participants performed exercises in the workplace. Trunk and abdominal muscle activities were evaluated while participants performed exercises on a dynamic office chair and were compared to those using a traditional exercise modality, the stability ball. Method Participants

Sixteen university-age participants volunteered for this study. Eight males (age, 24.3 ± 5.9 years; height, 181.9 ± 11.7 cm; mass, 79.8 ± 9.7 kg) and eight females (mean age, 20.6 ± 2.0 years; height, 166.0 ± 5.6 cm; mass, 63.9 ± 11.8 kg) participated. All participants self-identified that they had no previous history of musculoskeletal injury or pain to the lower back over the previous 12 months. Prior to participation, informed written consent was obtained and the study was approved by the University of Waterloo’s Ethics Review Committee. Instrumentation and Data Collection

Participants were prepared for surface electromyography (EMG) recordings from 12 muscles: three abdominal muscles bilaterally (rectus abdominis [RA], external oblique [EO], and internal oblique [IO]) and three back muscles bilaterally (thoracic erector spinae [TES] at the level of the T9 spinous process, lumbar erector spinae [LES] at the level of the L1 spinous process, and multifidus [MF] at the level of the L4/ L5 spinous process). All electrode placements were confirmed with palpation and direction from previous work (Callaghan, Gunning, & McGill, 1998; McGill, 1991; Zipp, 1982). Prior to electrode placement, each electrode site was

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prepared by shaving and rubbing the surface of the skin with alcohol. Pairs of disposable, pregelled, Ag-AgCl surface electrodes (Blue Sensor, Medicotest, Inc., Olstykke, Denmark) were placed over each muscle belly, with a center-tocenter interelectrode distance of 2 cm. All EMG signals were band-pass filtered (10–1000 Hz), differentially amplified (CMRR > 115 dB at 60 Hz; input impedance ~10GΩ; Model AMT-8, Bortec Biomedical Ltd., Calgary, AB, Canada), and collected with a sampling frequency of 2048 Hz. Maximal voluntary excitations (MVE) were determined for each muscle using musclespecific maximal voluntary isometric contractions (MVC). For each MVC, the participant held the contraction for 3 s, and contractions were performed twice for each muscle group, with a minimum of 30 s rest between exertions. Maximal contractions for the trunk extensors (TES, LES, MF) included a maximal back extension (modified Biering Sorensen test), which required participants to extend against resistance with their torso suspended off the end of a table. Maximal contractions for the trunk flexors (RA, EO, IO) included a series of maximum forward-flexion contractions, right and left lateral bend, and right and left trunk twisting with flexion. Participants were positioned on a table with knees flexed to approximately 90° and the trunk positioned approximately 45° from horizontal while manual resistance was provided by the investigators, restricting flexion and twisting movements. Next, participants performed four trunk exercises on both a dynamic office chair and a stability ball. The dynamic office chair was a prototype of an active seating solution (Figure 1). The dynamic office chair introduces a unique design that allows for additional seat pan rotation, not seen in traditional office chairs. The seat pan has 3° of rotational freedom (flexion/extension, lateral bend, and axial twist). The unique design allows for the seat pan resistance to be changed with a simple mechanism adjustment reducing the resistance to the rotations or increasing the stability of the surface. All chair exercises were performed with the seat pan resistance adjusted to the lowest setting, which corresponded to the least stiffness and greatest range of motion. The investigators used three sizes of standard stability balls (55-, 65-, and

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two within-subjects factors of seat condition (dynamic office chair and stability ball) and exercise (four seated exercises) was performed to evaluate differences in muscle activity for the sitting condition during different core-focused exercises. Alpha was set at p < .05, and any significant main effects or interactions were further compared using a Tukey’s honestly significant difference post hoc test. Figure 1. Prototype dynamic office chair that was evaluated in this study. The mechanism under the seat pan could adjust the three-degrees-of-freedom seat pan rotation resistance.

75-cm diameters) to determine the most appropriate for each participant based on ability to sit comfortably with feet flat on the floor and knees flexed to approximately 90°. The dynamic office chair was adjusted in the vertical direction to replicate the same knee position. Exercise order was randomly selected and participants performed each exercise for 20 s. The four exercises included (a) forward-backward pelvic rotation (FB), (b) side-to-side pelvic rotation (SS), (c) circular hip rotation (CR), and (d) alternating leg lifts (LL). Participants also performed an isometric side plank, which was used as a reference or comparison exercise because it is often considered an advanced and challenging core stabilization exercise (Lehman, Hoda, & Oliver, 2005). For each exercise, participants were given a set of instructions on how to perform the movement (Table 1). Data Analysis

All EMG signals were full-wave rectified and digitally low-pass filtered at 3 Hz (second-order, dual-pass Butterworth filter). Peak activity was found for each muscle during the MVC trials and used to normalize all subsequent exercise conditions. During each 20-s exercise collection, maximum and average muscle activities were determined. Statistical Analysis

A mixed analysis of variance (ANOVA) with one between-subjects factor (gender) and

Results Maximum Muscle Activity

For the 12 muscles monitored, only the right EO demonstrated a significant main effect of seat condition (p = .019). Averaged across exercises, the maximum activity for the right EO was 21.4 ± 14.0 %MVE and 14.7 ± 10.8 %MVE for the stability ball and chair, respectively. There were no other main effects found for seat condition or for seat condition and exercise interactions for any of the other muscles. Not surprisingly, there were muscle-specific differences due to the exercise condition (Figure 2). Significant main effects were found for all muscles except right and left EO and right TES (all, p < .025). The FB pelvic rotation and CR exercises generally produced the greatest muscle activities. The left and right RA and EO as well as the left MF muscles demonstrated the greatest activity during the FB exercise. The right and left TES and LES as well as the right MF muscles exhibited the greatest activity during the CR exercise. Finally, the right and left IO had the greatest activation during the LL exercise. For the right and left LES and MF muscles, maximum activity for the FB and CR exercises were both significantly greater (all, p < .024) than the LL exercise. For the right and left MF, the CR exercise produced maximum activations that were significantly greater than the SS exercise (all, p < .000). Table 2 summarizes the peak muscle activity for each exercise and notes the corresponding muscle to which that peak activity occurred. Average Muscle Activity

For the 12 muscles measured, only the right EO and left TES demonstrated a significant main effect of seat condition (p = .012 and p = .044,

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Table 1: Four Office Chair and Stability Ball Exercises and the Comparison Side Plank Exercise With Standardized Set of Instructions Given to Each Participant Prior to Performing the Exercises Exercise Forward-backward and side-side pelvic rotation



Circular hip rotation

Alternating leg lift

Isometric side plank

Instructions •  Sit in an upright position with feet flat on the floor and arms extended out to the side. •  Engage the abdominals and tilt the pelvis forward and backward for the duration of the collection. •  Try not to push with the feet and obtain as much pelvic rotation as possible at a self-selected speed. •  Sit in an upright position with feet flat on the floor and arms extended out to the side. •  Engage the abdominals and tilt the pelvis from side to side for the duration of the collection. •  Try not to push with the feet and obtain as much pelvic rotation as possible at a self-selected speed. •  Start in an upright position with feet flat on the floor and arms extended out to the side. •  Engage the abdominals and rotate the pelvis in a circular motion. •  Rotate in both the clockwise and counter clockwise directions. •  Try not to push with the feet and obtain as much pelvic rotation as possible at a self-selected speed. •  Sit in an upright position with feet flat on the floor and arms extended out to the side. •  Engage the abdominals and slowly lift one foot off the floor with the knee bent and torso remaining upright. •  Lower and perform with other foot. •  Continue alternating for the 20-s duration. •  Begin on the mat with right side of your body facing the floor. •  Place right forearm flat on the mat, directly in line with the shoulder. •  Place left foot on top of right foot, and lift your body up off the mat. At this point, only the right forearm and right foot should be in contact with the mat. Be sure to engage the abdominals to help keep your body straight (i.e., no spine flexion or hip hinge motion). •  Hold the elevated position for the duration of the collection. •  Return to the starting position and repeat for the left side.

respectively). Averaged across exercises, activity for the right EO was 6.1 ± 3.2 %MVE and 4.8 ± 3.2 %MVE for the stability ball and chair, respectively. For the left TES, the chair produced greater activity than the stability ball, with average activations of 5.8 ± 4.6 %MVE and 4.9 ± 4.6 %MVE for the chair and stability ball, respectively. Similar to maximum EMG, there were no main effects of seat condition or for seat condition and exercise interactions for any of the other muscles. There were muscle specific differences due to the exercise condition for average EMG (Figure

3). Significant main effects were found for all muscles except right and left RA, left EO, and left MF (all, p < .03). Similar to maximum activity, the FB and CR exercises generally produced the highest average EMG. The left and right RA and EO muscles produced the greatest average EMG during the FB trials, and the right and left lumbar erectors (TES, LES, and MF) produced the greatest average EMG during the CR exercise. The CR exercise produced significantly greater activity than the SS exercise for the right and left IO, TES, and MF muscles (all, p < .006).

