Submaximal Exercise Intensities Research Articles

Effects of Strength Training on Work Capacity and Parasympathetic Heart Rate Modulation During Exercise in Physically Inactive Men

This study was designed to assess the effects of strength training on work capacity and parasympathetic heart rate modulation during exercise in physically inactive men. Seventy-four men aged 20-45 were randomly assigned to training (n=52) and control (n=22) groups. Training groups underwent 10-weeks of progressive strength training. Body composition, one-repetition maximum half-squat and maximal oxygen uptake were measured before and after the intervention. Respiratory gases, heart rate and blood lactate were recorded during a VO2max test on a cycle ergometer. Parasympathetic heart rate modulation was analyzed based on the standard deviation of instantaneous beat-to-beat R-R interval variability (SD1) and its normalized unit (SD1n). Muscle strength and lean body mass increased in the training group. Compared to the control group, time to exhaustion increased significantly in the training group (p<0.05). SD1 and SD1n were elevated in the training group at submaximal exercise intensities (100 W, p<0.05). Blood lactate decreased at submaximal intensities when compared to the control group. Strength training increased exercise capacity, and improved vagal modulation of heart rate at submaximal exercise intensities. These changes may have favourable cardiovascular health implications for sedentary men during normal daily activities.

Oxygen deficits and oxygen delivery kinetics during submaximal intensity exercise in humans after 14 days of head-down tilt-bed rest

Beat-by-beat Q(a)O2 and breath-by-breath VO2 were assessed in ten male subjects (24 +/- 3.5 years; 78 +/- 7.7 kg; 182 +/- 5.6 cm) during cycling exercise at 50 W before and after a 14-day period of head-down tilt-bed rest (HDTBR). O2 deficit (DefO2) was calculated as the difference between the volume of O2 that would have been consumed if a steady state had been immediately attained minus that actually taken up during exercise. Q(a)O2 kinetics was described fitting the data with a non-linear mono-exponential model with time delay. Mean response times (MRT) of VO2 and Q(a)O2 kinetics were then calculated. DefO2 and MRT of VO2 response did not change after HDTBR, whereas MRT of Q(a)O2 kinetics increased. The invariance of VO2 kinetics after HDTBR suggests that, although Q(a)O2 response became slower after HDTBR, it did not affect the kinetics of peripheral gas exchange, which probably remained under the control of local muscular mechanisms.

Effect of low-dose endurance training on heart rate variability at rest and during an incremental maximal exercise test

We evaluated the effects of low-dose endurance training on autonomic HR control. We assessed the heart rate variability (HRV) of 11 untrained male subjects (36.8 +/- 7.2 years) at rest and during an incremental maximal aerobic exercise test prior to a 7-week preparatory period and prior to and following a 14-week endurance training period, including a low to high intensity exercise session twice a week. Total (0.04-1.2 Hz), low (0.04-0.15 Hz) and high (0.15-1.2 Hz) frequency power of HRV were computed by short-time Fourier transform. The preparatory period induced no change in aerobic power or HRV. The endurance training period increased peak aerobic power by 12% (P < 0.001), decreased the HR (P < 0.01) and increased all HRV indices (P < 0.05-0.01) at absolute submaximal exercise intensities, but not at rest. In conclusion, low-dose endurance training enhanced vagal control during exercise, but did not alter resting vagal HR control.

Oxidative Stress And Antioxidant Response In Trained Men After Different Exercise Intensities

Physical activity has been related to benefits in the organism. However, some research has shown that exercise may generate oxidative stress by increasing reactive oxygen species (ROS) production with an insufficient antioxidant response. The intensity of exercise seems to be associated with this oxidative damage. PURPOSE: The aim of this study was to evaluate the effect of different exercise intensities on oxidative stress and antioxidant response in trained sportsmen. METHODS: Twenty trained cyclists participated in this study performing two protocol test exercises of different intensity on a cycloergometer. Maximal effort consisted in a progressive incremental ergometric protocol test until voluntary exhaustion. The submaximal protocol was a steady state test performed at 75% VO2 max during 30 minutes. Trials were performed in an exercise laboratory room where temperature varied between 23 and 25°C and humidity was between 45 and 55%. Venous blood samples were collected from the antecubital vein before and after the exercise. Plasmatic and erythrocyte malondialdehyde (MDA) were determined as oxidative stress markers. Plasma and erythrocyte vitamin C and E were determined as antioxidant response systems. Plasma data were corrected by haematocrit. Erythrocyte parameters were expressed as U/g of haemoglobin. The Wilcoxon test was performed for statistical analysis. A p value of <0.05 was used to determine statistical significance. RESULTS: In maximal trial, the data showed an increase in plasma and erythrocyte MDA after test (from 40.64 ± 18.96 to 45.41 ± 18.44 μM; and from 0.21 ± 0.1 to 0.23 ± 0.12 μmol/g Hb; p<0.05). Plasma vitamin C increased after tests while erythrocyte vitamin C decreased (from 3.80 ± 1.60 to 5.20 ± 2.16 μg/mL; and from 130.53 ± 34.66 to 83.38 ± 30.01 μg/g Hb; p<0.05). Both plasma and erythrocyte vitamin E decreased after maximal efforts although no significant differences were found. In submaximal exercise, significant differences did not appear either in MDA, vitamin C or vitamin E. CONCLUSION: In trained sportsmen, maximal exercise intensity may influence more than submaximal exercise intensity on reactive oxygen species production and causes different responses in antioxidant vitamins.

Exercise Intensity Influences the Onset and Magnitude of Cardiovascular Drift

PURPOSE: While considerable research exists regarding the etiology of cardiovascular drift (CVD) its effects on metabolism are less clear. METHODS: Male competitive cyclists (n = 5) performed five exercise tests (2-day interval) on a calibrated cycle ergometer under standardized conditions: first, an incremental test, to determine VO2max and the lactate deflection point. The second test consisted of six incremental stages ranging in intensity from 30W below to 20W above the predetermined deflection point at 10W increments. The MLSS was then identified and participants performed three randomized 45-minute steady-state exercise bouts at 95%, 100%, and 105% of the intensity identified as the MLSS. Blood lactate samples were analyzed with a commercially available blood lactate analyzer, and oxygen consumption was analyzed with a metabolic gas analyzer. RESULTS: Onset of CVD (deflection from plateau) was different between the three exercise intensities (26±8 min for 95% MLSS, 21±6 min for 100%MLSS, and 17±4 min for 105%MLSS, p<0.05). The three exercise intensities yielded different heart rate, VO2 values, and blood lactate levels at every time point throughout the duration of exercise (p<0.05). CONCLUSIONS: We present evidence that small differences in submaximal exercise intensity result in differences in the onset and magnitude of cardiovascular drift. Supported by grants from the National Science Foundation (NSF-DUE-CCLI #0511219) the Mary Stuart Rogers Foundation, and an APS Undergraduate Summer Research Fellowship for 2007 (DBY).

The effect of caffeine ingestion on human neutrophil oxidative burst responses following time-trial cycling

Following fixed-duration exercise of submaximal intensity, caffeine ingestion is associated with an attenuation of the exercise-induced decline in N-formyl-methionyl-phenyl-alanine (f-MLP) stimulated neutrophil oxidative burst. However, the response following high-intensity exhaustive exercise is unknown. Nine endurance-trained male cyclists ingested 6 mg caffeine or placebo per kilogram of body mass 60 min before cycling for 90 min at 70% of maximal oxygen consumption ([Vdot]O2max) and then performing a time-trial requiring an energy expenditure equivalent to 30 min cycling at 70% maximum power output. Time-trial performance was 4% faster in the caffeine than in the placebo trial (P = 0.043). Caffeine was associated with an increased plasma adrenaline concentration after 90 min of exercise (P = 0.046) and immediately after the time-trial (P = 0.02). Caffeine was also associated with an increased serum caffeine concentration (P < 0.01) after 90 min of exercise and immediately after the time-trial, as well as 1 h after the time-trial. However, the f-MLP-stimulated neutrophil oxidative burst response fell after exercise in both trials (P = 0.002). There was no effect of caffeine on circulating leukocyte or neutrophil counts, but the lymphocyte count was significantly lower on caffeine (20%) after the time-trial (P = 0.003). Our results suggest that high-intensity exhaustive exercise negates the attenuation of the exercise-induced decrease in neutrophil oxidative burst responses previously observed when caffeine is ingested before exercise of fixed duration and intensity. This may be associated with the greater increase in adrenaline concentration observed in the present study.

Fitness, fatigue, disease activity, and quality of life in pediatric lupus

To measure aerobic fitness (maximum oxygen consumption [VO(2peak)]), fatigue, quality of life (QOL), and disease activity in young persons with systemic lupus erythematosus (SLE), and to determine an equation for predicting VO(2peak) from the distance walked in 6 minutes (6MW). Fifteen young patients ages 12-19 years with SLE participated. VO(2) was measured by a graded treadmill exercise test. Submaximal exercise intensity was determined from the ventilatory anaerobic threshold. Submaximal aerobic capacity was measured using the 6MW. Patient questionnaires included measures of fatigue, QOL, and physical activity. Physician questionnaires included the Systemic Lupus Erythematosus Disease Activity Index and the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index. Compared with age-matched norms, our patients had moderate impairment in aerobic fitness, with a mean +/- SD VO(2peak) of 31.1 +/- 7.9 ml/minute/kg and a mean 6MW distance Z score of -2.4 +/- 2.3. The regression equation to predict VO(2peak) (ml/minute/kg) from 6MW was as follows: 57.1 + [0.038 x distance (meters)] + (-0.35 x maximal heart rate) (R = 0.67, P = 0.027). Ten subjects (67%) reported significant fatigue. There was no significant correlation of fatigue with fitness measures. Neither fatigue nor fitness was significantly correlated with disease activity, disease damage, or QOL measures. Young SLE patients have lower aerobic fitness than reference norms. The 6MW may be used as a marker of fitness, but it is preferable to determine VO(2) with a graded exercise test. Fatigue is a significant symptom in young SLE patients. The application of fatigue measures in young persons is exploratory. The relationship between fatigue and aerobic fitness is not clear.

Validity of Values for Metabolic Equivalents of Task During Submaximal All-Extremity Exercise and Reliability of Exercise Responses in Frail Older Adults

Physical therapists and rehabilitation professionals in hospital and long-term care centers are using all-extremity semirecumbent exercise machines in their treatment programs. This study was undertaken to investigate the concurrent validity of values for software-generated metabolic equivalents of task (MET) from an all-extremity semirecumbent exercise machine and directly measured values for MET from a portable metabolic unit across a range of submaximal exercise intensities. A second purpose of this study was to determine the test-retest reliability of oxygen consumption and heart rate responses in older adults between standardized sessions of submaximal all-extremity aerobic exercise. The study participants were 18 older adults (mean age=82 years, SD=5; 3 women, 15 men) who were living in long-term care centers and who completed 2 test sessions of a standardized exercise protocol 1 week apart. The exercise protocol included a warm-up period, three 4-minute stages of exercise at incremental workload levels, and a cool-down period. The breath-by-breath metabolic data from the portable metabolic unit, heart rate, MET values from the exercise machine, Borg Rating of Perceived Exertion, and watts were recorded continuously throughout the exercise protocol. The concurrent validity of the MET values from the exercise machine and the portable metabolic unit ranged from very good to excellent on both day 1 and day 2 (r=.85-.97). The test-retest reliability of subjects' heart rate responses and MET values from the portable metabolic unit was moderate to high across submaximal exercise intensities (intraclass correlation coefficients [2,1]=.85-.91). The exercise machine software-generated MET values were representative of directly measured oxygen consumption values across a range of submaximal intensities during all-extremity semirecumbent exercise in older adults with multisystem impairments.

PGC-1α: important for exercise performance?

since the identification of the transcriptional coactivator peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α as a factor interacting with PPARγ in brown adipose tissue (BAT) ([12][1]), it has become clear that PGC-1α plays important roles in regulating several cellular processes

Recruitment of single muscle fibers during submaximal cycling exercise

In literature, an inconsistency exists in the submaximal exercise intensity at which type II fibers are activated. In the present study, the recruitment of type I and II fibers was investigated from the very beginning and throughout a 45-min cycle exercise at 75% of the maximal oxygen uptake, which corresponded to 38% of the maximal dynamic muscle force. Biopsies of the vastus lateralis muscle were taken from six subjects at rest and during the exercise, two at each time point. From the first biopsy single fibers were isolated and characterized as type I and II, and phosphocreatine-to-creatine (PCr/Cr) ratios and periodic acid-Schiff (PAS) stain intensities were measured. Cross sections were cut from the second biopsy, individual fibers were characterized as type I and II, and PAS stain intensities were measured. A decline in PCr/Cr ratio and in PAS stain intensity was used as indication of fiber recruitment. Within 1 min of exercise both type I and, although to a lesser extent, type II fibers were recruited. Furthermore, the PCr/Cr ratio revealed that the same proportion of fibers was recruited during the whole 45 min of exercise, indicating a rather constant recruitment. The PAS staining, however, proved inadequate to fully demonstrate fiber recruitment even after 45 min of exercise. We conclude that during cycling exercise a greater proportion of type II fibers is recruited than previously reported for isometric contractions, probably because of the dynamic character of the exercise. Furthermore, the PCr/Cr ratio method is more sensitive in determining fiber activation than the PAS stain intensity method.

Overall and peripheral ratings of perceived exertion during a graded exercise test to volitional exhaustion in individuals of high and low fitness

This study assessed the relationship between differentiated ratings of perceived exertion (RPE) and heart rate with oxygen uptake (VO2) during two graded exercise tests (GXT) to exhaustion on a cycle ergometer in 49 men and women (19-50 years) of high and low fitness. The study also assessed whether sub-maximal RPE values elicited during the GXTs could provide appropriate estimates of maximal aerobic power (VO2max) Peripheral RPE (RPEP) was higher than overall RPE (RPEO) at exhaustion in both groups (P<0.001), but the reliability of the terminal RPEO was higher (0.75 and 0.40, respectively). Fitness did not moderate the relationship of RPEO and RPEP with VO2 during the GXTs (P>0.05). However, the correlation for RPEP and VO2 was higher for women compared to men (0.98 and 0.96, respectively, P<0.05), although this is of little practical significance. In both groups, RPEO was almost as highly correlated with VO2 as heart rate during GXTs terminated at exhaustion (approximately 0.955-0.980). There were no differences between predicted and measured VO2max when VO2 values were extrapolated from sub-maximal RPEO (13, 15 and 17) intensities (42.1+/-12.5, 43.4+/-11.5, 44.2+/-11.3 and 43.3+/-10.0 ml kg(-1) min(-1), respectively). However, VO2max predicted from sub-maximal RPEP intensities was significantly lower (P<0.05). In conclusion, terminal RPEO was a more reliable measure of the RPE, and provided more accurate estimates of VO2max in healthy participants of high and low fitness when elicited from sub-maximal exercise intensities.

Prediction of maximal oxygen uptake from the ratings of perceived exertion and heart rate during a perceptually-regulated sub-maximal exercise test in active and sedentary participants

This study assessed whether the accuracy of predicting maximal oxygen uptake (VO2max) from sub-maximal heart rate (HR) and ratings of perceived exertion (RPE) values was moderated by gender and habitual activity. In total, 27 men and 18 women completed two GXTs to determine VO2max and three perceptually-regulated GXTs, incremented by RPE 9, 11, 13, 15 and 17. The RPE and HR were individually regressed against VO2max (approximately 0.96) to enable predictions of VO2max. The VO2max was predicted from three RPE ranges (9-17, 9-15, 9-13). The RPE ranges were extrapolated to RPE(19), RPE(20) and age-predicted maximal HR (HRmax(pred)). ANOVA revealed no differences between measured and predicted VO2max (P > 0.05) when the RPE range 9-17 was extrapolated to RPE(19) and HRmax(pred). Extrapolation of RPE 9-17 to RPE(20) overestimated VO2max (P < 0.05), but no differences were observed when predicted from the RPE ranges 9-15 and 9-13. The prediction of VO2max was not moderated by gender or activity status. Hierarchical regression analysis revealed that HR explained additional variance in VO2max when added to the RPE (2%). Hierarchical multiple regression analysis also indicated that VO2max was significantly correlated with power output at sub-maximal RPE values of 13 and 15 (P < 0.01) in men and women. The addition of HRmax(pred) improved the accuracy of the prediction equation for men (P = 0.05) but not for women. The study confirmed the validity of estimating VO2max from perceptually-regulated, sub-maximal GXT and indicated the potential utility of regression analysis to gauge appropriate sub-maximal exercise intensities.

Low doses of caffeine reduce heart rate during submaximal cycle ergometry

BackgroundThe purpose of this study was to examine the cardiovascular effects of two low-levels of caffeine ingestion in non habitual caffeine users at various submaximal and maximal exercise intensities.MethodsNine male subjects (19–25 yr; 83.3 ± 3.1 kg; 184 ± 2 cm), underwent three testing sessions administered in a randomized and double-blind fashion. During each session, subjects were provided 4 oz of water and a gelatin capsule containing a placebo, 1.5 mg/kg caffeine, or 3.0 mg/kg caffeine. After thirty minutes of rest, a warm-up (30 Watts for 2 min) the pedal rate of 60 rpm was maintained at a steady-state output of 60 watts for five minutes; increased to 120 watts for five minutes and to 180 watts for five minutes. After a 2 min rest the workload was 180 watts for one minute and increased by 30 watts every minute until exhaustion. Heart rate (HR) was measured during the last 15-seconds of each minute of submaximal exercise. Systolic blood pressure (BP) was measured at rest and during each of the three sub-maximal steady state power outputs. Minute ventilation (VE), Tidal volume (VT), Breathing frequency (Bf), Rating of perceived exertion (RPE), Respiratory exchange ratio (RER), and Oxygen consumption (VO2) were measured at rest and during each minute of exercise.ResultsCaffeine at 1.5 and 3.0 mg/kg body weight significantly lowered (p < 0.05) HR during all three submaximal exercise intensities compared to placebo (range – 4 to 7 bpm lower) but not at rest or maximal exercise. BP was significantly higher (p < 0.05) at rest and after the 3 mg/kg caffeine vs placebo (116 ± 13 vs 123 ± 10 mm Hg). Neither dose of caffeine had any effect on BP during submaximal exercise. Caffeine had no effect on VE, VT, VO2, RPE, maximal power output or time to exhaustion.ConclusionIn non habitual caffeine users it appears that consuming a caffeine pill (1.5 & 3.0 mg/kg) at a dose comparable to 1–3 cups of coffee lowers heart rate during submaximal exercise but not at near maximal and maximal exercise. In addition, this caffeine dose also only appears to affect systolic blood pressure at rest but not during cycling exercise.

Muscle Oxygenation during Incremental Arm and Leg Exercise in Professional Rugby Union Players

PURPOSE: The study was aimed to compare modifications of muscle oxygenation during arm and leg incremental exercise in rugby players. METHODS: 22 male players from a single professional team of the Italian senior A championship (25 ± 5 years; body mass 89 ± 14 Kg; high 177 ± 6 cm; Body fat 15 ± 7 %) performed incremental exercises to exhaustion on arm crank (ARM) and cycle ergometer (CYC). Ventilation, gas exchange and heart rate (HR) were measured breath by breath with a metabolic chart. Changes in concentration of deoxygenaed hemoglobin (δ[deoxyHb], an index of the ratio between O2 utilization and O2 delivery, that is conceptually similar to O2 extraction, were monitored non-invasively by near infrared spectroscopy at the vastus lateralis (for CYC) and at the biceps brachii (for ARM) and data were expressed as % of the values obtained during limb ischemia. Submaximal and maximal values were calculated as an average of the last 10s of each work load and upon exhaustion and data were compared by paired t test. RESULTS: VO2 increased as a function of power output (W), with a significantly higher slope in ARM test compared to CYC test. Oxygen pulse (O2p) and O2 extraction also increased as a function of workload in both ARM and CYC tests. At equal submaximal levels of VO2, O2p was significantly lower and O2 extraction was significantly higher in ARM compared to CYC exercise. Upon exhaustion maximal values of HR (overall average 176 ± 14 b*min-1) and respiratory quotient (1,11 ± 0,07) were reached, with no significant differences between testing modalities. Signifcantly higher values of maximal power W (172 ± 13 watt vs 263 ± 21) and VO2 (36 ± 6 ml*kg-1*min-1 vs 46 ± 6) were reached in CYC vs ARM, ARM VO2max representing 79±9% of CYC value. Maximal O2p was lower (18 ± 3 ml*b-1 vs 23 ± 3) and O2 extraction was significantly higher (81 ± 8 % of ischemia vs 70 ± 19%) in ARM compared to CYC exercise. CONCLUSION: Our data suggest, at both maximal and submaximal exercise intensity, a higher O2 extraction compared to O2 delivery in ARM vs CYC exercise in rugby players.

Plasma ghrelin responses to acute sculling exercises in elite male rowers

The regulatory effect of ghrelin on growth hormone (GH) is limited in describing ghrelin response to acute submaximal exercise intensities in elite athletes. We investigated the effects of a single sculling exercise performed above and below the individual anaerobic threshold (IAT) on total ghrelin concentration in highly trained male rowers. Nine elite male rowers (20.1 +/- 3.7 years; 190.0 +/- 5.2 cm; 89.6 +/- 4.6 kg; %body fat: 9.9 +/- 2.5%) volunteered for this study. Single scull rowing was performed below and above IAT using a mean of 5 bpm above and below the heart rate of the IAT during graded exercise test. Ghrelin, leptin, GH, insulin, and glucose were measured before, immediately after, and after 30 min of recovery. Plasma ghrelin concentration did not increase significantly in either exercise but was approaching significance after 30 min of recovery (P = 0.051) when the constant load sculling was performed at the intensity above the IAT. There were no changes in plasma leptin levels. GH increased significantly immediately after exercise and remained elevated during the 30 min of recovery in both exercise conditions, while insulin decreased significantly immediately after exercise and remained significantly lower after the 30 min of recovery in both exercise intensities. Baseline ghrelin was not correlated with the body composition, physical performance, or blood biochemical data. There was no significant relationship between plasma ghrelin and other blood variables immediately after the 30 min of recovery in both exercise tests and changes in ghrelin were not related to blood biochemical variables after the exercise tests. The acute constant load sculling exercise above or below IAT that increased GH concentrations did not significantly increase the circulating plasma ghrelin levels.

Inspiratory muscles do not limit maximal incremental exercise performance in healthy subjects.

We investigated whether the inspiratory muscles affect maximal incremental exercise performance using a placebo-controlled, crossover design. Six cyclists each performed six incremental exercise tests. For three trials, subjects exercised with proportional assist ventilation (PAV). For the remaining three trials, subjects underwent sham respiratory muscle unloading (placebo). Inspiratory muscle pressure (P(mus)) was reduced with PAV (-35.9+/-2.3% versus placebo; P<0.05). Furthermore, V(O2) and perceptions of dyspnea and limb discomfort at submaximal exercise intensities were significantly reduced with PAV. Peak power output, however, was not different between placebo and PAV (324+/-4W versus 326+/-4W; P>0.05). Diaphragm fatigue (bilateral phrenic nerve stimulation) did not occur in placebo. In conclusion, substantially unloading the inspiratory muscles did not affect maximal incremental exercise performance. Therefore, our data do not support a role for either inspiratory muscle work or fatigue per se in the limitation of maximal incremental exercise.

Effects of Hemopure™ on Maximal Oxygen Uptake and Endurance Performance in Healthy Humans

Haemoglobin-based oxygen carriers (HBOCs) such as Hemopure are touted as a tenable substitute for red blood cells and therefore potential doping agents, although the mechanisms of oxygen transport of HBOCs are incompletely understood. We investigated whether infusion of Hemopure increased maximal oxygen uptake (V.O 2max) and endurance performance in healthy subjects. Twelve male subjects performed two 4-minute submaximal exercise bouts equivalent to 60 % and 75 % of V.O (2max) on a cycle ergometer, followed by a ramped incremental protocol to elicit V.O (2max). A crossover design tested the effect of infusing either 30 g (6 subjects) or 45 g (6 subjects) of Hemopure versus a placebo. Under our study conditions, Hemopure did not increase V.O (2max) nor endurance performance. However, the infusion of Hemopure caused a decrease in heart rate of approximately 10 bpm (p=0.009) and an average increase in mean ( approximately 7 mmHg) and diastolic blood pressure ( approximately 8 mmHg) (p=0.046) at submaximal and maximal exercise intensities. Infusion of Hemopure did not bestow the same physiological advantages generally associated with infusion of red blood cells. It is conceivable that under exercise conditions, the hypertensive effects of Hemopure counter the performance-enhancing effect of improved blood oxygen carrying capacity.

Is the healthy respiratory system (always) built for exercise?

Is the healthy respiratory system (always) built for exercise?

A Comparison of Laryngoplasty and Modified Partial Arytenoidectomy as Treatments for Laryngeal Hemiplegia in Exercising Horses

To compare upper airway mechanics, arterial blood gases, and tracheal contamination in horses with induced left laryngeal hemiplegia (recurrent laryngeal neuropathy [RLN]) treated by laryngoplasty/vocal cordectomy (LPVC) or modified partial arytenoidectomy (MPA). Repeated measures under the following conditions: Control, RLN, LPVC, and MPA. Six horses. Two trials were conducted under all conditions at 80% and 100% of maximal heart rate (HR(max)). In Trial 1, arterial blood gases, tracheal and pharyngeal pressures, and laryngeal videoendoscopy were recorded. In Trial 2, upper airway pressure and airflow were determined. Tracheobronchial aspirates were performed after exercise to quantify airway contamination. Compared with control, RLN significantly increased inspiratory impedance and worsened exercise-induced hypoxemia. At 80% HR(max), LPVC restored most variables to control values. At 100% HR(max), LPVC improved all variables, but did not restore minute volume, arterial pH, and PaCO(2). At 80% HR(max), MPA restored all variables except bicarbonate to control values. At 100% HR(max), MPA improved all variables, but did not statistically restore minute ventilation or bicarbonate level. Only minor differences were noted between LPVC and MPA. Both resulted in equivalent tracheal contamination. Airway mechanics and arterial blood gas values were not restored to normal after either LPVC or MPA in horses exercising at HR(max). This does not affect ventilation at sub-maximal exercise, but has clinical implications at HR(max). Both procedures diminish normal laryngeal protective mechanisms. At sub-maximal exercise intensities both LPVC and MPA restore airway ventilation to normal. At maximal exercise the superiority of LPVC over MPA is slight.

The reliability of the i-STAT clinical portable analyser

The purpose of this investigation was to assess the reliability of the i-STAT clinical portable analyser and CG(4)(+) cartridge measures of blood pH, partial pressures of O(2) (pO(2)) and CO(2) (pCO(2)), bicarbonate ([HCO(3)(-)]), base excess (BE), total carbon dioxide (TCO(2)), oxygen saturation (sO(2)) and blood lactate ([BLa(-)]) at various exercise intensities. A comparison between [BLa(-)] measured by the i-STAT and the Accusport lactate analysers during an intermittent treadmill run was also undertaken. The technical error of measurement (TEM%) at rest, at moderate (200W) and maximal exercise (V O(2)max) was acceptable (<15%) for all parameters. The intra-class correlation coefficients for each analyte ranged from weak-to-strong across resting (ICC=0.19-0.96) and moderate (ICC=0.30-0.96) exercise intensities. The ICC for all analytes were observed to be strong following maximal intensity exercise (ICC=0.77-0.95). The comparison of the [BLa(-)] measures between the i-STAT and Accusport showed that the difference between measures was acceptable at both low (<4mmolL(-1)) (-0.39+/-0.27mmolL(-1)), moderate to high concentrations (>4mmolL(-1)) (0.58+/-1.22mmolL(-1)), and across all [BLa(-)] data (0.36+/-1.13mmolL(-1)). In conclusion, the i-STAT clinical analyser and CG(4)(+) cartridge provides reliable measures of a number of blood parameters across exercise intensities. The [BLa(-)] measures from the i-STAT analyser are consistent with that of the Accusport lactate analyser.