The effects of vibration therapy on muscle force loss following eccentrically induced muscle damage

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1 Eur J Appl Physiol (2012) 112: DOI /s SHORT COMMUNICATION The effects of vibration therapy on muscle force loss following eccentrically induced muscle damage Matthew J. Barnes Blake G. Perry Toby Mündel Darryl J. Cochrane Received: 13 February 2011 / Accepted: 27 June 2011 / Published online: 13 July 2011 Ó Springer-Verlag 2011 Abstract The purpose of this study was to investigate the effects of acute vibration therapy (VT) on performance recovery after a bout of strenuous eccentric exercise. Eight healthy males completed 300 maximal eccentric contractions of the quadriceps of one leg on an isokinetic dynamometer. Immediately after exercise and 12 and 24 h post-exercise, the subjects underwent either VT or a control treatment of no VT. Five sets of 1 min VT was performed at 26 Hz, with 6 mm peak-to-peak displacement, on a commercially available vibration machine. At least 2 weeks after the initial trial, the subjects completed the second trial using the contralateral leg and other treatment. Peak and average peak isometric tension and isokinetic concentric and eccentric torque were measured prior to exercise and 24 and 48 h post-exercise. Treatment with VT resulted in significantly (all P \ 0.05) greater decrements in peak (-38%) and average peak eccentric (-39%) torque 24 h after eccentric exercise as compared to a control treatment (-24 and -29%, respectively). These results suggest that the use of 26 Hz VT in the first 24 h after damaging exercise may be detrimental to the magnitude of force loss and/or recovery over this period. Keywords Muscle damage Muscle function Recovery Soft tissue injury Whole-body vibration Communicated by Susan A. Ward. M. J. Barnes (&) B. G. Perry T. Mündel D. J. Cochrane School of Sport and Exercise, Massey University, Private Bag, Palmerston North, New Zealand m.barnes@massey.ac.nz Introduction High loads and/or repetitive eccentric exercise are known to disrupt sarcomere structure resulting in localised inflammation, muscle soreness and reductions in muscle function and performance (Byrne et al. 2004). Whether it is in training and/or competition, running-based athletes face frequent exposure to eccentric actions and without appropriate recovery, a reduction in subsequent performance can occur (Cheung et al. 2003). Various recovery modalities are practiced by athletes in an attempt to accelerate the recovery process to minimise the performance decrements. Recently, vibration therapy (VT), in particular whole-body vibration (WBV), has gained popularity as a possible post-exercise recovery modality to reduce the pain and muscle soreness (Broadbent et al. 2010; Rhea et al. 2009). Aiding muscle recovery relies on increased blood flow (Weerapong et al. 2005), therefore the reported increase in blood flow from WBV (Kerschan-Schindl et al. 2001) could accelerate the recovery process by increasing oxygen delivery, raising muscle temperature, and enhancing waste product removal that inhibit tissue repair (Cafarelli et al. 1990; Weerapong et al. 2005). However, the efficacy of WBV for postexercise recovery remains equivocal; acute WBV showed no benefit on running performance recovery or metabolism following the high intensity intermittent running (Edge et al. 2009), whereas a repeated bout of WBV following downhill running reduced muscle soreness and muscle inflammation (Broadbent et al. 2010). Recent research has shown that applying acute WBV prior to eccentric exercise reduced muscle soreness and attenuated isometric torque loss (Aminian-Far et al. 2011), however, to date no published research has determined the effect of post-eccentric exercise WBV on muscle

2 1190 Eur J Appl Physiol (2012) 112: performance recovery. Therefore, the purpose of this study was to examine the effects of acute VT on muscle performance recovery after a bout of strenuous eccentric exercise. We hypothesised that VT would improve the recovery of muscular performance in the days after a strenuous bout of eccentric exercise, when compared with a control of no VT. Methods Subjects Eight healthy, resistance trained (3 times per week at a recreational level) male subjects (mean ± SD age: 23 ± 3 years, body mass: 82 ± 11 kg, height: 178 ± 8.9 cm) participated in the present study. The procedures used were approved by the Massey University Human Ethics Committee and written informed consent was obtained from each subject. Subjects were instructed to abstain from alcohol consumption, any form of exercise and practices that could influence their recovery from 48 h before each trial until the last performance measures were made 48 h post-exercise. An equal