strength training involving repetitive eccentric exercises can cause muscle damage , 
 resulting in muscle soreness , swelling and eventually reduction of muscle strength , 
 especially when an athlete is unaccustomed to this type of muscle contraction1,2,3 .
previous studies have found significant 
 increases in self - reported pain after performing eccentric exercises involving the elbow 
 flexor4 . a reduction in explosive force 
 and increase of muscle soreness
have also been reported after 12 sets of 10 eccentric squats 
 in active physical education students5 . 

this muscle damage is usually defined as delayed - onset muscle soreness ( doms ) , and it 
 appears between 8 to 20 hours after the exercise reaching its peak between 24 to 48 hours 
 after the damage6 . in physiological terms , 
 doms is characterized by a sensation of pain felt during movement or palpation of the 
 affected muscle7 .
inflammation , increased 
 serum creatine kinase ( ck ) levels , muscle force loss , and decrease in performance have also 
 been observed during this period8 , 9 .
recently , whole - body vibration ( wbv ) has been proposed as a recovery treatment for reducing 
 muscle soreness and muscle force loss after exercise10 , 11 .
rhea et al.12 reported that applying wbv after strenuous 
 resistance training and repeated sprints is effective at reducing the potential pain after a 
 training session .
similar results were found when wbv was applied before 6 sets of 10 
 maximal isokinetic eccentric contractions of the dominant - limb knee extensors13 .
also , the application of vibrations at a 
 frequency of 30  hz before 70%rm and 90%rm resistance exercises suppressed increases in the 
 stress hormone epinephrine levels immediately after exercise14 . therefore , wbv appears to be effective regardless of the exposure 
 time to vibration or moment ( i.e. before or after performing the eccentric exercise ) . 

wbv may 
 increase blood flow and oxygen delivery to the muscles15 , 16 , and decrease the pain 
 perception responses17 .
additionally , wbv 
 may avoid the disruption of muscle sarcomeres that occurs during eccentric exercises , and 
 therefore prevent doms18 .
however , the evidence regarding the use of wbv to reduce doms is controversial and limited . 

while some authors have found wbv to positively influence doms9 , 19 , others have concluded 
 that the application of wbv after eccentric exercise does not alleviate the signs of muscle 
 damage ( levels of serum ck and muscle soreness ) compared to other traditional ways of 
 recovery ( i.e. stretching exercise or massage)8 .
the large number of wbv training parameters ( vibration type , frequency , amplitude , rest 
 interval between bouts and body position)20 together with limited existing research on the topic make it 
 difficult to draw definitive conclusions on the effectiveness of wbv and the best recovery 
 treatment to reduce doms signs .
furthermore , the aforementioned studies implemented 
 protocols with several vibration sessions after exercise , but to date no research has 
 analyzed if a single session of wbv after eccentric exercise is enough to reduce muscle 
 damage and stimulate the recovery process . therefore , the aim of this study was to examine 
 whether or not a single whole - body vibration treatment after eccentric strength training can 
 reduce muscle soreness and enhance muscle recovery .
the experiment was approved by the committee of biomedical ethics of the university of 
 extremadura ( spain ) on may 6th , 2014 , whose chairman was mr .
fernando henao ( dossier number 
 31/2014 ) , and it was conducted in accordance with the principles of the declaration of 
 helsinki .
nine 
 participants were excluded from the study because they did not want to provide blood samples 
 ( n=4 ) , had some form of musculoskeletal problems ( n=2 ) or participated in a fitness program 
 more than once per week ( n=3 ) . as a result ,
20 participants were randomly assigned to the 
 vibration group ( n=10 ) or the control group ( n=10 ) .
the participants were asked to maintain 
 their lifestyle , not to take any medication or nutritional supplements , and not to perform 
 any exercise or sports activity during the period of the intervention .
the participants attended the laboratory on 4 occasions and had to complete all sessions at 
 the same time each day .
five days before their eccentric training , all the participants 
 performed a familiarization session involving the same kind of exercises to be performed in 
 the subsequent training sessions .
on the same day , peak quadriceps leg extension strength of 
 1 repetition maximum ( 1rm)21 was set and 
 the workload for the eccentric exercise at 120% 1rm was calculated . during the first 
 experimental visit , before starting the eccentric exercise session , blood samples were 
 collected and stored for subsequent analysis .
later , participants performed the eccentric strength training 
 consisting of a 5-minute warm - up ( 30% of 1rm ) and 4 sets of 5 repetitions at 120% 1rm , with 
 4  min rest between sets , on a quadriceps leg extension ( selection med machine , technogym , 
 spain ) .
movement was performed with both limbs in a neutral position and along a range of 
 motion of 90. subjects were asked to complete each repetition with maximal effort and a 
 slow controlled movement ( 2  s ) during the eccentric phase . during the concentric phase of 
 the movement
, two assistants replaced the lift arm of the weight machine in the initial 
 position using a mechanical jack , so participants did not make any effort during this phase . 

five minutes . after performing the eccentric training , the participants received 3 sets of 
 1  min whole body vibration ( 12  hz , 4  mm ) with 30 s of passive recovery between each set 
 ( vibration group ) , or an identical protocol with the vibratory platform turned off ( control 
 group ) .
no information about the potential effects of the vibration treatment was given to 
 the participants to minimize psychological effects .
an oscillating vibratory platform 
 ( galileo fitness , novotec medical , germany ) was used .
all the participants were asked to 
 stand on the platform barefoot in a static squat position with their knees bent 30 ( full 
 extension=0 ) , hands on hips , and trunk straight .
joint angle was measured with a goniometer 
 ( 12 - 1001hr , baseline , usa ) .
the vibration protocol was chosen based on previous research 
 that showed that using similar frequencies leads to improvements in muscle recovery7 , 12 . 

assessments occurred immediately after the vibration , and at 24  h and 48  h 
 post - exercise .
body weight and height were measured in the first session using a portable measuring 
 station ( seca 220 , germany ) .
blood samples ( 5  ml ) were collected to assess serum ck and blood urea nitrogen ( bun ) 
 concentrations .
samples were drawn from the antecubital vein at each measurement time point : 
 pre - exercise , post - exercise , and 24  h and 48  h post - exercise . before analysis
serum concentrations were determined by a dry - chemistry 
 automated multi - analyzer ( spotchem ez sp-4430 , menarini diagnostics , uk ) using standard 
 menarini test strips .
the level of muscle soreness was evaluated using a 100-mm visual 
 analogue scale ( vas ) , with 0 at the left endpoint representing no pain and 100 at the right 
 endpoint representing extreme pain .
all of the participants were asked to point to their 
 level of perceived soreness on the vas while they maintained a static squat position with 
 their knees flexed at 30 for 5 s. muscle strength was assessed by recording pit through 
 dominant - limb knee extensor testing on an isokinetic dynamometer ( system 3 , biodex medical 
 systems , usa ) .
participants performed two 5-s maximal isometric contractions at a knee joint 
 angle of 45 ( 0 was considered as full extension ) , with a 1  min rest between each maximal 
 effort .
they were asked to generate maximal force as fast as possible when the signal was 
 given .
dynamometer calibration and protocol procedures were performed in accordance with the 
 instructions provided by the manufacturer .
the 
 kolmogorov - smirnov test was conducted in order to verify the normality of the data 
 distribution , and levene s test was used to assess the homogeneity of variance .
comparisons 
 between the intervention conditions ( vibration vs control ) over time for each variable were 
 subjected to two - way repeated - measures anova .
post hoc pairwise comparisons were performed 
 using the bonferroni test to identify significant differences within groups from 
 pre - exercise values .
significance was accepted for p0.05 , a confidence level of 95% . means 
 and standard deviations ( sd ) were used as descriptive statistics .
the general characteristics of participants are shown in table 1table 1.general characteristics of the participantsvibration groupcontrol groupage ( years)24.2  0.523.4  1.4height ( cm)177.1  11.5175.6  5.3weight ( kg)75.2  11.573.2  5.9120% 1rm ( kg)123.0 
19.2118.1  18.8values are mean  sd .. there were no significant differences between the study groups .
table 2table 2.markers of muscle damage , muscle soreness and muscle strengthvariablesprepost 24 h48 hserum ck ( u / l)control 100.5  4.7108.0  3.4300.5  26.1 * 285.2  19.7*vibration90.7  5.3102.5  5.6200.2  8.2*175.2  12.5*bun ( mg / dl)control14.4  3.214.9  3.716.8  3.715.4  2.8vibration16.3  2.817.73  2.319.6  2.016.8  2.8vas score ( mm)control6.6  11.536.6  20.568.3  15.1 * 65.2  13.2*vibration6.0  5.533.2  16.454.4  16.3 * 34.1  11.4pit ( nm)control235.3  53.7205.7  48.2187.3  49.0189.1  60.0vibration225.4  56.9201.2  62.1172.6  48.0177.2
bun : blood urea nitrogen ; vas : visual analog scale ; pit : peak 
 isometric torque.*p0.05 , significant difference from pre - exercise .
. shows the values of muscle damage , muscle soreness and muscle strength at the 
 different measurement times .
eccentric training elicited significant ( 0.05 ) increases in 
 serum ck at 24  h and 48  h post - exercise in both groups , and vas scores were also 
 significantly higher at 24  h ( both groups ) and 48  h ( control group only ) after the eccentric 
 training .
compared to the vibration group , the control group showed significant ( 0.05 ) 
 increases in serum ck ( at 24  h and 48  h post - exercise ) and the vas score ( at 48  h 
 post - exercise ) .
bun : blood urea nitrogen ; vas : visual analog scale ; pit : peak 
 isometric torque . *
the participants baseline data was in the normal range for healthy people , showing that 
 the subjects were not fatigued and had not done any strenuous physical activity prior to the 
 experiment .
therefore , the changes observed in the experiment resulted from the performance 
 of the eccentric training .
previous studies have reported that repetitive eccentric contractions can cause broadening 
 or disruption of muscle sarcomeres18 .
it 
 is known that eccentric contractions may cause greater high - stress damage to recruited 
 muscle fibers than concentric contractions2 .
this muscle damage leads to inflammation , release of ck and an 
 increased perception of muscle soreness for several days after the exercise13 , 22 .
similar results were evident in our present research , which found 
 there were increased concentrations of serum ck and high pain vas scores at 24  h and 48  h 
 after eccentric exercise in both groups .
analysis of the influence of wbv on the values of serum parameters related to muscle damage 
 revealed that serum ck levels at 24  h and 48  h were lower in the vibration group than in the 
 control group . given that serum ck activity is defined as an index of muscle damage23 ,
these results indicate that the vibration 
 group sustained less muscle damage after eccentric training than the control group .
it was 
 previously demonstrated that muscle blood volume and lymphatic flow increase with vibration 
 treatment and that the magnitude of this increase is positively associated with vibratory 
 load15 .
this rise in muscle perfusion 
 may stimulate muscle recovery by improving oxygen delivery16 and removing pain substrates24 . to our knowledge , only two studies8
, 19 have investigated the 
 effects of post - exercise vibration treatment on the reduction of serum ck concentrations 
 after eccentric exercise in knee extensor muscles .
caution is necessary when making comparisons because the intervention protocols 
 and the type of vibration ( device , frequency and amplitude ) were different .
protein 
 catabolism produces urea , which may be a useful biomarker for monitoring fatigue and 
 overtraining25 .
however , fallon26 demonstrated that changes in serum urea 
 are more useful for monitoring training status than for assessing short term fatigue , which 
 may be the reason why there were no changes in bun after eccentric training in this 
 study .
vas scores of the vibration group at 48  h were lower than those reported by the control 
 group , indicating less muscle soreness .
this result is supported by previous research , which 
 noted that post - exercise vibration alleviated doms and provided an analgesic effect .
rhea et 
 al.12 reported an attenuation of pain 
 ranging from 2261% when untrained individuals received wbv .
similar results were found by 
 lau and nosaka22 for upper arm muscle 
 soreness , with peak soreness being 1830% less for the vibration group than for the control 
 group at 2 to 5 days after eccentric exercise .
the benefits of vibration treatment on pain 
 have been reported in both clinical and experimental settings for several decades27 .
muscle vibration activates afferent 
 inputs from sensory units in the muscle28 , and the subsequent afferent activity in myelinated sensory axons may 
 inhibit nociceptive messages , possibly at spinal segmental levels , modifying the pain 
 sensation and elevating the pain threshold29 , 30 .
several studies have reported muscle strength loss following repetitive maximal eccentric 
 contractions8 , 9 .
however , no significant decrease in pit values was observed in our 
 present study .
one possible explanation for these conflicting findings could be the type of 
 eccentric training performed .
the training performed in the present study consisted of few 
 repetitions of very high intensity , whereas the aforementioned studies used workouts with a 
 high volume ( 100 and 300 repetitions , respectively ) , so it is possible that muscle 
 involvement and fatigue were different in these trials .
these findings are similar to those obtained by other research that 
 concluded that standing on a vibrating platform9 or sitting on a vibrating cushion8 after a session of eccentric exercise did not improve the recovery 
 of the knee extensor s pit
. a limitation of our current study might be the choice of just 
 one angle to evaluate muscle strength because pit values could vary at different angles . 

moreover , other serum markers such as lactate dehydrogenase , myoglobin , troponin or 
 aspartate aminotransferase were not analyzed , and their analysis would have provided more 
 information about muscle damage .
the findings of the present study show that a single post - exercise wbv following eccentric 
 training alleviated muscle damage but did not attenuate muscle strength loss
. therefore , 
 recreational athletes should know that their performance in training or competition could 
 still be decreased at 48 hours after completing an intense eccentric training , regardless of 
 being subjected to a post - exercise vibration treatment that attenuates doms .
further studies 
 to establish the appropriate duration , frequency and amplitude of vibration are needed to 
 investigate the effectiveness of a single post - exercise wbv in the improvement of muscle 
 recovery after eccentric training .
 [ purpose ] the aim of this study was to investigate whether or not a single whole - body 
 vibration treatment after eccentric exercise can reduce muscle soreness and enhance muscle 
 recovery . [ subjects and methods ] twenty untrained participants were randomly assigned to 
 two groups : a vibration group ( n=10 ) and control group ( n=10 ) . 
 participants performed 
 eccentric quadriceps training of 4 sets of 5 repetitions at 120% 1rm , with 4  min rest 
 between sets . 
 after that , the vibration group received 3 sets of 1  min whole body 
 vibration ( 12  hz , 4  mm ) with 30  s of passive recovery between sets . 
 serum creatine kinase , 
 blood urea nitrogen , muscle soreness ( visual analog scale ) and muscle strength ( peak 
 isometric torque ) were assessed . 
 [ results ] creatine kinase was lower in the vibration 
 group than in the control group at 24  h ( 200.2  8.2 vs. 300.5  26.1 u / l ) and at 48  h 
 ( 175.2  12.5 vs. 285.2  19.7 u / l ) post - exercise . 
 muscle soreness decreased in vibration 
 group compared to control group at 48  h post - exercise ( 34.1  11.4 vs. 65.2  13.2  mm ) . 
 [ conclusion ] single whole - body vibration treatment after eccentric exercise reduced 
 delayed onset muscle soreness but it did not affect muscle strength recovery . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION