Index Of Exercise Intensity Research Articles

Quantitatively Predicting Effects of Exercise on Pharmacokinetics of Drugs Using a Physiologically Based Pharmacokinetic Model.

Exercise significantly alters human physiological functions, such as increasing cardiac output and muscle blood flow and decreasing glomerular filtration rate (GFR) and liver blood flow, thereby altering the absorption, distribution, metabolism, and excretion of drugs. In this study, we aimed to establish a database of human physiological parameters during exercise and to construct equations for the relationship between changes in each physiological parameter and exercise intensity, including cardiac output, organ blood flow (e.g., muscle blood flow and kidney blood flow), oxygen uptake, plasma pH and GFR, etc. The polynomial equation P = ΣaiHRi was used for illustrating the relationship between the physiological parameters (P) and heart rate (HR), which served as an index of exercise intensity. The pharmacokinetics of midazolam, quinidine, digoxin, and lidocaine during exercise were predicted by a whole-body physiologically based pharmacokinetic (WB-PBPK) model and the developed database of physiological parameters following administration to 100 virtual subjects. The WB-PBPK model simulation results showed that most of the observed plasma drug concentrations fell within the 5th-95th percentiles of the simulations, and the estimated peak concentrations (Cmax) and area under the curve (AUC) of drugs were also within 0.5-2.0 folds of observations. Sensitivity analysis showed that exercise intensity, exercise duration, medication time, and alterations in physiological parameters significantly affected drug pharmacokinetics and the net effect depending on drug characteristics and exercise conditions. In conclusion, the pharmacokinetics of drugs during exercise could be quantitatively predicted using the developed WB-PBPK model and database of physiological parameters. SIGNIFICANCE STATEMENT: This study simulated real-time changes of human physiological parameters during exercise in the WB-PBPK model and comprehensively investigated pharmacokinetic changes during exercise following oral and intravenous administration. Furthermore, the factors affecting pharmacokinetics during exercise were also revealed.

Plasma Lactate as a Marker for Metabolic Health

Blood lactate concentrations traditionally have been used as an index of exercise intensity or clinical hyperlactatemia. However, more recent data suggest that fasting plasma lactate can also be indicative of the risk for subsequent metabolic disease. The hypothesis presented is that fasting blood lactate accumulation reflects impaired mitochondrial substrate use, which in turn influences metabolic disease risk.

Degree of exercise intensity during continuous chest compression in upper-body-trained individuals.

BackgroundAlthough chest-compression-only cardiopulmonary resuscitation (CCO-CPR) is recommended for lay bystanders, fatigue is easily produced during CCO-CPR. If CCO-CPR can be performed at a lower intensity of exercise, higher resistance to fatigue is expected. Since chest compression is considered to be a submaximal upper body exercise in a steady rhythm and since the unit of load for chest compression is expressed as work rate, we investigated the possibility that peak work rate of the upper body determines the level of exercise intensity during CCO-CPR.MethodsTwelve sedentary individuals (group Se), 11 rugby players (group R), and 11 swimmers (group Sw) performed 10-min CCO-CPR, and heart rate (HR) and rating of perceived exertion (RPE) were measured as indices of exercise intensity. Multiple linear regression analysis was carried out to assess potential relationships of upper body weight, peak lumbar extension force, peak work rate, and peak oxygen uptake recorded during arm-crank exercise with HR and RPE during CCO-CPR.ResultsValues of peak work rate during arm-crank exercise (Peak WR-AC) in group Se, group R, and group Sw were 108 ± 12, 139 ± 27, and 146 ± 24 watts, respectively. Values of the latter two groups were significantly higher than the value of group Se (group R, P < 0.01; group Sw, P < 0.001). HR during CCO-CPR increased with time, reaching 127.8 ± 17.6, 114.8 ± 16.5, and 118.1 ± 14.2 bpm at the 10th minute in group Se, group R, and group Sw, respectively. On the other hand, RPE during CCO-CPR increased with time, reaching 16.4 ± 1.4, 15.4 ± 1.7, and 13.9 ± 2.2 at the 10th minute in group Se, group R, and group Sw, respectively. Multiple linear regression analysis showed that only peak WR-AC affects both HR and RPE at the 10th minute of CCO-CPR (HR, r = −0.458; P < 0.01; RPE, r = −0.384, P < 0.05).ConclusionsThe degree of exercise intensity during CCO-CPR is lower in individuals who have a higher peak work rate of the upper body.