number of subjects were randomly assigned to either the VT or control treatment for their first trial. Further, half of the subjects in these groups were assigned to use either their dominant or non-dominant leg in the first trial so that treatment and leg dominance was allocated in a counter-balanced, cross-over fashion. Briefly, subjects completed a bout of eccentric exercise after which they underwent either a treatment of VT or a control of no VT. Treatment was given immediately after exercise and at 12 and 24 h post-exercise. Measures of muscular performance were made prior to exercise and 24 and 48 h post-exercise. Measures of performance alone were used to quantify the muscle damage due to the reliability of this measure (Warren et al. 1999) and the direct application these results have to the rehabilitative setting. At least 2 weeks after the first trial subjects returned to the laboratory and completed an equivalent bout of exercise using the contralateral leg followed by the other treatment. Muscular performance At least 1 week before their first trial, the subjects were familiarised with the exercise, performance measures and treatments utilised in the study. Having been familiarised with the protocol, subjects returned to the laboratory and warmed up on a cycle ergometer (Monark, Varberg, Sweden) for 5 min at 100 W. As previous studies investigating the effects of VT on recovery after eccentric exercise have focused solely on isometric torque (Aminian-Far et al. 2011; Lau and Nosaka 2011), we chose to investigate whether a particular contraction type was affected more than others by the combination of eccentric exercise and VT. Therefore, pre-exercise measures of maximal isometric (ISO) tension and concentric (CON) and eccentric (ECC) torque produced by the quadriceps muscles of one leg were made on a Biodex Ò isokinetic dynamometer (Biodex Medical Systems, NY, USA). Due to the potential for inducing muscle damage, ECC measures were made last so as not to influence ISO or CON performance. This order was maintained throughout the study. Each test consisted of five maximal contractions with each test separated by 2 min of passive recovery. ISO was measured at a knee angle of 75 whilst CON and ECC were measured at an angular velocity of 30 s -1 over a comfortable, full range of motion. Range of motion was recorded and used during subsequent performance measurements. Follow-up measures of muscular performance were made 24 and 48 h post-exercise (Barnes et al. 2010a, b). Eccentric exercise After the measurement of muscular performance, the subjects remained seated on the isokinetic dynamometer and completed 3 sets of 100 maximal eccentric contractions, over a 60 range of motion (from full flexion (0 ) to60 extension) at an angular velocity of 30 s -1, using the quadriceps muscles of the tested leg. Each set was separated by 5 min of passive recovery (Barnes et al. 2010a, b). This protocol has previously been used to bring about significant reductions in muscular performance, elevations in creatine kinase activity in the blood (Barnes et al. 2010b) and changes in white blood cell concentrations (MacIntyre et al. 1996). Work completed in each of the three sets was recorded via the dynamometer software (System 3 v3, Biodex Medical Systems, NY, USA) and later analysed for the differences between treatments and trials. Treatment Immediately after the completion of the eccentric exercise bout and after performance measures at 12 and 24 h postexercise subjects were exposed to five sets of 1 min VT with 1 min passive recovery between each set (VT) or an identical protocol with the machine switched off (control). The VT protocol used in the present study was chosen as exposure to five 1 min bouts of vibration separated by 1 min rest at high frequency (26 30 Hz) has been shown to enhance muscle power (Bosco et al. 1999) and increase blood cell velocity of the femoral artery (Lythgo et al. 2009). VT was performed on a commercial machine (Galileo Sport, Novotec, Pforzheim, Germany), which had a

3 Eur J Appl Physiol (2012) 112: motorised teetering platform that produced side-to-side alternating sinusoidal vertical vibration (SAV) to the body that rotated about an anteroposterior horizontal axis. Subjects placed the damaged leg on a marked position on the platform; with the other leg positioned shoulder width apart on a box step at equal height to the platform. Peak-to-peak displacement (6 mm) at the marked foot position was recorded from a single axis accelerometer (Imems Ò, ADXL250, Analog Devices, Norwood, MA, USA) fixed to the edge of the vibrating platform. All subjects stood barefoot in a static squat position with hands on hips and distributed their body weight equally through mid-sole of each foot