Effects of alternating heat and cold stimulation using a wearable thermo-device on subjective and objective shoulder stiffness

Abstract Background Technological innovations have allowed the use of miniature apparatus that can easily control and program heat and cold stimulations using Peltier elements. The wearable thermo-device has a potential to be applied to conventional contrast bath therapy. This study aimed to examine the effects of alternating heat and cold stimulation (HC) using a wearable thermo-device on subjective and objective improvement of shoulder stiffness. Methods Twenty healthy young male individuals (20.3 ± 0.6 years) participated in this study. The interventions were randomly conducted under four conditions, including HC, heat stimulation, cold stimulation, and no stimulation on their bilateral trapezius muscle, after a 30-min typing task. Each intervention was administered at least 1 week apart. The analyzed limb was the dominant arm. Muscle hardness was assessed using a portable muscle hardness meter, as well as the skin temperature over the stimulated area. After each condition, the participants were asked for feedback regarding subjective improvement in refreshed feelings, muscle stiffness, and muscle fatigue using an 11-point numerical rating scale. Results With regard to muscle hardness, only the HC condition significantly decreased from 1.43 N to 1.37 N (d = 0.44, p < 0.05). Additionally, reduced muscle hardness in HC condition was associated with the degree of skin cooling during the intervention (cold max: r = 0.634, p < 0.01; cold change: r = −0.548, p < 0.05). Subjective improvement in refreshed feelings, muscle stiffness, and muscle fatigue was determined in the HC and heat stimulation conditions compared with the no stimulation condition (p < 0.01 and p < 0.05, respectively). Moreover, the HC condition showed significantly greater improvements in muscle stiffness and fatigue compared to the cold stimulation condition (p < 0.05). Conclusions The current study demonstrated that HC promoted not only better subjective symptoms, such as muscle stiffness and fatigue, but also lesser muscle hardness. Furthermore, an association was observed between the degree of skin temperature cooling and reduced muscle hardness during HC. Further investigations on the ratio and intensity of cooling should be conducted in the future to establish the optimal HC protocol for muscle stiffness or fatigue. Trial registration UMIN000040620. Registered 1 June 2020

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Reliability of Trapezius Muscle Hardness Measurement: A Comparison between Portable Muscle Hardness Meter and Ultrasound Strain Elastography

Sensors ◽

10.3390/s20247200 ◽

2020 ◽

Vol 20 (24) ◽

pp. 7200

Author(s):

Tomonori Sawada ◽

Hiroki Okawara ◽

Daisuke Nakashima ◽

Shuhei Iwabuchi ◽

Morio Matsumoto ◽

...

Keyword(s):

Trapezius Muscle ◽

Hardness Measurement ◽

Strain Ratio ◽

Muscle Stiffness ◽

Computer Work ◽

Shoulder Stiffness ◽

Strain Elastography ◽

Upper Trapezius ◽

Muscle Hardness ◽

Hardness Values

Prolonged computer work and smartphone use can cause stiffness of the neck and shoulder muscles, including the trapezius muscle. Hence, muscle hardness quantification is clinically beneficial. The present study aimed to examine the reliability of trapezius muscle hardness measurement using a portable muscle hardness meter and ultrasound strain elastography. Overall, 20 healthy young men participated in this study. Prior to measurement, the participant’s subjective symptoms, particularly shoulder muscle stiffness, were rated using an 11-point verbal scale. Furthermore, hardness of the right and left upper trapezius muscles was assessed. In the strain elastography assessment, muscle hardness was evaluated using strain ratio. Results showed that, in quantifying upper trapezius muscle hardness, both portable muscle hardness meter and strain elastography had an excellent intra-tester reliability (>0.9). However, the correlation coefficients between muscle hardness values assessed using a muscle hardness meter and those evaluated with strain elastography did not significantly differ, and the scores for subjective shoulder stiffness did not correspond to muscle hardness values. Therefore, the hardness of the trapezius muscle does not directly reflect the subjective shoulder stiffness. Future studies should thoroughly examine the location of the shoulder stiffness, and check whether it is accompanied by local pain or tenderness.

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Relationships Between Skin Temperature and Temporal Summation of Heat and Cold Pain

Journal of Neurophysiology ◽

10.1152/jn.01066.2002 ◽

2003 ◽

Vol 90 (1) ◽

pp. 100-109 ◽

Cited By ~ 30

Author(s):

Andre P. Mauderli ◽

Charles J. Vierck ◽

Richard L. Cannon ◽

Anthony Rodrigues ◽

Chiayi Shen

Keyword(s):

Skin Temperature ◽

Temporal Summation ◽

Heat Pain ◽

Cold Stimulation ◽

Cold Pain ◽

Heat Stimulation ◽

Second Pain ◽

Skin Temperatures ◽

Control Skin ◽

Temperature Surface

Temporal summation of heat pain during repetitive stimulation is dependent on C nociceptor activation of central N-methyl-d-aspartate (NMDA) receptor mechanisms. Moderate temporal summation is produced by sequential triangular ramps of stimulation that control skin temperature between heat pulses but do not elicit distinct first and second pain sensations. Dramatic summation of second pain is produced by repeated contact of the skin with a preheated thermode, but skin temperature between taps is not controlled by this procedure. Therefore relationships between recordings of skin temperature and psychophysical ratings of heat pain were evaluated during series of repeated skin contacts. Surface and subcutaneous recordings of skin temperatures revealed efficient thermoregulatory compensation for heat stimulation at interstimulus intervals (ISIs) ranging from 2 to 8 s. Temporal summation of heat pain was strongly influenced by the ISIs and cannot be explained by small increases in skin temperature between taps or by heat storage throughout a stimulus series. Repetitive brief contact with a precooled thermode was utilized to evaluate whether temporal summation of cold pain occurs, and if so, whether it is influenced by skin temperature. Surface and subcutaneous recordings of skin temperature revealed a sluggish thermoregulatory compensation for repetitive cold stimulation. In contrast to heat stimulation, skin temperature did not recover between cold stimuli throughout ISIs of 3–8 s. Psychophysically, repetitive cold stimulation produced an aching pain sensation that progressed gradually and radiated beyond the site of stimulation. The magnitude of aching pain was well related to skin temperature and thus appeared to be established primarily by peripheral factors.

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