the ability to differentiate force plays an important role not only in daily life activity ( e.g. , grasping a fragile object ) , but also in sports , where the appropriate sense of force often determines the accuracy task .
when developing strategies to prepare athletes for effort , measures to improve movement control are worth considering .
therefore , the kinesthetic differentiation ( kd ) also known as force sense ( tension or effort ) within training and rehabilitation process becomes more and more stressed . as proprioceptive sensations ,
the kinesthetic differentiation is defined as the ability of an individual to use different levels of muscular force ( perception of muscular force ) .
this skill allows an individual to adapt muscle tension to stabilize the joints , and it is responsible for the economy and precision of motor tasks .
adjusting kinesthetic differentiation takes place in the nervous system , and it is mostly based on the afferent information coming from golgi tendon organs ( gto ) and muscle spindles . apart from these two receptors , an important role of force differentiation is also played by pressure - sensitive skin receptors ( mechanoreceptors in the skin ) , which effectively complement proprioceptive information .
the perception of the muscular force ( kinesthetic differentiation ) is commonly assessed by using force production tests .
these tests involve using a reference force , usually determined as a percentage of a maximal voluntary isometric contraction ( mvc ) , and attempting to replicate a percentage of mvc  for instance , 25% , 50% or 75% . the difference between the target force and the force produced
is used to quantify the accuracy of kd and is referred to as a force production error ( fpe ) .
force matching is usually conducted without visual feedback and can occur in the same limb or in the contra  lateral limb . in this investigation ,
the grip strength by means of electronic hand dynamometer was conducted to evaluate kd , since it is a valid tool of measurement for cognitive function .
jones and hunter indicate that the use of 50% of maximum force as the target force generates a smaller error at the attempts to the model force .
furthermore , healthy individuals can reliably distinguish load changes of 5%10% in an active lifting movement .
several factors influencing kinesthetic differentiation have been investigated ( e.g. , age , cryotherapy , warm - up exercises , muscle fatigue ) . however to our knowledge , no one investigated how swedish massage influences kinesthetic differentiation . among many physiotherapy procedures ,
swedish massage is one of the common treatments that is used in order to ensure optimal start readiness of athletes .
swedish massage ( in europe also known as classic massage ) applied to the subjects of this study is defined as a mechanical manipulation of body tissues with rhythmical pressure and includes various combinations of stroking , rubbing , kneading , tapotement , and vibration .
is interesting to note that the therapeutic effects of the swedish massage are overestimated and underestimation equally often .
authors usually unanimously list the beneficial after massage effects , such as : ( a ) reduction of muscle tone ; ( b ) improvement in the flow of nerve impulses at synapses ; ( c ) improvement in reaction time and neuromuscular coordination ; ( d ) stimulation of nerve conduction ; improvement in muscular trophic ( provision of nutrients , disposal of metabolic waste products ) ; and ( e ) three- to five - fold increase in muscle readiness to work and in their ability to contract and relax . in light of the above assumptions , the idea of applying massage prior to
literature suggests that such procedure is designed to complement the warm - up and improve the physical properties of selected muscle groups and joints , thus to prepare an athlete for training and competition .
previous studies on massage have mainly been focused on the assessment of endurance , maximal force , and reaction time skills . nevertheless , there are not enough reports on the effects of massage on the kinesthetic differentiation .
this issue needs further exploration , taking into account the concept of a reflex - nervous activity of the massage and the role of this ability in the structure of motor skills . from the perspective of this paper
, the impact of the classical massage on the nervous and muscular systems seems particularly interesting , because these systems determine the ability of kinesthetic differentiation .
thus , the main objective of the study was to assess the impact of the classical massage on kinesthetic differentiation under static conditions .
the study group consisted of 30 purposely selected healthy students from the academy of physical education in katowice .
it was a homogeneous sampling in terms of age between 2025 ( 17 females , age : 21.90.78 years , height : 167.46.59 cm , body mass : 59.74.51 kg , and bmi : 21.31.46 and 13 males , age : 22.51.33 years , height : 180.84.88 cm , body mass : 8012.57 kg , and bmi : 24.53.15 ) .
individuals were excluded from the investigation if they had any neurological or orthopedic disorders , cardiovascular disease , sensory disturbances , as well as any contraindications against massage .
the experimental methodology was approved by the research ethics board at the academy of physical education in katowice and in accordance with the ethical standards of the helsinki declaration .
all data collection was performed in the human motor behavior laboratory at the academy of physical education in katowice .
the kinesthetic differentiation test consisted in the assessment of hand grip force for both dominant and nondominant hand .
the first three trials were done for 100% of the participants capabilities , which allowed the researchers to assess the participants maximal isometric voluntary contraction force ( fmax ) , then five trials were done trying to use 50% of the maximum force , and in the last five trials , the participants tried to use only 50% of their previous force ( 1/2 of 50% ) .
the result was the difference of force recorded in relation to the norm ( 1/2 of the maximum result and 1/2 of 50% of force result ) .
the absolute force production error ( fpe ) expressed in percentage ( accuracy of kinesthetic differentiation ) was calculated according to the formula : 
 ( 1)fpe  =  ( |model    score| )  /  model    100% analysis took into account the mean values of forces expressed in kilograms .
it was the mean value of isometric force measured for 6 s , the first second of the measurement was rejected in order to eliminate any possible delay .
the average of three trials was used in the analysis of the maximum hand grip force ( fmax ) .
the average of five trials was considered in the analysis of kinesthetic differentiation of 50% and 25% .
each trial lasted for 6 s ( the first second of the measurement was rejected in order to eliminate any possible delay ) and there were 30 s breaks between them .
reference values were calculated in the kinesthetic differentiation test ( 50% of maximum force and 1/2 of 50% force ) and on this basis , the percentage value of the absolute force production error was computed for 50% ( fpe_50% ) and 25% ( fpe_25% ) .
instructions for the participants were as follows : 
 for the first three trials  tighten your hand with 100% of your capabilities.for the five consecutive trials  tighten your hand with half the value ( i.e. , 50% of your capabilities).for the five consecutive trials  tighten your hand with half the previous value ( i.e. , 1/2 of 50% force ) .
for the five consecutive trials  tighten your hand with half the value ( i.e. , 50% of your capabilities ) .
for the five consecutive trials  tighten your hand with half the previous value ( i.e. , 1/2 of 50% force ) .
the first measurement showed the natural kinesthetic differentiation of a participant , while the second one was preceded by a 15-min swedish massage .
dh = dominant hand , ndh = nondominant hand , fmax = maximal force . during the measurement ,
the participants were sitting in a chair , with the forearm of the examined limb in a neutral position and the flexion at the elbow joint of approximately 90 ( figure 2 ) .
this is the standard position to assess the hand grip force , proposed by the american society of hand therapists ( asht ) , supported by the research results of other scientists . during the measurements ,
the participants were blindfolded and did not receive any feedback on the course of trial or their scores .
irvington , ny , usa ) with hercules 2000 software , jamar handy ( orthopartner ag , seon , south korea ) was used for measurement ( see figure 3 )
massage prior to the second measurement was performed on the hand and forearm of the dominant limb .
applied massage strokes were based on the methodology proposed by podgorski . during the massage ,
the participants were sitting with the forearm resting on the table in front of them .
the massage included the following proportions of different techniques : 10% of stroking ( 1.5 min ) , 30% of rubbing ( 4.5 min ) , 40% of kneading ( 6 min ) , 10% of tapping ( 1.5 min ) , 5% of vibration ( 45 s ) , 5% of final stroking ( 45 s ) ( see table 1 ) .
the massage was performed on the dorsal and palmar side of the hand , as well as the front and back side of the forearm .
a metronome with a frequency of 1 hz was used in order to standardize the pace of the massage .
techniques and strokes applied during the classical massage results obtained in the study were analyzed based on the commonly applied methods of statistical analysis , using statistica 10 software package ( statsoft , inc .
the basic parameters of descriptive statistics were calculated , such as : arithmetic mean , standard deviation , skewness , and kurtosis of distributions .
normality of distribution of the variables was checked with the shapiro - wilk test . in order to compare the impact of massage on the kinesthetic differentiation for the dominant and non - dominant limbs , two - way analysis of variance 2  2 anova for repeated measures
post - hoc analysis , the bonferroni test for multiple pairwise comparisons , was applied to determine the level of statistical significance of differences . in order to correlate maximal force tests and kinesthetic differentiation tests ,
the average value of maximum force ( fmax dh ) for the dominant hand ( dh ) , after the massage , decreased by 0.49 kg .
there was no statistical significance after the application of massage f(1.29 ) = 5.5 , p = .46 . the average value of maximum force ( fmax ndh ) for the nondominant hand ( ndh ) , after the massage , decreased by 1.3 kg .
the dependencies for the dominant and nondominant hand are shown in figure 4 average values of maximal force ( fmax ) in dominant ( dh ) and nondominant ( ndh ) hand before and after massage .
for the dominant hand , after the massage , the percentage value of error in the assessment of 50% of maximum force ( fpe_50% dh ) increased by 1.63% .
there was no statistically significant difference found f(1.29 ) = 3.2 , p = .57 .
the percentage value of error in the assessment of 25% of maximum force ( fpe_25% dh ) after the massage decreased by 2.2% .
percentage value of force production error ( fpe ) in dominant hand ( dh ) estimated for 50% and 25% of maximal force before and after massage .
kd = kinesthetic differentiation . in the nondominant hand , after the massage , the percentage value of error in the assessment of 50% of maximum force ( fpe_50% ndh ) increased by 3.27% .
the percentage value of error in the assessment of 25% of maximum force ( fpe_25% ndh ) after the massage increased by 0.62% .
percentage value of force production error ( fpe ) in nondominant hand ( ndh ) estimated for 50% and 25% of maximal force before and after massage .
correlations of maximal grip strength force ( fmax ) between pre- and postmassage were significant both for dominant ( r = 0.92 , p = .01 ) , and nondominant hand ( r = 0.94 , p = .01 ) .
correlation between pre- and postmassage for maximal grip strength ( fmax ) for dominant hand ( dh ) .
correlation between pre- and postmassage for maximal grip strength ( fmax ) for nondominant hand ( ndh ) . for kinesthetic differentiation tests ,
correlation reveal significant relationship between pre- and post - massage of 50% force production error ( r = 0.67 , p = .01 ) for dh and ( r = 0.71 , p = .01 ) for ndh .
for the pre- and postmassage of 25% force production error , the correlations were insignificant both for dominant ( r = 0.06 , p = .72 ) , and nondominant hand ( r = 0.22 , p = .25 ) . correlation between pre- and postmassage for kinesthetic differentiation expressed as force production error of 50% for dominant hand ( dh ) .
correlation between pre- and postmassage for kinesthetic differentiation expressed as force production error of 50% for nondominant hand ( ndh ) .
the present study indicates that the swedish massage of the hand and the forearm does not affect the kinesthetic differentiation , manifesting itself in the sense of hand grip force .
it could be assumed that some differences in this area would be noted as a result of mechanical influence on the chosen analyzers of the nervous system ( muscle spindles , golgi tendon organs , and pressure - sensitive skin receptors ) .
magiera and walaszek suggest that , by stimulating different kinds of receptors , a massage induces the stimulation of certain areas of the cerebral cortex , which translates into faster and more efficient implementation of operations by organs .
this process is associated with a central ( general ) impact of the swedish massage .
the influence of the swedish massage on the kinesthetic receptors has not been examined yet .
numerous scientific reports have updated the current state of knowledge on the subject and discovered new dependencies , often in opposition to the information contained in the published books .
some studies suggest that massage , similar to stretching , causes a decrease in the activation of motor units and reduces muscle tone , which can translate into motor efficiency in motor tasks requiring a high level of force .
this phenomenon is explained by , among other factors , a decrease in the number of potential actin - myosin bridges in elongated muscles .
this relationship has been shown in several publications that have demonstrated that massage has a negative impact on the scores in speed and explosive power tests .
however , some researchers have not noticed any changes in this area after the treatment , compared with the control group .
there is no complete agreement with regard to the impact of massage on the sphere of human motor skills . in the face of insufficient evidence and conflicting research results , it is difficult to draw unequivocal conclusions . however , also it is difficult to give an unequivocal assessment , as it is usually subjective and qualitative .
some researchers observed a sedative impact of a massage on the tension of massaged muscles by reducing neuromuscular excitability , measured with changes in hoffman reflex amplitudes ( so - called h - reflex ) .
interestingly , the inhibitory effect of massage on alpha motor neurons maintained only during the treatment . after its completion , the excitability of motor units quickly returned to their previous levels , which suggests that the change would not be recorded in the results of posttreatment measurements .
therefore , some researchers believe that the possible differences in the muscle tone after the massage should not be explained by the reduced activity of alpha motor neurons , but the change in the structure of the muscle ( fiber elongation , reduction in soft tissue adhesion ) . nevertheless , the impact of massage on the neurological aspects of muscle tension needs further examination .
the present study also evaluated the influence of the swedish massage on the maximum force of isometric contraction during the hand grip test .
it has been found that the massage did not affect the mean values of maximum force , which had been concluded also by hemmings et al .
, jnhagen et al . , and mckechnie et al . , who did not find any influence of massage on the results of force tests .
yet , some authors claim that massage by mechanical pressure exerted on the soft tissues increases their deformability and causes stretching of the shortened muscle fibers , which in turn results in a decrease of the muscles potential force .
the process is explained by the lower number of possible actin - myosin connections in the elongated muscle .
there is also the neurological factor hypothesis , which blames the reduced activation of muscle fibers or a change in their reflex sensitivity for a decrease in force after the massage .
, hunter et al . , and arroyo - morales et al . , among others .
however , a comparison of the above results with the findings of the present study is problematic , since the said researchers had taken into account the manifestations of force under dynamic conditions , tested larger muscle groups and used different massage protocols .
it was not assessed whether the pauses between measurements were sufficient to eliminate fatigue , which could have affected the results .
only subjective preferences of the subjects were taken into account when setting the grip span of dynamometer .
since the efficiency of hand grip is determined by the grip span , it is suggested to base the adjustment of dynamometer also on the hand size , which will make the measurements more objective . assuming that , massage contributes to a decline in muscle force
, the results of the present study may have been affected by the hawthorne effect ( observer effect ) .
the participants of the experiment could expect that after the massage , their hand grip would be stronger , making them more motivated to achieve higher results , which could have eliminated the negative impact of the treatment . in future studies ,
subjective feelings of the participants should be taken into account with regard to the impact of massage on the psychological sphere .
the results could have also been affected by the therapist s experience and training , since they imply particular pressure force , choice of techniques , and professional skills . moreover , it is important to note that the message applied aimed neither at sedation , nor stimulation of muscles , but it rather combined existing techniques .
in addition , the results of the present experiment should be interpreted only with reference to young and fit individuals , as no other subjects were examined .
correlations before and after massage intervention revealed that there is strong relationship for maximum grip strength and for kinesthetic differentiation tests as a cognitive functional , only when subjects were asked to differentiate force at the 50% level of maximal grip strength .
however , the anova did not showed any significant differences after 15-min swedish massage intervention .
the 25% force differentiation test showed that force production error ( fpe_25% ) demonstrated high individual variability and indicated that this test should be conducted with particular caution in the future .
the results of this investigation suggest that massage does not improve the examined parameters ; therefore , it does not constitute a significant component of preparation to a physical activity . on the other hand , massage does not affect the kinesthetic differentiation and it can be safely used before activities which demand high movement precision .
the applied swedish massage does not significantly affect the kinesthetic differentiation and the values of maximum force in this particular studied group .
 background : swedish massage is one of the common treatments to provide optimal start and readiness of athletes . the ability of kinesthetic differentiation ( kd ) is crucial in sport performance . 
 this skill allows to adapt demanded muscle forces to optimize the motor tasks , and it is responsible for the precision . in the literature 
 , there is no evidence how swedish massage influences the kinesthetic differentiation.purpose:the objective of the study was to evaluate the impact of swedish massage on the kinesthetic differentiation and muscle strength of hand grip.methods:thirty participants took part in this investigation ( 17 women and 13 men ) . 
 the assessment consisted of kd tests conducted on the dominant ( dh ) and nondominant hand ( ndh ) after 15 minutes of hand and forearm swedish massage . 
 the procedure consisted of 13 trials for each extremity . 
 the first three were done for 100% of the participants capabilities ( fmax ) , the next five trials were done using 50% of maximum force ( 50% of fmax ) , and in the last five trials , the participants tried to use only 50% of their previous force ( 1/2 of 50% ) . 
 finally , the absolute force production error ( fpe ) was calculated for 50% ( fpe_50% ) and 25% ( fpe_25%).results : the two - way repeated measure analysis of variance anova did not reveal any statistically significant changes in maximal strength grip and kd between pre- and postmassage intervention in both dh and ndh hand . 
 correlations showed strong relationship between pre- and postmassage for maximum force ( r = 0.92 , p = .01 for dh , and r = 0.94 , p = .01 for ndh ) , and only for the fpe_50% ( r = 0.67 , p = .01 for dh , and r = 0.71 , p = .01 for ndh).conclusions : the results obtained indicated that the application of the swedish massage did not affect the kinesthetic differentiation in this particular young adult group . 
INTRODUCTION
METHODS
RESULTS
DISCUSSION
CONCLUSION