whilst keeping their trunk straight and eyes focused forward. A manual goniometer was used to set the knee angle to approximately 30 of flexion (full extension = 0 ). A vibration frequency of 26 Hz was selected based on previous WBV research that reported an increase in blood flow (Kerschan-Schindl et al. 2001) and muscle temperature (Cochrane et al. 2008), both of which are central to aiding muscle recovery (Barnett 2006; Drust et al. 2003). At least 2 weeks after the initial trial, the subjects completed the protocol again using the contralateral leg and the opposite treatment. Statistical analyses ISO, CON and ECC peak and the average (AV) peak torque from five contractions was analysed using the Statistical Program for Social Sciences (SPSS) for Windows (version 15.0, SPSS Inc., Chicago, IL, USA). A general linear-model two-way repeated-measures ANOVA (treatment 9 time) was used to compare treatments over time for each measurement. Post hoc pairwise comparisons were made using Bonferroni adjustment to investigate changes in performance over time within each treatment. Data was analysed as absolute (Table 1) and percentage change from pre-exercise values as different legs were used in each trial. Reported values are means ± SD. Statistical significance was set at P \ Results Total work completed during the eccentric exercise bouts was not significantly different between trial one (40.9 ± 9.3 kj) and trial two (36.6 ± 5.2 kj) (P = 0.23) or between VT (38.4 ± 10.5 kj) and control (39.1 ± 3.8 kj) (P = 0.87). Repeated-measures ANOVA of trial one versus trial two and dominant versus non-dominant leg found no significant effect of order or leg for any of the muscular performance measures (all P [ 0.1). Strenuous eccentric exercise resulted in a significant decrease in all performance measures over time under both treatments (all P \ 0.01, Table 1). Changes in peak and average peak ECC strength over time were different between conditions with significant treatment 9 time interactions observed for peak ECC (P = 0.025) and AV ECC (P = 0.039); however, this was not the case for ISO and CON strength. Greatest decrements in performance occurred 24 h post-exercise with VT resulting in greater decreases in peak ECC (-38%) and AV ECC (-39%) as Table 1 Changes in torque (Nm) over time following strenuous eccentric exercise Significant treatment and treatment 9 time interactions observed for peak and average peak ECC (all P \ 0.05) only. Data presented as mean ± SD ISO isometric, CON concentric, ECC eccentric torque (Nm), VT vibration therapy * P \ 0.05, significant difference from pre-exercise value P \ 0.05, significant difference between treatments Pre 24 h 48 h Peak ISO Control ± ± ± 72.2* VT ± ± 49.9* ± 36.6* Average ISO Control ± ± 60.5* ± 70.3* VT ± ± 47.1* ± 36.8* Peak CON Control ± ± 43.2* ± 46.1 VT ± ± 26.8* ± 33.0 Average CON Control ± ± 37.1* ± 45.2* VT ± ± 16.9* ± 31.2* Peak ECC Control ± ± 67.5* ± 68.9 VT ± ± 57.5*, ± 58.5*, Average ECC Control ± ± ± 73.1 VT ± ± 50.4*, ± 59.1

4 1192 Eur J Appl Physiol (2012) 112: compared to control (-24 and -29%, respectively). No significant differences in the changes in ISO and CON strength measures were observed between the VT and the control treatment (all P [ 0.1). Muscular performance recovered significantly towards pre-exercise values at 48 h for all measures (all P \ 0.05) except VT peak ISO and ECC and AV ISO under both treatments. Discussion The aim of the present study was to investigate the effects of acute VT on muscle performance recovery after a bout of strenuous eccentric exercise. The results of this study show that acute VT failed to attenuate muscle force loss in ISO and isokinetic (CON and ECC) contractions following eccentric exercise, which does not support our hypothesis that VT improves the recovery of muscular performance in the days after a strenuous bout of eccentric exercise. Previous VT studies have reported that in post-exercise recovery muscle soreness and pain is reduced (Broadbent et al. 2010; Rhea et al. 2009) and that an acute bout of VT prior to eccentric exercise-induced muscle-damage reduces muscle soreness and attenuates ISO torque loss (Aminian- Far et al. 2011; Bakhtiary et al. 2007). The expectation of the present study was to apply VT after eccentric exerciseinduced muscle-damage to promote blood flow, muscle temperature and neurogenic aspects to improve recovery in the various muscle contraction types. Currently, there is no consensus on the mechanism(s) of VT however, VT does improve muscular performance in non-damaged muscle (Cochrane and Stannard 2005; Cochrane et al. 2008; Torvinen et al. 2002). This transient effect is thought to be mediated by a rapid reflex-mediated stretch shortening (Rittweger et al. 2003; Rittweger