Clinical effect of real time pulse rate monitoring with a portable pulsimeter on physical exercise therapy for male patients with type 2 diabetes.

In patients with type 2 diabetes, it is recommended that exercise therapy is performed using heart rate as an index of exercise intensity. This study was designed to clinically evaluate whether continuous exercise therapy with a portable pulsimeter for self-monitoring of the pulse rate influences glycemic control in patients with type 2 diabetes. We randomly assigned 23 male patients to a pulse displayed group (in which the portable pulsimeter displayed a pulse rate) or a pulse non-displayed group (in which the portable pulsimeter only recorded the data and did not display a pulse rate). The patients then received exercise therapy for 1month. Patients in the pulse displayed group were instructed to regulate their walking speed by maintaining their portable pulsimeter in the target pulse rate zone, whereas patients in the pulse non-displayed group were instructed to regulate their walking speed while taking their pulse rate and using the Borg scale to maintain the target pulse rate zone using the conventional method. We found the mean walking time within the target pulse rate zone during exercise therapy was significantly increased in the pulse displayed group (p<0.01). Similarly, glycoalbumin and 1,5-anhydro-D-glucitol improved significantly in the pulse displayed group after 1month of exercise therapy (p<0.01, respectively). Our results suggest that this therapeutic device might be useful for improving glycemic control in patients with type 2 diabetes.

Validity of cadence as an index of exercise intensity in elderly Japanese women

Validity of cadence as an index of exercise intensity in elderly Japanese women

身体活動のタイプの違いはどのように気分に影響するのか？

Generally, typical physical activities (e.g. walking and cycling) increase positive affect and decrease negative affect. However, few studies have investigated the effects on mood of activities that are frequently pursued during leisure time (e.g. dynamic stretching and video games). The purpose of the present study was to investigate the influences of different types of physical activity on mood. We selected 16 activities (kendama, active video games [“Wii Sports” tennis, baseball, boxing], static and dynamic stretching, jumping rope, step exercise, table tennis, darts, ball juggling, cycling, balance ball exercise, golf putting, walking, and dumbbell exercise) for investigation and divided them into 4 protocols. The duration of each activity was 10 min, except for dynamic stretching and step exercise (3 min). Fifteen young adults (8 males and 7 females) participated in at least 2 protocols (8 activities). Before and after each activity, levels of arousal and pleasure were measured using a two-dimensional mood scale. Metabolic equivalent (MET) as an index of exercise intensity was monitored throughout all activities using a portable indirect calorimeter (MetaMax 3B). The changes in arousal and pleasure levels were tested by paired t test. The influence of activity type on changes in arousal and pleasure levels was analyzed by ANCOVA (factor: activity type 16 levels; covariate: METs) using a Mixed model. In ANCOVA models, the influence of each activity was evaluated in comparison with walking. All activities except static stretching (p=0.199) significantly increased the arousal level (p<0.010). The pleasure level was significantly increased after 3 sessions of active video games, static stretching, table tennis, and balance ball exercise (p<0.044). The results of the ANCOVA models revealed that the main effect of activity type on changes in arousal and pleasure levels was significant (p≤0.007), while MET showed no significant regression coefficient (p≥0.075). Increases in pleasure level during an active video game (baseball) and table tennis were significantly higher than during walking (p≤0.025), whereas the influence of step exercise was significantly lower than during walking. These findings suggest that physical activity generally increases arousal level independently of exercise intensity, and that performing activities with another person such as conducting active video games or table tennis, significantly increases pleasure level in comparison to walking.

