IJSPT

ORIGINAL RESEARCH

THE INFLUENCE OF UPPER BODY FATIGUE ON DYNAMIC STANDING BALANCE Craig A. Wassinger, PT, PhD¹ Hayley McKinney, DPT¹ Stephanie Roane, DPT¹ Mary Jo Davenport, PT, PhD¹ Bea Owens, PT, PhD¹ Ute Breese, PT, PhD¹ Geri Ann Sokell, PT, M.Ed, DPT, ACCE¹

ABSTRACT Purpose/Background: Muscle fatigue is related to a decline in force output and proprioception. These can ultimately have an adverse effect on neuromuscular control and functional performance. Local muscle fatigue has been shown to have adverse consequences on dynamic standing balance; however, much less is known regarding the relationship between distant fatigue and dynamic standing. The purpose of this study was to investigate the effects of upper body fatigue on dynamic standing balance. It was hypothesized that distant fatigue in upper body musculature would show a significant decrease in dynamic standing balance as assessed by the Lower Quarter Y-Balance Test (YBT-LQ). Methods: Twenty healthy individuals (age: 25.0 ± 3.42 years, height: 172.72 ± 13.11 cm, mass: 71.36 ± 13.50 kg) participated in this study. A kayak ergometer was used to implement a fatigue protocol for the upper body. The protocol consisted of a graded intensity session ranging from 50% to 90% of maximum effort lasting ten minutes in duration (2 minutes each at 50% 60%, 70%, 80%, and 90%). The anterior (ANT), posteromedial (PM), and posterolateral (PL) reach directions were normalized to leg length and measured on the YBT-LQ before and after the fatigue protocol for each participant. A fourth value termed overall balance was calculated as the sum of the furthest reach distance of the three directions. Blood lactate analysis taken before and immediately after the fatigue protocol was used to quantify fatigue. Multiple paired t-tests were performed for prefatigue and post-fatigue balance assessment. A Bonferroni correction was applied to set the significance value ≤ 0.0125 a priori. Effect size was calculated using the effect size index. Results: Blood lactate values immediately following the fatigue protocol had an average concentration of 6.15 millimoles (pre: 2.3, post: 8.4). The ANT reach direction (ρ=0.004) and the calculated overall balance (ρ=0.011) significantly decreased post-fatigue in the dominant lower extremity. No significant differences were found for the PM (ρ=0.017) or PL (ρ=0.021) directions. The ANT reach direction (0.64) and overall balance (0.44) also showed a moderate effect size based on the effect size index. Conclusions: ANT and overall dynamic standing balance were negatively affected after completing the upper body fatigue protocol. The findings of this research demonstrate that upper body fatigue has adverse effects on dynamic standing balance, as measured by performance on the YBT-LQ. Significant and clinically relevant differences were noted in ANT and overall dynamic standing balance. Clinical Relevance: Physical therapists should be aware of the adverse influence distant fatigue may exhibit on neuromuscular control in muscles not actively involved in the fatiguing exercise. The balance deficits noted may indicate an increased risk of injury with muscle fatigue in muscles not directly contributing to standing balance. Level of Evidence: 3b, Case-control study Key Words: Distant fatigue, dynamic standing balance, Lower Quarter Y-Balance Test

1

East Tennessee State University, Department of Physical Therapy, Johnson City, TN, USA

This project was partially funded by the Tennessee Physical Therapy Association. This project was approved by the Institutional Review Board at ETSU.

CORRESPONDING AUTHOR Craig Wassinger PO BOX 70624 Johnson City, TN 37614 Email: [email protected]