et al. 2001) likely to involve the tonic vibration reflex, which stimulates the muscle spindles (Rittweger et al. 2001). Further, this increase in muscle spindle response could optimise motor unit firing and synchronisation (Cochrane 2011) of the disrupted sarcolemma and allow excitation contraction coupling to take place in the damaged muscle. However, our results showed no benefit of using VT posteccentric exercise to improve the recovery of muscular performance and no changes in ISO strength have been previously reported (Lau and Nosaka 2011). The most significant finding of the present study was that peak (-38%) and average peak (-39%) ECC torque was dramatically reduced 24 h post-eccentric exercise as compared to the control treatment (-24 and -29%, respectively). Conversely, it has been reported knee extensor ISO torque loss was attenuated by WBV as compared to no WBV (Aminian-Far et al. 2011). However, these researchers administered one set of 60 s WBV on a synchronous vertically vibrating (SVV) machine (platform moved vertically up-and-down) prior to eccentric exercise (6 sets 9 10 reps). Therefore, the different vibration and exercise protocols, timing of WBV (before vs. after), and vibration platforms [synchronous vertical vibration (SVV) vs. side-alternating vertical vibration (SAV)] may explain the dissonance between the two studies. Muscle damage occurs through eccentric actions and from prolonged or intense eccentric concentric activities such as distance running, plyometrics and resistance training (Byrne et al. 2004). Likewise, VT performed on an SAV platform can be classified as an eccentric concentric modality where muscles are quickly lengthened and shortened during a cyclic transition (Cochrane et al. 2009). According to Rittweger et al. (2001) during the push-phase of the SAV platform, the leg extensors work eccentrically whilst the flexors act concentrically indicating that both concentric and eccentric muscle actions are present. In the current study, the five sets of 26 Hz vibration would have produced an additional eccentric concentric activity of approximately 7,800 (26 Hz 9 60 s 9 5 min) muscle contractions. These rapid but small muscle contractions would have increased the total number of muscle lengthening-shortening cycles and/or caused additional muscle elongation. Therefore, it is conceivable that in the present study performing 26 Hz vibration immediately after 300 maximal eccentric contractions produced additional work and lengthening of the damaged muscle, which exacerbated losses in ECC force. This is supported by previous muscle damage studies that show when the number of muscle contractions increase there is a significant reduction in muscle force (Chapman et al. 2008; Hesselink et al. 1996). Although dynamic muscular contractions are more prevalent than isometric contractions in sport and exercise, to our knowledge the present study is the first to investigate the effects of VT on recovery of all three contraction types after eccentric exercise-induced muscle damage. In the present study, ECC, but not ISO or CON, was affected by the combination of damaging exercise and VT. Previous work investigating the magnitude of response and rate of recovery in the different contraction types after eccentric exercise is inconclusive with no one contraction type shown to be more or less susceptible than another (Byrne and Eston 2002; Golden and Dudley 1992; Hortobágyi et al. 1998). This lack of consensus coupled with the fact that previous, similar VT research has only investigated isometric forces (Aminian-Far et al. 2011; Bakhtiary et al. 2007; Lau and Nosaka 2011) makes it difficult to speculate on a mechanism behind our finding. However, although purely speculative at this time, one possible explanation for this observation is that the greater damage that occurs to fast twitch fibres, compared to other fibre types, after eccentric exercise (Friden et al. 1983; Linnamo et al. 2000), coupled

5 Eur J Appl Physiol (2012) 112: with the recruitment and eccentric loading of predominantly large motor units during high frequency VT (Rittweger et al. 2003), may result in a greater level of damage in this motor unit population. Given the unique motor unit activation strategies that occur during eccentric contraction (Enoka 1996), the combined damaging effects of eccentric exercise and VT on motor units involved in eccentric force production may result in a greater loss in ECC force, compared to CON or ISO force, when these motor units are required during subsequent performance measures. The combination of VT and eccentric exercise appears to have been most detrimental to performance in the first 24 h period after exercise; after this time performance improved by a similar