The aim was to examine the validity of heart rate variability (HRV) measurements from photoplethysmography (PPG) via a smartphone application pre- and post-resistance exercise (RE) and to examine the intraday and interday reliability of the smartphone PPG method. Thirty-one adults underwent two simultaneous ultrashort-term electrocardiograph (ECG) and PPG measurements followed by 1-repetition maximum testing for back squats, bench presses, and bent-over rows. The participants then performed RE, where simultaneous ultrashort-term ECG and PPG measurements were taken: two pre- and one post-exercise. The natural logarithm of the root mean square of successive normal-to-normal (R-R) differences (LnRMSSD) values were compared with paired-sample t-tests, Pearson product correlations, Cohen’s d effect sizes (ESs), and Bland–Altman analysis. Intra-class correlations (ICC) were determined between PPG LnRMSSDs. Significant, small–moderate differences were found for all measurements between ECG and PPG: Base_Pre1 (ES = 0.42), Base_Pre2 (0.30), RE_Pre1 (0.26), RE_Pre2 (0.36), and RE_Post (1.14). The correlations ranged from moderate to very large: Base_Pre1 (r = 0.59), Base_Pre2 (r = 0.63), RE_Pre1 (r = 0.63), RE_Pre2 (r = 0.76), and RE_Post (r = 0.41)—all p < 0.05. The agreement for all the measurements was “moderate” (0.10–0.16). The PPG LnRMSSD exhibited “nearly-perfect” intraday reliability (ICC = 0.91) and “very large” interday reliability (0.88). The smartphone PPG was comparable to the ECG for measuring HRV at rest, but with larger error after resistance exercise.

This study examined the acute effects of high-intensity resistance exercise with blood flow restriction (BFR) on performance and fatigue, metabolic stress, and markers of inflammation (interleukin-6 (IL-6)), muscle damage (myoglobin), angiogenesis (vascular endothelial growth factor (VEGF)). Thirteen resistance-trained participants (four female, 24.8 ± 4.7 years) performed four sets of barbell back-squats (75% 1RM) to failure under two conditions: blood flow restriction (BFR, bilateral 80% occlusion pressure) and control (CTRL). Completed repetitions and pre–post-exercise changes in maximal voluntary isometric contractions, countermovement jump, barbell mean propulsive velocity, and surface electromyography were recorded. Pre–post blood lactate (BLa) and venous blood samples for analysis of IL-6, myoglobin, and VEGF were collected. Ratings of perceived exertion (RPE) and pain were recorded for each set. Fewer repetitions were performed during BFR (25.5 ± 9.6 reps) compared to CTRL (43.4 ± 14.2 reps, p < 0.001), with greater repetitions performed during sets 1, 2, and 4 (p < 0.05) in CTRL. Although RPE between conditions was similar across all sets (p > 0.05), pain was greater in BFR across all sets (p < 0.05). Post-exercise fatigue was comparable between conditions. BLa was significantly greater in CTRL compared to BFR at two minutes (p = 0.001) but not four minutes post-exercise (p = 0.063). IL-6 was significantly elevated following BFR (p = 0.011). Comparable increases in myoglobin (p > 0.05) and no changes in VEGF were observed (p > 0.05). BFR increases the rate of muscular fatigue during high-intensity resistance exercise and acutely enhances IL-6 response, with significantly less total work performed, but increases pain perception, limiting implementation.

Winchester, LJ, Morris, CE, Badinger, J, Wiczynski, TL, and VanWye, WR. Blood flow restriction at high resistance loads increases the rate of muscular fatigue, but does not increase plasma markers of myotrauma or inflammation. J Strength Cond Res 34(9): 2419–2426, 2020—High-load resistance training and blood flow restriction (BFR) training at low loads both promote protein synthesis and growth through different cell signaling mechanisms. Therefore, co-activation of these pathways could result in a synergistic effect for additional growth enhancement. The purpose of this study was to evaluate how BFR effects performance and physiological responses after an acute bout of high-load barbell squat training. Twelve resistance-trained, college-aged men and women performed 5 sets of barbell squats at 75% of 1 repetition maximum until failure under traditional (TRAD; control) or intermittent BFR conditions. Perceived limb pain and number of repetitions performed were recorded after each set. Blood samples were collected at baseline and 1-hour postexercise after each trial for analysis of myoglobin and interleukin-6 (IL-6). An alpha level of p < 0.05 was used to determine significance. Blood flow restriction trial performance significantly declined at set 3 and was lower than performance during control, whereas control performance did not decrease until set 5. Perceived limb pain was statistically increased with BFR use for the whole trial and was significantly higher with BFR during set 3 than observed during TRAD. Plasma myoglobin and IL-6 were significantly increased after both trials when compared with baseline, but were not significantly different between trials. Intermittent BFR use during high-load barbell squats increases the rate of muscular fatigue and perceived limb pain, but does not increase muscular damage or inflammatory response. Data obtained from this study can be used by fitness professionals as a means of potentially enhancing the rate of muscular hypertrophy.

