Hemodynamic and Lactate Response to Exhaustive Exercise with L-Arginine Supplementation

Introduction: To further understand the effects of L-arginine on both its ability to enhance lactate clearance and increase overall blood flow before, during, and after exhaustive anaerobic exercise. Methods: Twelve healthy male subjects between the ages of 18-25 first completed an initial visit where baseline data was recorded. Subjects completed three additional visits, in which they ingested either a placebo, two-gram or four-gram dose of L-arginine. Blood flow (BF) and lactate were recorded before ingestion of the treatment, 5 and 15-minutes post-ingestion prior to performing a push-up test to volitional fatigue. Immediately following the push-up test, BF and lactate were assessed and again 15-minutes post exercise. Results: Blood lactate did not differ across condition (p=0.569). Lactate clearance was not influenced by L-arginine when analyzing the Area Under Curve. Blood flow increased with ingestion of the four-gram dose while at rest (the 15-minute mark). Blood flow was also enhanced in the four-gram dose immediately after exercise at the 25-minute mark. Conclusions: The data suggests that a four-gram dose of L-arginine plays a more significant role in blood flow than the clearance of lactate after exercise compared to a two-gram dose or placebo.

Does the Multistage 20-m Shuttle Run Test Accurately Predict VO2max in NCAA Division I Women Collegiate Field Hockey Athletes?

Laboratory assessments of maximal oxygen uptake (VO2max) are considered the “gold standard” for ascertaining cardiovascular fitness, but they are not always practical for use in team sport settings. Therefore, the purpose of the current study was to compare the criterion assessment of VO2max on a treadmill to the progressive, multistage 20-m shuttle run test (i.e., Beep test), and to determine the predictability of 6 previously established Beep test predictive equations (i.e., Chatterjee, Flouris, Leger, Leger and Gadoury, Ramsbottom, St. Clair-Gibson). Collegiate women field hockey athletes (n = 65, mean±SD: age 19.6 ± 1.2 years; weight 64.7 ± 6.1 kg) completed criterion VO2max (mean ± SD: 46.4 ± 4.6 mL·kg−1·min−1) and Beep tests to volitional fatigue. According to Bland–Altman and Ordinary Least Products Regressions, the Ramsbottom (46.5 ± 4.2 mL·kg−1·min−1) and Flouris (46.3 ± 3.8 mL·kg−1·min−1) equations were considered valid predictions of criterion measured VO2max (46.4 ± 4.6). The Chatterjee, Leger, Leger and Gadoury, and St. Clair-Gibson equations overestimated VO2max, and are not recommended for use with women collegiate field hockey athletes. The Ramsbottom and Flouris estimates of VO2max from 20-m shuttle performances may be used in this population. For accurate estimates of VO2max, the clientele’s age, fitness level, and training history should be considered when selecting equations.

Concurrent Validity of a Stationary Cycling Test and Buffalo Concussion Treadmill Test in Adults with Concussion

Context: Following concussion, a multi-faceted assessment is recommended, including tests of physical exertion. The current gold standard for exercise testing following concussion is the Buffalo Concussion Treadmill Test (BCTT); however, there is a lack of validated tests that utilize alternative exercise modalities. Objective: To assess the feasibility and concurrent validity of a novel cycling test of exertion compared to the BCTT. Design: Crossover Study Setting: University Sport-Medicine Clinic Patients: Twenty adults (aged 18–60 years) diagnosed with a Sport-Related Concussion Intervention: Participants completed the BCTT and a cycling test of exertion in a random order, approximately 48 hours apart. Main Outcome Measures: The primary outcome of interest was maximum heart rate [HRmax; beats per minute (bpm)]. Secondary outcomes of interest included whether the participant reached volitional fatigue (yes/no), symptom responsible for test cessation (Post Concussion Symptom Scale), and Symptom Severity on a Visual Scale (/10). Results: Of the 20 participants, 19 (10 male, 9 female) completed both tests. One participant did not return for the second test and was excluded from the analysis. No adverse events were reported. The median HRmax for the BCTT [171 bpm; (IQR: 139–184bpm)] was not significantly different than the median HRmax for the Cycle [173 bpm; (IQR: 160–182)] (z=–0.63, p=0.53). For both tests, the three most frequently reported symptoms responsible for test cessation were Headache, Dizziness, and Pressure in the head. Of interest, the majority of participants (64%) reported a different symptom responsible for test cessation on each test. Conclusion: The novel cycling test of exertion achieved similar HRmax and test duration and may be a suitable alternative to the BCTT. Future research to understand the physiological reason for the heterogeneity in symptoms responsible for test cessation is warranted.

The Effect of Stride Frequency on Running Economy and Running Distance During High Intensity Treadmill Running

Running economy (RE; ml·kg-1·km1) considers as a valid predictor of endurance running performance. Theoretically, improving RE allows runners to cover more distance at constant speed or run faster at a given distance. Stride frequency (SF) is one of the important parameters that affects running performance. The purpose of this study was to investigate the effect of SF on RE and distance while running on the treadmill at the speed of V̇O2max (sV̇O2max) until volitional fatigue. The second purpose was to determine a relationship between RE and running distance during high intensity running. We hypothesized that both RE and running distance would affect significantly by SF variations and there is a positive relationship between RE and running distance. Ten male recreational runners (age: 25.8 ± 5.0 yrs, height: 171.4 ± 6.2 cm, mass: 71.9 ± 7.5 kg) completed total seven experimental sessions including graded exercise test and running session for determining V̇O2max (55.4 ± 5.9 ml·kg-1·min1) and preferred SF (PSF; 88.0±3.9 strides/min), respectively. Running speed was calculated based on V̇O2max using the metabolic equation; V̇O2 (ml·kg-1·min1) = [0.2 × Speed(m/min)] + 3.5(ml·kg-1·min1). Participants performed five separate running sessions (PSF, ±5%, ±10%) on the treadmill at the sV̇O2max with 0% gradient until volitional fatigue. A computer-based metronome was played in order to help maintain a target SF while running. The running distance was significantly different among SF variations (p < 0.01) and all participants ran the greater distance at 105% PSF. However, RE was not statistically significant (p = 0.19) across the SF conditions. There was a low correlation between RE and running distance (r = 0.214, p = 0.14). SF variations have a significant influence on running distance, but not RE during high intensity running. Recretional runners may use 105% PSF during high intensity running to train both aerobic and anaerobic capacity.

Impact of resistance training status on trunk muscle activation in a fatiguing set of heavy back squats

Purpose In this study we measured neural activation (EMG) in four trunk stabilizer muscles and vastus lateralis (VL) in trained and novice participants during a set of squat repetitions to volitional fatigue at 85% 1RM. Methods Forty males were recruited into two groups, novice (NG: n = 21) and experienced (EG: n = 19), according to relative squat 1RM. Participants were tested twice to: (1) determine squat 1RM, and (2) complete a single set of repetitions to volitional fatigue at 85% 1RM. Relative squat 1RM; NG < 140% body mass, EG > 160% body mass. Neuromuscular activation was measured by EMG for the following: rectus abdominus (RA), external oblique (EO), lumbar sacral erector spinae (LSES), upper lumbar erector spinae (ULES) and VL in eccentric and concentric phase. Completed repetitions, RPE and EMG in repetition 1 and at 20, 40, 60, 80 and 100% of completed repetitions were analysed. Results No group differences were found between number repetitions completed and RPE in repetitions to volitional fatigue at 85% 1RM. Neuromuscular activation increased significantly in all muscle groups in eccentric and concentric phase apart from RA in the eccentric phase. Trunk neuromuscular activation was higher in NG compared to EG and this was significant in EO, LSES and ULES in eccentric phase and LSES in the concentric phase. VL activation increased in both phases with no group differences. Conclusion Trunk neuromuscular activation increases in a fatiguing set of heavy squats regardless of training status. Increased back squat strength through training results in lower neuromuscular activation despite greater absolute external squat loads.

Longitudinal study of cerebral blood flow regulation during exercise in pregnancy

Cerebrovascular adaptation to pregnancy is poorly understood. We sought to assess cerebrovascular regulation in response to visual stimulation, hypercapnia and exercise across the three trimesters of pregnancy. Using transcranial Doppler (TCD) ultrasound, middle and posterior cerebral artery mean blood velocities (MCAvmean and PCAvmean) were measured continuously at rest and in response to (1) visual stimulation to assess neurovascular coupling (NVC); (2) a modified Duffin hyperoxic CO2 rebreathe test, and (3) an incremental cycling exercise test to volitional fatigue in non-pregnant ( n = 26; NP) and pregnant women (first trimester [ n = 13; TM1], second trimester [ n = 21; TM2], and third trimester [ n = 20; TM3]) in total 47 women. At rest, MCAvmean and PETCO2 were lower in TM2 compared to NP. PCAvmean was lower in TM2 but not TM1 or TM3 compared to NP. Cerebrovascular reactivity in MCAvmean and PCAvmean during the hypercapnic rebreathing test was not different between pregnant and non-pregnant women. MCAvmean continued to increase over the second half of the exercise test in TM2 and TM3, while it decreased in NP due to differences in ΔPETCO2 between groups. Pregnant women experienced a delayed decrease in MCAvmean in response to maximal exercise compared to non-pregnant controls which was explained by CO2 reactivity and PETCO2 level.

Lactate response during acute exercise in cancer survivors undergoing exercise rehabilitation.

e23047 Background: Cancerous cells express a markedly different metabolic profile characterized by lactate production even when oxygen is plentiful. Lactate accumulation is a common marker for energy production and utilization, yet it is currently unclear how blood lactate responds during acute exercise to volitional fatigue in individuals with cancer and how this response is modified with exercise-based rehabilitation. The purpose of the current study is to assess the effect of an acute exercise bout to volitional fatigue on lactate accumulation before and after an exercise-based rehabilitation program for cancer survivors. Methods: 33 cancer survivors (female, n = 18; male, n = 15) were recruited to participate in a 12-week exercise-based rehabilitation program. All participants performed an initial assessment of physiological parameters, including blood lactate accumulation (LA) during a progressive treadmill protocol to volitional fatigue. LA was quantified every 2 minutes during treadmill testing via finger stick. The exercise intervention consisted of one hour sessions, three days per week, and included cardiovascular endurance, muscular strength, balance, and flexibility exercises. After 12 weeks of rehabilitation, participants completed a follow-up evaluation of physiological parameters. Results: There was a significant increase in LA at volitional fatigue after 12 weeks of training (Initial: 6.17 ± 2.61 mM, Post 12 Weeks: 7.26 ± 2.10 mM; p = 0.04), with no significant difference in resting blood lactate. The workload at which anaerobic lactate threshold presented was significantly increased after 12 weeks (Initial: 5.87 ± 1.59 METs, Post 12 weeks: 7.35 ± 1.85 METs; p = 0.02). Conclusions: Cancer survivors respond to acute exercise to volitional fatigue in a manner similar to healthy controls. Furthermore, similar to the response observed in healthy populations, cancer survivors exhibited an increase in lactate threshold and an increase in peak lactate accumulation at volitional fatigue after completing an exercise-based rehabilitation program. Thus, although many cancerous cells have a unique glycolytic profile, this does not appear to influence training-induced adaptations in blood lactate.

PO-076 High and moderate intensity strength exercises to exhaustion activate different signaling cascades regulating protein metabolism in trained skeletal muscle

Objective The aim of the study was to evaluate the activation of signaling cascades regulating protein synthesis and degradation after strength exercise sessions of high and moderate intensity in the muscles of athletes adapted to strength training. Methods Eight strength-trained men were recruited for the experiment. The volunteers performed 4 sets of leg press to volitional fatigue with moderate intensity (65% 1RM) for one leg and 4 sets of leg press to volitional fatigue with high intensity (85% of 1RM) for contralateral leg. The sets for both legs were performed in turn with rest intervals of 2 min. Biopsy from m. vastus lateralis was performed before, 1, 5 and 10 hours after cessation of exercise. Content of signaling proteins was evaluated using Western blot. Results Total work performed by the leg during moderate intensity strength exercise was 32% (P˂0,001) higher in comparison with contralateral leg performing high intensity exercise. The phosphorylation levels of p70S6kThr389 and 4E-BP1Thr37 / 46 increased only after the exercise of moderate intensity (P˂0.05). On the contrary, the phosphorylation level of ERK1 / 2Thr202 / Tyr204 increased only after the exercise of high intensity (P˂0.05). The level of phosphorylation of eEF2Thr56 significantly decreased after 1 (P˂0.001), 5 (P˂0.01) and 10 (P˂0.01) hours after the exercise of high intensity. The phosphorylation level of ACCSer79, an AMPK activation marker, was significantly increased 1 hour after the exercise of moderate intensity (P˂0.01). The phosphorylation level of FOXO1Ser256 significantly decreased after the exercises of both intensities (5 hours after the exercise of moderate intensity, P˂0.001; 1 hour after the exercise of high intensity, P˂0.05). Conclusions Strength exercises of high and moderate intensity, performed to volitional fatigue, may cause activation of different signaling cascades. Herewith, activation of mTORC1 after strength exercise is more dependent on the total work, whereas the ERK1 / 2 and eEF2 activation on the exercise intensity. The work was supported by RFBR grant №17-04-00878.