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Figure 2. Maximum muscle activity (standard deviation) for each muscle during the (A) forward-backward, (B) side-to-side, (C) circular, and (D) leg-lift exercises.

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Table 2: Summary of the Maximum Activity and the Corresponding Muscle to Produce That Activity While Using the Dynamic Office Chair for Each Exercise Greatest Flexor Activity (Corresponding Muscle) Exercise FB SS CR LL

Greatest Extensor Activity (Corresponding Muscle)

Dynamic Chair

Stability Ball

Dynamic Chair

Stability Ball

18.5 ± 12.7 %MVE (REO) 11.7 ± 10.2 %MVE (LEO) 13.0 ± 8.9 %MVE (REO) 20.3 ± 15.0 %MVE (RIO)

21.4 ± 11.7 %MVE (REO) 18.7 ± 10.9 %MVE (REO) 20.0 ± 9.0 %MVE (REO) 18.2 ± 9.3 %MVE (REO)

18.4 ± 12.3 %MVE (RMF) 15.4 ± 12.4 %MVE (RTES) 19.4 ± 16.7 %MVE (RMF) 13.3 ± 13.0 %MVE (RTES)

17.3 ± 15.9 %MVE (RMF) 16.5 ± 14.0 %MVE (RTES) 22.5 ± 18.1 %MVE (RMF) 13.2 ± 14.1 %MVE (RTES)

Note. FB = forward-backward pelvic rotation; SS = side-to-side pelvic rotation; CR = circular hip rotation; LL = alternating leg lift; %MVE = percent maximal voluntary excitation; REO = right external oblique; RMF = right multifidus; LEO = left external oblique; RTES = right thoracic erector spinae; RIO = right internal oblique.

The CR exercise also produced significantly greater activity than the LL exercise for the right and left LES and MF muscles (all, p < .000). Although there were no significant Seat × Exercise interactions, average EMG was higher while sitting on the chair than on the ball for the right and left TES and LES for all exercises. To provide reference to the maximum activations experienced during the chair and stability ball exercises, an isometric side bridge (plank) exercise was performed. When compared to a demanding static side plank exercise, maximum activations on both the chair and stability ball were lower. Across all exercises, the range for average EMG was 5.2 to 15.2 %MVE, 7.1 to 21.4 %MVE, and 22.2 to 55.5 %MVE on the chair, on the stability ball, and during the plank, respectively (Figure 4). Discussion

Sitting for prolonged periods can contribute to a sedentary lifestyle, known to increase the risk of obesity, cardiovascular disorders (Hu et al., 2003; Katzmarzyk et al., 2009; Mummery et al., 2005), and lower-back pain (Frymoyer et al., 1980; Hales & Bernard 1996; Wilder et al., 1988). Advances in workplace technology have contributed to increases in the amount of time spent sitting. We evaluated the effectiveness of a dynamic office chair as a simple, nondisruptive workplace

alternative to a stability ball that allows for body movement and frequent changes in posture while sitting. It has been shown that during many core exercises, abdominal muscle activity is enhanced when using a stability ball (Marshall & Murphy, 2005; Vera-Garcia et al., 2000) as compared to more traditional abdominalfocused exercises. This study did not evaluate the stability ball as an office chair alternative; rather, the stability ball was the exercise modality of choice used to compare with the dynamic office solution. In terms of maximum muscle activity, we found that only one muscle (right EO) demonstrated a significant difference due to the sitting condition, producing greater activity on the stability ball than on the dynamic chair (21.4 ± 14.0 %MVE and 14.7 ± 10.8 %MVE for the stability ball and chair, respectively). In terms of average EMG, the left TES produced greater activations on the chair than the stability ball (5.8 ± 4.6 %MVE and 4.9 ± 4.6 %MVE for the chair and stability ball, respectively). For all other muscles evaluated, there were no significant differences in activity between the stability ball and chair, suggesting that the four exercises tested on the dynamic chair produced activations that are comparable to those found when using a stability ball. Admittedly, this work does not account for many of the considerations for properly selecting an office chair;

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Figure 3. Average muscle activity (standard deviation) for each muscle during the (A) forward-backward, (B) side-to-side, (C) circular, and (D) leg-lift exercises.