The aim of this study was to examine the potential differences in acute hemodynamic responses and muscular performance outcomes following resistance exercise between traditional blood flow restriction (TRA_BFR) and a novel band tissue flossing method (BTF_BFR). METHODS: Fifteen healthy young adults (23.27 ± 2.69 years) visited the lab for three sessions (≥72 h apart). Each session’s exercise consisted of three sets of 20 maximum-effort seated leg extensions and flexions with one of three conditions: control (CON), TRA_BFR (50% limb occlusion pressure (LOP)), or BTF_BFR. During TRA_BFR and BTF_BFR sessions, occlusion was applied immediately prior to exercise and removed immediately after. Heart rate was collected prior to exercise, after onset of occlusion, immediately after exercise, and one-minute after removal of occlusion. Ultrasonography was performed prior to, and at least 30 s after, occlusion. RESULTS: BTF_BFR caused greater reductions in arterial distance (14.28%, p = 0.010) and arterial area (28.43%, p = 0.020) than TRA_BFR. BTF_BFR was able to significantly reduce arterial flow below pre-occlusion values, while TRA_BFR did not. Both conditions caused significant elevations in heart rate following occlusion (TRA_BFR: +4.67 bpm, p = 0.046 and BTF_BFR: +6.07 bpm, p = 0.034), immediately post-exercise (TRA_BFR: +56.93 bpm, p < 0.001 and BTF_BFR: +52.79 bpm, p < 0.001) and one-minute post-exercise (TRA_BFR: +15.71, p = 0.003 and BTF_BFR: +14.57, p < 0.001). Only BTF_BFR caused significant reductions in performance as measured by average power per repetition. CONCLUSIONS: BTF_BFR causes a more exaggerated decrease in arterial blood flow as well as muscular power when compared to traditional TRA_BFR at 50% of LOP.

There are rising concerns about the health of classroom teachers in the United States, including stress, hypertension, and frequent urinary tract infections. Teacher working conditions are likely a contributor to their health concerns. Many teachers report that they cannot easily take a restroom break at work, and therefore, they consume minimal water or other fluids. This study investigated the relationship between restroom access and fluid consumption and the prevalence of renal and cardiovascular health complications in classroom teachers. The responses of 844 teachers (92% women, 8% men, age: 65.1% between 26 - 45 years) to an online survey about restroom accessibility, fluid consumption, and health were analyzed using descriptive statistics, χ² analyses, and logistic regression. 59.0% of teachers could not easily take a restroom break, and 54.7% consumed less than 2 cups of water per workday. Furthermore, 44.8% reported being pre-hypertensive, and 4.9% reported being hypertensive. Teachers with insufficient restroom access were significantly more likely to report frequent urinary tract infections. This study demonstrates a relationship between restroom access, fluid consumption, and renal/cardiovascular health in classroom teachers. Future research should directly investigate how teacher work environment impacts renal and cardiovascular health.

Background: Force plates are commonly used as a non-fatiguing measure of recovery. However, the recovery time course captured via the force plate assessment of vertical jumps has yet to be established. Therefore, the objective of this systematic review and meta-analysis was to examine the change in vertical jump performance and the time course of recovery following an acute bout of strenuous exercise using force plates. Methods: Peer-reviewed articles (n = 22) published prior to 8 November 2023, were identified by searching three electronic databases (PubMed, Scopus, Web of Science). Studies included in this review met the following criteria: (1) available in English; (2) involved adult participants >18 years of age; (3) measured the change in vertical jump performance over consecutive days using a force plate system. Individual effect sizes (ESs) were calculated by dividing the change in vertical jump at each timepoint (24 h, 48 h, etc.) by the pooled standard deviation (SD), and they were aggregated using a three-level random-effects model. Results: Vertical jump performance decreased following an acute strenuous exercise bout (ES = −0.2639; p < 0.0001) and returned to baseline after 3 days of recovery, with larger decreases observed when assessed using Peak Height rather than Peak Power (ES = −0.4687 vs. ES = −0.1399; p = 0.0393). Older participants showed a larger decrease in vertical jump (β = −0.0489; p < 0.0001). Conclusions: Force plates can be used to evaluate recovery post-exercise, with a decline in performance on Days 1 and 2, and full recovery by Day 3. The findings from this study support the use of force plates for the evaluation of recovery.