Local Pain Dynamics during Constant Exhaustive Exercise

Short-Term Effects of Isometric Quadriceps Muscle Exercise with Auditory and Visual Feedback on Pain, Physical Function, and Performance after Total Knee Arthroplasty: A Randomized Controlled Trial

Severe acute pain after total knee arthroplasty (TKA) may cause delay in muscle strength and functional recovery, and it is a risk factor for chronic postoperative pain. Although pharmacological approaches are the typical firstline to treat acute pain; recently, nonpharmacological approaches such as exercise have been increasingly applied. The purpose of this investigation was to evaluate the effects of a rehabilitation program involving isometric quadriceps exercise with auditory and visual feedback to improve the short-term outcome after TKA. Sixty-two patients, planning a primary unilateral TKA, were randomly assigned to either an intervention group (n = 31) involving isometric quadriceps exercise with auditory and visual feedback in usual rehabilitation after TKA or a control group (n = 31) involving a standardized program for TKA. Patients in the intervention group performed the isometric quadriceps muscle exercise using the Quadriceps Training Machine from 2 to 14 days after TKA instead of the traditional quadriceps sets. Pain intensity, isometric knee extension strength, range of motion, timed up and go test (TUG), 10-m gait speed, 6-minute walking distance, the Western Ontario and McMaster University Osteoarthritis index (WOMAC), the hospital anxiety and depression scale, and the pain catastrophizing scale were assessed before TKA (baseline) and 1 to 3 weeks after TKA. Pain intensity significantly decreased in the intervention group than in the control group at 1 (p = 0.005), 2 (p = 0.002), and 3 (p = 0.010) weeks after TKA. Greater improvements in TUG (p = 0.036), 10-m gait speed (p = 0.047), WOMAC total score (p = 0.017), pain (p = 0.010), and function (p = 0.028) 3 weeks after TKA were observed in the intervention group. These results suggest that isometric quadriceps exercises with auditory and visual feedback provided early knee pain relief, possibly leading to better improvements in physical performance, and patient's perception of physical function in the early stages of postoperative TKA. Further studies should investigate whether this short-term effect is sustainable.

Integrative Proposals of Sports Monitoring: Subjective Outperforms Objective Monitoring

Current trends in sports monitoring are characterized by the massive collection of tech-based biomechanical, physiological and performance data, integrated through mathematical algorithms. However, the application of algorithms, predicated on mechanistic assumptions of how athletes operate, cannot capture, assess and adequately promote athletes' health and performance. The objective of this paper is to reorient the current integrative proposals of sports monitoring by re-conceptualizing athletes as complex adaptive systems (CAS). CAS contain higher-order perceptual units that provide continuous and multilevel integrated information about performer-environment interactions. Such integrative properties offer exceptional possibilities of subjective monitoring for outperforming any objective monitoring system. Future research should investigate how to enhance this human potential to contribute further to athletes' health and performance. This line of argument is not intended to advocate for the elimination of objective assessments, but to highlight the integrative possibilities of subjective monitoring.

Endurance Performance is Influenced by Perceptions of Pain and Temperature: Theory, Applications and Safety Considerations

Models of endurance performance now recognise input from the brain, including an athlete's ability to cope with various non-pleasurable perceptions during exercise, such as pain and temperature. Exercise training can reduce perceptions of both pain and temperature over time, partly explaining why athletes generally have a higher pain tolerance, despite a similar pain threshold, compared with active controls. Several strategies with varying efficacy may ameliorate the perceptions of pain (e.g. acetaminophen, transcranial direct current stimulation and transcutaneous electrical stimulation) and temperature (e.g. menthol beverages, topical menthol products and other cooling strategies, especially those targeting the head) during exercise to improve athletic performance. This review describes both the theory and practical applications of these interventions in the endurance sport setting, as well as the potentially harmful health consequences of their use.

Metastable Pain-Attention Dynamics during Incremental Exhaustive Exercise

Background: Pain attracts attention on the bodily regions. Attentional allocation toward pain results from the neural communication across the brain-wide network "connectome" which consists of pain-attention related circuits. Connectome is intrinsically dynamic and spontaneously fluctuating on multiple time-scales. The present study delineates the pain-attention dynamics during incremental cycling performed until volitional exhaustion and investigates the potential presence of nested metastable dynamics. Method: Fifteen young and physically active adults completed a progressive incremental cycling test and reported their discomfort and pain on a body map every 15 s. Results: The analyses revealed that the number of body locations with perceived pain and discomfort increased throughout five temporal windows reaching an average of 4.26 ± 0.59 locations per participant. A total of 37 different locations were reported and marked as painful for all participants throughout the cycling task. Significant differences in entropy were observed between all temporal windows except the fourth and fifth windows. Transient dynamics of bodily locations with perceived discomfort and pain were spanned by three principal components. The metastable dynamics of the body pain locations groupings over time were discerned by three time scales: (1) the time scale of shifts (15 s); (2) the time scale of metastable configurations (100 s), and (3) the observational time scale (1000 s). Conclusion: The results of this study indicate that body locations perceived as painful increase throughout the incremental cycling task following a switching metastable and nested dynamics. These findings support the view that human brain is intrinsically organized into active, mutually interacting complex and nested functional networks, and that subjective experiences inherent in pain perception depict identical dynamical principles to the neural tissue in the brain.