Reply: On the Methodology of the Conconi Test

The aim of our study was to investigate the relationship between “anaerobic thresholds” obtained from incremental exercise testing and the maximal lactate steady-state (MLSS) in elite cyclists. Because the vast majority of cyclists use heart rate as an index of exercise intensity, we were particularly interested to find out the threshold procedure yielding the most precise prediction of heart rate corresponding with the MLSS. Dr. Grazzi and his co-workers criticize the test protocol we have used to eventually conclude that the “Conconi threshold” (deflection of the heart rate/power curve) is an inadequate method to predict MLSS exercise intensity. We acknowledge the criticism that we did not use the test procedures as originally described by Grazzi and his co-workers [[5]]. Thus, we cannot exclude that this procedure still might yield a good prediction of MLSS. However, it must at the same time be emphasized that experimental evidence is entirely missing which proves that the test protocol by Grazzi et al. allows to adequately predict MLSS heart rate or power output. In fact, the reliability and validity of the Conconi threshold principle has been a matter of debate at several earlier occasions [[2], [3], [7], [8]].

Functional investigations of exercising muscle: a noninvasive magnetic resonance spectroscopy-magnetic resonance imaging approach.

Muscle fatigue, which is defined as the decline in muscle performance during exercise, may occur at different sites along the pathway from the central nervous system through to the intramuscular contractile machinery. Historically, both impairment of neuromuscular transmission and peripheral alterations within the muscle have been proposed as causative factors of fatigue development. However, according to more recent studies, muscle energetics play a key role in this process. Intramyoplasmic accumulation of inorganic phosphate (P(i)) and limitation in ATP availability have been frequently evoked as the main mechanisms leading to fatigue. Although attractive, these hypotheses have been elaborated on the basis of experimental results obtained in vitro, and their physiological relevance has never been clearly demonstrated in vivo. In that context, noninvasive methods such as 31-phosphorus magnetic resonance spectroscopy and surface electromyography have been employed to understand both metabolic and electrical aspects of muscle fatigue under physiological conditions. Mapping of muscles activated during exercise is another interesting issue which can be addressed using magnetic resonance imaging (MRI). Exercise-induced T2 changes have been used in order to locate activated muscles and also as a quantitative index of exercise intensity. The main results related to both issues, i.e. the metabolic and electrical aspects of fatigue and the MRI functional investigation of exercising muscle, are discussed in the present review.

Exercise induces gastric ischemia in healthy volunteers: a tonometry study.

Heavy physical exercise may cause gastrointestinal signs and symptoms, and, although splanchnic blood flow may decrease through redistribution by more than 50%, it is unclear whether these signs and symptoms relate to gastrointestinal ischemia. In 10 healthy volunteers, we studied the effect of exercise on gastric mucosal perfusion adequacy using air tonometry. Two relatively short (10 min) exercise stages were conducted on a cycle ergometer, aiming for 80 and 100% of maximum heart rate, respectively. The intragastric-arterial PCO(2) gradient (Delta PCO(2)) was elevated by 1.1 +/- 1.0 kPa over baseline values (-0.1 +/- 0.3 kPa) only after maximal exercise (P < 0.001). Delta PCO(2) positively correlated with the arterial lactate level taken as an index of exercise intensity (Spearman's rank test: r = 0.76, P < 0.0001). By bilinear regression analysis, a lactate level of 12 mmol/l, above which a sharp rise in the Delta PCO(2) occurred, was calculated. We conclude that, in healthy volunteers with normal splanchnic vasculature, gastric ischemia may develop during maximal exercise as judged from intragastric PCO(2) tonometry.

