Perceived Pain in Athletes: A Comparison between Endurance Runners and Powerlifters through a Cold Experimental Stimulation and Two Sessions of Various Physical Activation

w studies in the literature have illustrated cold hypoalgesia induced by strength training. Objectives of this contribution were to compare the ratings of perceived pain in endurance running (n = 22) and powerlifting (n = 22) male athletes and controls (n = 22) at baseline and after two bouts of 40 min aerobic/strength training respectively, using the Cold Pressor Test (CPT) and simultaneously monitoring changes in blood pressure (BP), heart rate (HR), and body temperature. A two-way repeated measures ANOVA was conducted to examine the effects of training sessions in endurance runners vs. powerlifting athletes vs. controls on the intensity of perceived pain at CPT. A statistically signi cant two-way interaction between the group and training resulted inp< 0.001, p 2 = 0.513. A simple main effects analysis showed that as the participants went through the strength training session, pain perception at CPT was signi cantly

of training sessions in endurance runners vs. powerlifting athletes vs. controls on the intensity of perceived pain at CPT. A statistically signi cant two-way interaction between the group and training resulted inp< 0.001, p 2 = 0.513. A simple main effects analysis showed that as the participants went through the strength training session, pain perception at CPT was signi cantly lower in powerlifters compared to runners and controls. Considering the physiological parameters, powerlifters reported signi cantly higher values of BP and HR. This difference was present at baseline but after training as well, and before and after CPT, despite a slight hypotensive effect. The differences reported after CPT at baseline, but very signi cantly after the strength activation session in the powerlifters, provide interesting insights into the hypoalgesic effect of high-intensity strength training. Keywords: perceived pain; endurance runners; powerlifters; cold pressor test; aerobic training; strength training; blood pressure 1. Introduction Exercise-induced hypoalgesia (EIH) is characterized by a decrease in sensitivity to painful stimuli, with variable duration, lasting up to 30 min after a single bout of exercise. According to Rice et al. [1], the precise physiological mechanisms underlying exercise- induced hypoalgesia are currently unknown. Analgesia following exercise appears to be most consistent when the exercise stimulus involves exercise performed at higher intensities (i.e., >70% of maximal aerobic capacity), and animal research suggests that properties of the exercise stressor are important in determining which analgesic system is activated during exercise [2]. Hypoalgesia after aerobic exercises (e.g., cycling or running), dynamic resistance exercises (e.g., circuit training), and isometric exercises (e.g., a wall squat) often produce an increase in pressure pain thresholds [3,4]. It has been pointed out that exercise intensity quite consistently affects the EIH response after aerobic exercise [5–7] and also after isometric exercises [8–11]. Some studies have demonstrated that exercise which is presumed to be more painful (higher intensity submaximal isometric exercise) produces a greater EIH response than exercises that are presumed to be less painful (lower intensity submaximal isometric) [8]. However, others have found pain ratings to be unrelated to Sports2022,10, 211.

after isometric exercises [8–11]. Some studies have demonstrated that exercise which is presumed to be more painful (higher intensity submaximal isometric exercise) produces a greater EIH response than exercises that are presumed to be less painful (lower intensity submaximal isometric) [8]. However, others have found pain ratings to be unrelated to Sports2022,10, 211.

Sports2022,10, 211 2 of 17 EIH response [12]. Considering the few studies of EIH that assess the effects on cold pain, the majority examines aerobic exercise [13–15], some focus on isometric exercises [11], while there appear to be few studies in the literature that have illustrated cold hypoalgesia induced by strength training. These include Samuelly-Leichtag et al. [16], who revealed that high-intensity exercise, even for a short duration, induced a hypoalgesic effect for pressure, heat, and cold modalities. The analgesic effect of aerobic and anaerobic exercise is usually associated with an increase in the peripheral concentration of Beta-endorphin and with the activation of (supra)spinal nociceptive inhibitory mechanisms orchestrated by the brain [17]. In the rst case (anaerobic), hypoalgesia occurs when the anaerobic threshold is exceeded as a result of short-duration exercise with a progressive increase in intensity [16,18]; in the second case (aerobic), it occurs after about an hour of continuous exercise with a constant condition of production and elimination of lactate [19,20]. As already reported in Vaegter and Jones [4]., a single session of exercise has repeatedly been observed to reduce pain sensitivity in pain-free individuals. Scheef et al. [21] suggested that running exercise reduced the pain- induced activation in the periaqueductal gray, a key area in descending pain inhibition which, in turn, was associated with lower pain unpleasantness ratings to thermal stimuli. Although athletes, in general, seem less responsive to noxious stimuli than non-athletes, the type of sport differentially affects pain perception. A recent study comparing aerobic and anaerobic hypoalgesia in athletes was carried out by Assa et al. [22]. They compared endurance athletes, who perform continuous intense activity for prolonged periods, with strength athletes who perform short-duration exercises at very high intensity, reporting signi cant differences related to pain sensitivity and inhibition of the nociceptive stimulus: athletes in endurance sports showed greater pain inhibition, whereas strength athletes showed reduced pain sensitivity. They distinguished between two distinct processes: inhibition as an ef cient top-down inhibitory control mechanism that results in conditioned pain modulation (CPM) and which in endurance athletes is closely related to motivational components, such as the

to pain sensitivity and inhibition of the nociceptive stimulus: athletes in endurance sports showed greater pain inhibition, whereas strength athletes showed reduced pain sensitivity. They distinguished between two distinct processes: inhibition as an ef cient top-down inhibitory control mechanism that results in conditioned pain modulation (CPM) and which in endurance athletes is closely related to motivational components, such as the will to resist pain, and reduced pain sensitivity, which would correspond in powerlifters primarily to a different distribution/density of skin nociceptors, attributable to the muscle hypertrophy that accompanies this type of training. They, therefore, with this work, emphasized the contribution of training speci city on pain perception. Very few studies have examined the relationship between resistance training and pain modulation. However, a study carried out by Koltyn and Arbogast [23] concluded that a single bout of resistance exercise can achieve a hypoalgesic response. The resistance exercise consisted of 45 min of lifting 3 sets of 10 reps at 75% of 1-Repetition Maximum (1 RM), which included bench presses, leg presses, pull-downs, and arm extensions. A further study performed by Vaegter et al. [24] had their subjects perform two isometric contractions of dominant biceps brachii and quadriceps at 30% and 60% Maximum Voluntary Contraction (MVC). They concluded that high-intensity isometric contraction by biceps brachii and quadriceps produced a larger local EIH compared to low-intensity contraction. From the literature review, we could see that there have been numerous studies on how long-distance runners perceive and cope with pain, while no research has been performed with athletes practicing disciplines of short-duration and maximal force development such as jumping, wrestling, and powerlifting [25]. Other studies have previously applied CPT as pain evoking stimulus to evaluate the analgesic effect of pharmacological and psychological treatments [26,27]. Our aims were to measure differences in perceived pain intensity between the groups of athletes both in the baseline condition (i.e., after a 120 s immersion test of the non-dominant hand in the ice-water container) and with a second measurement after stimulating the athletes with two 40 min training sessions, conducted on a treadmill and with pyramid strength training, respectively.

Our aims were to measure differences in perceived pain intensity between the groups of athletes both in the baseline condition (i.e., after a 120 s immersion test of the non-dominant hand in the ice-water container) and with a second measurement after stimulating the athletes with two 40 min training sessions, conducted on a treadmill and with pyramid strength training, respectively. Only one prior study has examined the analgesic effect of aerobic training in runners using multiple pain stimuli (including CPT) and was conducted by Janal et al. [13]. They showed that no signi cant analgesic response was found for the cold pressor test. A