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INTRODUCTION There are several mechanisms that may negatively affect neuromuscular motor control, fatigue being one of them. Fatigue is a complex phenomenon that is not entirely understood, although the immediate effects have been described as a reduction in the ability of muscles to apply force as well as a decrease in depolarization frequency when assessed with electromyography (EMG).1-3 This may be due to a decline in force production at or distal to the neuromuscular junction or the failure of voluntary activation of the muscle itself.4-6 Numerous authors have assessed whole body and local fatigue and their relationship to static and dynamic standing balance.2,7-9 Few authors have investigated the effect of distant fatigue of upper body muscles on standing balance.2,7 In studying the relationship between distant muscular fatigue and balance, components of neuromuscular motor control may be better understood. Local fatigue may be described as the failure of an muscle group that is a primary mover of any joint involved in one’s base of support.10 An example of this would be the involvement of the lower extremity musculature on standing balance. General fatigue has multi-system involvement encompassing several muscle groups throughout the whole body. General fatigue will likely incorporate core and trunk musculature as well as muscles of the upper and lower extremities.7,8 On the contrary, distant fatigue has rarely been discussed. The authors of the current research will describe distant fatigue as affecting an isolated muscle group or groups that is disassociated with the primary movement of joints involved in one’s base of support. An example of this would be the involvement of the upper body musculature on standing balance. Balance has been defined as the dynamics of body posture to prevent falling and is affected by the inertial forces acting on the body, which encompasses movement about a base of support.11 An example of this involves tasks such as standing on one limb while performing functional movements with the other limb without disrupting the established base of support.12 A number of authors have correlated local and general fatigue to balance deficits.2,7 Fatigue of trunk and lower extremity musculature has been shown to have a significantly greater negative effect on static standing balance when compared to dynamic standing balance.7

Other authors have indicated that local fatigue also adversely affects dynamic standing balance.9 Thus, evidence exists that static and dynamic standing balance are adversely affected by general body fatigue and the local fatigue of lower extremity muscles.7,8 The impact of decreased balance has been described as both a result of and risk for lower extremity injury.13-16 Helbostad et al indicated that balance and functional tasks are impaired under fatigue conditions; however, whether an increased risk for injury or falls exists is unknown.17 The majority of studies included in the systematic review assessed local or general fatigue. What remains to be demonstrated is the relationship between distant fatigue and balance, about which little is known. The purpose of this study was to investigate the effects of upper body fatigue on dynamic standing balance. It was hypothesized that distant fatigue in upper body musculature will show a significant decrease in dynamic standing balance as assessed by the Lower Quarter Y-Balance Test (YBT-LQ). METHODS Design This study used a repeated measures design. The independent variable was fatigue, which was quantified using blood lactate levels. The furthest Y balance reach distance of 2 attempts in the anterior (ANT), posterior-medial (PM), and posterior-lateral (PL) and the sum total of the three directions (overall balance) served as the dependent variables. Participants Twenty healthy individuals between the ages of 18 and 35 who did not describe themselves as a recreational or competitive kayaker were invited to participate in this study. Exclusion criteria, obtained by subject interview, included: any current (past 6 months) upper extremity or torso injury that limited upper body exercise, current lower extremity injury, individuals with known balance disorders, any limitation to cardiovascular exercise, pregnancy, and individuals with clotting disorders. All qualifying participants signed informed consent as per institutional guidelines. This study was approved by the Institutional Review Board at East Tennessee State University.

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Figure 2. Kayak ergometer setup.

Figure 1. Y-Balance Test with reach directions shown: Anterior (ANT), Posteromedial (PM), and Posterolateral (PL).

Instruments The Y-Balance Test Kit™ (Move2Perform, Evansville, IN) was used for this study. Lower extremity reach distances in the ANT, PM and PL directions were recorded for each participant. Overall balance was also calculated as the sum of the furthest reach in each of the three directions.9 The naming direction of reach distance is based on the stance leg as indicated in Figure 1. Test-retest reliability of the Y-balance test was performed a-priori on 15 individuals without balance disorder. Intraclass correlation coefficient (ICC 3,1) and standard error of measurement (SEM) were calculated for each normalized reach distance and overall balance. Intrasession reliability values are noted in Table 1. A kayak ergometer (KayakPro, Miami Beach, FL, USA) was used for the upper body fatigue protocol (Figure 2). Upper body fatigue was quantified using whole blood lactate analysis (Lactate Pro, Carlton, NSW, Australia) before and after the fatigue protocol.18

Procedures Testing was completed over 2 test sessions on separate days. On day 1, a 20-minute instructional session was provided to familiarize the participants with the kayak ergometer, proper kayak technique and the balance testing procedures. Kayak technique instruction was provided by an expert kayaker (CAW) based on prior research describing the kayak stroke.19 Briefly, the participants were educated on the use of both upper extremities for propulsion as well as torso rotation as an important component to kayak technique. The participants’ feet were maintained on a foot platform during testing but were not fixed (Figure 2). Day 2 consisted of additional balance familiarization and all data collection procedures (balance testing pre- and post-fatigue, maximal power output determination, and upper body fatigue protocol). Nutritional or hydration intake was not recorded at any time. Balance Testing Leg length was measured, with participants in supine, from the anterior superior iliac spine to the center of the medial malleolus for normalization of reach distances. Balance testing was performed with the dominant lower extremity reaching in the various directions while the non-dominant leg was in stance. The dominant lower extremity was identi-

Table 1. A-Priori Reliability for the Normalized Y-Balance Test

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fied by answering the question, “Which leg do you use to kick a ball?” Participants were then instructed on the appropriate way to perform the standing balance test on the YBT-LQ in all three directions in the following order ANT, PM, then PL. Participants practiced six trials for their dominant leg reach in each of the three reach directions prior to formal testing.9 For data collection, participants completed the Y balance test two times in each direction, and the furthest reach distance was recorded. A fourth value termed overall balance was calculated as the sum of the furthest reach distance in each of the three directions. A retrial was performed if a participant was unable to maintain unilateral stance, moved the stance foot, or if they kicked the reach indicator. Upper Body Fatigue Protocol Following a self-directed warm up on the kayak ergometer, the participants performed a maximum effort for 30 seconds on the kayak ergometer to determine their maximum power output as measured by the ergometer. Calculations were performed to determine 50%, 60%, 70%, 80%, and 90% of maximum power for each participant based on their maximum power output. The protocol was created for this study to create a novel stimulus to achieve upper body fatigue in a group of non-kayakers based on general graded exercise testing protocols.20 Participants were then instructed to begin the fatigue protocol: two minutes at 50%, two minutes at 60%, two minutes at 70%, two minutes at 80%, and two minutes at 90% for a total of 10 minutes. No prescribed paddle stroke frequency was used. The paddle stroke frequency was self-determined in order to maintain the target power as displayed on the ergometer monitor for each time period. To quantify fatigue incurred, blood lactate was measured immediately prior to and following fatigue procedures.21 Immediately following the fatigue protocol and lactate measurement, dynamic standing balance was reassessed as described previously. Statistical Analysis Paired t-tests were performed for each reach direction and overall balance score for pre-fatigue and postfatigue measurements. To limit the chance of type I error, a Bonferroni correction was applied to the data to set significance at 0.0125 a priori. Data was then analyzed with SPSS 21.0 (SPSS Inc, Chicago, IL, USA).

Effect size (ES) was calculated using the effect size index. The formula was the difference between prefatigue and post-fatigue reach distances divided by the standard deviation of the control, which was the pre-fatigue reach distance [(pre-post)/standard deviation control]. The following was used for effect size interpretation: small effects = 0.20, moderate effects = 0.50, and large effects = 0.80.22 RESULTS Participants’ were 25.0 ± 3.42 years of age, 172.72 ± 13.11 centimeters in height, and 71.36 ± 13.50 kilograms in weight (Table 2). Twelve female and eight male participants completed the study of which eighteen participants were right leg dominant. Blood lactate increased by 6.15 millimoles (mM) from 2.3 mM pre-fatigue testing to 8.4 mM post-fatigue testing. Dynamic standing balance was shown to significantly decrease post-fatigue in the ANT direction (p = 0.004, ES = 0.64) as well as overall balance (p = 0.011, ES = 0.44). No significant differences and small effects were found for the PM (p = 0.246, ES = 0.20) and PL (p = 0.188, ES = 0.22) directions (Table 3). DISCUSSION The findings of the current investigation support the proposed hypothesis, demonstrating that distant (upper body) fatigue has significant adverse effects on dynamic standing balance, specifically seen in the ANT reach direction and the calculated overall balance. A moderate clinical effect, based on the effect size index, was also noted for both the ANT direction (0.64) and overall balance (0.44). Fatigue has been described as having either a central or peripheral effect on the body4-6 with differences based on the neuromuscular processes disrupted. A decline in force production at or distal to the neuromuscular junction may be considered a peripheral effect, while the failure of muscle activation (proportion or type motor unit recruited and/or motor neuTable 2. Participant Demographics

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Table 3. Reach Differences, normalized to limb length

ron excitability) may be considered a centrally driven effect.4-6,23 Given the protocol of the current study, the decreased balance noted may be attributed, in part, to central fatigue, as the lower body was minimally involved in the fatiguing exercise (kayaking). Central fatigue has been shown to affect the body’s ability to facilitate a muscle contraction when performing functional tasks such as maintaining the base of support.4-7,12 This explanation of altered balance is theoretical, as no methods were employed to quantify the centrally driven influence on dynamic balance in this study. The decreased balance found in the study may also have been due to decreased attention paid to balance testing immediately following the fatiguing event.24,25 The role of attention on balance has rarely been studied; yet, one prior investigation studied the relationship between a noxious stimulus to the neck and standing balance.25 The painful sensation administered to the neck adversely affected static standing balance, thus supporting the theory that balance can be influenced by centrally driven effects either through decreased activation or attention.25 The effects of local versus distant fatigue on balance have been studied sparingly.2 Prior investigations have used varied methods to induce local (lower extremity) or distant (trunk or upper extremity) fatigue. Generally it has been reported that standing static balance is decreased following distant or generalized fatiguing exercises using trunk isokinetic exercise or squat thrusts.7,8 Using tilt platform measures, dynamic standing balance has yielded more equivocal results with some investigators, indicating a reduction in balance, while others report no changes.16,26,27 The current study used the YBT-LQ which is believed to better mimic normal function as bodily movement occurs over a stable base of support, as opposed to tilt platforms, which utilize a dynamic base of support while attempting to maintain stability.28

Previous investigations have utilized the YBT-LQ to prospectively assess injury risk.13 Differences of greater than 4 cm in any direction have been associated with increased lower extremity injury risk (2.5 times) among high school female basketball players.13 The results of the current study yielded an average decreased reach distance of 4.4 cm in the ANT direction, which may indicate that distant fatigue could place athletes at greater injury risk. Further, female athletes with an overall balance score of less than 94% of lower extremity length are 6.5 times more likely to sustain a lower extremity injury.13 The calculated overall balance score in this study went from 97% in the control condition to 94% in the fatigued condition. The score found in this study was not less than the 94% cutoff for injury risk; however, the combination of an individual directional score change greater than 4 cm and overall balance scores equal to 94% of lower extremity length suggest that distant fatigue could play a substantive role in increased injury risk among athletes. Statistically significant differences and moderate effects were noted between the pre- and post-fatigue measures only for the ANT direction. Previous investigation comparing four different fatigue protocols based on anatomic locations (fatiguing exercise to the ankle, knee, hip, or lunge for the entire lower limb) and gender has also described an ANT directional specificity to fatigue.29 These authors reported significant decreases in various directions of lower extremity reach distances (anterior, medial and posterior) for the varying fatigue locations. The posteriorly oriented reach exhibited gender differences (males exhibited a greater decline in balance) and did not find reach differences for hip muscle fatigue.29 Males also demonstrated a greater decline in reach distance compared to females for the medial reach although all locations of fatigue reduced reach dis-