ISOMETRIC EXERCISE TRAINING EFFECTS REACTIVE OXYGEN AND NITROGEN SPECIES IN HYPERTENSIVE HUMANS

Increased production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are associated with hypertension via oxidation of low density lipoproteins (LDL), effects on the endothelial wall, and the pathogenesis of atherosclerosis. In this study, we measured RNS, and the following ROS biomarkers: ascorbic acid (AA), total thiols (TSH), lipid peroxidation (LIPOX), glutathione (GSH), total antioxidants (ORAC) before and after six weeks of isometric exercise training (IET). Blood lactate, pre-post acute exercise and pre-post six weeks of IET, was also measured as an index of exercise intensity and effort. Four middle-aged hypertensive female subjects, mean systolic blood pressure (SBP) = 143.0 ± 1.23 mmHg, mean diastolic blood pressure (DBP) = 93.4 ± 2.96 mmHg, mean heart rate (HR) = 70.0 ± 5.26 beats/min at rest, performed a submaximal exercise test pre and post six weeks IET. After six weeks IET, SBP = 135.0 ± 8.10 mmHg (−5.6%), DBP = 82.0 ± 4.71mmHg (−12.2%), and HR = 67.75 ± 5.78 beats/min (−3.2%), all showed reductions as a result of IET, but none reached statistical significance. No significant changes in blood levels of RNS and ROS were found in this limited sample size. The following trends occurred: resting blood pressure decreased and antioxidant protection, as indicated by TSH and AA, were preserve in hypertensives following IET. In conclusion, IET may contribute to lower blood pressure and an increased proficiency of select antioxidants, although in this small sample, changes did not reach significance. There was a statistically significant increase in lactate buildup following IET, evidence that IET increased submaximal exercise efforts, which may be important in regulating antioxidant activity.

The physiological response of instructors and participants to three aerobics regimens

This study was designed to test the hypothesis that there are regimen-specific differences in the thermal, metabolic, and cardiovascular responses of nonpregnant women when they perform their chosen type of aerobics at their usual performance level. Thirty-six instructors and 53 participants were studied while performing their chosen aerobics regimen under simulated field conditions using oxygen consumption as the index of exercise intensity. Under these conditions no significant differences were observed in the physiological response to low impact, high impact, or step regimens. However, although their ratings of perceived exertion were lower, the participants worked at a much higher exercise intensity than the instructors (76 +/- 1 vs 62 +/- 2% VO2max). As a result they attained a higher respiratory exchange ratio (0.96 vs 0.90), rectal temperature (38.62 vs 38.12 degrees C), and blood levels of glucose (5.70 vs 4.95 mmol.l-1), lactate (3.65 vs 1.60 mmol.l-1), and norepinephrine (2656 vs 1191 pg.ml-1). We conclude that both intensity and physiological response to aerobics are individual specific not regimen specific and that participants consistently underestimate their level of performance.

Validity of ratings of perceived exertion as an index of exercise intensity in swimming training.

The validity of ratings of perceived exertion (RPE), proposed by Borg (1962), as an index of exercise intensity in swimming training was discussed based on the following four experiments. Experiment I: VO2 and heart rate (HR) were measured and RPE was asked in ten female and seven male physical education students with different levels of swimming skill performing submaximal and maximal work in tethered swimming. The increases in HR and RPE with increase in %VO2max were fitted well by straight lines with high correlation coefficients of r = 0.957-0.999 and r = 0.893-0.988, respectively. RPE was increased in a linear fashion with increase in HR except for a few subjects. The correlation coefficients for linear regression for individuals were 0.862-0.987. Experiment II: Swimming velocity and HR were measured in four groups with different levels of swimming skill. The breast stroke in a 50-m pool for 5 min at three RPE ratings, i.e., very light (RPE 9), somewhat hard (RPE 13) and very hard (RPE 17) was requested of these groups. In good skilled well trained college swimmers, %HRmax was fairly higher than the RPE at the RPE 9 and RPE 13 levels but coincided with the RPE at the RPE 17 level. In skilled trained physical education students, the HR increased with a corresponding increase in RPE. But in the group with low or lower levels of swimming skill, the HR kept about the same values in spite of the increase in RPE. Experiment III: Two male and six female low skilled physical education students took the swimming training in the swimming pool for 2.0-2.5 hours a day, 6 days a week, for 2 weeks. The students also received the swimming training in the sea which lasted for 2 hours each in the morning and in the afternoon for 6 days. The same RPE test, as mentioned in Experiment II, was done before, during and after swimming training. Mean swimming velocity during and after training was slightly higher than that before training at the RPE 9 and RPE 13 levels, and was much higher at the RPE 17 level. Before training, the HR was fairly higher than the RPE at the RPE 9 and RPE 13 level. But during and after training, the HR was much closer to the RPE at the RPE 9 and RPE 13 levels. Experiment IV: Two male and three female lower skilled middle-aged swimmers performed the same RPE test as mentioned in Experiment II.(ABSTRACT TRUNCATED AT 400 WORDS)