Sports2022,10, 211 3 of 17 similar result is reported by Ruble et al. [14], where, however, the participants were healthy volunteers and not athletes. Although there is no speci c evidence for the category of powerlifters, we found useful what was indicated regarding the hypoalgesic effects of a resistance exercise session by Koltyn and Arbogast [23]. Following the aforementioned literature, ratings of perceived pain intensity at CPT were therefore hypothesized to be in any case lower in the athletes compared with controls at baseline and signi cantly even lower than the controls when the athletes later performed the training session corresponding to their discipline (aerobic for runners and anaerobic for powerlifters). We, therefore, hypothesized that the training session corresponding to the type of physical work usually performed by the athlete could produce a rapid activation of the usual physiological adaptation processes of the athlete's body, also involving the sphere of modulation of perceived pain. 2. Materials and Methods 2.1. Participants The population was characterized by university student athletes who attend the Uni- versity of Cassino and Southern Lazio. Given the ongoing collaboration agreement between the university where this study took place and FIPE (Italian Weightlifting Federation), we chose to involve powerlifters among the maximal force development disciplines. We, there- fore, believed that this comparison (running vs. powerlifting athletes) could contribute to increasing knowledge of the mechanisms that lead to pain inhibition and different pain sensitivity in sports. Therefore, in our study, we have chosen the line of comparison of pain sensitivity between athletes from different disciplines [22,25], and among the univer- sity student athletes, we involved a group of endurance runners, a group of competitive powerlifters, and a control group of healthy non-athlete students. The differences in pain perception have been assessed through the pain induction achieved by the Cold Pressor Test (CPT). A statistical power analysis was performed for sample size estimation. The effect size (ES) in this study was set to 0.30, considered to be medium, using Cohen's criteria. Through the G*Power 3.1 software (Düsseldorf, Germany), the minimum number of participants needed with this effect size and appropriate

been assessed through the pain induction achieved by the Cold Pressor Test (CPT). A statistical power analysis was performed for sample size estimation. The effect size (ES) in this study was set to 0.30, considered to be medium, using Cohen's criteria. Through the G*Power 3.1 software (Düsseldorf, Germany), the minimum number of participants needed with this effect size and appropriate to perform an intergroup com- parison was preliminarily set at 33. Through an open invitation sent out to the entire study population and supported by the University Sports Center, the sample was gathered in a non-probabilistic manner. The students were made aware of their involvement in a lab experiment to gauge individual sensitivity to cold. Inclusion criteria were: (1) age range of 18–28 years, and (2) competitive athletes of endurance running or powerlifting at regional level at least, who have trained regularly over the last three years. Exclusion criteria were: (1) inability to understand and follow instructions in verbal and written Italian, (2) any health conditions potentially causing sensory de cits, such as diabetes mellitus or neurological disorders, (3) any history of chemotherapy, (4) the current assumption of medication that can affect sensation, and (5) a current pregnancy. Students who were interested in participating were encouraged to sign up by clicking a special link in the announcement. Once the link was opened, it allowed students to enter their contact information as well as their gender and sport preference (endurance running; powerlifting). The researchers then planned and informed the students of the precise dates and times they would be required to report to the lab. Regarding the study's design, since it compared how endurance runners and powerlifters perceived pain on the CPT test, the list of those booked for the study was divided so as to randomly allocate the same number of participants to both groups. A total of 51 student-athletes, all of whom were male, expressed a desire to participate in the study; however, 7 of them, who had been placed on the list after random group assignment, were unable to take the test. As a result, 44 athletes participated

was divided so as to randomly allocate the same number of participants to both groups. A total of 51 student-athletes, all of whom were male, expressed a desire to participate in the study; however, 7 of them, who had been placed on the list after random group assignment, were unable to take the test. As a result, 44 athletes participated in the nal count. As control subjects, 22 healthy non-athlete students engaged in general tness activities (gym, amateur sports) belonging to the same age group (18–28) were also recruited

Sports2022,10, 211 4 of 17 on a voluntary basis, and the same exclusion criteria as above were applied. Therefore, our nal sample size of 66 participants should be considered more than suf cient to achieve the main objective of this study. No drop-outs were noted because everyone who began the test nished it on time. Prior to the testing session, selected participants were instructed to abstain from caffeine, alcohol, and any medications that might make them drowsy or analgesic for 24 h. Before data collection started, the procedure was explained, and written informed consent was obtained. The study was carried out in accordance with the Helsinki Declaration guidelines and was approved by the Institutional Review Board of the University of Cassino and Southern Lazio (IRB_SUSS_08:18/04/19). Table data of the participants. Table 1.Baseline anthropometric data of participants. Endurance Runners (n = 22) (Mean SD) Powerlifters (n = 22) (Mean SD) Controls (n = 22) (Mean SD) p-Value Age (years) 22.36 2.59 23.09 4.83 22.70 3.68 0.82 Height (cm) 175.57 2.78 178.21 3.72 169.03 3.24 <0.001 Weight (kg) 64.22 1.75 80.32 9.81 71.34 6.20 <0.001 Body mass index (kg/m 2 ) 20.82 0.31 25.29 4.08 24.05 1.22 <0.001 Training hours (h*week) 10.21 2.30 11.42 2.80 <0.01 Sessions (sessions per week) 3.38 0.77 4.93 1.41 <0.001 Training experience (years) 6.18 4.29 5.23 6.92 0.59 Data is presented as the mean (SD). Training hours: self-reported hours of weekly training/physical exercise; Sessions: number of self-reported training/physical exercise sessions per week. 2.2. Procedures Each of the participants—all volunteers—was called to the lab for morning sessions (in the 9 a.m.–12 p.m. time slot). Following FigureSports 2022, 10, x FOR PEER REVIEW 4 of 17 test, the list of those booked for the study was divided so as to randomly allocate the same number of participants to both groups. A total of 51 student-athletes, all of whom were male, expressed a desire to partici- pate in the study; however, 7 of them, who had been placed on the list after random group assignment, were unable to take the test. As a result, 44 athletes participated in the final

to randomly allocate the same number of participants to both groups. A total of 51 student-athletes, all of whom were male, expressed a desire to partici- pate in the study; however, 7 of them, who had been placed on the list after random group assignment, were unable to take the test. As a result, 44 athletes participated in the final count. As control subjects, 22 healthy non-athlete students engaged in general fitness ac- tivities (gym, amateur sports) belonging to the same age group (18–28) were also recruited on a voluntary basis, and the same exclusion criteria as above were applied. Therefore, our final sample size of 66 participants should be considered more than sufficient to achieve the main objective of this study. No drop-outs were noted because everyone who began the test finished it on time. Prior to the testing session, selected participants were instructed to abstain from caf- feine, alcohol, and any medications that might make them drowsy or analgesic for 24 h. Before data collection started, the procedure was explained, and written informed consent was obtained. The study was carried out in accordance with the Helsinki Declaration guidelines and was approved by the Institutional Review Board of the University of Cas- sino and Southern Lazio (IRB_SUSS_08:18/04/19). Table 1 shows the baseline anthropo- metric data of the participants. Table 1. Baseline anthropometric data of participants. Endurance Runners (n = 22) (mean ± SD) Powerlifters (n = 22) (mean ± SD) Controls (n = 22) (mean ± SD) p-Value Age (years) 22.36 ± 2.59 23.09 ± 4.83 22.70 ± 3.68 0.82 Height (cm) 175.57 ± 2.78 178.21 ± 3.72 169.03 ± 3.24 <0.001 Weight (kg) 64.22 ± 1.75 80.32 ± 9.81 71.34 ± 6.20 <0.001 Body mass index (kg/m 2 ) 20.82 ± 0.31 25.29 ± 4.08 24.05 ± 1.22 <0.001 Training hours (h*week) 10.21 ± 2.30 11.42 ± 2.80 <0.01 Sessions (sessions per week) 3.38 ± 0.77 4.93 ± 1.41 <0.001 Training experience (years) 6.18 ± 4.29 5.23 ± 6.92 0.59 Data is presented as the mean (SD). Training hours: self-reported hours of weekly training/physical exercise; Sessions: number of

) 20.82 ± 0.31 25.29 ± 4.08 24.05 ± 1.22 <0.001 Training hours (h*week) 10.21 ± 2.30 11.42 ± 2.80 <0.01 Sessions (sessions per week) 3.38 ± 0.77 4.93 ± 1.41 <0.001 Training experience (years) 6.18 ± 4.29 5.23 ± 6.92 0.59 Data is presented as the mean (SD). Training hours: self-reported hours of weekly training/physical exercise; Sessions: number of self-reported training/physical exercise sessions per week. 2.2. Procedures Each of the participants—all volunteers—was called to the lab for morning sessions (in the 9 am–12 pm time slot). Following Figure 1 shows the method flowchart employed. Figure 1. Method flowchart. Figure 1.Method owchart. All athletes were invited to the laboratory four times. The rst time, they (a) obtained information about the study from the researchers, (b) gave informed consent to take part, and were told about the safety of the scienti c and aggregate use of the data they gave, as required by the Declaration of Helsinki, (c) lled out a preliminary questionnaire to collect demographic data, and (d) took part in the CPT session. The CPT was chosen as a method for inducing and measuring changes in pain per- ception. Participants could stop the test whenever they thought the pain was too much

This research compares pain perception in endurance runners and powerlifters using cold stimulation.