Effects of Acute Low-Frequency Pulsed Electromagnetic Field Therapy on Aerobic Performance during a Preseason Training Camp: A Pilot Study

io-electromagnetic-energy-regulation (BEMER) therapy is a technology using a low- frequency pulsed electromagnetic eld (PEMF) in a biorhythmic format. BEMER has been shown to optimize recovery and decrease fatigue by increasing blood ow in microvessels. Our aim was to determine its effects during preseason training in endurance athletes. A total of 14 male cross-country runners (19.07 0.92 y.o.) were placed in either the intervention (PEMF;n= 8) or control (CON; n= 6) group using a covariate-based, constrained randomization. Participants completed six running sessions at altitudes ranging from 881.83 ( 135.98 m) to 1027.0 ( 223.44 m) above sea level. PEMF group used BEMER therapy before and after each training session, totaling 12 times. There were no signi cant changes in absolute or relative VO2Peak, ventilation or maximum

or control (CON; n= 6) group using a covariate-based, constrained randomization. Participants completed six running sessions at altitudes ranging from 881.83 ( 135.98 m) to 1027.0 ( 223.44 m) above sea level. PEMF group used BEMER therapy before and after each training session, totaling 12 times. There were no signi cant changes in absolute or relative VO2Peak, ventilation or maximum respiration rate for either the PEMF or CON group (p> 0.05). There was a signi cant effect of time for absolute and relative ventilatory threshold (VT), and maximum heart rate, heart rate at VT and respiration rate at VT. This study was the rst of its kind to study PEMF technology in combination with elevated preseason training. Results indicate some evidence for the use of PEMF therapy during short-term training camps to improve VT. Keywords: aerobic performance; low-frequency pulsed electromagnetic eld therapy; ventilatory threshold; runners 1. Introduction Pulsed electromagnetic eld (PEMF) treatment has been used for therapeutic purposes for almost half a century [1]. The application of external electrical, mechanical, and/or electromagnetic energy to the area of injury induces changes to the cell environment and restores the integrity and function of tissues within the organisms. This form of therapy has also been approved for the treatment of delayed and nonunion fractures in humans by the United States Food and Drug Administration since 1979 [2]. PEMF was also found to be effective for (1) pain management and edema after soft-tissue injury, (2) osteoarthritis- related injuries, (3) repairing ligaments and tendons, (4) wound [3–6] and bone fracture healing [7–9], (5) reducing subjective soreness [10,11], and (6) promotion of regeneration of nerves [4,12–15]. However, these devices are primarily advertised and distributed over the internet and are often used without medical supervision. According to their manufacturers, the therapeutic indications cover a wide range of diagnoses such as insomnia, back pain, osteo- porosis, arthritis, cardiovascular disorders, and neurodegenerative diseases. In addition, Int. J. Environ. Res. Public Health2021,18, 7691.

their manufacturers, the therapeutic indications cover a wide range of diagnoses such as insomnia, back pain, osteo- porosis, arthritis, cardiovascular disorders, and neurodegenerative diseases. In addition, Int. J. Environ. Res. Public Health2021,18, 7691.

Int. J. Environ. Res. Public Health2021,18, 7691 2 of 9 whole-body PEMF mats are also frequently proposed as wellness items [16]. Thus far, a biological mechanism that could explain the therapeutic effects of whole-body PEMF devices has not been proven; yet, the manufacturers postulate a large variety of mecha- nisms including the stimulation of cell protein synthesis, antioxidants, and osteoblasts, as well as increases in microcirculation, leading to improved oxygen supply and enhanced immunological functions [17]. Bio-electromagnetic-energy-regulation (BEMER) therapy is a technology using low-frequency PEMF of ux density 35–50 Tesla in a biorhythmic format [18] and has been shown to optimize recovery and decrease fatigue by increasing blood ow, speci cally in microvessels, which make up a majority of the vasculature [19]. Interestingly, the positive effects seen from PEMF therapy have primarily been seen in extreme situations, while effects for healthy adults have been inconclusive [17]. Athletes often undergo training camps in the preseason phase, to perform intensi ed training loads, hoping to maximize adaptations for the upcoming competitive season [20]. The onset of such a training regimen, following a period of sedentary behavior, represents a signi cant physical challenge to athletes. Previous evidence has shown this type of training camp produces a state of physiological fatigue, reduces subjective wellness of athletes [20], and can also affect sleep quantity and quality [21], further affecting recovery. Methods that permit an expedited physiological adaption to a training load could be advantageous to athletic performance. Considering the previous evidence, along with the common-place usage of these devices in practical settings, PEMF, speci cally BEMER- PEMF therapy, could potentially improve athletic performance when the athletes return to the regular training season by increasing recovery and decreasing fatigue during the training camp. Previous research has shown the positive effects of PEMF on recovery from exercise. For example, Grote et al. [22] showed improved autonomic recovery during short- term usage of PEMF after physical exercise, while Rasmussen et al. [11] and Jeon et al. [10] showed decreased symptoms of DOMS after usage of PEMF. Performance in aerobic sports such as cross-country running is typically measured through

shown the positive effects of PEMF on recovery from exercise. For example, Grote et al. [22] showed improved autonomic recovery during short- term usage of PEMF after physical exercise, while Rasmussen et al. [11] and Jeon et al. [10] showed decreased symptoms of DOMS after usage of PEMF. Performance in aerobic sports such as cross-country running is typically measured through multiple cardiopulmonary parameters [23–25]. A key determinate of endurance performance is the measurement of maximum aerobic capacity (VO2Max) [26], and improve- ments for this parameter are dependent on factors including training intensity over multiple sessions [27]. Improved recovery times could therefore potentially increase VO2Maxat a quicker rate, providing a competitive edge to the athlete. Another predictor of endurance performance, especially in long-distance runners is the ventilatory threshold (VT), de ned as the intensity at which ventilation increases disproportionately to oxygen consumption, which is also expressed in relation to VO2Maxpercentage [28]. Interestingly, despite the common use of acute PEMF therapy in practical settings, no study, to the best of the author's knowledge, has investigated the effects of this technology on sports performance. For this reason, the current pilot study is intended to explore the viability of PEMF for athletic performance. Therefore, the aim of the current pilot study was to see the effects of BEMER-PEMF therapy on aerobic performance during a collegiate preseason training camp in endurance athletes. Given the above evidence of PEMF-induced recovery and regeneration, we hypothesized that BEMER-PEMF would result in improved aerobic performance parameters. 2. Materials and Methods 2.1. Study Design The pilot study utilized a randomized-controlled study design to measure the effects of the BEMER therapy. Participants were divided into either the intervention group, who received the BEMER therapy, or a control group, who did not receive the intervention during a preseason elevated training camp. Training intervention, sleep duration, nutri- tion, and other environmental factors were similar for all the participants throughout the duration of the study.

receive the intervention during a preseason elevated training camp. Training intervention, sleep duration, nutri- tion, and other environmental factors were similar for all the participants throughout the duration of the study.

Int. J. Environ. Res. Public Health2021,18, 7691 3 of 9 2.2. Participants A total of 14 male National Collegiate Athletic Association (NCAA) Division 2 cross- country runners (age: 19.07 0.92 y.o.) from the university's cross-country running team, with initial peak aerobic capacity (VO 2Peak) of 73.13 5.65 mL/kg/min, participated in the study. Participants were placed in either the intervention (PEMF) or control (CON) group using a covariate-based, constrained randomization, executed via a computer program [29]. The VO 2Peakof the participants from baseline testing (i.e., the covariate) were inserted into the program, which then looped through randomly generated groups. The nal groups' output by the algorithm was the combination in which the two groups met the prede ned criterion (i.e., <1% coef cient of variation between groups). If the criterion could not be met, the output was the combination of groups with the lowest coef cient of variation. All participants signed written informed consents prior to participation, and the study was approved by the university's institutional review board. 2.3. Assessments Participants were tested at sea level in the university's Human Performance Lab for their peak aerobic capacity using a metabolic system (ParvoMedics TrueOne 2400, Salt Lake City, UT, USA), which was calibrated prior to each test. Data were also collected for absolute VO 2Peak(AbsVO 2Peak[L/min]), relative VO 2Peak(RelVO 2Peak[mL/kg/min]), ventilation (VE [L/min]), absolute ventilatory threshold (VT Abs[L/min]), relative VT (VT Rel[% of VO 2Peak]), heart rate at VO 2Peak(HRMax[Beats/min]), heart rate at VT (HRVT [Beats/min]), respiration rate at at VO 2Peak(RRMax[Breaths/min]), and respiration rate at VT (RRVT[Breaths/min]). The testing protocol consisted of an incremental graded exercise test (GXT) performed on a treadmill (TuffTread, Conroe, TX, USA). GXT started with a warm-up at 4.8 km/h for 3 min, followed by gradual increments in speed over the next 5 min (i.e., until minute 8) to achieve a speed that the participant(s) could maintain for the remainder of the test (~70% of heart rate reserve [HRR]). After 8 min, the speed was held constant, while the inclination grade was increased by 2% every 2 min. The test was terminated when the participant(s) reached volitional

in speed over the next 5 min (i.e., until minute 8) to achieve a speed that the participant(s) could maintain for the remainder of the test (~70% of heart rate reserve [HRR]). After 8 min, the speed was held constant, while the inclination grade was increased by 2% every 2 min. The test was terminated when the participant(s) reached volitional failure or if a respiratory exchange ratio (RER) of 1.15 was achieved. The ventilatory threshold was determined using a data plot created by the metabolic system software [ParvoMedics, OUSW4.3.4] by two independent researchers and con rmed by a third researcher who was not involved in the testing process. VT was considered as the point when VCO2started increasing disproportionately to VO2(Wasserman). The nal VT values used for analysis were those concurred by all three researchers. 2.4. Intervention Runners traveled from sea level to an altitude of 1322 m above sea level for 6 days of training. They completed 6 training sessions of running at altitudes ranging from 881.83 135.98 m to 1027.0 223.44 m above sea level. The team trained together, and both groups had the same training per day. On average, each training session was 64.50 19.05 min at a speed of 3.62 0.44 m/s (13.02 1.60 km/h), covering an average distance of 16,415 2950 m. Altitude was measured using two separate GPS altitude devices (Ambit 3 Sport, Suunto Oy, Vantaa, Finland). The daily training regime for the team is presented in Table. The athletes trained on their own and workload was not monitored prior to the pre-season camp in compliance with NCAA regulations. Eight men (age: 19.01 0.69 years; VO 2Peak: 72.90 6.39 mL/kg/min) were assigned to the PEMF group, while six (age: 19.12 0.99 y.o.; VO 2Peak: 72.41 4.79 mL/kg/min) were assigned to the CON group. The uneven number of participants in the groups is due to the failure to follow up by two participants from the control group. PEMF group used BEMER therapy 12 times across a 6-day period, before and after each training session. PEMF protocol included 8 min of laying on the BEMER mat, which

4.79 mL/kg/min) were assigned to the CON group. The uneven number of participants in the groups is due to the failure to follow up by two participants from the control group. PEMF group used BEMER therapy 12 times across a 6-day period, before and after each training session. PEMF protocol included 8 min of laying on the BEMER mat, which transmitted a low-frequency electromagnetic eld of ux density 35–50 Tesla (highest level) in a biorhythmic format.

Int. J. Environ. Res. Public Health2021,18, 7691 4 of 9 Table 1.Daily training regime. Day Distance Time Altitude MinAltitudeMaxAltitude AvgSpeed Avg m mins m m m m/s Day 1 16,093.44 74 1007.36 1205.79 1106.58 3.62 Day 2 16,093.44 71 753.77 809.85 781.81 3.78 Day 3 19,312.13 76.5 892.30 902.82 897.5598 4.21 Day 4 19,312.13 87 667.82 822.05 744.93 3.70 Day 5 16,415.31 77 1061.31 1388.36 1224.84 3.55 Day 6 11,265.41 66 904.95 1157.33 1031.14 2.84 2.5. Statistical Analyses All results are expressed as mean standard deviation (SD). Independent t-test analysis was used to check for differences between groups at pretesting to con rm balanced groups after dropouts. Repeated measures mixed-model analysis was used to measure the difference between groups from pre- to post-testing using groups and time as a xed factor and participants as a random factor and Tukey post hoc analysis. Mean differences are presented along with 95% con dence intervals (CI). Additionally, effect sizes were assessed to measure the magnitude of change within each group to measure the change from the elevated training camp, and between groups to measure the difference in change between PEMF and CON. All analyses were performed using SAS (Version 9.4, SAS Institute, Cary, NC, USA) and Prism (Version 8.4.0, GraphPad, San Diego, CA, USA). 3. Results Outcomes Despite dropouts, both groups were similar at baseline for AbsVO 2Peak(p= 0.2497), RelVO 2Peak(p= 0.5685), VE (p= 0.1098), VT Abs(p= 0.0965), VT Rel(p= 0.3674), HRMax (p= 0.3840), HRVT(p= 0.2718), RRMax(p= 0.3296), or RRVT(p= 0.3577). There were no signi cant changes in AbsVO 2Peak(p= 0.1727) or RelVO 2Peak(p= 0.1149) for either the PEMF group or the CON group after the training camp; There was no significant difference for VE pre- to post-testing for any groups (p= 0.9305). There was a signi cant effect of time for both VT Abs(p= 0.009) and VT Rel(p 0.001). For PEMF, VT Abschanged signi cantly from pretesting to post-testing (p= 0.001), but CON showed a nonsigni cant trend towards difference (p= 0.061). Furthermore, VT Relwas signi cantly different between pre- and post-tests for PEMF (p 0.001), and a nonsigni cant difference was

There was a signi cant effect of time for both VT Abs(p= 0.009) and VT Rel(p 0.001). For PEMF, VT Abschanged signi cantly from pretesting to post-testing (p= 0.001), but CON showed a nonsigni cant trend towards difference (p= 0.061). Furthermore, VT Relwas signi cantly different between pre- and post-tests for PEMF (p 0.001), and a nonsigni cant difference was observed for CON (p= 0.098). HRMaxwas signi cantly different from pre- to post-testing for both PEMF (p= 0.0212) and CON (p= 0.0251). Additionally, there was a signi cant time effect for HRVT(p= 0.0326). However, the post hoc test showed that while PEMF had a signi cant difference (p< 0.0422), CON did not (p= 0.9477). There was no signi cant difference for RRMaxpre- to post-testing for any groups (p= 0.2557). There was a signi cant time effect for RRVT(p= 0.0005). Table

Int. J. Environ. Res. Public Health2021,18, 7691 5 of 9 Table 2.Changes for cardiopulmonary variables between intervention and control groups. PEMF CON Pre Post MD 95% CI Pre Post MD 95% CI AbsVO 2Peak L/min 4.35 0.52 4.27 0.63 0.08 0.07 0.23 to 0.07 4.75 0.66 4.68 0.65 0.07 0.08 0.24 to 0.10 RelVO 2Peak mL/kg/min 72.40 6.67 70.94 6.03 1.46 1.06 3.77 to 0.84 74.10 4.28 72.82 3.32 1.28 1.22 3.94 to 1.38 VE L/min 150.98 13.00 146.58 17.78 4.4 2.62 10.11 to 1.31 162.96 12.58 167.00 14.30 4.04 3.03 2.55 to 10.64 VT Abs L/min 3.14 0.39 3.80 0.57 * 0.66 0.15 0.33 to 1.00 3.64 0.57 4.01 0.54 0.37 0.18 0.02 to 0.75 VT Rel % of RelVO 2Peak 72.38 7.14 88.95 2.41 * 16.58 2.95 10.16 to 22.99 76.97 10.07 85.72 4.19 ˆ 8.75 3.40 1.34 to 16.16 HR Max Beats/min 189.63 10.88 184.88 10.08 * 4.75 1.37 7.74 to 1.76 194.67 9.87 189.33 11.38 * 5.33 1.58 8.79 to 1.88 HR VT Beats/min 164.50 14.02 176.00 10.56 * 11.50 3.75 3.33 to 19.67 173.83 15.50 176.17 12.64 2.33 4.33 7.10 to 11.77 RR Max Breaths/min 62.56 3.62 64.02 4.33 1.46 1.23 1.22 to 4.14 59.18 7.22 59.97 7.79 0.78 1.42 2.31 to 3.88 RR VT Breaths/min 44.69 8.10 54.04 4.29 * 9.35 2.53 0.01 to 3.84 41.09 5.97 49.89 8.66 * 8.80 2.92 2.44 to 15.16 Note: Values are mean standard deviation. Abbreviations: PEMF: pulsed electromagnetic eld; CON: control; MD: Mean difference; CI: con dence interval; AbsVO 2Peak: absolute VO 2Peak; RelVO 2Peak: relative VO 2Peak; VE: ventilation; VT Abs: absolute ventilatory threshold; VT Rel: relative ventilatory threshold; HRMax: maximum heart rate; HRVT: heart rate @ ventilatory threshold; RRMax: maximum respiration rate; RRVT: respiration rate @ ventilatory threshold. * indicates signi cantly different, compared to pre (p< 0.05). ˆ indicates trending toward signi cant, compared to pre (0.05 <p< 0.10).Int. J. Environ. Res. Public Health 2021, 18, x FOR PEER REVIEW 5 of 10 • There was no significant difference for RR Max pre- to post-testing for any groups (p = 0.2557). • There was

The study explores PEMF therapy's impact on aerobic performance in collegiate runners.