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tance.29 While the reach directions differed between the prior29 and the current study the summary of these findings suggest the ANT reach direction may be most discriminating direction to assess local or distant fatigue in uninjured participants. There are several potential reasons this may be the case in the current study. First, the ANT reach direction requires the trunk and upper body, and thus the center of mass, to displace posteriorly. This stance position is uncommon during functional tasks and may be more of a novel activity requiring greater concentration and/or effort. Whereas the posteriorly oriented reaching tasks which require trunk and upper body displacement anteriorly, are more common functionally. An example of this would be bending over to pick up an object in front of the body. Therefore the PM and PL reaches may utilize more practiced motor patterns. The concentration and effort required for the ANT reach, simulating a less common functional task, may make it more susceptible to decline due to central mechanisms compared to posteriorly oriented reach directions.30 Additionally, the order of balance testing for all participants was set as ANT, PM, then PL. It is possible that the fatigue levels waned as the post fatigue balance testing was performed. However, the total time for test measurement in all directions was less than 3-4 minutes with all directions tested twice in the same order. Only the furthest reach distances were recorded for each limb. The authors feel decreased fatigue was unlikely given the short time for testing and the repeated trials used for measurement. Clinicians training or treating upper extremity athletes should be aware of the adverse effects of upper body fatigue on dynamic standing balance. Specifically, the ANT reach direction of the YBT-LQ has similarities with a unilateral squat; thus clinicians treating patients using this exercise should consider the potential for decreased functional performance on this exercise due to fatigue. Additionally, it may be beneficial for injured upper extremity athletes to participate in a lower extremity balance training program in order to prepare for their sport and reduce the risk of a balance related injury. However, this may not be applicable to elite athletes who are well conditioned against such injury potential. From a more global perspective, patients who have an increased risk of falls or who are more susceptible

to fatigue (such as following immobilization post operatively or with decreased sport participation secondary to injury) may require additional supervision during their exercises, including upper body based programs. Adding trunk and lower extremity balance and stabilization exercises may also be considered for the younger athletic population who experience upper extremity pathologies. Populations with general balance deficits may also benefit from the results of this study. Recently Douris and colleagues2 provided corroborating evidence that demonstrates the importance of upper extremity function on the ability to maintain overall standing balance. Therefore, adding upper extremity, scapular, and spinal stabilization exercises to improve global dynamic balance may be considered for patients with balance disorders. Limitations The participants in this study were not injured. The role of fatigue may differ in individuals with joint injury and/or pain.31 Further, the participants were not trained upper body athletes or kayakers. This sampling was done purposefully to provide a novel upper body fatigue stimulus in healthy individuals. Varying results may occur in athletes who commonly perform fatiguing upper body exercise. Future studies are advocated to assess the role of distant fatigue functional performance in upper and lower extremity athletes. Clinical studies quantifying the role of distant fatigue on individuals at risk of falls or with balance disorders may provide details to help better treat or prevent injury in these populations. CONCLUSION The findings of this research demonstrate that upper body fatigue has adverse effects on dynamic standing balance, measured by performance on the YBTLQ. Significant and clinically relevant differences were noted in ANT and overall dynamic standing balance. The balance deficits noted may indicate an increased risk of injury with muscle fatigue in muscles not contributing to standing balance. REFERENCES 1. Bigland Ritchie B, Woods J. Changes in muscle contractile properties and neural control during human muscular fatigue. Muscle Nerve. 1984;7(9):691-699.

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2. Douris PC, Handrakis JP, Gendy J, et al. Fatiguing upper body aerobic exercise impairs balance. J Strength Cond Res. 2011;25(12):3299. 3. Hagg GM. Interpretation of EMG spectral alterations and alteration indexes at sustained contraction. J Appl Physiol. 1992;73(4):1211-1217. 4. Gandevia S. Spinal and supraspinal factors in human muscle fatigue. Physiol Rev. 2001;81(4):1725-1789. 5. Taylor JL, Gandevia SC. Transcranial magnetic stimulation and human muscle fatigue. Muscle Nerve. 2001;24(1):18-29. 6. Taylor JL, Gandevia SC. A comparison of central aspects of fatigue in submaximal and maximal voluntary contractions. J Appl Physiol. 2008;104(2):542-550. 7. Cetin N, Bayramoglu M, Aytar A, Surenkok O, Yemisci OU. Effects of lower-extremity and trunk muscle fatigue on balance. Open Sports Med. J. 2008;2:16-22. 8. Nelson JK, Johnson BL. Effects of local and general fatigue on static balance. Percept Mot Skills. 1973;37(2):615-618. 9. Plisky PJ, Gorman PP, Butler RJ, Kiesel KB, Underwood FB, Elkins B. The Reliability of an Instrumented Device for Measuring Components of the Star Excursion Balance Test. N Amer J Sports Phys Ther. 2009;4(2):92. 10. Adlerton AK, Moritz U. Does Calf Muscle Fatigue affect Standing Balance? Scand J Med Sci Sports. 1996;6(4):211-215. 11. Winter DA. Human balance and posture control during standing and walking. Gait Posture. 1995;3(4):193-214. 12. Gribble PA, Hertel J, Plisky P. Using the Star Excursion Balance Test to Assess Dynamic PosturalControl Deficits and Outcomes in Lower Extremity Injury: A Literature and Systematic Review. J Athl Train. 2012;47(3):339-357. 13. Plisky PJ, Rauh MJ, Kaminski TW, Underwood FB. Star Excursion Balance Test as a Predictor of Lower Extremity Injury in High School Basketball Players. J Orthop Sports Phys Ther. 2006;36(12):911. 14. McGuine TA, Greene JJ, Best T, Leverson G. Balance as a predictor of ankle injuries in high school basketball players. Clin J Sport Med. 2000;10(4):239. 15. Docherty CL, McLeod TCV, Shultz SJ. Postural control deficits in participants with functional ankle instability as measured by the balance error scoring system. Clin J Sport Med. 2006;16(3):203-208. 16. Akbari M, Karimi H, Farahini H, Faghihzadeh S. Balance Problems after Unilateral Lateral Ankle Sprains. J Rehab Res Dev. 2006;43(7):819.

17. Helbostad JL, Sturnieks DL, Menant J, Delbaere K, Lord SR, Pijnappels M. Consequences of lower extremity and trunk muscle fatigue on balance and functional tasks in older people: A systematic literature review. BMC Geriatr. 2010;10(1):56. 18. Pyne DB, Boston T, Martin DT, Logan A. Evaluation of the Lactate Pro blood lactate analyser. Eur J Appl Physiol. 2000;82(1-2):112-116. 19. Wassinger CA, Myers JB, Sell TC, Oyama S, Rubenstein EN, Lephart SM. Scapulohumeral kinematic assessment of the forward kayak stroke in experienced whitewater kayakers. Sports Biomech. 2011;10(2):98-109. 20. Powers SK, Howley ET. Exercise Physiology: McGrawHill; 1997. 21. Cairns SP. Lactic acid and exercise performance. Sports Med. 2006;36(4):279-291. 22. Portney L, Watkins M. Foundations of Clinical Research: Applications to Practice; 3rd Edition: Prentice Hall Upper Saddle River, NJ; 2009. 23. Lephart SM, Fu FH. Proprioception and Neuromuscular Control in Joint Stability: Human Kinetics; 2000. 24. Wassinger CA, Sole G, Osborne H. The role of experimentally-induced subacromial pain on shoulder strength and throwing accuracy. Man Ther. 2012. 25. Vuillerme N, Pinsault N. Experimental neck muscle pain impairs standing balance in humans. Exp Brain Res. 2009;192(4):723-729. 26. Gioftsidou A, Malliou P, Pafis G, Beneka A, Godolias G, Maganaris CN. The effects of soccer training and timing of balance training on balance ability. Eur J Appl Physiol. 2006;96(6):659-664. 27. Salavati M, Moghadam M, Ebrahimi I, Arab AM. Changes in postural stability with fatigue of lower extremity frontal and sagittal plane movers. Gait Posture. 2007;26(2):214-218. 28. Arnold BL, Schmitz RJ. Examination of balance measures produced by the Biodex Stability System. J Athl Train. 1998;33(4):323. 29. Gribble PA, Robinson RH, Hertel J, Denegar CR. The effects of gender and fatigue on dynamic postural control. J Sport Rehabil. 2009;18(2):240. 30. Banister E, Cameron B. Exercise-induced hyperammonemia: peripheral and central effects. Int J Sports Med. 1990;11(S 2):S129-S142. 31. Gribble PA, Hertel J, Denegar CR, Buckley WE. The effects of fatigue and chronic ankle instability on dynamic postural control. J Athl Train. 2004;39(4):321.

The International Journal of Sports Physical Therapy | Volume 9, Number 1 | February 2014 | Page 46

The influence of upper body fatigue on dynamic standing balance.

Muscle fatigue is related to a decline in force output and proprioception. These can ultimately have an adverse effect on neuromuscular control and fu...
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