HRpeak Values Research Articles

Poultry Gastrointestinal-derived Lactic Acid Bacteria (pGIT-d-LAB) Inhibit Multiple Antibiotics Resistance Bacterial and Fungal Pathogens.

To develop a probiotic formulation for poultry feed, a few poultry gastrointestinal derived lactic acid bacteria (pGIT-d-LAB) were isolated from chicken intestinal specimens and in vitro experiment was performed to evaluate their efficacy as potential probiotic candidate. A total of 6 strains of LAB: Lactobacillus brevis (L. brevis), Lactobacillus acidophilus (L. acidophilus), Lactobacillus casei (L. casei), Pediococci spp, Lactobacillus fermentum (L. fermentum) and Lactobacillus plantarum (L. plantarum) were isolated and cultured for collection of Cell Free Supernatant (CFS). CFS collected was tested against pathogenic bacterial isolated from chicken feces as well as prevalent fungal pathogens, utilizing agar-well diffusion techniques. A preliminary investigation into the susceptibility of the pathogens to diverse antibiotics and antifungal drugs was conducted. Bacterial pathogens exhibiting resistance to a minimum of three classes of antibiotics were subsequently identified for pGIT-d-LAB CFS screening. The observed results revealed that the CFS derived from the isolates exhibited varying degrees of growth inhibition against different pathogens. Among the tested pGIT-d-LAB isolates, L. acidophilus demonstrated the most prominent zone of inhibition, measuring 18 mm against Klebsiella pneumoniae ZTAC 1233. Notably, Citrobacter diversus ZTAC 1255 showed resistance to all tested pGIT-d-LAB. Quantification of the metabolites produced was performed, and peak production levels was determined. L. acidophilus produced the highest amount of lactic acid (1.789g/l), Pediococci spp. produced the highest amount of diacetyl and H202 (1.918g/l) (0.0025g/l) at 48 hr peak values respectively. The test isolates are potential probiotic candidates for controlling pathogens in poultry.

Physical exercise may improve problem-solving skills and emotional intelligence in patients with relapsing-remitting multiple sclerosis: A cross-sectional study

BackgroundMultiple sclerosis is a disease that can reduce the quality of life with a physical disability, neuropsychiatric disorders, and cognitive dysfunctions. Therefore, multiple sclerosis treatment should include treatments for cognitive and neuropsychiatric disorders and pharmacological treatments. This study aimed to examine the effects of exercise on neuropsychiatric disorders, problem-solving skills, and emotional intelligence in multiple sclerosis patients. MethodsThirty-six female relapsing-remitting multiple sclerosis patients aged between 18 and 45 years, with an Expanded Disability Status Scale between 1 and 3, who were diagnosed with definitive multiple sclerosis according to the revised McDonald criteria were included in the study. Participants completed outcome measures before and after the 12-week exercise program. Demographic/clinical information of the participants was obtained at baseline, neurological examinations were performed, and graded exercise testing on a bicycle ergometer was performed to determine aerobic capacity. Short Form-12 Version 2, Hospital Anxiety and Depression Scale, Modified Fatigue Impact Scale, Problem-Solving Inventory, Emotional Intelligence Scale were evaluated before and after the exercise program of the participants. ResultsWhile a significant increase was observed in the HRpeak values ​​of the participants after the exercise (p < 0.05), the VO2max values also showed a highly significant difference compared to the pre-treatment values. (p < 0.01). While a significant difference was detected in the mental subparameter of Short Form-12 (p < 0.05), a high level of significant difference was found in the physical subparameter (p < 0.01). While no significant difference was observed in the Hospital Anxiety and Depression Scale anxiety subparameter (p > 0.05), a significant difference was found in the depression subparameter (p < 0.01). There was a significant difference in Modified Fatigue Impact Scale physical and cognitive subparameters compared to pre-treatment (p < 0.01). A significant difference was observed in the Emotional Intelligence Scale total score after the treatment (p < 0.01). ConclusionsThe results of our study showed that exercise in relapsing-remitting multiple sclerosis patients provided significant improvements in emotional intelligence, improved neuropsychiatric parameters, and increased problem-solving skills. In addition, to the best of our knowledge, this study is the first study in the literature to investigate the effect of physical activity exercises on problem-solving skills in multiple sclerosis patients.

O Exercício Físico em Meio Aquático e o seu Papel na Fase III de um Programa de Reabilitação Cardíaca

Introduction : The benefits of land-based aerobic physical training in patients with cardiac pathology are well studied. However, there are patients who, for personal reasons or osteoarticular limitations, prefer to exercise in water, so it is important to understand the advantages, disadvantages and precautions to be taken when the rehabilitation plan is carried out in an aquatic environment. Methods : To carry out this narrative review, the following databases were accessed: MEDLINE, SCOPUS and Web of Science. Results :With the increase of the immersion depth, the heart fills and consequent systolic volume increases, but the heart rate (HR) decreases. Peak oxygen uptake (VO2peak) and HRpeak values are 84% and 95% lower in water compared to those observed out of water, respectively. Therefore, a reduction of 13% or 10 bpm in relation to the target HR values established out of water is recommended. Aquatic exercise induces an increase in heart rate variation and cardiac autonomic modulation, both of which have a positive impact on the prognosis of these patients. Conclusion : Physical exercise in water is safe, provides cardiovascular protection and improves the prognosis in low-risk cardiac patients who are in phase III of the cardiac rehabilitation program and who, for musculoskeletal or personal reasons, prefer to perform exercise in this context.

Quantifying the Physical Response to a Contemporary Amateur Boxing Simulation.

Finlay, MJ, Greig, M, and Page, RM. Quantifying the physical response to a contemporary amateur boxing simulation. J Strength Cond Res 32(4): 1005-1012, 2018-This study examined the physical response to a contemporary boxing-specific exercise protocol (BSEP), based on notational analysis of amateur boxing. Nine male senior elite amateur boxers completed a 3 × 3-minute BSEP, with a 1-minute passive recovery period interspersing each round. Average (HRave) and peak (HRpeak) heart rates, average (V[Combining Dot Above]O2ave) and peak oxygen consumptions (V[Combining Dot Above]O2peak), blood lactate (BLa) concentrations, rating of perceived exertion, and both triaxial and uniaxial PlayerLoad metrics were recorded during the completion of the BSEP. Blood lactate concentration increased significantly in each round (Round 1 = 2.4 ± 1.3 mmol·L; Round 2 = 3.3 ± 1.7 mmol·L; Round 3 = 4.3 ± 2.6 mmol·L). Significantly lower HRave and HRpeak values were found in the first round (HRave: 150 ± 15 b·min; HRpeak: 162 ± 12 b·min) when compared with the second (HRave: 156 ± 16 b·min; HRpeak: 166 ± 13 b·min) and third (HRave: 150 ± 15 b·min; HRpeak: 169 ± 14 b·min). No significant differences were found in any of the V[Combining Dot Above]O2 or PlayerLoad metrics recorded during the BSEP. The BSEP based on notational analysis elicited a fatigue response across rounds, confirming its validity. The BSEP can be used as a training tool for boxing-specific conditioning with implications for reduced injury risk, and to assess the physical response to boxing-specific interventions. Moreover, the BSEP can also be manipulated to suit all levels of participants or training phases, with practical applications in performance monitoring and microcycle periodization.

The Use of a Wheelchair Propulsion Field Test to Determine Peak Heart Rate in Children and Adolescents With Myelomeningocele.

We analyzed the evolution and pattern of heart rate (HR) during the 12-minute wheelchair propulsion field test (WPFT) and compared the peak HR (HRpeak) from the WPFT to the HRpeak obtained in the progressive cardiopulmonary exercise test on arm cranking ergometer (ACT). We aimed to determine if the field test detects the HRpeak consistently and could be used in clinical practice. Eleven wheelchair-using children and adolescents with myelomeningocele (aged 8-15y) performed a maximal ACT and a 12-minute WPFT. HR was recorded continuously at rest, during each minute of the tests, and at recovery. Mixed analysis of variance was used to compare the variables at rest and peak. Bland-Altman plot and Lin's concordance correlation coefficient were used to show agreement between the tests. During minute 2 of the WPFT, participants reached 73%-96% of the HRpeak values recorded in the ACT. From minutes 4 to 12, participants reached HRpeak values ranging 86%-109% of the values recorded in the ACT. There is agreement between the ACT and the WPFT tests. WPFT with minimal duration of 4minutes may be an alternative tool to obtain HRpeak in children and adolescents with myelomeningocele.

Physiological Responses and Time-Motion Analysis of Small Combat Games in Kickboxing: Impact of Ring Size and Number of Within-Round Sparring Partners.

Ouergui, I, Houcine, N, Marzouki, H, Davis, P, Franchini, E, Gmada, N, and Bouhlel, E. Physiological responses and time-motion analysis of small combat games in kickboxing: impact of ring size and number of within-round sparring partners. J Strength Cond Res 31(7): 1840-1846, 2017-The study aimed to investigate the physiological responses and time-structure of small combat games (SCGs) in kickboxing according to ring sizes and number of sparring partners. Twenty athletes from regional (n = 13) and national levels (n = 7) participated in the study (mean ± SD, age: 20.3 ± 0.9 years; height: 177 ± 4.8 cm; body mass: 71.8 ± 10.5 kg). Blood lactate concentration [La] was measured before and after bouts, and the delta (Δ) was determined. Heart rate (HR) was measured throughout and HR and rating of perceived exertion (RPE) were also measured postbout. The HRpre, HRmean, and percentage of peak HR (%HRpeak) were used for analysis. The HRpeak was determined during a cycle ergometer graded exercise test. Each athlete was confronted by 1 (1 vs. 1; no sparring partner change), 2 (1 vs. 2) and 4 opponents (1 vs. 4) within-round (sparring partner change every 1 minute or 30 seconds, respectively) in different ring sizes (i.e., 2×2 m, 4×4 m, and 6×6 m). All combats were recorded and analyzed to determine the duration of different activity phases (high-intensity activities [HIA], low-intensity actions [LIA], and referee pause [P]). Results showed that values for HRpre and HRmean when opposed by a single individual (1 vs. 1) were lower than other conditions (all p < 0.001). Moreover, %HRpeak values in 1 vs. 1 were lower than in other conditions and higher in 4 × 4 m compared with other sizes. [La]pre, post, and the Δ did not differ among all conditions (p > 0.05). The RPE scores were lower in 1 vs. 1 compared with other conditions (p < 0.001), with no ring sizes effect (p > 0.05). For time-motion variables, HIA values were lower in 1 vs. 1 than in the 2 other conditions and was longer in 2 × 2 m compared with 4 × 4 m and 6 × 6 m, whereas LIA values were higher in 1 vs. 1 and lower in the 2 × 2 m. In conclusion, SCGs seem to be a good form of exercise for sufficient cardiovascular conditioning specific to kickboxing activity in comparison with data from previous studies.

Treadmill vs. Cycle Ergometry Graded Exercise Test Responses in Multiple Sclerosis Patients

INTRODUCTION: Cardiorespiratory fitness is measured by peak oxygen consumption (VO2max) and is one of the strongest predictors of all-cause and cardiovascular disease mortality. In a healthy adult population, VO2max values obtained on a treadmill are approximately 10-15% higher than those yielded by cycle ergometry. VO2max testing in those with multiple sclerosis (MS) is typically performed on a cycle ergometer, as loss of walking mobility or balance issues may limit treadmill walking. Therefore, potential mode-specific differences in VO2max may result in the inability to accurately assess MS patients’ risk and lead to inaccurate exercise prescriptions in this cohort. PURPOSE: To compare hemodynamic, ventilatory, and cardiorespiratory responses between graded exercise tests performed on both a treadmill and cycle ergometer in individuals with relapsing-remitting MS. METHODS: Twenty persons with MS (42±11 years, 11±10 years since Dx, 26.9±6.5 kg[BULLET OPERATOR]m-2) completed two VO2max tests approximately 1 week apart, with random order of testing. Treadmill tests consisted of a constant, self-determined speed with an increase in grade of 2% every two minutes. Cycle ergometry tests increased wattage by 15 watts per minute. A repeated measures ANOVA was used to investigate differences in testing response to both treadmill and cycle ergometry. RESULTS: Treadmill testing resulted in VO2max values that were 11% higher and respiratory exchange ratio (RER) values that were 8% lower than those obtained via cycle ergometry. See Table 1. DISCUSSION: Relapsing-remitting MS patients exhibit a mode-related difference in VO2max similar to healthy adults. Therefore, exercise prescriptions or study designs cannot directly calculate submaximal workloads for one mode based on maximal data obtained from the other. Additionally, while HRpeak values are within normal limits, they’re bordering chronotropic incompetence.Table 1: Mean ± SD. *p<0.05 between Treadmill and Cycle Ergometer

FOVEX – An expert system for the detection of overreaching

Introduction Overreaching is defined as a stress-induced (training and non-training) state resulting in the short-term decrement of performance. Overtraining, in contrast, results in a long-term decrement of performance (Kreider, Fry, & O’Toole, 1998). A diagnosis for overreaching can, per definition, be solely made by identifying a reduction in performance (Halson & Jeukendrup, 2004). However, a resulting reduction of training load based on such a diagnosis might not be accepted since some coaches intentionally lead their athletes to fatigued states in order to achieve supercompensation (Halson & Jeukendrup, 2004). Several studies have investigated factors influencing overreaching and overtraining. However, the number of factors might be too high and, additionally, their individual contribution cannot be fixed to a single formula. What is more, some of these factors, such as the blood-lactate kinetic during a graded exercise test, can only be determined in an invasive manner. Moreover, other parameters, such as the leucocyte number (Mackinnon, 2000), require laboratory equipment for their correct determination. Another drawback of these studies is that most of the parameters were determined after an overloading period i.e. at a moment when it might have been too late to react to the possible overreaching or overtraining in a real-world coaching scenario. This paper presents the expert system FOVEX for the early detection of a possible overreaching. Expert systems are a special case of knowledge-based systems (KBS) deriving knowledge from facts using rules. They are composed of a knowledge base (initial facts) and an interference engine. Using rules, additional facts can be asserted from the knowledge base and thus a conclusion can be derived.  Methods The system requires the athletes to send data about their training sessions (for example heart rate and power) and well-being to a server where it is stored and analysed. In addition to their training data, the athletes are required to give answers to a short questionnaire which asks for factors such as perceived exertion, pain and mood state as these parameters have been found to have an influence on overreaching (Le Meur et al., 2013; Mackinnon, 2000). Based on the data of a training session various metrics are computed. These metrics can include the maximal heart rate during a session HRpeak, Heart rate recovery rate (HRR) after an interval (Aubry et al., 2015). Changes in these parameters indicate symptoms of overreaching. Another parameter is the training load of each session which is also computed as an accumulated metric, i.e. the weekly training load as an increase in training load is a factor contributing to overreaching. From these metrics and parameters the rules from the KBS are used to derive facts such as “Performance decrease” and “HRR increase”. Based on these facts additional rules are then used to check whether there is an indication for overreaching. In case that an athlete shows signs of overreaching due to the newly added data, the coach receives a notification.  Results The system was evaluated using the data provided by Aubry et al. The findings of the study were transformed into rules as follows: Since decreased performances in the laboratory test were used as main predictor for the classification of overreaching by Aubry et al., the provided peak power output was set to be monitored for decreases. The main finding of the study was that the overreaching athletes “demonstrated a very large increase in HRR” (Aubry et al., 2015), so these values were monitored for increases. Additionally, HRR60s (heart rate 60 seconds after cessation of the test) and HRpeak values were monitored for decreases. Using these four assertions the system was able to classify all 31 datasets correctly as “overreached” or “not overreached” according to the classification by Aubry et al. Discussion The presented system derives a warning for possible overreaching from training data and data about the mood state as well as pain of the athlete. Rather than a post-hoc classification of athletes as overreaching, FOVEX aims at providing coaches a tool to detect early warning signs and thus avoid complications posed by overreaching.

Acute Cardiopulmonary and Metabolic Responses to High-Intensity Interval Training Protocols Using 60 s of Work and 60 s Recovery.

Rozenek, R, Salassi III, JW, Pinto, NM, and Fleming, JD. Acute cardiopulmonary and metabolic responses to high-intensity interval training protocols using 60 s of work and 60 s recovery. J Strength Cond Res 30(11): 3014-3023, 2016-Low-volume, high-intensity interval training (HIIT) consisting of 60 s work and 60 s recovery (60 s/60 s) repeated for 10 times has previously been found to produce beneficial cardiopulmonary, cellular, and metabolic adaptations in healthy and at-risk populations. There is currently relatively little information pertaining to the acute changes that take place during individual training sessions. The purpose of this study was to examine the acute physiological responses to 60 s/60 s × 10 HIIT protocols using several combinations of work and recovery intensities. Eleven healthy adults (mean age ± SD = 26.0 ± 5.3 years) performed 4 HIIT trials on separate days at varying percentages of peak power output that consisted of the following work/recovery intensities: (a) 80% PPO/0% PPO (80/0); (b) 80% PPO/50% PPO (80/50); (c) 100% PPO/0% PPO (100/0); and (d) 100% PPO/50% PPO (100/50). Compared with the other protocols, 100/50 produced higher (p ≤ 0.05) peak, average, and nadir %V[Combining Dot Above]O2peak. Other than the nadir values resulting from the 80/0 trial, all trials produced average, peak, and nadir %V[Combining Dot Above]O2peak and %HRpeak values that were within exercise intensity ranges (≈45-90% V[Combining Dot Above]O2max; ≈65-90% HRmax) recommended by the American College of Sports Medicine for improvement of cardiopulmonary function. Similar average HR and peak HR, RPE, blood lactate, and %V[Combining Dot Above]O2peak values were produced by 80/50 and 100/0 protocols. However, the average %V[Combining Dot Above]O2peak was significantly higher (∼9.3% absolute) in 80/50. It appeared that use of the 80/0, 80/50, and 100/0 protocols would be appropriate for individuals who are at the low to moderate end of the cardiopulmonary fitness spectrum.

An Accelerated Step Test to Assess Dancer Pre-season Aerobic Fitness

As the technical performance demands of dance increase, professional companies and pre-professional schools are implementing pre-season screenings that require an efficient, cost effective way to measure dancer aerobic fitness. The aim of this study was to assess an accelerated 3-minute step test (112 beats·min(-1)) by comparing it to the well-studied YMCA step test (96 beats·min(-1)) and a benchmark standard, an incremental treadmill test, using heart rate (HR) and oxygen consumption (VO2) as variables. Twenty-six professional and pre- professional dancers (age 20 ± 2.02 years) were fitted with a telemetric gas analysis system and HR monitor. They were tested in the following order: 96 step, 112 step, and treadmill test, with rest to return to baseline heart rate between each test. The step and treadmill tests were compared using Intra-class Correlation Coefficients [ICC (3, k)] calculated with analysis of variance (p < 0.05). To determine whether there was a relationship between peak and recovery HR (HRpeak, HRrecov) and VO2(VO2peak, VO2recov) variables, Pearson product moment correlations were used. Differences due to gender or group (pre- professionals versus professionals) were explored with MANOVAs for HRpeak, VO2peak, HRrecov, VO2recov, and fitness category. The 112 step test produced higher HRpeak and VO2peak values than the 96 step test, reflecting a greater workload (p < 0.001). For HRpeak, there were high correlations (r = 0.71) and for HRrecov, moderate correlations (r = 0.60) between the 112 step test and treadmill test. For VO2peak and VO2recov, there were moderate correlations between the 112 step test and treadmill test (r = 0.65 and 0.73). No differences between genders for VO2peak values were found for either step test, but males displayed lower HRpeak values for both step tests and higher VO2peak values during the treadmill test (p < 0.001). Recovery HR was lower in males for the 96 and 112 step tests (p < 0.05). This was reflected in higher fitness scores. There were no differences between groups in any of the variables when only females were compared. For the 112 step test, correlations between HRpeak and HRrecov were high (r = 0.85), and correlations between HRpeak and fitness category were very high (r = 0.98). It is concluded that the 112 step test provides an efficient, acceptable tool for testing dance populations, though further testing in larger groups of dancers representing a diverse range of genres and training levels is needed.

Reduced Peak Cycle Exercise Heart Rate in Obese, African American Children

Limited research has shown that peak heart rate (HRpeak) is reduced in obese children compared to normal weight children. However, few studies have assessed the relationships between peak oxygen consumption (VO2peak), peak respiratory exchange ratio (RERpeak), rating of perceived exertion (RPE), total test time (TT) and HRpeak in obese children. PURPOSE: To compare VO2peak, RERpeak, RPE, and TT in children with differing HRpeak values. METHODS: Subjects were 18 pre-pubertal, African American obese children (age 9.2 ± 1.6 years). Height and weight were measured using standard protocols. Body Mass Index (BMI) was calculated from measured height and weight, and all children were ≥95th percentile based on the Centers for Disease Control BMI-for-age and sex growth charts. Pubertal status was assessed by a physician using Tanner's Criteria. Lean and fat mass were measured using Dual X-Ray Absorptiometry (Hologic, Discovery A). A cycle test was performed using the McMaster protocol. Children were instructed to pedal to volitional exhaustion. VO2peak and RERpeak were measured using a metabolic system (Cardiocoach 9000, Korr), and scaled using kilograms of lean mass. HRpeak was determined using telemetry (Polar). The Children's Omni-cycle Scale was used to obtain RPE. Children were categorized into two groups for HRpeak: <190 beats/min (n = 12) and ≥190 beats/min (n = 6). Independent-samples t-tests were used to assess differences in VO2peak, RERpeak, RPE, and TT between the groups. RESULTS: There were no significant differences in VO2peak between the <190 beats/min and >190 beats/min groups (37.5 ± 9.8 vs. 41.7 ± 10.8 ml·kg lean mass-1·min-1). There were also no differences in RERpeak (1.03 ± 0.08 vs 1.03 ± 0.08), RPE (7.3 ± 1.1 vs. 8.8 ± 2.5) or TT (7.9 ± 2.5 vs 9.2 ± 2.0 min) between groups. CONCLUSIONS: Results demonstrate that although HRpeak during cycle exercise may be reduced in some obese children, this does not appear to be associated with reductions in VO2peak, RERpeak, RPE, or TT. However, additional research is needed to determine the prevalence of blunted HRpeak in obese children, and the physiological determinants of this exercise response.

Ball-Sport Endurance and Sprint Test (BEAST90): Validity and Reliability of a 90-Minute Soccer Performance Test

The aim of this study was to determine the validity and reliability of a 90-minute soccer performance test: Ball-sport Endurance and Sprint Test (BEAST90). Fifteen healthy male amateur soccer players participated and attended 5 testing sessions over a 10-day period to perform physiologic and soccer-specific assessments. This included familiarization sessions and 2 full trials of the BEAST90, separated by 7 days. The total 90-minute distance, mean percent peak heart rate (HRpeak), and estimated percent peak oxygen uptake of the BEAST90 were 8,097 ± 458 m, 85 ± 5% and 82 ± 14%, respectively. Measures obtained from trial 1 and trial 2 were not significantly different (p > 0.05). Reliability of measures over 90 minutes ranged from 0.9-25.5% (% typical error). The BEAST90 protocol replicated soccer match play in terms of time, movement patterns, physical demands (volume and intensity), distances, and mean and HRpeak values, as well as having an aerobic load similar to that observed during a soccer match. Reproducibility of key physical measures during the BEAST90 were mostly high, suggesting good reliability. The BEAST90 could be used in studies that wish to determine the effects of training or nutritional interventions on prolonged intermittent physical performance.

Oxygen uptake-heart rate relationship in élite wheelchair racers.

The American College of Sports Medicine (ACSM) recommends that, as a general rule for health purposes, individuals should exercise at 40%-85% of their maximal oxygen uptakes. Moreover, it has been suggested that 55%-90% of the maximal heart rate may be used as an alternative estimate of these percentage maximal oxygen uptake values. The present study examined the relationship between percentage peak heart rate (% HRpeak) and percentage peak oxygen uptake (% VO2peak) during steady-state incremental intensity wheelchair propulsion of 16 élite, male wheelchair racers (WR). Oxygen uptake was determined during each submaximal exercise stage and heart rate (HR) was continuously monitored. The VO2peak was subsequently determined using a separate protocol. Linear regression equations of % HRpeak versus % VO2peak for each participant included % HRpeak values corresponding to 40%, 60%, 80% and 85% VO2peak. The linear regression equation, derived as the group mean of the slope and intercept terms determined for each individual, was: % peak HR = 0.681 x % peak VO2 + 33.2. The group mean of the individual correlation coefficients for the VO2-HR relationship was 0.99. The values of % HRpeak for each of the % VO2peak values below 85% were significantly greater (P<0.01) than those suggested by the ACSM. This suggests that the ACSM guidelines below 85% VO2peak, based on % HRpeak, may underestimate the relative exercise intensity (i.e. % VO2peak) in the WR population. However, in élite level WR, % HRpeak can be recommended as an alternative estimate of % VO2peak at wheelchair propulsion intensities of 85% VO2peak or more.

Chronotropic competence in endurance trained heart transplant recipients: heart rate is not a limiting factor for exercise capacity.

The purpose of this study was to show that the chronotropic potential of the well trained heart transplant recipient (HTR) does not limit exercise capacity. Chronotropic incompetence is considered to be the main limiting factor of the functional capacity of heart transplant recipients. However, no systematic study had been published on patients who had spontaneously undergone heavy endurance training for several years. Heart rate (HR) and respiratory gas exchanges (VO2, VCO2, VE) were measured in 14 trained HTRs (T-HTRs) during exercise tests on a bicycle, on a treadmill and by Holter electrocardiography during a race. Peak values observed in T-HTRs during the treadmill test were higher than those reached during the bicycle test (VO2peak: 39.8+/-6.9 vs. 32.5+/-7.8 ml x kg(-1) x min(-1), p < 0.001; HRpeak: 169+/-14 vs. 159+/-16 bpm, p < 0.01). During treadmill exercise VO2peak and HRpeak values observed were very close to the mean predicted VO2pmax and HRpmax. The maximum heart rate during the race (HRrace) was greater than HRpeak values during the treadmill test (179+/-14 vs 169+/-14 bpm, p < 0.01) and slightly above the mean predicted values (HRrace/HRpmax X 100 = 101+/-10%). The treadmill exercise test yields more reliable data than does the bicycle test. Extensive endurance training enables heart transplant recipients to reach physical fitness levels similar to those of normal sedentary subjects; heart rate does not limit their exercise capacity.

Cardiovascular response to exercise in humans following acclimatization to extreme altitude.

The purpose of this study was to assess the effects of acclimatization to extreme altitude on the cardiovascular system, using vagal and adrenergic blockade and acute restoration of normoxia during exercise to maximum with one and two legs. Fourteen climbers on an expedition to the Himalayas were studied at a lower base camp (5250 m) following 56-81 days at altitudes between 5250 and 8700 m. After acclimatization, peak heart rate (HRpeak), oxygen uptake (VO2peak) and noradrenaline (NA) were similar during maximal one- and two-legged cycling, whereas peak plasma lactate was higher during the one-legged protocol. HRpeak (range 113-168 beats min-1) was lowest when subjects returned from the higher camps. The degree of partial restoration of HRpeak to more normal values within seconds of 60% O2 inhalation (range 5-35 beats min-1 HRpeak increase) was greatest in subjects with low HRpeak. HR responses to beta-1 blockade increased as a function of HRpeak and the HR responses to atropine were the least in subjects with high HRpeak. These findings suggest that (a) the reduction in HRpeak is linked to the duration and severity of the hypoxaemia, (b) the degree of restoration of HRpeak with acute normoxia is dependent on the level of attenuation or down-regulation of cardiac sympathetic activation (SNA), (c) cardiac vagal drive is masked to a lesser extent in chronic hypoxia because of attenuated SNA and lower HRpeak values, and (d) the lower blood lactate levels at altitude is a function of muscle mass involvement rather than adrenergic activation, as normal peak values were reached during exercise with a small muscle mass.

Haemocyte changes in the pacific oyster, crassostrea gigas, caused by exposure to domoic acid in the diatom pseudonitzschia pungens f. multiseries

The physiological effects of domoic acid on the immune system of marine invertebrates, which are known to accumulate this neurotoxin, have not been investigated previously. Changes in the number and relative phagocytic activity of circulating haemocytes in Crassostrea gigas exposed to domoic acid in the diatom Pseudonitzschia pungens f. multiseries for 48 hr, followed by clearance for 240 hr, were investigated using chemiluminescence. An initial stress response to the toxin assimilation was characterized by a marked increase in number and activity of haemocytes with 4 hr of exposure to the algae. Although the toxin level in the oyster increased during the 48 hr exposure, both number and activity of haemocytes declined from the 4 hr peak values to those significantly lower than control values after 24 hr clearance. This suppression in number and activity of circulating haemocytes following the initial toxin response was rectified only after 48 hr clearance, when domoic acid levels in the oyster tissue had declined to trace levels, allowing blood cells to regain their normal characteristics.

Chronologic Aging Alters the Response to Ultraviolet-induced Inflammation in Human Skin

In order to determine the effect of age on the capacity of human skin to mount an inflammatory response, the sunburn reaction was studied quantitatively in 4 subjects aged 22-26 yr and 7 subjects aged 62-86 yr. Buttock skin of each subject was exposed to 3 time his minimal erythema dose, using the Hanovia mercury vapor lamp; 1 micrometer histologic sections and determinations of histamine and prostaglandin E2 (PGE2) from suction blister aspirates were used to monitor the reaction. Clinically, erythema and edema were less (p less than .05) in irradiated skin of the old subjects during the first 24 hr. Nonirradiated skin contained less histamine and PGE2 in old adults (p less than .05), approximately 50% of young adult levels. Histamine levels rose early in the reaction and returned to baseline by 24 hr; 4 hr peak values averaged 9.2 ng/ml in old vs. 18.3 ng/ml in young adults. PGE2 rose more slowly in blister aspirates from old adults (P less than .05), but reached comparable peaks, 6-9 pg/T.V., in both groups at 24 hr. Biopsies of control skin from old adult specimens contained fewer mast cells and venules (P less than .01). At 4 and 24 hr, old specimens revealed fewer sunburn cells and less striking alterations of perivenular mast cells and endothelial cells, but at 72 hr these changes were more prominent than in young adult specimens. The data suggest that with advancing age the sunburn reaction is quantitatively reduced and evolves more slowly following a standardize ultraviolet exposure.