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Figure 4. Maximum muscle activity found during the isometric side plank exercise. L-plank represents an isometric plank lying on the left side of the body; R-plank represents an isometric plank lying on the right side of the body.

however, it does indicate that this dynamic sitting approach could be an effective solution to promote active sitting and core strengthening while in the office. As an exercise device, the dynamic office chair provided maximal and average muscle activity that was comparable to the stability ball across the 12 trunk muscles during four common exercises. The dynamic office chair has a seat pan safety limit of 14° to prevent excessive movement and potentially provides an added stability/safety feature that would not be possible while using a traditional stability ball (Karakolis, Holmes, & Callaghan, 2013). The right and left LES and MF produced the highest activations during the FB exercise, the right and left LES and left TES produced the highest activations during the SS exercise, the right and left LES and TES and right MF produced the highest activations during the CR exercise, and the right and left LES and left TES produced the highest activations during the LL exercise. Also, the right RA and EO produced greater activations during the CR exercise, and right IO was greater during the LL exercise. It has been suggested that trunk muscle activation of about 10% of maximum is sufficient for spinal stability purposes, especially during activities of daily living (McGill, 2002). Our core exercises were dominated by pelvic tilting (rotation)

exercises and produced peak muscle activity larger than 10% of maximum across all muscles. Further, the four exercises elicited different responses from the muscles, achieving maximal activation from differing combinations of the measured muscle groups, indicating that the four exercises form a suitable initial set of exercises to activate the core musculature. Most studies of prolonged sitting during simulated office work have documented very low levels of EMG, often less than 2% of maximum (Beach, Mooney, & Callaghan, 2003; Van Dieen et al., 2001). Gregory et al. (2006) compared muscle activations during prolonged sitting (1 hr) on an office chair and on a stability ball, and the highest average activity was for the right TES at 3.1% of maximum during a reading activity. All other muscles (LES, RA, and EO) were below 3% and often below 2% of maximum during all the simulated tasks. Similarly, van Dieen et al. (2001) simulated office work (computer-aided design and word processing) for 3 hr of prolonged sitting and also documented very low muscle activity, with a mean across subjects of less than 2% of maximum. Arokoski, Valta, Kankaanpää, and Airaksinen (2002) used an unsupported sitting condition (no backrest) as an exercise rehabilitation program and documented RA and EO activity that ranged

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from 1.2% to 5.6% of maximum during longduration sitting on their unsupported office chair. This finding suggests that the pelvic rotation exercises performed on the dynamic office chair is capable of producing activations much larger than those found during long-duration static sitting, which could be valuable for core strengthening, especially in the earlier stages of an office exercise program. The focus of this manuscript was to determine if a dynamic office chair could produce muscle activity at magnitudes similar to more traditional exercise approaches, including a stability ball. Evaluating the effectiveness of a dynamic office chair as a replacement for a traditional office chair during simulated computer and deskwork is a valuable next step, as is the impact of performing exercises as breaks within prolonged seated working periods and the influence on lower-back pain reporting. There has been substantial work on exercise programs that enhance lumbar stability and core strengthening (Arokoski et al., 2002; Marshall & Murphy, 2005; McGill, 1998; McGill & Karpowicz, 2009; Norris, 1995). Primarily, low-back and abdominal exercise programs are focused on rehabilitation, injury prevention, or fitness (McGill, 1998). One of the primary goals has been to determine spine stabilization exercises that enhance spine stability and muscle activity while minimizing spine loads (McGill & Karpowicz, 2009). The stabilization exercises most often recommended are a variation of the curl-up (Axler & McGill, 1997), the side bridge (McGill, 1998), and the birddog (Callaghan et al., 1998). Many of the pelvic rotation exercises presented here demonstrated abdominal and low-back muscle activations that are comparable to some of the more favorable spine stabilization exercises (McGill & Karpowicz, 2009) but can be performed while sitting in an office chair. The dynamic office chair provided muscle activations that demonstrate recruitment of the entire core musculature at levels that are comparable to traditional exercise programs. The side plank is a challenging trunk exercise that has been shown to produce RA and EO activity close to 50% of maximum (McGill, 1998), and our results demonstrate similar findings. Further work on spine stability and spine loading during pelvic rotation exercises could help strengthen the