magnitude with both treatments. Given the potentially damaging affect of the eccentric component of VT, the combination of eccentric exercise and VT may be considered as a single damaging event. Nosaka and Newton (2002) have previously shown that additional eccentric exercise in the days following an initial bout of damaging exercise does not exacerbate muscle damage or impact recovery. Therefore, as with direct eccentric exercise (Chen and Hsieh 2000; Nosaka and Newton 2002; Smith et al. 1994), VT does not appear to induce further damage in an already affected muscle group. To date, there is little scientific evidence on the optimal WBV recovery regimen due to the limited research and infinite number of combinations of WBV variables, such as vibration frequency, peak-to-peak displacement, duration of vibration bouts and rest interval between bouts. Our aim was to investigate the post-recovery VT effects of muscle performance, where blood flow and muscle temperature are central to the recovery process (Weerapong et al. 2005). The VT protocol used in the current study was based on the previous side-alternating platform research where 26 Hz vibration significantly increased muscle blood flow (Kerschan-Schindl et al. 2001) and muscle temperature (Cochrane et al. 2008). Although, no direct measurements of muscle blood flow or muscle temperature were taken, it is likely that both would have been elevated, thus promoting oxygen and nutrient delivery (Weerapong et al. 2005) but in doing so, the vibration frequency (26 Hz) may have compromised muscle recovery. A limitation of the present study is that muscular performance was not measured immediately, post-eccentric exercise and therefore we cannot be completely confident that the magnitude of damage, prior to treatment, was exactly the same under each condition, even though total work was not different between trials. However, whether this would have provided an accurate measure of damage is questionable given the large contribution metabolic fatigue has on decreases in performance after such strenuous exercise (Proske and Morgan 2001). An additional limitation may be the small sample size used in the current study. Although all measures show a similar trend, that is a greater decrease in muscular performance with VT compared to the control, only changes in ECC torque are statistically significant. It is possible that if the sample size was larger the greater changes in torque observed with VT may have resulted in significant treatment x time interactions for ISO and CON muscular performance. In conclusion, using a SAV platform at 26 Hz, with a peak-to-peak amplitude of 6 mm did not attenuate muscle force loss after strenuous eccentric exercise; rather it appears to have magnified losses in muscle function over the first 24 h after exercise. Therefore, caution is required when using high vibration frequency (26 Hz) to promote blood flow for muscle recovery as it is likely to have little effect or may be detrimental to the magnitude of force loss. Future research should determine the appropriate vibration frequency, duration, exposure, and rest intervals when using VT for muscle recovery. Acknowledgments Blake Perry was supported by a summer studentship provided by the Physiological Society. References Aminian-Far A, Hadian MR, Olyaei G, Talebian S, Bakhtiary AH (2011) Whole-body vibration and the prevention and treatment of delayed-onset muscle soreness. J Athl Train 46:43 49 Bakhtiary AH, Safavi-Farokhi Z, Aminian-Far A (2007) Influence of vibration on delayed onset of muscle soreness following eccentric exercise. Br J Sports Med 41:145 Barnes M, Mündel T, Stannard S (2010a) Post-exercise alcohol ingestion exacerbates eccentric-exercise induced losses in performance. Eur J Appl Physiol 108: Barnes MJ, Mündel T, Stannard SR (2010b) Acute alcohol consumption aggravates the decline in muscle performance following strenuous eccentric exercise. J Sci Med Sport 13: Barnett A (2006) Using recovery modalities between training sessions in elite athletes does it help? Sports Med 36: Bosco C, Colli R, Introini E, Cardinale M, Tsarpela O, Madella A, Tihanyi J, Viru A (1999) Adaptive responses of human skeletal muscle to vibration exposure. Clin Physiol 19: Broadbent S, Rousseau J, Thorp RM, Choate SL, Jackson FS, Rowlands DS (2010) Vibration therapy reduces plasma IL-6 and muscle soreness after downhill running. Br J Sports Med 44: Byrne C, Eston R (2002) The effect of exercise-induced muscle damage on isometric and dynamic knee extensor strength and vertical jump performance. J Sports Sci 20: Byrne C, Twist C, Eston R (2004) Neuromuscular function after exercise-induced muscle damage theoretical and applied implications. Sports Med 34:49 69 Cafarelli E, Sim J, Carolan B, Liebesman J (1990) Vibratory massage and short-term recovery from muscular fatigue. Int J Sports Med 11: Chapman DW, Newton M, McGuigan M, Nosaka K (2008) Effect of lengthening contraction velocity on muscle damage of the elbow flexors. Med Sci Sports Exerc 40: Chen TC, Hsieh SS (2000) The effects of repeated maximal voluntary isokinetic eccentric exercise on recovery from muscle damage. Res Q Exerc Sport 71:260

