ResearchPad - endurance-and-performance https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Changes in strength and power performance and serum hormone concentrations during 12 weeks of task‐specific or strength training in conscripts]]> https://www.researchpad.co/article/Na43b4246-7b22-450e-9ad9-3ec7b3f4d206 Successful strength and conditioning program for conscripts cannot be built without taking into account the fracture nature of training caused by military specific training requirements. It is important in the future that the leadership prioritizes quality‐controlled physical training and supports necessary changes. Strength and task‐specific training can lead to improvements in the battlefield, reduce the risk of overtraining, and prevent injuries caused by excessive running and loaded marching during the traditional military training.

]]>
<![CDATA[Effect of somatic maturity on the aerobic and anaerobic adaptations to sprint interval training]]> https://www.researchpad.co/article/Nee9d9b91-1e50-4da1-ad79-8a26873d15df After 4 weeks of sprint interval training, improvements in aerobic and anaerobic exercise performance were observed in youth male athletes. However, prepubertal participants had no changes following training.

]]>
<![CDATA[Effects of enhanced cutaneous sensory input on interlimb strength transfer of the wrist extensors]]> https://www.researchpad.co/article/N08ffa642-454e-4f30-b8c6-8d1b6331a5d3

Abstract

The relative contribution of cutaneous sensory feedback to interlimb strength transfer remains unexplored. Therefore, this study aimed to determine the relative contribution of cutaneous afferent pathways as a substrate for cross‐education by directly assessing how “enhanced” cutaneous stimulation alters ipsilateral and contralateral strength gains in the forearm. Twenty‐seven right‐handed participants were randomly assigned to 1‐of‐3 training groups and completed 6 sets of 8 repetitions 3x/week for 5 weeks. Voluntary training (TRAIN) included unilateral maximal voluntary contractions (MVCs) of the wrist extensors. Cutaneous stimulation (STIM), a sham training condition, included cutaneous stimulation (2x radiating threshold; 3sec; 50Hz) of the superficial radial (SR) nerve at the wrist. TRAIN + STIM training included MVCs of the wrist extensors with simultaneous SR stimulation. Two pre‐ and one posttraining session assessed the relative increase in force output during MVCs of isometric wrist extension, wrist flexion, and handgrip. Maximal voluntary muscle activation was simultaneously recorded from the flexor and extensor carpi radialis. Cutaneous reflex pathways were evaluated through stimulation of the SR nerve during graded ipsilateral contractions. Results indicate TRAIN increased force output compared with STIM in both trained (85.0 ± 6.2 Nm vs. 59.8 ± 6.1 Nm) and untrained wrist extensors (73.9 ± 3.5 Nm vs. 58.8 Nm). Providing ‘enhanced’ sensory input during training (TRAIN + STIM) also led to increases in strength in the trained limb compared with STIM (79.3 ± 6.3 Nm vs. 59.8 ± 6.1 Nm). However, in the untrained limb no difference occurred between TRAIN + STIM and STIM (63.0 ± 3.7 Nm vs. 58.8 Nm). This suggests when ‘enhanced’ input was provided independent of timing with active muscle contraction, interlimb strength transfer to the untrained wrist extensors was blocked. This indicates that the sensory volley may have interfered with the integration of appropriate sensorimotor cues required to facilitate an interlimb transfer, highlighting the importance of appropriately timed cutaneous feedback.

]]>
<![CDATA[The effect of acute exercise on environmentally induced symptoms of dry eye]]> https://www.researchpad.co/article/N70a39e83-f5fd-4a95-b441-b886ea493768

Abstract

The purpose of this study was to investigate the effects of acute exercise on environmentally induced symptoms of dry eye. Twelve participants without dry eye disease volunteered to complete three experimental visits in a randomized order; (1) control condition seated for 1 h at a relative humidity (RH) of 40% (CONT), (2) dry condition seated for 1 h at a RH of 20% (DRY), and (3) exercise condition seated for 40 min followed by 20 min of cycling exercise at a RH of 20% (EXER). Tear volume, tear matrix metalloproteinase 9 (MMP‐9), perception of dry eye symptoms (frequency and severity), core temperature, and ocular surface temperature (OST) were measured at the end of each exposure. The perception of dry eye frequency and MMP‐9 concentration were significantly higher in DRY compared to CONT (P < 0.012), with no differences in EXER compared to CONT. The results suggest that an acute bout of exercise may attenuate symptoms of environmentally induced dry eye, and warrant further research.

]]>
<![CDATA[Effects of low and moderate treadmill exercise on liver of d ‐galactose‐exposed aging rat model]]> https://www.researchpad.co/article/N2be5e038-ffb2-46ec-8682-ae56c086c142

Abstract

Aging increases liver susceptibility to diseases and it causes inflammation in liver tissue which can lead to fibrosis. Studies suggest that aging is caused by the accumulation of free radicals. Lack of physical activity can lower hormone levels and increase free radicals that can accelerate the aging process. Hence, physical activity is very important to maintain functions of organs. This research was aimed to study the effects of low and moderate treadmill exercise on d‐Galactose‐exposed aging rat model by evaluating the degree of hepatic fibrosis, number of M1 and M2, and M1/M2 ratio. Twenty‐four 3‐month‐old male Wistar aging model rats were randomly divided into four groups, that is, three treatment groups with daily 300 mg kgBW−1 d‐Galactose injection administrated intraperitoneally for 4 weeks and 1 control group with normal saline injection. Two of the d‐Galactose treated groups were given low and moderate treadmill exercise for 4 weeks. It was concluded that low intensity treadmill exercise significantly lowered the degree of d‐Galactose‐exposed hepatic fibrosis, and moderate treadmill exercise was able to restore the injured liver tissue back to the non‐aging state. Administration of d‐Galactose causes inflammation marked by the elevated number of M1 and M2 macrophages. Moderate treadmill exercise drove M1/M2 ratio back to the control condition.

]]>
<![CDATA[The influence of fibrillin‐1 and physical activity upon tendon tissue morphology and mechanical properties in mice]]> https://www.researchpad.co/article/Na08d555f-83fc-46e0-b756-33e03a090a85

Abstract

Fibrillin‐1 mutations cause pathological changes in connective tissue that constitute the complex phenotype of Marfan syndrome. In this study, we used fibrillin‐1 hypomorphic and haploinsufficient mice (Fbn1mgr/mgR and Fbn1+/− mice, respectively) to investigate the impact of fibrillin‐1 deficiency alone or in combination with regular physical activity on tendon tissue morphology and mechanical properties. Morphological and biomechanical analyses revealed that Fbn1mgr/mgR but not Fbn1+/− mice displayed smaller tendons with physical properties that were unremarkable when normalized to tendon size. Fbn1mgR/mgR mice (n = 43) Fbn1+/−mice (n = 27) and wild‐type mice (WT, n = 25) were randomly assigned to either control cage conditions (n = 54) or to a running on a running wheel for 4 weeks (n = 41). Both fibrillin‐1‐deficient mice ran voluntarily on the running wheel in a manner similar to WT mice (3–4 km/24 h). Regular exercise did not mitigate aneurysm progression in Fbn1mgR/mgR mice (P < 0.05) as evidenced by unmodified median survival. In spite of the smaller size, tendons of fibrillin‐1‐deficient mice subjected to regular exercise showed no evidence of overt histopathological changes or tissue overload. We therefore concluded that lack of optimal fibrillin‐1 synthesis leads to a down regulation of integrated tendon formation, rather than to a loss of tendon quality, which also implies that fibrillin‐1 deficiency in combination with exercise is not a suitable animal model for studying the development of tendon overuse (tendinopathy).

]]>
<![CDATA[Maternal exercise upregulates mitochondrial gene expression and increases enzyme activity of fetal mouse hearts]]> https://www.researchpad.co/article/5b378353463d7e6b6e6f5900

Abstract

Maternal exercise during pregnancy has been shown to improve the long‐term health of offspring in later life. Mitochondria are important organelles for maintaining adequate heart function, and mitochondrial dysfunction is linked to cardiovascular disease. However, the effects of maternal exercise during pregnancy on mitochondrial biogenesis in hearts are not well understood. Thus, the purpose of this study was to test the hypothesis that mitochondrial gene expression in fetal myocardium would be upregulated by maternal exercise. Twelve‐week‐old female C57BL/6 mice were divided into sedentary and exercise groups. Mice in the exercise group were exposed to a voluntary cage‐wheel from gestational day 1 through 17. Litter size and individual fetal weights were taken when pregnant dams were sacrificed at 17 days of gestation. Three to four hearts from the same group were pooled to study gene expression, protein expression, and enzyme activity. There were no significant differences in litter size, sex distribution, and average fetal body weight per litter between sedentary and exercised dams. Genes encoding mitochondrial biogenesis and dynamics, including nuclear respiratory factor‐1 (Nrf1), Nrf2, and dynamin‐related GTPase termed mitofusin‐2 (Mfn2) were significantly upregulated in the fetal hearts from exercised dams. Cytochrome c oxidase activity and ATP production were significantly increased, while the hydrogen peroxide level was significantly decreased in the fetal hearts by maternal exercise. Our results demonstrate that maternal exercise initiated at day 1 of gestation could transfer the positive mitochondrial phenotype to fetal hearts.

]]>
<![CDATA[Greater V˙O2peak is correlated with greater skeletal muscle deoxygenation amplitude and hemoglobin concentration within individual muscles during ramp‐incremental cycle exercise]]> https://www.researchpad.co/article/5bd4080ed5eed0c484786841

Abstract

It is axiomatic that greater aerobic fitness (V˙O2peak) derives from enhanced perfusive and diffusive O2 conductances across active muscles. However, it remains unknown how these conductances might be reflected by regional differences in fractional O2 extraction (i.e., deoxy [Hb+Mb] and tissue O2 saturation [StO2]) and diffusive O2 potential (i.e., total[Hb+Mb]) among muscles spatially heterogeneous in blood flow, fiber type, and recruitment (vastus lateralis, VL; rectus femoris, RF). Using quantitative time‐resolved near‐infrared spectroscopy during ramp cycling in 24 young participants (V˙O2peak range: ~37.4–66.4 mL kg−1 min−1), we tested the hypotheses that (1) deoxy[Hb+Mb] and total[Hb+Mb] at V˙O2peak would be positively correlated with V˙O2peak in both VL and RF muscles; (2) the pattern of deoxygenation (the deoxy[Hb+Mb] slopes) during submaximal exercise would not differ among subjects differing in V˙O2peak. Peak deoxy [Hb+Mb] and StO2 correlated with V˙O2peak for both VL (= 0.44 and −0.51) and RF (= 0.49 and −0.49), whereas for total[Hb+Mb] this was true only for RF (= 0.45). Baseline deoxy[Hb+Mb] and StO2 correlated with V˙O2peak only for RF (= −0.50 and 0.54). In addition, the deoxy[Hb+Mb] slopes were not affected by aerobic fitness. In conclusion, while the pattern of deoxygenation (the deoxy[Hb+Mb] slopes) did not differ between fitness groups the capacity to deoxygenate [Hb+Mb] (index of maximal fractional O2 extraction) correlated significantly with V˙O2peak in both RF and VL muscles. However, only in the RF did total[Hb+Mb] (index of diffusive O2 potential) relate to fitness.

]]>
<![CDATA[Riding posture affects quadriceps femoris oxygenation during an incremental cycle exercise in cycle‐based athletes]]> https://www.researchpad.co/article/5c0cb663d5eed0c4849e4ea6

Abstract

Although oxygenation levels and muscle recruitment patterns of the quadriceps femoris during an incremental cycling exercise has been reported, oxygenation and activation profiles of the quadriceps femoris in racing posture in cycle‐based athletes remain unknown. This study aimed to examine the effects of riding posture on oxygenation and neuromuscular activation of quadriceps femoris during an incremental cycling exercise in cycle‐based athletes. Nine cycle‐based athletes and nine nonathletic subjects performed an incremental cycling exercise at a constant cadence of 90 rpm. Riding postures were the racing posture using an aero‐handle bar (aero posture) and the usual upright racing posture as the control (upright posture). Near‐infrared spectroscopy and surface electromyography were recorded from vastus lateralis and rectus femoris. Changes in the tissue oxygenation index of the near‐infrared spectroscopy from baseline were calculated, and the amplitudes of electromyographic signals were normalized to the initial values of the exercise in each muscle. In cycle‐based athletes, changes in the tissue oxygenation index of vastus lateralis and rectus femoris in the aero posture were significantly lower than those obtained in the upright posture throughout the exercise, whereas no significant differences between the postures were observed in the normalized electromyographic amplitudes of vastus lateralis and rectus femoris. A significant difference between the postures was only occurred in changes of the tissue oxygenation index of rectus femoris in the final phase of exercise in nonathletic subjects. It appears that riding posture affects the oxygenation pattern of quadriceps femoris during incremental cycling exercise in cycle‐based athletes. The main results of this study suggest that aero posture during incremental cycle exercise enhanced the muscular oxygen consumption of the quadriceps femoris in the trained cyclists.

]]>
<![CDATA[Oral contraceptives augment the exercise pressor reflex during isometric handgrip exercise]]> https://www.researchpad.co/article/5b4bcd2f463d7e7d623b6a8d

Abstract

We sought to determine whether oral contraception alters the gender‐related differences observed in the exercise pressor reflex during isometric handgrip exercise. Fifteen men, fifteen normally menstruating women (WomenNM), and fifteen women taking monophasic oral contraceptives (WomenOC) completed two trials of a 3‐min isometric handgrip exercise protocol performed at 30% of their maximal voluntary contraction: (1) where arterial occlusion was applied to the previously exercising arm during a 3‐min recovery period (Occlusion trial); (2) where no arterial occlusion was applied during recovery (Control trial). Handgrip exercise elicited greater increases in mean arterial pressure (MAP) in MEN compared to both female groups (< 0.05), and in WomenOC compared to WomenNM in both trials (= 0.01, = 0.03). After 3 min of recovery, sBP was 12% (= 0.01) and 9% (= 0.02) higher in the Occlusion trial when compared to the Control trial for MEN and WomenOC. Conversely, arterial occlusion in recovery from handgrip did not sustain elevated sBP in the Occlusion trial, and sBP returned to recovery levels not different to the Control trial, in WomenNM (= 0.41). These data indicate that gender‐related differences in the metaboreflex during isometric handgrip exercise exist between men and normally menstruating women, but are blunted when men are compared to women taking oral contraceptives. We conclude that the suppression of 17β‐estradiol and/or progestogen in women via the administration of oral contraceptives attenuates sex‐related differences in the metaboreflex during isometric handgrip exercise.

]]>
<![CDATA[The serine protease, dipeptidyl peptidase IV as a myokine: dietary protein and exercise mimetics as a stimulus for transcription and release]]> https://www.researchpad.co/article/5affbbc8463d7e29ff2936c6

Abstract

Dipeptidyl‐peptidase IV (DPPIV) is an enzyme with numerous roles within the body, mostly related to regulating energy metabolism. DPPIV is also a myokine, but the stimulus for its release is poorly understood. We investigated the transcription and release of DPPIV from skeletal muscle in a three‐part study using C2C12 myotube cultures, an acute rat exercise and postexercise feeding model, and human feeding or human exercise models. When myotubes were presented with leucine only, hydrolyzed whey protein, or chemicals that cause exercise‐related signaling to occur in cell culture, all caused an increase in the mRNA expression of DPPIV (1.63 to 18.56 fold change, P < 0.05), but only whey protein caused a significant increase in DPPIV activity in the cell culture media. When rats were fed whey protein concentrate immediately following stimulated muscle contractions, DPPIV mRNA in both the exercised and nonexercised gastrocnemius muscles significantly increased 2.5‐ to 3.7‐fold (P < 0.05) 3–6 h following the exercise/feeding bout; of note exercise alone or postexercise leucine‐only feeding had no significant effect. In humans, plasma and serum DPPIV activities were not altered by the ingestion of whey protein up to 1 h post consumption, after a 10 min bout of vigorous running, or during the completion of three repeated lower body resistance exercise bouts. Our cell culture and rodent data suggest that whey protein increases DPPIV mRNA expression and secretion from muscle cells. However, our human data suggest that DPPIV is not elevated in the bloodstream following acute whey protein ingestion or exercise.

]]>
<![CDATA[Prediction of lung function using handgrip strength in healthy young adults]]> https://www.researchpad.co/article/5c48fb62d5eed0c4841fc8ad

Abstract

Positive association between physical activity and spirometry has been reported to be possibly attributed to handgrip strength (HGS), particularly in the elderly. However, the nature of the association between HGS and lung function in young adults is still unclear. This study investigated the prediction of lung function using HGS in young adults. A cross‐sectional analytical study was carried out on four hundred (400) apparently healthy medical students who are aged 16–30 years. Handgrip strength (dominant and nondominant) and lung function (FEV 1, FVC and PEFR) of these students were assessed using Jamar dynamometer and a portable spirometer, respectively. Data were analyzed using inferential statistics. Independent t‐test showed that the mean values of HGS and lung function of the males were significantly higher than the females (P < 0.0005). The relationship between HGS and lung function indices was significant (P < 0.0005) in all the participants but strongest for FEV 1 (r = 0.64). The regression analysis showed that in addition to gender and height, HGS was a significant (P < 0.0005) predictor of lung function. Regression equations were also proposed for the prediction of these lung function indices using HGS, gender and height. This study is the first to report HGS as a significant predictor of pulmonary function in healthy young adults living in a low‐resource country. Hence, its use could enhance medical practice in being an indicator of lung function status in healthy young adults.

]]>
<![CDATA[Deep‐targeted exon sequencing reveals renal polymorphisms associate with postexercise hypotension among African Americans]]> https://www.researchpad.co/article/5b04c2d5463d7e27b5abe310

Abstract

We found variants from the Angiotensinogen‐Converting Enzyme (ACE), Angiotensin Type 1 Receptor (AGTR1), Aldosterone Synthase (CYP11B2), and Adducin (ADD1) genes exhibited intensity‐dependent associations with the ambulatory blood pressure (BP) response following acute exercise, or postexercise hypotension (PEH). In a validation cohort, we sequenced exons from these genes for their associations with PEH. Obese (30.9 ± 3.6 kg m−2) adults (n = 23; 61% African Americans [AF], 39% Caucasian) 42.0 ± 9.8 years with hypertension (139.8 ± 10.4/84.6 ± 6.2 mmHg) completed three random experiments: bouts of vigorous and moderate intensity cycling and control. Subjects wore an ambulatory BP monitor for 19 h. We performed deep‐targeted exon sequencing using the Illumina TruSeq Custom Amplicon kit. Variant genotypes were coded as number of minor alleles (#MA) and selected for further statistical analysis based upon Bonferonni or Benjamini–Yekutieli multiple testing corrected p‐values under time adjusted linear models for 19 hourly BP measurements per subject. After vigorous intensity over 19 h among ACE,AGTR1,CYP11B2, and ADD1 variants passing multiple testing thresholds, as the #MA increased, systolic (SBP) and/or diastolic BP decreased 12 mmHg (P = 4.5E‐05) to 30 mmHg (P = 6.4E‐04) among AF only. In contrast, after moderate intensity over 19 h among ACE and CYP11B2 variants passing multiple testing thresholds, as the #MA increased, SBP increased 21 mmHg (P = 8.0E‐04) to 22 mmHg (P = 8.2E‐04) among AF only. In this replication study, ACE,AGTR1,CYP11B2, and ADD1 variants exhibited associations with PEH after vigorous, but not moderate intensity exercise among AF only. Renal variants should be explored further with a multi‐level “omics” approach for associations with PEH among a large, ethnically diverse sample of adults with hypertension.

]]>
<![CDATA[Exercise training and α1‐adrenoreceptor‐mediated sympathetic vasoconstriction in resting and contracting skeletal muscle]]> https://www.researchpad.co/article/5af92bee463d7e145b4b1ef7

Abstract

Exercise training (ET) increases sympathetic vasoconstrictor responsiveness and enhances contraction‐mediated inhibition of sympathetic vasoconstriction (i.e., sympatholysis) through a nitric oxide (NO)‐dependent mechanism. Changes in α2‐adrenoreceptor vasoconstriction mediate a portion of these training adaptations, however the contribution of other postsynaptic receptors remains to be determined. Therefore, the purpose of this study was to investigate the effect of ET on α1‐adrenoreceptor‐mediated vasoconstriction in resting and contracting muscle. It was hypothesized that α1‐adrenoreceptor‐mediated sympatholysis would be enhanced following ET. Male Sprague Dawley rats were randomized to sedentary (S; n = 12) or heavy‐intensity treadmill ET (n = 11) groups. Subsequently, rats were anesthetized and instrumented for lumbar sympathetic chain stimulation and measurement of femoral vascular conductance (FVC) at rest and during muscle contraction. The percentage change in FVC in response to sympathetic stimulation was measured in control, α1‐adrenoreceptor blockade (Prazosin; 20 μg, IV), and combined α1 and NO synthase (NOS) blockade (lNAME; 5 mg·kg−1 IV) conditions. Sympathetic vasoconstrictor responsiveness was increased (< 0.05) in ET compared to S rats at low, but not high (> 0.05) stimulation frequencies at rest (S: 2 Hz: −25 ± 4%; 5 Hz: −45 ± 5 %; ET: 2 Hz: −35 ± 7%, 5 Hz: −52 ± 7%), whereas sympathetic vasoconstrictor responsiveness was not different (> 0.05) between groups during contraction (S: 2 Hz: −11 ± 8%; 5 Hz: −26 ± 11%; ET: 2 Hz: −10 ± 7%, 5 Hz: −27 ± 12%). Prazosin blunted (< 0.05) vasoconstrictor responsiveness in S and ET rats at rest and during contraction, and abolished group differences in vasoconstrictor responsiveness. Subsequent NOS blockade increased vasoconstrictor responses (< 0.05) in S at rest and during contraction, whereas in ET vasoconstriction was increased (< 0.05) in response to sympathetic stimulation at 2 Hz at rest and unchanged (> 0.05) during contraction. ET enhanced (< 0.05) sympatholysis, however the training‐mediated improvements in sympatholysis were abolished by α1‐adrenoreceptor blockade. Subsequent NOS inhibition did not alter (> 0.05) sympatholysis in S or ET rats. In conclusion, ET augmented α1‐adrenoreceptor‐mediated vasoconstriction in resting skeletal muscle and enhanced α1‐adrenoreceptor‐mediated sympatholysis. Furthermore, these data suggest that NO is not required to inhibit α2‐adrenoreceptor‐ and nonadrenoreceptor‐mediated vasoconstriction during exercise.

]]>
<![CDATA[Bi‐exponential modeling derives novel parameters for the critical speed concept]]> https://www.researchpad.co/article/5c8bfad0d5eed0c484b23136

Abstract

All‐out exercise testing (AOT) has emerged as a method for quantifying critical speed (CS) and the curvature constant (D′). The AOT method was recently validated for shuttle running yet how that method compares with linear running is unknown. In the present study, we utilized a novel bi‐exponential model that derives CS and D′ with additional new parameters from the AOT method. Fourteen male athletes (age = 21.6 ± 2.2 years; height = 177 ± 70 cm; weight = 83.0 ± 11.8 kg) completed a graded exercise test (GXT) to derive maximum oxygen uptake (V˙O2max) and the average speed between gas exchange threshold and V˙O2max (sΔ50%), a linear AOT, and two shuttle AOTs. Measurement agreement was determined using intraclass correlation coefficient (ICC α), typical error (TE), and coefficient of variation (CV). The y‐asymptote (S0) of the speed‐time curve (3.52 ± 0.66 m·sec−1) did not differ from sΔ50% (3.49 ± 0.41 m·sec−1) or CS (3.77 ± 0.56 m·sec−1) (P = 0.34). Strong agreement was observed for estimates of CS (ICC α = 0.92, TE = 0.18 m·sec−1, and CV = 5.7%) and D′ (ICC α = 0.94, TE = 16.0 m, CV = 7.6%) with significant (P < 0.01) correlations observed between V˙O2max and CS and between S0 and V˙O2max (r values of 0.74 and 0.84, respectively). The time constant of the decay in speed (τd) and the amplitude between maximal speed and S0 (Ad) emerged as unique metrics. The Ad and τd metrics may glean new insights for prescribing and interpreting high‐intensity exercise using the AOT method.

]]>
<![CDATA[ ST/HR variables in firefighter exercise ECG – relation to ischemic heart disease]]> https://www.researchpad.co/article/5c61b98dd5eed0c48493ca07

Abstract

Exercise electrocardiography (ExECG) is regularly performed by Swedish firefighters by law. Heart rate‐corrected analysis of ST segment variables (ST/HR) has shown improved prediction of ischemic heart disease (IHD) compared to ST depression alone. This has not previously been extensively studied in asymptomatic persons with a low probability of IHD. We therefore evaluated the predictive performance of ST/HR analysis in firefighter ExECG. ExECG was studied in 521 male firefighters. During 8.4 ± 2.1 years, 2.3% (= 12) were verified with IHD by catheterization or myocardial scintigraphy (age 51.5 ± 5.5 years) and were compared with firefighters without imaging proof of IHD (44.2 ± 10.1 years). The predictive value of ST depression, ST/HR index, ST/HR slope, and area and rotation of the ST/HR loop was calculated as age‐adjusted odds ratios (OR), in 10 ECG leads. Predictive accuracy was analyzed with receiver operating characteristics (ROC) analysis. ST/HR index ≤−1.6 μV/bpm and ST/HR slope ≤−2.4 μV/bpm were associated with increased IHD risk in three individual leads (all OR > 1.0, < 0.05). ST/HR loop area lower than the fifth percentile of non‐IHD subjects indicated IHD risk in V4, V5, aVF, II, and –aVR (P < 0.05). ST depression ≤−0.1 mV was associated with IHD only in V4 (OR, 9.6, CI, 2.3‐40.0). ROC analysis of each of these variables yielded areas under the curve of 0.72 or lower for all variables and leads. Clockwise‐rotated ST/HR loops was associated with increased risk in most leads compared to counterclockwise rotation. The limited clinical value of ExECG in low‐risk populations was emphasized, but if performed, ST/HR analysis should probably be given more importance.

]]>
<![CDATA[Expiratory flow limitation under moderate hypobaric hypoxia does not influence ventilatory responses during incremental running in endurance runners]]> https://www.researchpad.co/article/5c75647bd5eed0c484cbb9c2

Abstract

We tested whether expiratory flow limitation (EFL) occurs in endurance athletes in a moderately hypobaric hypoxic environment equivalent to 2500 m above sea level and, if so, whether EFL inhibits peak ventilation (V˙Epeak), thereby exacerbating the hypoxia‐induced reduction in peak oxygen uptake (V˙O2peak). Seventeen young male endurance runners performed incremental exhaustive running on separate days under hypobaric hypoxic (560 mmHg) and normobaric normoxic (760 mmHg) conditions. Oxygen uptake (V˙O2), minute ventilation (V˙E), arterial O2 saturation (SpO2), and operating lung volume were measured throughout the incremental exercise. Among the runners tested, 35% exhibited EFL (EFL group, n = 6) in the hypobaric hypoxic condition, whereas the rest did not (Non‐EFL group, n = 11). There were no differences between the EFL and Non‐EFL groups for V˙Epeak and V˙O2peak under either condition. Percent changes in V˙Epeak (4 ± 4 vs. 2 ± 4%) and V˙O2peak (−18 ± 6 vs. −16 ± 6%) from normobaric normoxia to hypobaric hypoxia also did not differ between the EFL and Non‐EFL groups (all P > 0.05). No differences in maximal running velocity, SpO2, or operating lung volume were detected between the two groups under either condition. These results suggest that under the moderate hypobaric hypoxia (2500 m above sea level) frequently used for high‐attitude training, ~35% of endurance athletes may exhibit EFL, but their ventilatory and metabolic responses during maximal exercise are similar to those who do not exhibit EFL.

]]>