argument for such exercises while sitting at a workstation. These four pelvic rotation exercises are meant not to be a replacement for traditional spine stabilization exercises but, rather, as a method to introduce movement into an often static workplace environment. Although most programs advocate appropriate rest days via periodization of exercises, there is evidence to suggest that low-back exercises can be performed daily (McGill, 1998). In addition, it is recommended that endurance exercise should be the focus of low-back programs rather than strength (McGill, 1998), and interestingly, there has also been support of cardiovascular programs, like walking, to effectively help rehabilitate low-back injury (Nutter, 1988). There could be a cardiovascular aspect to dynamic sitting as well as an endurance aspect, as individuals can perform these movements easily throughout the workday. Posterior pelvic-tilting maneuvers have been recommended in concert with other core strengthening exercises in the treatment of low-back pain (McKenzie & May, 2003; Neumann, 2009; Richardson, Jull, Hodges, & Hides, 1999). Evidence suggests that pelvic rotation exercises recruit global spine muscles, with the RA and oblique muscles most commonly recruited (Drysdale, Earl, & Hertel, 2004; Richardson, Jull, Toppenberg, & Comerford, 1992; Vezina & Hubley-Kozey, 2000). Most investigations into pelvic tilt as an exercise for the trunk have been performed with subjects lying supine on an exercise mat and being instructed to tighten the abdominals while rolling the pelvis and flattening the low back. Richardson et al. (1992) has shown that normalized muscle amplitudes between supine and reclined sitting differ significantly, with lower levels of RA found in sitting. However, levels of oblique muscle activity, considered more important for spine stability, were not different between the two positions. Indeed, the activation profiles found in our study were similar to those reported in the literature for anterolateral pelvic tilting (Bressel, Dolny, & Gibbons, 2011; Vezina & Hubley-Kozey, 2000), mediolateral pelvic tilting (Bressel et al., 2011), and leg lifts (Escamilla et al., 2010). Queiroz, Cagliari, Amorim, and Sacco (2010) evaluated muscle activity during four Pilates core

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stability exercises in a quadruped position and found that moving from a neutral to retroverted pelvic orientation consistently increased EO activity and decreased MF activity. Interestingly, EO (in particular, right EO) produced the greatest flexor activity for the FB and CR exercises while on the chair (Table 2). Changes in pelvic orientation from retroversion to neutral and from neutral to anteversion demonstrated increased MF activity from 18% to 39% of maximum. During our FB pelvic rotation exercise on the chair, the right MF produced the largest activity at 18.4 %MVE. Although pelvic rotation exercises may not be suggested at the beginning stages of a rehabilitation program (Drysdale et al., 2004), the recruitment of global muscles as a means to develop active sitting behaviors is positive, and our maximum activations are in a similar range of those found during other pelvic rotation exercises. There are a few limitations that should be discussed. Our participants were from a young, healthy, university population. Although this group may not be representative of a working population, this group is accustomed to sitting for extended periods of the workday. This young population may be more amenable to trying a new chair design, and given that this group is often free from degenerative disk and other spine problems often found in older adults, it is an advantageous population for the first evaluation of the design. Additionally, as with any ergonomic chair, incorporating a new device into an office ergonomics program must include training and education to have an effect (Amick et al., 2003). Similar findings have been reported in the sit-stand literature. Office workers who receive training on proper device use experience reduced discomfort scores and fewer reported symptoms (Robertson, Ciriello, & Garabet, 2013). This chair could potentially replace the traditional office chair; however, proper training and education are critical in parallel with implementation. Future directions for this work could be to evaluate older office workers in their work environment and to evaluate how the chair functions as a traditional office chair during office tasks (not just for exercises and movement). Conclusions

This work demonstrates that the dynamic sitting option evaluated was capable of producing

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similar muscle activity and recruitment patterns during selected exercises as found while using a stability ball. Many core exercises produce greater abdominal activity when using a stability ball as compared to more traditional (stable) methods (Marshall & Murphy, 2005; Vera-Garcia et al., 2000). Participants’ recruitment patterns and activation magnitudes for the abdominal muscles were similar when using the dynamic chair or the stability ball. Although not significant, the trunk extensor muscles often produced greater activity while performing the four exercises on the chair. This finding suggests that the dynamic sitting option produces muscle activity at magnitudes similar to those found when using a stability ball. This dynamic sitting approach appears to be effective at providing muscle activation changes during exercises performed while sitting, and the work demonstrates that a dynamic office chair can be a suggested mechanism to encourage movement. Adopting multiple postures and promoting movement can prevent static spine loading (Callaghan & McGill, 2001) while nourishing spinal structures (Holm & Nachemson, 1983) and preventing muscle fatigue (Jonsson, 1978). Our variety of pelvic rotation maneuvers demonstrated recruitment of all the core muscles and at magnitudes that are comparable to traditional spine stabilization exercises. The ability to frequently change posture while sitting, and also to easily incorporate trunk exercises into a daily office routine, is a beneficial approach to help reduce static sitting time as well as increase strength and endurance to the trunk musculature, which could provide benefits to help combat the known dangers of prolonged sitting. Acknowledgments Funding was provided for this project by a Natural Science and Engineering Research Council of Canada (NSERC) Engage grant. No funding was provided by Core Chair Inc. J. P. Callaghan is also supported by the Canada Research Chair in Spine Biomechanics and Injury Prevention.

Key Points •• Four pelvic rotation exercises were performed on both a dynamic office chair and a stability ball. Muscle activations were comparable across both products.

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12 Month XXXX - Human Factors •• All four pelvic rotation exercises produced different responses from the muscles evaluated. The muscles activated and the largest activations changed for each exercise, indicating that these four exercises are suitable for activating the core musculature while sitting. •• This dynamic office chair solution can facilitate exercises that activate the core musculature to similar levels found using a stability ball. With appropriate education and awareness, this type of chair may promote movement and exercise while sitting at work.

References Amick, B. C., Robertson, M. M., DeRango, K., Bazzani, L., Moore, A., Rooney, T., & Harrist, R. (2003). Effect of office ergonomics intervention on reducing musculoskeletal symptoms. Spine, 28, 2706–2711. Arokoski, J. P., Valta, T., Kankaanpää, M., & Airaksinen, O. (2002). Activation of paraspinal and abdominal muscles during manually assisted and nonassisted therapeutic exercise. American Journal of Physical Medicine & Rehabilitation, 81, 326–335. Axler, C. T., & McGill, S. M. (1997). Low back loads over a variety of abdominal exercises: Searching for the safest abdominal challenge. Medicine and Science in Sports and Exercise, 29, 804–811. Beach, T. A., Mooney, S. K., & Callaghan, J. P. (2003). The effects of a continuous passive motion device on myoelectric activity of the erector spinae during prolonged sitting at a computer workstation. Work: A Journal of Prevention, Assessment and Rehabilitation, 20, 237–244. Beach, T. A., Parkinson, R. J., Stothart, J. P., & Callaghan, J. P. (2005). Effects of prolonged sitting on the passive flexion stiffness of the in vivo lumbar spine. Spine Journal, 5, 145–154. Bentsen, H., Lindgärde, F., & Manthorpe, R. (1997). The effect of dynamic strength back exercise and/or a home training program in 57-year-old women with chronic low back pain: Results of a prospective randomized study with a 3-year follow-up period. Spine, 22, 1494–1500. Bressel, E., Dolny, D., & Gibbons, M. (2011). Trunk muscle activity during exercises performed on land and in water. Medicine and Science in Sports and Exercise, 43, 1927–1932. Callaghan, J. P., Gunning, J. L., & McGill, S. M. (1998). The relationship between lumbar spine load and muscle activity during extensor exercises. Physical Therapy, 78, 8–18. Callaghan, J. P., & McGill, S. (2001). Low back joint loading and kinematics during standing and unsupported sitting. Ergonomics, 44, 280–294. Damkot, D., Pope, M., Lord, J., & Frymoyer, J. (1984). The relationship between work history, work environment and lowback pain in men. Spine, 9, 395–399. Drake, J. D., Fischer, S. L., Brown, S. H., & Callaghan, J. P. (2006). Do exercise balls provide a training advantage for trunk extensor exercises? A biomechanical evaluation. Journal of Manipulative and Physiological Therapeutics, 29, 354–362. Drysdale, C. L., Earl, J. E., & Hertel, J. (2004). Surface electromyographic activity of the abdominal muscles during pelvictilt and abdominal-hollowing exercises. Journal of Athletic Training, 39, 32–36.

Escamilla, R. F., Lewis, C., Bell, D., Bramblet, G., Daffron, J., Lambert, S., Pecson, A., Imamura, R., Paulos, L., & Andrews, J. R. (2010). Core muscle activation during Swiss ball and traditional abdominal exercises. Journal of Orthopaedic and Sports Physical Therapy, 40, 265–276. Frymoyer, J. W., Pope, M. H., Costanza, M. C., Rosen, J. C., Goggin, J. E., & Wilder, D. G. (1980). Epidemiologic studies of low-back pain. Spine, 5, 419–423. Gregory, D. E., Dunk, N. M., & Callaghan, J. P. (2006). Stability ball versus office chair: Comparison of muscle activation and lumbar spine posture during prolonged sitting. Human Factors, 48, 142–153. Grooten, W. J. A., Conradsson, D., Ang, B. O., & Franzen, E. (2013). Is active sitting as active as we think? Ergonomics, 56, 1304–1314. Hales, T. R., & Bernard, B. P. (1996). Epidemiology of workrelated musculoskeletal disorders. Orthopedic Clinics of North America, 27, 679–709. Holm, S., & Nachemson, A. (1983). Variations in the nutrition of the canine intervertebral disc induced by motion. Spine, 8, 866–874. Hu, F. B., Li, T. Y., Colditz, G. A., Willett, W. C., & Manson, J. E. (2003). Television watching and other sedentary behaviors in relation to risk of obesity and type 2 diabetes mellitus in women. JAMA, 289, 1785–1791. Jackson, J. A., Banerjee-Guenette, P., Gregory, D. E., & Callaghan, J. P. (2013). Should we be more on the ball? The efficacy of accommodation training on lumbar spine posture, muscle activity, and perceived discomfort during stability ball sitting. Human Factors, 55, 1064–1076. Jans, M. P., Proper, K. I., & Hildebrandt, V. H. (2007). Sedentary behavior in Dutch workers: Differences between occupations and business sectors. American Journal of Preventive Medicine, 33, 450–454. Jonsson, B. (1978). Kinesiology: With special reference to electromyographic kinesiology. In W. A. Cobb & H. Duija (Eds.), Contemporary clinical neurophysiology (pp. 417–428). Amsterdam, Netherlands: Elsevier. Karakolis, T., Holmes, M. W. R., & Callaghan, J. P. (2013, September). Using a stability ball as a task chair: Spine angles during lateral reaching. Paper presented at the conference of the American Society of Biomechanics, Omaha, NE. Katzmarzyk, P. T., Church, T. S., Craig, C. L., & Bouchard, C. (2009). Sitting time and mortality from all causes, cardiovascular disease, and cancer. Medicine & Science in Sports & Exercise, 41, 998–1005. Kingma, I., & van Dieen, J. H. (2009). Static and dynamic postural loadings during computer work in females: Sitting on an office chair versus sitting on an exercise ball. Applied Ergonomics, 40, 199–205. Kroemer, K. H. E. (1994). Sitting (or standing?) at the computer workplace. In R. Leuder & K. Noro (Eds.), Hard facts about soft machines (pp. 181–191). London, UK: Taylor & Francis. Lehman, G. J., Hoda, W., & Oliver, S. (2005). Trunk muscle activity during bridging exercises on and off a Swissball. Chiropractic and Osteopathy, 13, 14. Marshall, P. W., & Murphy, B. A. (2005). Core stability exercises on and off a Swiss ball. Archives of Physical Medicine and Rehabilitation, 86, 242–249. McGill, S. M. (1991). Electromyographic activity of the abdominal and low back musculature during the generation of isometric and dynamic axial trunk torque: Implications for lumbar mechanics. Journal of Orthopaedic Research, 9, 91–103.

Downloaded from hfs.sagepub.com at Bobst Library, New York University on July 1, 2015