6 1194 Eur J Appl Physiol (2012) 112: Cheung K, Hume PA, Maxwell L (2003) Delayed onset muscle soreness treatment strategies and performance factors. Sports Med 33: Cochrane DJ (2011) The potential neural mechanisms of acute indirect vibration. J Sports Sci Med 10:19 30 Cochrane DJ, Stannard SR (2005) Acute whole body vibration training increases vertical jump and flexibility performance in elite female field hockey players. Br J Sports Med 39: Cochrane DJ, Stannard SR, Sargeant T, Rittweger J (2008) The rate of muscle temperature increase during acute whole-body vibration exercise. Eur J Appl Physiol 103: Cochrane DJ, Loram ID, Stannard SR, Rittweger J (2009) Changes in joint angle, muscle-tendon complex length, muscle contractile tissue displacement and modulation of EMG activity during acute whole-body vibration. Muscle Nerve 40: Drust B, Atkinson G, Gregson W, French D, Binningsley D (2003) The effects of massage on intra muscular temperature in the vastus lateralis in humans. Int J Sports Med 24: Edge J, Mundel T, Weir K, Cochrane DJ (2009) The effects of acute whole body vibration as a recovery modality following highintensity interval training in well-trained, middle-aged runners. Eur J Appl Physiol 105: Enoka RM (1996) Eccentric contractions require unique activation strategies by the nervous system. J Appl Physiol 81:2339 Friden J, Sjostrom M, Ekblom B (1983) Myofibrillar damage following intense eccentric exercise in man. Int J Sports Med 4: Golden CL, Dudley GA (1992) Strength after bouts of eccentric or concentric actions. Med Sci Sports Exerc 24:926 Hesselink MKC, Kuipers H, Geurten P, vanstraaten H (1996) Structural muscle damage and muscle strength after incremental number of isometric and forced lengthening contractions. J Muscle Res Cell M 17: Hortobágyi T, Houmard J, Fraser D, Dudek R, Lambert J, Tracy J (1998) Normal forces and myofibrillar disruption after repeated eccentric exercise. J Appl Physiol 84:492 Kerschan-Schindl K, Grampp S, Henk C, Resch H, Preisinger E, Fialka-Moser V, Imhof H (2001) Whole-body vibration exercise leads to alterations in muscle blood volume. Clin Physiol 21: Lau WY, Nosaka K (2011) Effect of vibration treatment on symptoms associated with eccentric exercise-induced muscle damage. Am J Phys Med Rehab. doi: /phm.0b013e ac8 Linnamo V, Bottas R, Komi PV (2000) Force and EMG power spectrum during and after eccentric and concentric fatigue. J Electromyogr Kinesiol 10: Lythgo N, Eser P, de Groot P, Galea M (2009) Whole-body vibration dosage alters leg blood flow. Clin Physiol Funct Imaging 29:53 59 MacIntyre DL, Reid WD, Lyster DM, Szasz IJ, McKenzie DC (1996) Presence of WBC, decreased strength, and delayed soreness in muscle after eccentric exercise. J Appl Physiol 80: Nosaka K, Newton M (2002) Repeated eccentric exercise bouts do not exacerbate muscle damage and repair. J Strength Cond Res 16: Proske U, Morgan DL (2001) Muscle damage from eccentric exercise: mechanism, mechanical signs, adaptation and clinical applications. J Physiol 537: Rhea MR, Bunker D, Marín PJ, Lunt K (2009) Effect of itonic whole-body vibration on delayed-onset muscle soreness among untrained individuals. J Strength Cond Res 23: Rittweger J, Schiessl H, Felsenberg D (2001) Oxygen uptake during whole-body vibration exercise: comparison with squatting as a slow voluntary movement. Eur J Appl Physiol 86: Rittweger J, Mutschelknauss M, Felsenberg D (2003) Acute changes in neuromuscular excitability after exhaustive whole body vibration exercise as compared to exhaustion by squatting exercise. Clin Physiol Funct Imaging 23:81 86 Smith LL, Fulmer MG, Holbert D, McCammon MR, Houmard JA, Frazer DD, Nsien E, Israel RG (1994) The impact of a repeated bout of eccentric exercise on muscular strength, muscle soreness and creatine kinase. Br J Sports Med 28:267 Torvinen S, Kannus P, Sievanen H, Jarvinen TAH, Pasanen M, Kontulainen S, Jarvinen TLN, Jarvinen M, Oja P, Vuori I (2002) Effect of a vibration exposure on muscular performance and body balance. Randomized cross-over study. Clin Physiol Funct Imaging 22: Warren GL, Lowe DA, Armstrong RB (1999) Measurement tools used in the study of eccentric contraction-induced injury. Sports Med 27:43 59 Weerapong P, Hume PA, Koht GS (2005) The mechanisms of massage and effects on performance, muscle recovery and injury prevention. Sports Med 35: