Short all-out isokinetic cycling exercises of 90 and 15 s unlock exercise-induced hypoalgesia

Reference Values of Joint-Specific Pressure Pain Thresholds in Healthy Male Individuals: A Retrospective Study

BACKGROUND

Pressure pain thresholds (PPT) are a component of Quantitative Sensory Testing and are used to assess mechanical pain sensitivity. Joint-specific PPT measurements are relevant because many joint disorders involve altered pain processing at and around joints. This study aims to establish such reference values that might contribute to evaluate deviations in pain sensitivity in specific patient populations.

METHODS

This study retrospectively analysed PPT data from 407 healthy male individuals. Pressure was applied in a standardised manner using an algometer at eight anatomical landmarks: bilaterally at the elbow, knee and ankle joints, as well as the sternum and forehead. Percentile-based, landmark-discriminative normative data were calculated for PPT in general and segmented for age, BMI and mean subjective pain over 4 weeks.

RESULTS

Median (IQR) PPT values (N/cm2) for anatomical landmarks are as follows: ankle = 47.2 (35.9, 63.8), knee = 65.9 (48.6, 89.1), elbow = 58.0 (40.5, 81.1), sternum = 39.8 (30.2, 53.3) and forehead = 35.5 (26.8, 45.0). Between-group analyses revealed no significant effect of BMI on PPT at any landmark assessed, no significant effect of age, except for the elbow joint (p = 0.035) and no effect of the presence of pain, except for the ankle (p = 0.020) and elbow joint (p = 0.010).

CONCLUSION

This study provides normative joint-specific PPT values in healthy male individuals, offering reference values for both clinical and research applications. These values can assist in interpreting PPT measured in clinical settings and in identifying abnormal pain sensitivity.

SIGNIFICANCE STATEMENT

Pressure pain thresholds are an important measure in Quantitative Sensory Testing, yet comprehensive normative data for joint-specific PPT in healthy individuals have been lacking. This study establishes reference values across multiple anatomical landmarks, providing a critical benchmark for evaluating pain sensitivity deviations in musculoskeletal disorders. These findings enhance the interpretation of PPT measurements, supporting improved pain assessment and diagnostic accuracy.

Pre-Stress Exposure and Psychophysiological Responses During Cycling

Successfully managing physical discomfort and stress during exercise is essential for fostering resilience and a sense of accomplishment. Previous research suggests that individuals vary in their ability to cope with exercise-induced stress, and repeated exposure to stressors may enhance stress management skills. This study aims to investigate how demographic, psychological, and physiological baseline characteristics influence psychological states during moderate- and high-intensity exercise. Thirty-one healthy participants completed two randomized conditions: a 6-min cycling task alone or the same task preceded by a cold-pressor test. Self-reported perceptual and affective responses and heart rate variability were measured throughout each condition. Random Forest and Gradient-Boosting Regressors predicted psychological states. Baseline attention emerged as a key determinant of attentional focus at both intensities, whereas higher BMI and age aligned with elevated stress and pain. A high-tolerance profile mitigated stress and arousal during the high-intensity phase of the exercise trial while boosting positive states such as affect and dominance. Preference played a dual role, intensifying both positive experiences (affect, dominance) and discomfort (stress, pain). Notably, during the high-intensity exercise phase, greater cold-water stress exposure was associated with higher arousal and affect, as well as lower perceived pain at the end of this phase. These findings highlight the complex interplay among psychological and physiological factors in shaping the exercise experience. While individual baseline characteristics influenced responses to exercise stress, exposure to a prior stressor modulated perceptual and affective states, particularly under high-intensity conditions. This study provides insight into the mechanisms underlying stress adaptation in physically demanding contexts.

Exercise induced hypoalgesia after a high intensity functional training: a randomized controlled crossover study

BACKGROUND

Acute physical activity often induces an acute reduction in pain sensitivity known as exercise induced hypoalgesia (EIH). The aim of this study was to investigate the effects of a high intensity functional training (HIFT) on EIH compared to a control session.

METHODS

50 (age: 26.0 ± 2.7; 23 female) participants successfully conducted this study consisting of a pre-experimental test as well as a 12-minute HIFT (body-weight exercises) and a 12-minute control (supervised breathing) session in a randomized crossover design. Pre and post, pressure pain thresholds (PPT) were measured at the ankles, knees, elbows, and forehead.

RESULTS

The HIFT resulted in a relative maximum and average heart rate of 96.2% (± 3.6%) and 91.1% (± 4.2%), respectively, and maximum and average RPE values of 19.1 (± 1.2) and 16.2 (± 1.4), respectively. Results reveal a significant 'Intervention' × 'Time point' interaction (p < 0.001) for PPT (pooled for one average value) with hypoalgesia observed following the HIFT (p < 0.001; pre: 56.0 ± 16.8, post: 61.6 ± 19.0 [Newton]) and no change following the control (p = 0.067; pre: 56.6 ± 18.4, post: 55.3 ± 18.9 [Newton]). Further, a significant 'Time' × 'Intervention' × 'Landmark' interaction effect (p = 0.024) is observed and all landmarks showed significant hypoalgesia following HIFT (p < 0.01), except for the right elbow and forehead. Following control, no hypoalgesia was observed at any landmark. Analysing male and female participants separately, it was observed that EIH occured only in men.

CONCLUSION

A HIFT using bodyweight exercises reduces pain sensitivity. Hence, combining strength and aerobically demanding exercises in a short but high intensity manner, as done in HIFT, can be seen as a usable tool to induce hypoalgesia. Yet, these results were observed only in male participants, necessitating future sex-specific research.

TRIAL REGISTRATION

DRKS00034391, retrospectively registered on the 4th of June 2024.