| Background and Objective: The mechanical properties of the muscle-tendon stiffness provide information on the material properties of the tissue and its function.The gastrocnemius muscle-tendon unit(MTU)can be extended because of its viscoelastic properties,which are critical for storing elastic energy.Normally,MTU,as a mechanical buffer,are mainly responsible for transmitting and absorbing energy of motion in life activities such as walking,running,and jumping.They are more likely to be injured if MTU is too stiff and hence not being able to absorb sufficient energy in life activities.Previous studies reported that MTU stiffness was measured by the movement of the myotendinous junction of the gastrocnemius muscle during passive ankle dorsiflexion.Considering that each muscle fiber being attached to the tendon aponeurosis,this method may be attributed to a lack of accurate techniques permitting quantitative assessment of muscle and tendon respectively.In our study,we evaluated local points stiffness of MTU using a novel hand-held,non-invasive MyotonPRO device.The aims of this study were(1)to examine the inter and intra-rater reliability and validity of MyotonPRO in assessment of MTU stiffness.(2)to investigate between-limb symmetry between dominant and non-dominant leg;to examine the relationships between gender and MTU stiffness;to assess the influence of the body weight in MTU stiffness;to investigate differences in the medial and lateral head of the gastrocnemius muscle stiffness;to determine changes in MTU stiffness on 3 positions(30° plantar flexion,neutral anatomical position and 10° dorsiflexion).(3)to examine the acute effect of paraffin therapy and static stretching on the passive stiffness of MTU stiffness.Material and Method:(1)Twenty healthy subjects(male: n=10;female: n=10;total: n=20)were recruited to measure MTU stiffness using a novel hand-held MyotonPRO device by two raters,one of the raters re-tested 5d later.Reliability was assessed using intra-class correlation coefficients(ICCs)and Bland and Altman analysis.Ten healthy subjects were recruited to compare MTU stiffness values determined by shear wave elastography(SWE)with those obtained using a novel hand-held MyotonPRO device and to verify the correspondence in the resting MTU.(2)Forty healthy subjects(men: n=20;women: n=20;total: n=40)were recruited and between-limb symmetry were examined.Influencing factors of MTU stiffness were analyzed.(3)In paraffin therapy group,MTU stiffness were measured before and after the 30 min of paraffin therapy.In static stretching group,the measurements were performed prior to the 5 min of static stretching and immediately after the static stretching.Result: The inter and intra-rater reliability of the medial head of the gastrocnemius muscle stiffness were high or very high(ICC=0.865~0.957);The inter and intra-rater reliability of the lateral head of the gastrocnemius muscle stiffness were high or very high(ICC=0.845~0.929).The inter and intra-rater reliability of Achilles tendon stiffness were high or very high(ICC=0.875~0.945).Examples of Bland and Altman plots are given which showed good agreement.Spearman Correlation coefficients for stiffness and shear elastic modulus ranged from 0.642 to 0.875(all r>0.642,P<0.05).There was no significant difference between dominant and non-dominant leg for MTU stiffness(t<0.451,P>0.05).Gender and body weight differences have important effects on MTU properties in healthy subjects(gender: t>2.275,P<0.05;body weight: r>0.333,P<0.05).There was significant difference between the medial and lateral head of the gastrocnemius muscle stiffness(t>4.321,P<0.01).MTU stiffness was significantly correlated with passive ankle joint positions(P<0.01).MTU stiffness of the experimental group significantly decreased after paraffin therapy(P<0.01).There was no significant difference in the gastrocnemius muscle stiffness after the static stretching(P>0.05),whereas the tendon stiffness after the static stretching was significantly higher(P<0.05).Conclusion: The inter and intra-rater reliability of MyotonPRO were good in measuring MTU stiffness in healthy subjects.The MyotonPRO can provide a valid measure of MTU stiffness.Between-side symmetry was high in MTU stiffness in healthy subjects.Gender and body weight differences have important effects on MTU stiffness.There was significant difference between the medial and lateral head of the gastrocnemius muscle stiffness.Paraffin therapy inducing a decrease in MTU stiffness may be more effective than static stretching. |
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