Background: Cryotherapy is widely recognised as a simple and effective intervention for pain management after acute musculoskeletal injuries and remains an essential adjunct to physiotherapy practice. It has been suggested that to optimise the clinical effectiveness of cryotherapy induced analgesia, a critical level of tissue cooling must be achieved. Previous research has indicated that a skin surface temperature of 13.6 °C is required to induce local analgesia. However there is some debate in the current research regarding the optimum temperature for inducing local analgesia and the longevity of the analgesic effect. Purpose: This study aimed to establish the optimum point in the cooling profile for cryotherapy induced analgesia using a crushed ice pack and also to map the duration of the analgesic effect as tissues re-warm. This information could then be used to inform clinical practice and to enhance soft tissue rehabilitation following the application of cryotherapy. Methods: An experimental design was used to quantify and record superficial skin temperature and pain pressure threshold following a routine cryotherapy treatment. Baseline measurements of skin temperature and pain pressure thresholds were taken from 15 healthy volunteers who had consented to be participants. Each participant underwent a twenty minute treatment with a standardised ice pack made from crushed ice contained within a wet towel and applied to the anterior thigh. Using a standardised approach, skin surface temperature and pain pressure threshold readings were taken at baseline, immediately upon removal of the ice pack and every 5 minutes thereafter until surface skin temperature had returned to baseline values. Results: The results indicated that following the crushed ice pack treatment, 13 out of 15 participants achieved a reduction in skin surface temperature sufficient to achieve local analgesia (13.6 °C). However this state persisted for less than 5 minutes before tissues began to re-warm which diminished the cryotherapy induced effect when above the recognised minimum skin surface temperature required for analgesia. Conclusion(s): For the majority of participants a crushed ice pack applied for 20 minutes induced local analgesia however, the duration of the analgesic effect was relatively short lived with no indication of a period of prolonged analgesia. Implications: It is clear from this research that there is no guarantee that a crushed ice pack will induce local analgesia in all recipients and of those who achieve local analgesia the effect is relatively short lived. Further research is required to test the cooling profiles of other cryotherapy modalities to determine if any produce a longer duration of analgesia which would be clinically beneficial to patients.
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- Pain perception