Strategies to mitigate acute kidney injury risk during physical work in hot environments

Prolonged physical work in the heat can reduce renal function and increase the risk of acute kidney injury (AKI). This is concerning given that the latest climate change projections forecast a rise in global temperature as well as the frequency, intensity, and duration of heatwaves. This means that outdoor and indoor workers in the agriculture or construction industries will be exposed to higher heat stress in the years ahead. Several studies indicate a higher incidence of chronic kidney disease from nontraditional origins (CKDnt) in individuals exposed to high temperatures, intense physical work, and/or recurrent dehydration. It has been proposed that prolonged physical work in the heat accompanied by dehydration results in recurrent episodes of AKI that ultimately lead to permanent kidney damage and the development of CKDnt. Thus, there is a need to identify and test strategies that can alleviate AKI risk during physical work in the heat. The purpose of this review is to present strategies that might prevent and mitigate the risk of AKI induced by physical work in the heat.

Effect of heat stress on heat shock protein expression and hypertrophy-related signaling in the skeletal muscle of trained individuals

Muscle mass is balanced between hypertrophy and atrophy by cellular processes, including activation of the protein kinase B-mechanistic target of rapamycin (Akt-mTOR) signaling cascade. Stressors apart from exercise and nutrition, such as heat stress, can stimulate the heat shock protein A (HSPA) and C (HSPC) families alongside hypertrophic signaling factors and muscle growth. The effects of heat stress on HSP expression and Akt-mTOR activation in human skeletal muscle and their magnitude of activation compared with known hypertrophic stimuli are unclear. Here, we show a single session of whole body heat stress following resistance exercise increases the expression of HSPA and activation of the Akt-mTOR cascade in skeletal muscle compared with resistance exercise in a healthy, resistance-trained population. Heat stress alone may also exert similar effects, though the responses are notably variable and require further investigation. In addition, acute heat stress in C2C12 muscle cells enhanced myotube growth and myogenic fusion, albeit to a lesser degree than growth factor-mediated hypertrophy. Though the mechanisms by which heat stress stimulates hypertrophy-related signaling and the potential mechanistic role of HSPs remain unclear, these findings provide additional evidence implicating heat stress as a novel growth stimulus when combined with resistance exercise in human skeletal muscle and alone in isolated murine muscle cells. We believe these findings will help drive further applied and mechanistic investigation into how heat stress influences muscular hypertrophy and atrophy.NEW & NOTEWORTHY We show that acute resistance exercise followed by whole body heat stress increases the expression of HSPA and increases activation of the Akt-mTOR cascade in a physically active and resistance-trained population.

Circulating markers of intestinal barrier injury and inflammation following exertion in hypobaric hypoxia

Hypoxia induced intestinal barrier injury, microbial translocation, and local/systemic inflammation may contribute to high-altitude associated gastrointestinal complications or symptoms of acute mountain sickness (AMS). Therefore, we tested the hypothesis that six-hours of hypobaric hypoxia increases circulating markers of intestinal barrier injury and inflammation. A secondary aim was to determine if the changes in these markers were different between those with and without AMS. Thirteen participants were exposed to six hours of hypobaric hypoxia, simulating an altitude of 4572 m. Participants completed two 30-minute bouts of exercise during the early hours of hypoxic exposure to mimic typical activity required by those at high altitude. Pre- and post-exposure blood samples were assessed for circulating markers of intestinal barrier injury and inflammation. Data below are presented as mean ± standard deviation or median [interquartile range]. Intestinal fatty acid binding protein (Δ251 [103-410] pg•mL-1; p = 0.002, d = 0.32), lipopolysaccharide binding protein (Δ2 ± 2.4 μg•mL-1; p = 0.011; d = 0.48), tumor necrosis factor-α (Δ10.2 [3-42.2] pg•mL-1; p = 0.005; d = 0.25), interleukin-1β (Δ1.5 [0-6.7] pg•mL-1 p = 0.042; d = 0.18), and interleukin-1 receptor agonist (Δ3.4 [0.4-5.2] pg•mL-1p = 0.002; d = 0.23) increased from pre- to post-hypoxia. Six of the 13 participants developed AMS; however, the pre- to post-hypoxia changes for each marker were not different between those with and without AMS (p > 0.05 for all indices). These data provide evidence that high altitude exposures can lead to intestinal barrier injury, which may be an important consideration for mountaineers, military personnel, wildland firefighters, and athletes who travel to high altitudes to perform physical work or exercise.

Could Orthostatic Stress Responses Predict Acute Mountain Sickness Susceptibility Prior to High Altitude Travel? A Pilot Study

Bellovary, Bryanne N., Andrew D. Wells, Zachary J. Fennel, Jeremy B. Ducharme, Jonathan M. Houck, Trevor J. Mayschak, Ann L. Gibson, Scott N. Drum, and Christine M. Mermier. Could orthostatic stress responses predict acute mountain sickness susceptibility before high altitude travel? A pilot study. High Alt Med Biol. 24:19-26, 2023. Purpose: This study assessed head-up tilt (HUT) responses in relation to acute mountain sickness (AMS)-susceptibility during hypoxic exposure. Materials and Methods: Fifteen participants completed three lab visits: (1) protocol familiarization and cycle maximal oxygen consumption (VO₂max) test; (2) HUT test consisting of supine rest for 20 minutes followed by 70° tilting for ≤40 minutes; and (3) 6 hours of hypobaric hypoxic exposure (4,572 m) where participants performed two 30-minute cycling bouts separated by 1 hour at a 50% VO₂max workload within the first 3 hours and rested when not exercising. During HUT, systolic blood pressure (SBP), diastolic blood pressure, heart rate (HR), and variability (blood pressure variability [BPV] and HR variability [HRV]) were measured continuously. The AMS scores were determined after 6 hours of exposure. Correlations determined relationships between HUT cardiovascular responses and AMS scores. Repeated-measures analysis of variance (ANOVA) assessed differences between those with and without AMS symptoms during HUT. Results: Higher AMS scores correlated with greater change in SBP variability (r = 0.52, p = 0.048) and blunted changes in HRV (root mean square of successive differences between normal heartbeats r = 0.81, p = 0.001, percentage of adjacent normal sinus intervals that differ by more than 50 milliseconds [pNN50] r = 0.87, p < 0.001) during HUT. A pNN50 interaction (p = 0.02) suggested elevated cardiac sympathetic activity at baseline and a blunted increase in cardiac sympathetic influence throughout HUT in those with AMS (pNN50 baseline: AMS = 26.2% ± 15.3%, no AMS = 51.0% ± 13.5%; first 3 minutes into HUT: AMS = 17.2% ± 19.1%, no AMS = 17.1% ± 10.9%; end of HUT: AMS = 6.2% ± 9.1%, no AMS 11.0% ± 10.0%). Conclusions: The results suggest autonomic responses via HUT differ in AMS-susceptible individuals. Changes in HRV and BPV during HUT may be a promising predictive measurement for AMS-susceptibility, but further research is needed for confirmation.