Muscle Activity With Stability Ball Versus Dynamic Chair McGill, S. M. (1998). Low back exercises: Evidence for improving exercise regimens. Physical Therapy, 78, 754–765. McGill, S. M. (2002). Low back disorders: Evidence based prevention and rehabilitation. Champaign, IL: Human Kinetics. McGill, S. M., & Karpowicz, A. (2009). Exercises for spine stabilization: Motion/motor patterns, stability progressions, and clinical technique. Archives of Physical Medicine and Rehabilitation, 90, 118–126. McGill, S. M., Kavcic, N. S., & Harvey, E. (2006). Sitting on a chair or an exercise ball: Various perspectives to guide decision making. Clinical Biomechanics, 21, 353–360. McKenzie, R., & May, S. (2003). The lumbar spine: Mechanical diagnosis and therapy (Vol. 1). Waikanae, New Zealand: Spinal Publications. Miller, R., & Brown, W. (2004). Steps and sitting in a working population. International Journal of Behavioral Medicine, 11, 219–224. Mummery, W. K., Schofield, G. M., Steele, R., Eakin, E. G., & Brown, W. J. (2005). Occupational sitting time and overweight and obesity in Australian workers. American Journal of Preventive Medicine, 29, 91–97. Neumann, D. A. (2009). Kinesiology of the musculoskeletal system: Foundations for physical rehabilitation. St. Louis, MO: Mosby. Norris, C. M. (1995). Spinal stabilisation: An exercise programme to enhance lumbar stabilisation. Physiotherapy, 81, 138–146. Nutter, P. (1988). Aerobic exercise in the treatment and prevention of low back pain. Occupational Medicine (Philadelphia, PA), 3, 137–145. Ontario Ministry of Labour, Health and Safety Guidelines. (2004). Computer ergonomics: Workstation layout and lighting. Ontario, Canada: Queen’s Printer for Ontario. O’Sullivan, K., McCarthy, R., White, A., O’Sullivan, L., & Dankaerts, W. (2012). Lumbar posture and trunk muscle activation during a typing task when sitting on a novel dynamic ergonomic chair. Ergonomics, 55, 1586–1595. O’Sullivan, K., O’Sullivan, P., O’Keeffe, M., O’Sullivan, L., & Dankaerts, W. (2013). The effect of dynamic sitting on trunk muscle activation: A systematic review. Applied Ergonomics, 44, 628–635. Queiroz, B. C., Cagliari, M. F., Amorim, C. F., & Sacco, I. C. (2010). Muscle activation during four Pilates core stability exercises in quadruped position. Archives of Physical Medicine and Rehabilitation, 91, 86–92. Richardson, C., Jull, G., Hodges, P., & Hides, J. (1999). Therapeutic exercises for spinal segmental stabilization in low back pain. Toronto, Canada: Churchill Livingstone. Richardson, C., Jull, G., Toppenberg, R., & Comerford, M. (1992). Techniques for active lumbar stabilisation for spinal protection: A pilot study. Australian Journal of Physiotherapy, 38, 105–112. Robertson, M. M., Ciriello, V. M., & Garabet, A. M. (2013). Office ergonomics training and a sit-stand workstation: Effects on musculoskeletal and visual symptoms and performance of office workers. Applied Ergonomics, 44, 73–85. Schult, T. M., Awosika, E. R., Schmunk, S. K., Hodgson, M. J., Heymach, B. L., & Parker, C. D. (2013). Sitting on stability balls: Biomechanics evaluation in a workplace setting. Journal of Occupational and Environmental Hygiene, 10(2), 55–63.

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Statistics Canada. (2011). Canadian Health Measures Survey (CHMS) data user guide: Cycle 1. 2010. Retrieved from http://www.statcan.gc.ca/imdb-bmdi/document/5071_D2_T1_ V1-eng.pdf van Dieen, J. H., de Looze, M. P., & Hermans, V. (2001). Effects of dynamic office chairs on trunk kinematics, trunk extensor EMG and spinal shrinkage. Ergonomics, 44, 739–750. Vera-Garcia, F. J., Grenier, S. G., & McGill, S. M. (2000). Abdominal muscle response during curl-ups on both stable and labile surfaces. Physical Therapy, 80, 564–569. Vezina, J., & Hubley-Kozey, C. L. (2000). Muscle activation in therapeutic exercises to improve trunk stability. Archives of Physical Medicine and Rehabilitation, 81, 1370–1379. Videman, T., & Battié, M.C. (1999). Spine update: The influence of occupation on lumbar degeneration. Spine, 24, 1164–1168. Visser, B., & van Dieen, J. H. (2006). Pathophysiology of upper extremity muscle disorders. Journal of Electromyography and Kinesiology, 16, 1–16. Wilder, D. G., Pope, M. H., & Frymoyer, J. W. (1988). The biomechanics of lumbar disc herniation and the effect of overload and instability. Journal of Spinal Disorders & Techniques, 1, 16–32. Zipp, P. (1982). Recommendations for the standardization of lead positions in surface electromyography. European Journal of Applied Physiology and Occupational Physiology, 50, 41–54.

Michael W. R. Holmes is an assistant professor in the Faculty of Health Sciences at the University of Ontario Institute of Technology (UOIT). He received a PhD in biomechanics from McMaster University in 2011 and he currently runs the Neuromechanics and Ergonomics Lab at UOIT. Diana E. De Carvalho is an assistant professor in the Faculty of Medicine at Memorial University of Newfoundland. She completed her PhD in biomechanics at the University of Waterloo (2015) and DC at the Canadian Memorial Chiropractic College (2006). Thomas Karakolis obtained a PhD in biomechanics from the University of Waterloo in 2014. Jack P. Callaghan is a professor in the Department of Kinesiology at the University of Waterloo. He received a PhD in kinesiology from the University of Waterloo in 1999. He is also a Canada Research Chair in Spine Biomechanics and Injury Prevention. Date received: September 12, 2014 Date accepted: May 25, 2015

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Evaluating Abdominal and Lower-Back Muscle Activity While Performing Core Exercises on a Stability Ball and a Dynamic Office Chair.

The purpose of this study was to evaluate the ability of a dynamic office chair to activate the core muscles while participants performed exercises si...
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