The physiological, perceptual, and thermoregulatory responses to facemask use during exercise

The use of masks in public settings and when around people has been recommended to limit the spread of Coronavirus disease 2019 (COVID-19) by major public health agencies. Several different types of masks classified as either medical- or non-medical grade are commonly used among the public. However, concerns with difficulty breathing, re-breathing exhaled carbon dioxide, a decrease in arterial oxygen saturation, and a decrease in exercise performance have been raised regarding the use of mask during exercise. We review the current knowledge related to the effect of different masks during exercise on cardiorespiratory, metabolic, thermoregulatory, and perceptual responses. As such, the current literature seems to suggest that there are minimal changes to cardiovascular, metabolic, and no changes to thermoregulatory parameters with facemask use. However, differences in ventilatory parameters have been reported with submaximal and maximal intensity exercise to volitional fatigue. Literature on perceptual responses to exercise indicate an impact on ratings of perceived exertion, dyspnea, and overall discomfort dependent on mask use as well as exercise intensity. In conclusion, data from the current literature suggests a minimal impact on physiological, perceptual, and thermoregulatory responses dependent on the type of mask used during exercise.

Ibuprofen Increases Markers of Intestinal Barrier Injury But Suppresses Inflammation at Rest and After Exercise in Hypoxia

PURPOSE

The purpose of this study was to evaluate the effects of acute ibuprofen consumption (2 × 600-mg doses) on markers of enterocyte injury, intestinal barrier dysfunction, inflammation, and symptoms of gastrointestinal (GI) distress at rest and after exercise in hypobaric hypoxia.

METHODS

Using a randomized double-blind placebo-controlled crossover design, nine men (age, 28 ± 3 yr; weight, 75.4 ± 10.5 kg; height, 175 ± 7 cm; body fat, 12.9% ± 5%; V̇O 2 peak at 440 torr, 3.11 ± 0.65 L·min -1 ) completed a total of three visits including baseline testing and two experimental trials (placebo and ibuprofen) in a hypobaric chamber simulating an altitude of 4300 m. Preexercise and postexercise blood samples were assayed for intestinal fatty acid binding protein (I-FABP), ileal bile acid binding protein, soluble cluster of differentiation 14, lipopolysaccharide binding protein, monocyte chemoattractant protein-1, tumor necrosis factor α (TNF-α), interleukin-1β, and interleukin-10. Intestinal permeability was assessed using a dual sugar absorption test (urine lactulose-to-rhamnose ratio).

RESULTS

Resting I-FABP (906 ± 395 vs 1168 ± 581 pg·mL -1 ; P = 0.008) and soluble cluster of differentiation 14 (1512 ± 297 vs 1642 ± 313 ng·mL -1 ; P = 0.014) were elevated in the ibuprofen trial. Likewise, the urine lactulose-to-rhamnose ratio (0.217 vs 0.295; P = 0.047) and the preexercise to postexercise change in I-FABP (277 ± 308 vs 498 ± 479 pg·mL -1 ; P = 0.021) were greater in the ibuprofen trial. Participants also reported greater upper GI symptoms in the ibuprofen trial ( P = 0.031). However, monocyte chemoattractant protein-1 ( P = 0.007) and TNF-α ( P = 0.047) were lower throughout the ibuprofen trial compared with placebo (main effect of condition).

CONCLUSIONS

These data demonstrate that acute ibuprofen ingestion aggravates markers of enterocyte injury and intestinal barrier dysfunction at rest and after exercise in hypoxia. However, ibuprofen seems to suppress circulating markers of inflammation.

A Metabolic Profile of Peripheral Heart Action Training

Purpose: Peripheral heart action (PHA) is a style of circuit training that alternates upper and lower body resistance exercises with minimal rest between sets. The purpose of this study was to compare the metabolic demands of PHA to traditional hypertrophy training (TRAD) and to provide between sex comparison for both types of resistance training (RT). Methods: Twenty resistance-trained individuals underwent two bouts of volume-load matched RT: PHA and TRAD. We measured oxygen uptake (VO₂), heart rate (HR), blood lactate (BL) concentration, rating of perceived exertion (RPE), excess post-exercise oxygen consumption (EPOC), and duration of each session. Results: PHA elicited significantly greater %VO₂max (p < .001), %HRmax (p < .001), RPE (p < .001), and EPOC (p < .001) compared to TRAD. PHA was also completed in less time (p < .001). Compared to TRAD, BL was significantly higher at mid-exercise (p < .001), post-exercise (p < .001), and 5-min post-exercise (p < .001) during PHA. There were no between-sex differences for BL at any time-point for TRAD. However, during PHA, BL was significantly higher for males at mid-exercise (p = .04), post-exercise (p = .02), and 5-min post-exercise (p = .002). No between-sex differences were detected for HR, VO₂, RPE, or duration for either style of RT. Conclusions: PHA is a time-effective and metabolically demanding circuit that may lead to strength and cardiorespiratory adaptations. Males produced more BL than females during PHA, but not TRAD, suggesting that they incurred more metabolic stress during the bout of circuit training.

The Heat Shock Connection: Skeletal Muscle Hypertrophy and Atrophy

Skeletal muscle is an integral tissue system that plays a crucial role in the physical function of all vertebrates and is a key target for maintaining or improving health and performance across the lifespan. Based largely on cellular and animal models, there is some evidence that various forms of heat stress with or without resistance exercise may enhance skeletal muscle growth or reduce its loss. It is not clear whether these stimuli are similarly effective in humans or meaningful in comparison to exercise alone across various heating methodologies. Furthermore, the magnitude by which heat stress may influence whole body thermoregulatory responses and the connection to skeletal muscle adaptation remains ambiguous. Finally, the underlying mechanisms, which may include interaction between relevant heat shock proteins and intracellular hypertrophy and atrophy related factors, remain unclear. In this narrative mini-review we examine the relevant literature regarding heat stress alone or in combination with resistance exercise emphasizing skeletal muscle hypertrophy and atrophy across cellular and animal models, as well as human investigations. Additionally, we present working mechanistic theories for heat shock protein mediated signaling effects regarding hypertrophy and atrophy related signaling processes. Importantly, continued research is necessary to determine the practical effects and mechanisms of heat stress with and without resistance exercise on skeletal muscle function via growth and maintenance.

Exercise in hypobaric hypoxia increases markers of intestinal injury and symptoms of gastrointestinal distress

NEW FINDING

What is the central question of this study? What is the effect of hypobaric hypoxia on markers of exercise-induced intestinal injury and symptoms of GI distress? What is the main finding and its importance? Exercise performed at 4300 m of simulated altitude increased I-FABP, CLDN-3, and LBP which together suggest that exercise-induced intestinal injury may be aggravated by concurrent hypoxic exposure. Increases in I-FABP, LBP, CLDN-3 were correlated to exercise-induced GI symptoms, providing some evidence of a link between intestinal barrier injury and symptoms of GI distress.

ABSTRACT

We sought to determine the effect of exercise in hypobaric hypoxia on markers of intestinal injury and gastrointestinal (GI) symptoms. Using a randomized and counterbalanced design, 9 males completed two experimental trials: one at local altitude of 1585 m (NORM) and one at 4300 m of simulated hypobaric hypoxia (HYP). Participants performed 60-minutes of cycling at a workload that elicited 65% of their NORM VO₂ max. GI symptoms were assessed before and every 15-minutes during exercise. Pre- and post-exercise blood samples were assessed for intestinal fatty acid binding protein (I-FABP), claudin-3 (CLDN-3), and lipopolysaccharide binding protein (LBP). All participants reported at least one GI symptom in HYP compared to just 1 participant in NORM. I-FABP significantly increased from pre- to post-exercise in HYP (708±191 to 1215±518 pg mL^-1 ; p = 0.011, d = 1.10) but not NORM (759±224 to 828±288 pg mL^-1 ; p>0.99, d = 0.27). CLDN-3 significantly increased from pre- to post-exercise in HYP (13.8±0.9 to 15.3±1.2 ng mL^-1 ; p = 0.003, d = 1.19) but not NORM (13.7±1.8 to 14.2±1.6 ng mL^-1 ; p = .435, d = 0.45). LBP significantly increased from pre- to post-exercise in HYP (10.8±1.2 to 13.9±2.8 μg mL^-1 ; p = 0.006, d = 1.12) but not NORM (11.3±1.1 to 11.7±0.9 μg mL^-1 ; p>0.99, d = 0.32). I-FABP (d = 0.85), CLDN-3 (d = 0.95), and LBP (d = 0.69) were all significantly higher post-exercise in HYP compared to NORM (p≤0.05). Overall GI discomfort was significantly correlated to ΔI-FABP (r = 0.71), ΔCLDN-3 (r = 0.70), and ΔLBP (r = 0.86). These data indicate that cycling exercise performed in hypobaric hypoxia can cause intestinal injury, which might cause some commonly reported GI symptoms. This article is protected by copyright. All rights reserved.

Can linear regression confirm VO2max was attained in middle-aged and older adults?

PURPOSE

Evaluate the efficacy of a regression method for identifying a VO₂ plateau to confirm the attainment of VO₂max compared to a verification trial in middle-aged and older adults.

METHODS

Eleven men and ten women (age 61.0 ± 8.1, VO₂max 21.8-50.3 ml/kg/min, n = 21) completed an individualized ramp graded exercise test (GXT) on the cycle ergometer, and one hour later, a verification trial at 105% of their maximal work rate (WR) achieved during the GXT. A plateau in VO₂ was used to confirm VO₂max was attained. VO₂ plateau was identified using the difference between the highest VO₂ between the two trials and a linear regression analysis of the VO₂-WR relationship during the GXT. McNemar's test of marginal homogeneity was used to detect differences in the proportion of paired data of individuals' attainment of VO₂max criteria.

RESULTS

Of the 21 participants, 15 (71.4%) met the verification criterion while 6 (28.6%) did not, compared to the regression method where 16 (76.2%) achieved the regression criterion while 5 (23.8%) did not. McNemar's test revealed no significant difference between participants' ability to achieve the regression and verification criteria (p = 0.999).

CONCLUSION

The regression method is an effective strategy for confirming VO₂max was attained with middle-aged and older adults on a cycle ergometer. This time-efficient regression method is comparable with the verification criterion but does not require a second maximal test, which may be advantageous for those where the verification trial may not be practical.

High altitude exposures and intestinal barrier dysfunction

Gastrointestinal complaints are often reported during ascents to high altitude (> 2500 m), though their etiology is not known. One potential explanation is injury to the intestinal barrier which has been implicated in the pathophysiology of several diseases. High altitude exposures can reduce splanchnic perfusion and blood oxygen levels causing hypoxic and oxidative stress. These stressors might injure the intestinal barrier leading to consequences such as bacterial translocation and local/systemic inflammatory responses. The purpose of this mini review is to 1) discuss the impact of high-altitude exposures on intestinal barrier dysfunction, and 2) present medications and dietary supplements which may have relevant impacts on the intestinal barrier during high-altitude exposures. There is a small but growing body of evidence which shows that acute exposures to high altitudes can damage the intestinal barrier. Initial data also suggests that prolonged hypoxic exposures can compromise the intestinal barrier through alterations in immunological function, microbiota, or mucosal layers. Exertion may worsen high-altitude related intestinal injury via additional reductions in splanchnic circulation and greater hypoxemia. Collectively these responses can result in increased intestinal permeability and bacterial translocation causing local and systemic inflammation. More research is needed to determine the impact of various medications and dietary supplements on the intestinal barrier during high-altitude exposures.

Predictive model specific to young adults for estimating thoracic gas volume for air-displacement plethysmography

BACKGROUND

Thoracic gas volume either measured (mTGV) or predicted by the BodPod® (bpTGV) is used during air-displacement plethysmography to obtain a better estimate of percent body fat. Evidence suggests that bpTGV underestimates mTGV for young adults and this is especially evident for young males.

AIMS

We developed, validated, and cross-validated a TGV prediction model (pTGV) for males and females 18-30 years of age to address this underestimation.

MATERIALS & METHODS

Participants (N = 181; 18-30 years) that had their body composition assessed with the BodPod® were retrospectively randomly assigned to one of two independent subgroups, a validation (n = 145) or cross-validation (n = 36) sample. Ten iterations of the k-fold validation procedure were performed to assess the internal replicability of pTGV within the validation sample. External replicability of pTGV was evaluated by assessing the difference and standard error of the estimate (SEE) compared to mTGV in the cross-validation group.

RESULTS

The model using height, sex and body mass yielded the highest adjusted R² (0.627) and the lowest SEE (0.56 L): pTGV = 0.615338 × Sex (0 = Female, 1 = Male) + 0.056267 × Height (cm) - 0.011006 × Body Mass (kg) - 5.358839. R² remained stable across 10 iterations of the k-fold procedure (average R²  = 0.64). Differences between pTGV and mTGV were not significantly different than zero for the total cross-validation sample (-0.06 ± 0.7 L; SEE = 3.0%), for males (-0.11 ± 0.7 L; SEE = 3.7%), or for females (-0.02 ± 0.7 L; SEE = 5.3%).

CONCLUSION

We recommend that when it is impractical to obtain mTGV, the strong internal and external replicability of the new prediction model supports its use for males and females ages 18-30 years old during air-displacement plethysmography.

Comparison of resting metabolic rate prediction equations in college-aged adults

Prediction equations have been considered an accurate method for estimating resting metabolic rate (RMR) across multiple populations, but their accuracy for college-aged individuals not on an athletics team remains to be determined. Sixty-two college-aged (18-30 yrs) males (n = 31) and females (n = 31) had their RMR measured (RMRm), using indirect calorimetry, and body composition assessed via air-displacement plethysmography. The World Health Organization (WHO), Mifflin-St Jeor (Mifflin), Harris-Benedict (HB), Cunningham, and Nelson equations were used to estimate RMR. No difference was observed between the Cunningham and RMRm regardless of sex (p ≥ 0.05). All other prediction equations estimated a significantly lower RMR for males (p < 0.05). The Mifflin and Nelson equations predicted an RMR that was significantly lower than RMRm for females (p < 0.05). When compared with RMRm, no difference was detected for females using the WHO, HB, or Cunningham (p ≥ 0.05). Only the Nelson equation predicted an RMR that was outside of the clinically acceptable range (±10% of RMRm) regardless of sex. The Cunningham, WHO, and HB equations can accurately predict RMR for college-aged males and females. RMR prediction equations used in this study are less accurate for those with greater RMRs. Novelty: For adults 18-30 years old that are not on an athletics team, the Cunningham equation can accurately predict RMR. The Nelson equation should not be used to predict RMR for this population. There is a systematic bias for RMR prediction equations to underestimate higher measured RMR values.

New Multisite Bioelectrical Impedance Device Compared to Hydrostatic Weighing and Skinfold Body Fat Methods

The purpose of this study was to compare the Skulpt Chisel™ to seven-site skinfold (SKF) and hydrostatic weighing (HW) body fat percentage (%BF) estimates. Twenty-six participants (aged 24 ± 4 years; BMI 23.1 ± 3.5 kg·m^-2) were assessed. Significant differences in %BF estimates were found for all methodological pairings; p < 0.05. The SKF method underestimated %BF compared to HW (-2.52 ± 3.42 %BF). The Skulpt Chisel™ overestimated %BF compared to both HW (3.38 ± 6.10 %BF) and SKF (5.90 ± 5.26 %BF). Limits of agreement comparing HW to Skulpt Chisel™ indicated a difference between 95% confidence interval bounds (Upper bound: 5.84 %BF, Lower bound 0.92 %BF) and for HW to SKF (Upper bound: -1.14 %BF, Lower bound: -3.91 %BF). Regression analysis showed no significant bias for any methodological pairing; (p > 0.05). In conclusion, the Skulpt Chisel™ method should be used with caution when evaluating %BF of adults with similar demographics reported in this study.

Variations in exercise ventilation in hypoxia will affect oxygen uptake

Reports of VO2 response differences between normoxia and hypoxia during incremental exercise do not agree. In this study VO2 and VE were obtained from 15-s averages at identical work rates during continuous incremental cycle exercise in 8 subjects under ambient pressure (633 mmHg ≈1,600 m) and during duplicate tests in acute hypobaric hypoxia (455 mmHg ≈4,350 m), ranging from 49 to 100% of VO2 peak in hypoxia and 42-87% of VO2 peak in normoxia. The average VO2 was 96 mL/min (619 mL) lower at 455 mmHg (n.s. P = 0.15) during ramp exercises. Individual response points were better described by polynomial than linear equations (mL/min/W). The VE was greater in hypoxia, with marked individual variation in the differences which correlated significantly and directly with the VO2 difference between 455 mmHg and 633 mmHg (P = 0.002), likely related to work of breathing (Wb). The greater VE at 455 mmHg resulted from a greater breathing frequency. When a subject's hypoxic ventilatory response is high, the extra work of breathing reduces mechanical efficiency (E). Mean ∆E calculated from individual linear slopes was 27.7 and 30.3% at 633 and 455 mmHg, respectively (n.s.). Gross efficiency (GE) calculated from mean VO2 and work rate and correcting for Wb from a VE-VO2 relationship reported previously, gave corresponding values of 20.6 and 21.8 (P = 0.05). Individual variation in VE among individuals overshadows average trends, as also apparent from other reports comparing hypoxia and normoxia during progressive exercise and must be considered in such studies.

Impact of Varying Dosages of Fish Oil on Recovery and Soreness Following Eccentric Exercise

Fish oils (FOs) are rich in omega-3 long-chain polyunsaturated fatty acids, which have been purported to enhance recovery of muscular performance and reduce soreness post-exercise. However, the most effective FO dose for optimizing recovery remains unclear. The purpose of this investigation was to examine the effect of FO supplementation dosing on the recovery of measures of muscular performance, perceived soreness, and markers of muscle damage following a rigorous bout of eccentric exercise. Thirty-two college-aged resistance-trained males (~23.6 years, 71.6 kg, 172.1 cm) were supplemented with 2, 4, 6 g/day (G) FO or placebo (PL) for ~7.5 weeks. Following 7 weeks of supplementation, pre-exercise (PRE) performance assessments of vertical jump (VJ), knee extensor strength, 40-yard sprint, T-test agility, and perceived soreness were completed prior to a bout of muscle-damaging exercise and were repeated immediately post (IP), 1-, 2-, 4-, 24-, 48-, and 72-h (H) post-exercise. Repeated measures analysis of variance indicated a treatment × time interaction (p < 0.001) for VJ and perceived soreness, but no group differences were observed at any time point. VJ returned to PRE (54.8 ± 7.9 cm) by 1H (51.8 ± 6.5 cm, p = 0.112) for 6G, while no other groups returned to baseline until 48H. Lower soreness scores were observed in 6G compared to PL at 2H (mean difference [MD] = 2.74, p = 0.046), at 24H (MD: 3.45, p < 0.001), at 48H (MD = 4.45, p < 0.001), and at 72H (MD = 3.00, p = 0.003). Supplementation with 6G of FO optimized the recovery of jump performance and muscle soreness following a damaging bout of exercise.

Metabolic effects of two high-intensity circuit training protocols: Does sequence matter?

Background/objective

The integration of high-intensity interval training (HIIT) and circuit weight training (CWT) is seamless and practical for meeting recommended exercise guidelines. The purpose of this study was to determine the ideal combination of HIIT and CWT to elicit desired acute cardiorespiratory and metabolic responses in variables such as energy expenditure (EE), oxygen consumption (VO₂), heart rate (HR), blood lactate (BLa^-), excess post-exercise oxygen consumption (EPOC), rating of perceived exertion (RPE), and enjoyment.

Methods

Fourteen trained males (25.7 ± 4.4 yr) completed two exercise protocols matched for volume and recovery periods. On one day, participants performed six HIIT bouts prior to three rounds of a nine exercise CWT protocol (HIC). The second day (separated by ≥ 72 h) consisted of three rounds of three mini-circuits (three exercises per circuit) integrated with three HIIT bouts between the first and second and second and third mini-circuits (TRI). VO₂, HR, and EE were monitored throughout both protocols. EPOC for a 20-min duration, [BLa^-] (five time points), RPE, and enjoyment were measured post-exercise.

Results

Energy expenditure was significantly higher during the HIC compared to the TRI protocol (p = .012), as well as EPOC (p = .034). [BLa^-] was significantly greater immediate-, 5min-, 10min- and 20min-post-exercise following HIC as compared to TRI. Mean values for HIC and TRI were similar (p > .05) for HR and RPE.

Conclusion

Performing HIIT prior to CWT elicits a higher metabolic perturbation compared to the TRI protocol. Although a significant EE difference was detected between the two trials, the practical difference (∼20 kcal) between protocols indicates both protocols are similarly effective for caloric expenditure, metabolic and cardiorespiratory response.

Effect of Acute Aerobic Exercise and Rapamycin Treatment on Autophagy in Peripheral Blood Mononuclear Cells of Adults With Prediabetes

OBJECTIVES

Recently, a malfunction of the autophagic pathway has been implicated with impaired glucose metabolism and progression from prediabetes to type 2 diabetes. The aims of this study were to investigate the effect of exercise and rapamycin (RAPA) treatment on the autophagic process in peripheral blood mononuclear cells (PBMCs) from people with prediabetes compared with control subjects.

METHODS

Two groups matched for age and sex served as participants and included 6 participants with prediabetes (42.4±11.7 years) and 6 control subjects (44.4±11.9 years). Participants exercised at 50% of maximal oxygen consumption for 60 min with 5 min of rest interspersed every 20 min. PBMCs were isolated pre-exercise, immediately postexercise and 4 h after exercise recovery. Additional PBMCs were incubated for 24 h and either exposed to bafilomycin, rapamycin with bafilomycin (RAPA), or no treatment with vehicle (dimethyl sulfoxide). Proteins and mRNA were analyzed via western blot and quantitative real-time polymerase chain reaction, respectively.

RESULTS

Exercise increased autophagy immediately postexercise and recovered 4 h after exercise in control participants but not in participants with prediabetes. Autophagy increased in PBMCs from people with prediabetes and control participants after RAPA treatment; however, a significantly impaired autophagic response was observed in people with prediabetes when compared with control subjects.

CONCLUSIONS

Our results indicate an impairment in autophagic flux in PBMCs from people with prediabetes when compared with control subjects in response to both exercise and RAPA treatment. Future methods of autophagic upregulation should be investigated to spare malfunctions in autophagy in people with prediabetes.

Autophagy and aging: Maintaining the proteome through exercise and caloric restriction

Accumulation of dysfunctional and damaged cellular proteins and organelles occurs during aging, resulting in a disruption of cellular homeostasis and progressive degeneration and increases the risk of cell death. Moderating the accrual of these defunct components is likely a key in the promotion of longevity. While exercise is known to promote healthy aging and mitigate age‐related pathologies, the molecular underpinnings of this phenomenon remain largely unclear. However, recent evidences suggest that exercise modulates the proteome. Similarly, caloric restriction (CR), a known promoter of lifespan, is understood to augment intracellular protein quality. Autophagy is an evolutionary conserved recycling pathway responsible for the degradation, then turnover of cellular proteins and organelles. This housekeeping system has been reliably linked to the aging process. Moreover, autophagic activity declines during aging. The target of rapamycin complex 1 (TORC1), a central kinase involved in protein translation, is a negative regulator of autophagy, and inhibition of TORC1 enhances lifespan. Inhibition of TORC1 may reduce the production of cellular proteins which may otherwise contribute to the deleterious accumulation observed in aging. TORC1 may also exert its effects in an autophagy‐dependent manner. Exercise and CR result in a concomitant downregulation of TORC1 activity and upregulation of autophagy in a number of tissues. Moreover, exercise‐induced TORC1 and autophagy signaling share common pathways with that of CR. Therefore, the longevity effects of exercise and CR may stem from the maintenance of the proteome by balancing the synthesis and recycling of intracellular proteins and thus may represent practical means to promote longevity.

Telemedicine-Based Health Coaching Is Effective for Inducing Weight Loss and Improving Metabolic Markers

BACKGROUND

To assess the efficacy of health coaching (HC) delivered through videoconferencing (VC) to favorably change physical activity (PA), weight, and metabolic markers in adults with high body mass index (BMI).

MATERIALS AND METHODS

Thirty adults (BMI ≥30 kg/m2) were randomly assigned to one of three groups: VC, in-person (IP), or control group (CG). Participants received wireless watches and weight scales to sync with their personal smartphones; recorded data were wirelessly uploaded to a secure database. Participants assigned to VC and IP received individualized HC by a multidisciplinary team (registered dietitian, exercise physiologist, and medical doctor) based on data uploaded over the 12-week intervention. Steps/day and weight loss were analyzed through analyses of covariance.

RESULTS

Within- and between-group changes in weight (kg), glucose, insulin, hemoglobin A1c (HbA1c), and Homeostasis Model Assessment estimate of insulin resistance (HOMA-IR) were analyzed through analyses of variance. Weight loss was greater (p < 0.05) for VC (8.23 ± 4.5 kg; 7.7%) than IP (3.2 ± 2.6 kg; 3.4%) and CG (2.9 ± 3.9 kg; 3.3%), respectively. Steps/day were significantly higher in VC than IP at week 4 and VC was significantly higher than the CG at weeks 6, 8, 9, and 11 (p ≤ 0.05). No within- or between-group differences were found for glucose, insulin, or HbA1C. HOMA-IR decreased for VC only (p ≤ 0.05).

CONCLUSIONS

Our innovative, multidisciplinary, telemedicine HC delivered through VC led to more favorable changes in weight loss, PA (steps/day), and HOMA-IR than IP or no HC. VC may be an economical approach to improve health and promote behavior change in obese adults.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier NCT03278951.

The effect of aging on the autophagic and heat shock response in human peripheral blood mononuclear cells

Autophagy is a lysosome degradation pathway through which damaged organelles and macromolecules are degraded within the cell. A decrease in activity of the autophagic process has been linked to several age-associated pathologies, including triglyceride accumulation, mitochondrial dysfunction, muscle degeneration, and cardiac malfunction. Here, we examined the differences in the autophagic response using autophagy-inducer rapamycin (Rapa) in peripheral blood mononuclear cells (PBMCs) from young (21.8 ± 1.9 years) and old (64.0 ± 3.7 years) individuals. Furthermore, we tested the interplay between the heat shock response and autophagy systems. Our results showed a significant increase in LC3-II protein expression in response to Rapa treatment in young but not in old individuals. This was associated with a decreased response in MAP1LC3B mRNA levels, but not SQSTM1/p62. Furthermore, HSPA1A mRNA was upregulated only in young individuals, despite no differences in HSP70 protein expression. The combined findings suggest a suppressed autophagic response following Rapa treatment in older individuals.

Mitochondrial efficiency and exercise economy following heat stress: a potential role of uncoupling protein 3

Heat stress has been reported to reduce uncoupling proteins (UCP) expression, which in turn should improve mitochondrial efficiency. Such an improvement in efficiency may translate to the systemic level as greater exercise economy. However, neither the heat‐induced improvement in mitochondrial efficiency (due to decrease in UCP), nor its potential to improve economy has been studied. Determine: (i) if heat stress in vitro lowers UCP3 thereby improving mitochondrial efficiency in C2C12 myocytes; (ii) whether heat acclimation (HA) in vivo improves exercise economy in trained individuals; and (iii) the potential improved economy during exercise at altitude. In vitro, myocytes were heat stressed for 24 h (40°C), followed by measurements of UCP3, mitochondrial uncoupling, and efficiency. In vivo, eight trained males completed: (i) pre‐HA testing; (ii) 10 days of HA (40°C, 20% RH); and (iii) post‐HA testing. Pre‐ and posttesting consisted of maximal exercise test and submaximal exercise at two intensities to assess exercise economy at 1600 m (Albuquerque, NM) and 4350 m. Heat‐stressed myocytes displayed significantly reduced UCP3 mRNA expression and, mitochondrial uncoupling (77.1 ± 1.2%, P < 0.0001) and improved mitochondrial efficiency (62.9 ± 4.1%, P < 0.0001) compared to control. In humans, at both 1600 m and 4350 m, following HA, submaximal exercise economy did not change at low and moderate exercise intensities. Our findings indicate that while heat‐induced reduction in UCP3 improves mitochondrial efficiency in vitro, this is not translated to in vivo improvement of exercise economy at 1600 m or 4350 m.

Hemodynamic and metabolic responses to self-paced and ramp-graded exercise testing protocols

Recent examinations have shown lower maximal oxygen consumption during traditional ramp (RAMP) compared with self-paced (SPV) graded exercise testing (GXT) attributed to differences in cardiac output. The current study examined the differences in hemodynamic and metabolic responses between RAMP and SPV during treadmill exercise. Sixteen recreationally trained men (aged23.7 ± 3.0 years) completed 2 separate treadmill GXT protocols. SPV consisted of five 2-min stages (10 min total) of increasing speed clamped by the Borg RPE6-20 scale. RAMP increased speed by 0.16 km/h every 15 s until volitional exhaustion. All testing was performed at 3% incline. Oxygen consumption was measured via indirect calorimetry; hemodynamic function was measured via thoracic impedance and blood lactate (BLa^-) was measured via portable lactate analyzer. Differences between SPV and RAMP protocols were analyzed as group means by using paired-samples t tests (R Core Team 2017). Maximal values for SPV and RAMP were similar (p > 0.05) for oxygen uptake (47.1 ± 3.4 vs. 47.4 ± 3.4 mL·kg^-1·min^-1), heart rate (198 ± 5 vs. 200 ± 6 beats·min^-1), ventilation (158.8 ± 20.7 vs. 159.3 ± 19.0 L·min^-1), cardiac output (26.9 ± 5.5 vs. 27.9 ± 4.2 L·min^-1), stroke volume (SV) (145.9 ± 29.2 vs. 149.8 ± 25.3 mL·beat^-1), arteriovenous oxygen difference (18.5 ± 3.1 vs. 19.7 ± 3.1 mL·dL^-1), ventilatory threshold (VT) (78.2 ± 7.2 vs. 79.0% ± 7.6%), and peak BLa^- (11.7 ± 2.3 vs. 11.5 ± 2.4 mmol·L^-1), respectively. In conclusion, SPV elicits similar maximal hemodynamic responses in comparison to RAMP; however, SV kinetics exhibited unique characteristics based on protocol. These results support SPV as a feasible GXT protocol to identify useful fitness parameters (maximal oxygen uptake, oxygen uptake kinetics, and VT).

VESTPD as a measure of ventilatory acclimatization to hypobaric hypoxia

This study compared the ventilation response to an incremental ergometer exercise at two altitudes: 633 mmHg (resident altitude = 1,600 m) and following acute decompression to 455 mmHg (≈4,350 m altitude) in eight male cyclists and runners. At 455 mmHg, the V_ESTPD at RER <1.0 was significantly lower and the V_EBTPS was higher because of higher breathing frequency; at VO₂max, both V_ESTPD and V_EBTPS were not significantly different. As percent of VO₂max, the V_EBTPS was nearly identical and V_ESTPD was 30% lower throughout the exercise at 455 mmHg. The lower V_ESTPD at lower pressure differs from two classical studies of acclimatized subjects (Silver Hut and OEII), where V_ESTPD at submaximal workloads was maintained or increased above that at sea level. The lower V_ESTPD at 455 mmHg in unacclimatized subjects at submaximal workloads results from acute respiratory alkalosis due to the initial fall in HbO₂ (≈0.17 pHa units), reduction in PACO₂ (≈5 mmHg) and higher PAO₂ throughout the exercise, which are partially pre-established during acclimatization. Regression equations from these studies predict V_ESTPD from VO₂ and P_B in unacclimatized and acclimatized subjects. The attainment of ventilatory acclimatization to altitude can be estimated from the measured vs. predicted difference in V_ESTPD at low workloads after arrival at altitude.

Proceedings of the Thirteenth International Society of Sports Nutrition (ISSN) Conference and Expo

P1 Impact of antioxidant-enriched nutrient bar supplementation on the serum antioxidant markers and physical fitness components of track and field athletes

Lalitha Ramaswamy, Supriya Velraja

P2 The effects of phosphatidic acid supplementation on fitness levels in resistance trained women

Guillermo Escalante, Phil Harvey, Michelle Alencar, Bryan Haddock

P3 The effects of phosphatidic acid supplementation on cardiovascular risk factors in resistance trained men

Phil Harvey, Guillermo Escalante, Michelle Alencar, Bryan Haddock

P4 The efficacy of sodium bicarbonate supplementation on physical capacity and selected biochemical markers in elite wrestlers

Krzysztof Durkalec-Michalski, Jan Jeszka, Bogna Zawieja, Tomasz Podgórski

P5 Effects of different nutritional strategies in hydration and physical performance in healthy well-trained males

Ana Paula Trussardi Fayh, Alexandre Hideki Okano, Amanda Maria de Jesus Ferreira

P6 Reduction of plasma creatine concentrations as an indicator of improved bioavailability

Ralf Jäger, Martin Purpura, Roger C Harris

P7 Effect of three different breakfast meals on energy intake and nutritional status in college-age women

Molly M. Krause, Kiley A. Lavanger, Nina O. Allen, Allison E. Lieb, Katie A. Mullen, Joan M. Eckerson

P8 Accuracy of the ASA24® Dietary Recall system for assessing actual dietary intake in normal weight college-age women.

Kiley A. Lavanger, Molly M. Krause, Nina O. Allen, Allison E. Lieb, Katie A. Mullen, Joan M. Eckerson

P9 β-aminoisobutyric acid does not regulate exercise induced UCP-3 expression in skeletal muscle

Elisa Morales, Jeffrey Forsse, Thomas Andre, Sarah McKinley, Paul Hwang, Grant Tinsley, Mike Spillane, Peter Grandjean, Darryn Willoughby

P10 The ability of collegiate football athletes to adhere to sport-specific nutritional recommendations

A. Jagim, G. Wright, J. Kisiolek, M. Meinking, J. Ochsenwald, M. Andre, M.T. Jones, J. M. Oliver

P11 A single session of low-volume high intensity interval exercise improves appetite regulation in overweight men

Victor Araújo Ferreira, Daniel Costa de Souza, Victor Oliveira Albuquerque dos Santos, Rodrigo Alberto Vieira Browne, Eduardo Caldas Costa, Ana Paula Trussardi Fayh

P12 Acute effects of oral peppermint oil ingestion on exercise performance in moderately-active college students

Suresh T. Mathews, Haley D. Bishop, Clara R. Bowen, Yishan Liang, Emily A. West, Rebecca R. Rogers, Mallory R. Marshall, John K. Petrella

P13 Associations in body fat and liver triglyceride content with serum health markers in sedentary and exercised rats fed a ketogenic diet, Western diet or standard chow over a 6-week period

A. Maleah Holland, Wesley C. Kephart, Petey W. Mumford, C. Brooks Mobley, Ryan P. Lowery, Jacob M. Wilson, Michael D. Roberts

P14 Physiological changes following competition in male and female physique athletes: A pilot study

Eric T. Trexler, Katie R. Hirsch, Bill I. Campbell, Meredith G. Mock, Abbie E. Smith-Ryan

P15 Relationship between cognition and hydration status in college students at a large Southwestern university

Kate Zemek, Carol Johnston

P16 Whey protein-derived exosomes increase protein synthesis in C2C12 myotubes

C. Brooks Mobley, Petey W. Mumford, David D. Pascoe, Christopher M. Lockwood, Michael E. Miller, Michael D. Roberts

P17 The effect of three different energy drinks on 1.5-mile running performance, oxygen consumption, and perceived exertion

Gabriel J. Sanders, Willard Peveler, Brooke Warning, Corey A. Peacock

P18 The Ketogenic diet improves rotarod performance in young and older rats

Wesley C. Kephart, Petey W. Mumford, Ryan P. Lowery, Michael D. Roberts, Jacob M. Wilson

P19 Absorption of bonded arginine silicate compared to individual arginine and silicon components

David Sandler, Sara Perez Ojalvo, James Komorowski

P20 Effects of a high (2.4 g/kg) vs. low/moderate (1.2 g/kg) protein intake on body composition in aspiring female physique athletes engaging in an 8-week resistance training program

Bill I. Campbell, Danielle Aguilar, Andres Vargas, Laurin Conlin, Amey Sanders, Paola Fink-Irizarry, Layne Norton, Ross Perry, Ryley McCallum, Matthew R. Wynn, Jack Lenton

P21 Effects of a high (2.4 g/kg) vs. low/moderate (1.2 g/kg) protein intake on maximal strength in aspiring female physique athletes engaging in an 8-week resistance training program

Bill I. Campbell, Chris Gai, Seth Donelson, Shiva Best, Daniel Bove, Kaylee Couvillion, Jeff Dolan, Dante Xing, Kyshia Chernesky, Michael Pawela, Andres D. Toledo, Rachel Jimenez

P22 Monitoring of female collegiate athletes over a competitive season reveals changes in nutritional biomarkers

M. Rabideau, A. Walker, J. Pellegrino, M. Hofacker, B. McFadden, S. Conway, C. Ordway, D. Sanders, R. Monaco, M. S. Fragala, S. M. Arent

P23 Comparison of prediction equations to indirect calorimetry in men and women athletes

Jason D. Stone, Andreas Kreutzer, Jonathan M. Oliver, Jacob Kisiolek, Andrew R. Jagim

P24 Regional variations in sweat-based electrolyte loss and changes in plasma electrolyte content in Division I female athletes over the course of a competitive season

M. Hofacker, A. Walker, J. Pellegrino, M. Rabideau, B. McFadden, S. Conway, D. Sanders, C. Ordway, R. Monaco, M. S. Fragala, S. M. Arent

P25 In-season changes in plasma amino acid levels in Division I NCAA female athletes

Ozlem Tok, Joseph K. Pellegrino, Alan J. Walker, David J. Sanders, Bridget A. McFadden, Meaghan M. Rabideau, Sean P. Conway, Chris E. Ordway, Marissa Bello, Morgan L. Hofacker, Nick S. Mackowski, Anthony J. Poyssick, Eddie Capone, Robert M. Monaco, Maren S. Fragala, Shawn M. Arent

P26 Effects of a ketogenic diet with exercise on serum markers of bone metabolism, IGF-1 and femoral bone mass in rats

Petey W. Mumford, A. Maleah Holland, Wesley C. Kephart, Ryan P. Lowery, C. Brooks Mobley, Romil K. Patel, Annie Newton, Darren T. Beck, Michael D. Roberts, Jacob M. Wilson, Kaelin C. Young

P27 Casein supplementation in trained men and women: morning versus evening

Tobin Silver, Anya Ellerbroek, Richard Buehn, Leo Vargas, Armando Tamayo, Corey Peacock, Jose Antonio

P28 A high protein diet has no harmful effects: a one-year crossover study in resistance-trained males

Anya Ellerbroek, Tobin Silver, Richard Buehn, Leo Vargas, Armando Tamayo, Corey Peacock, Jose Antonio

P29 SUP (Stand-up Paddling) athletes: nutritional intake and body composition

Adam Pollock, Anya Ellerbroek, Tobin Silver, Corey Peacock, Jose Antonio

P30 The effects of 8 weeks of colostrum and bio-active peptide supplementation on body composition in recreational male weight lifters

A. Kreutzer, P. Zavala, S. Fleming, M. Jones, J. M. Oliver, A. Jagim

P31 Effects of a Popular Women’s Thermogenic Supplement During an Energy-Restricted High Protein Diet on Changes in Body Composition and Clinical Safety Markers

Cody T. Haun, Petey W. Mumford, Parker N. Hyde, Ciaran M. Fairman, Wesley C. Kephart, Darren T. Beck, Jordan R. Moon, Michael D. Roberts, Kristina L. Kendall, Kaelin C. Young

P32 Three days of caffeine consumption following caffeine withdrawal yields small strength increase in knee flexors

Geoffrey M Hudson, Tara Hannings, Kyle Sprow, Loretta DiPietro

P33 Comparison of cellular nitric oxide production from various sports nutrition ingredients

Doug Kalman, Sara Perez Ojalvo, James Komorowski

P34 The effects of 8 weeks of bio-active peptide supplementation on training adaptations in recreational male weight lifters

P. Zavala, S. Fleming, M. Jones, J. Oliver, A. Jagim

P35 Effects of MusclePharm Assault Black^TM on lower extremity spinal excitability and postactivation potentiation: A pilot study

Brian Wallace, Haley Bergstrom, Kelly Wallace

P36 Effects of four weeks of Ketogenic Diet alone and combined with High intensity Interval Training or Continuous-Moderate intensity on body composition, lipid profile and physical performance on healthy males

Matias Monsalves-Alvarez, Sebastian Oyharçabal, Victoria Espinoza

P37 Effect of branched-chain amino acid supplementation on creatine kinase, muscular performance, and perceived muscle soreness following acute eccentric exercise

Trisha A. VanDusseldorp, Kurt A. Escobar, Kelly E. Johnson, Nathan Cole, Terence Moriarty, Matthew Stratton, Marvin R. Endito, Christine M. Mermier, Chad M. Kerksick

P38 Effects of endurance training on markers of ribosome biogenesis in rodents fed a high fat diet

Matthew A. Romero, C. Brooks Mobley, Melissa Linden, Grace Margaret-Eleanor Meers, R. Scott Rector, Michael D. Roberts

P39 The effects of acute citrulline-malate on lower-body isokinetic performance in recreationally active individuals

Joshua L Gills, Hocheng Lu, Kimberly Parker, Chris Dobbins, Joshua N Guillory, Braden Romer, David Szymanski, Jordan Glenn

P40 The effect pre-ingested L-isoleucine and L-leucine on blood glucose responses and glycemic hormones in healthy inactive adults: Preliminary data.

Daniel E. Newmire, Eric Rivas, Sarah E. Deemer, Robert Wildman, Victor Ben-Ezra

P41 Does protein and source impact substrate oxidation and energy expenditure during and after moderate intensity treadmill exercise?

C Kerksick, B Gieske, R Stecker, C Smith, K Witherbee

P42 Effects of a pre-workout supplement on peak power and power maintenance during lower and upper body testing

Michael T. Lane, M. Travis Byrd, Zachary Bell, Emily Frith, Lauren M.C. Lane

P43 Effects of a pre-workout supplement on peak power production during lower and upper body testing in college-age females

Michael T. Lane, M. Travis Byrd, Zachary Bell, Emily Frith, Lauren M.C. Lane

P44 A comparison of whey versus casein protein supplementation on resting metabolic rate and body composition: a pilot study

Corey A. Peacock, Tobin A. Silver, Megan Colas, Mauricio Mena, Winter Rodriguez, Gabriel J. Sanders, Jose Antonio

P45 A novel mixed-tocotrienol intervention enhances recovery after eccentric exercise: preliminary findings

Andrea Vansickle, Brittany DiFiore, Stephanie Stepp, Grant Slack, Bridget Smith, Kayla Ruffner, Ronald Mendel, Lonnie Lowery

P46 The effects of post-exercise ingestion of a high molecular weight glucose on cycle performance in female cyclists

Katie R. Hirsch, Meredith G. Mock, Malia M.N. Blue, Eric T. Trexler, Erica J. Roelofs, Abbie E. Smith-Ryan

P47 Inclusive vs. exclusive dieting and the effects on body composition in resistance trained individuals

Laurin Conlin, Danielle Aguilar, Bill I. Campbell, Layne Norton, Katie Coles, Eric T. Trexler, Nic Martinez

P48 A whey protein hydrolysate may positively augment resting metabolism compared to intact whey protein

Jordan M. Joy, Roxanne M. Vogel, Thomas H. Hoover, K. Shane Broughton

P49 Seven days of high and low dose creatine nitrate supplementation I: hepatorenal, glucose and muscle enzyme function

R Dalton, R Sowinski, T Grubic, PB Collins, A Colletta, A Reyes, B Sanchez, M Kozehchain, YP Jung, C Rasmussen, P Murano, CP Earnest, M Greenwood, RB Kreider

P50 Seven days of high and low dose creatine nitrate supplementation II: performance

T Grubic, R Dalton, R Sowinski, PB Collins, A Colletta, A Reyes, B Sanchez, M Kozehchain, YP Jung, C Rasmussen, P Murano, CP Earnest, M Greenwood, RB Kreider

P51 Seven days of high and low dose creatine nitrate supplementation III: hemodynamics

R Sowinski, R Dalton, T Grubic, PB Collins, A Colletta, A Reyes, B Sanchez, M Kozehchain, YP Jung, C Rasmussen, P Murano, CP Earnest, M Greenwood, RB Kreider

P52 The efficacy of a β-hydroxy-β-methylbutyrate supplementation on physical capacity, body composition and biochemical markers in highly-trained combat sports athletes

Krzysztof Durkalec-Michalski, Jan Jeszka, Tomasz Podgórski

P53 Does protein and source impact substrate oxidation and energy expenditure during and after moderate intensity treadmill exercise?

C Kerksick, B Gieske, R Stecker, C Smith, K Witherbee

P54 Effects of 30 days of Cleanse™ supplementation on measure of body composition, waist circumference, and markers of gastrointestinal distress in females

Stacie Urbina, Emily Santos, Katelyn Villa, Alyssa Olivencia, Haley Bennett, Marissa Lara, Cliffa Foster, Colin Wilborn, Lem Taylor

P55 The effects of moderate- versus high-load training on body composition, muscle growth, and performance in college aged females

Jason M Cholewa, Amy Hewins, Samantha Gallo, Ashley Micensky, Christian De Angelis, Christopher Carney, Bill Campbell, Laurin Conlin, Layne Norton, Fabricio Rossi

P56 Effect of a multi-ingredient preworkout supplement on cognitive function and perceptions of readiness to perform

MS Koozehchian, PB Collins, R Sowinski, T Grubic, R Dalton, A O’Connor, SY Shin, Y Peter Jung, BK Sanchez, A Coletta, M Cho, A Reyes, C Rasmussen, CP Earnest, PS Murano, M Greenwood, RB Kreider

The effects of gait retraining in runners with patellofemoral pain: A randomized trial

BACKGROUND

Running popularity has increased resulting in a concomitant increase in running-related injuries with patellofemoral pain most commonly reported. The purpose of this study was to determine whether gait retraining by modifying footstrike patterns from rearfoot strike to forefoot strike reduces patellofemoral pain and improves associated biomechanical measures, and whether the modification influences risk of ankle injuries.

METHODS

Sixteen subjects (n=16) were randomly placed in the control (n=8) or experimental (n=8) group. The experimental group performed eight gait retraining running sessions over two weeks where footstrike pattern was switched from rearfoot strike to forefoot strike, while the control group performed running sessions with no intervention. Variables were recorded pre-, post-, and one-month post-running trials.

FINDINGS

Knee pain was significantly reduced post-retraining (P<0.05; effect size=0.294) and one-month follow-up (P<0.05; effect size=0.294). Knee abduction was significantly improved post-retraining (P<0.05; effect size=0.291) and one-month follow-up (P<0.05; effect size=0.291). Ankle flexion was significantly different post-retraining (P<0.05; effect size=0.547), as well as ankle range of motion post-retraining (P<0.05; effect size=0.425) and one-month follow-up (P<0.05; effect size=0.425).

INTERPRETATION

Findings suggest running with a forefoot strike pattern leads to reduced knee pain, and should be considered a possible strategy for management of patellofemoral pain in recreational runners. This trial is registered at the US National Institutes of Health (clinicaltrials.gov) #NCT02567123.