Validity of heart rate and ratings of perceived exertion as indices of exercise intensity in a group of children while swimming

The purpose of this study was to investigate the validity of heart rate (fc) and ratings of perceived exertion (RPE) as indices of exercise intensity in a group of children while swimming. Six healthy male swimmers, aged 10-12, swam tethered using the breast-stroke in a flume. The resistance started at 1.0 kg and increased in 1.0 kg steps up to the point of their exhaustion. The subjects swam for 5 min during each period, with a rest of 10-20 min until they had returned to their resting fc level. The last exercise intensity was with the maximal mass the subjects could support for 2 min. The last min of oxygen consumption (VO2) and 30 s of fc were measured during each exercise period. The subjects gave their RPE assessment at the end of exercise. The individual relationships between fc and VO2, and percentage maximal oxygen consumption (%VO2max) were linear with a high correlation r = 0.962-0.996 and r = 0.962-0.996, respectively. Therefore, it was concluded that fc was valid as an index of the exercise intensity of children while swimming. Compared to the results found in adults using a similar protocol, the children's fc were 8.3-26.9 beats.min-1 higher than those of the adults at the given %VO2max. The present study showed two different patterns in the relationship between VO2 and RPE in individuals. In two subjects the RPE increased linearly with VO2 while in the other four subjects the increase was discontinuous. If fc and RPE were to be applied to the setting and evaluation of exercise intensity during swimming, it would seem that fc would be a more useful guide than RPE for some children.

Dependence on exercise intensity of changes in electrolyte secretion from the skin sampled by a simple method

Secreta from the palm and forearm was sampled for 1-min periods by a new technique, using a glass cylinder. Subjects exercised for 10-min periods at successive intensities of 40%, 50% and 65% VO2max with a leg ergometer operated in the supine position. Changes in the concentrations (values) of Na+, K+ and Cl- in their secreta during exercise were investigated. Significant positive correlations were found between the values of any two electrolytes in samples from the palm or the forearm, but the correlations between values for any one of the three electrolytes from the two sites were not significant. Values for concentrations of the electrolytes were significantly higher in samples from the palm than in those from the forearm at rest, 10 min after the beginning of exercise and at the end of exercise. No significant correlation was found between values for electrolytes in samples from the palm and the exercise intensity, but values for Na+ in samples from the forearm increased stepwise with increase in exercise intensity, and similar tendencies were observed for values of K+ and Cl-. The values for the three electrolytes in samples from the forearm, but not the palm, were significantly correlated with values for blood lactate, the percentage of VO2max and the heart rate. These results suggest that the present technique is suitable for successive samplings of secreta from the forearm, and that values for the electrolytes in samples are useful indices of exercise intensity.

A comparison of heart rate methods for predicting endurance training intensity

Comparing results of various training studies is often confounded by use of different indices of exercise intensity. Two frequently used indices are: 1) the % HR max method (exercise at a HR corresponding to a chosen percentage of maximal HR), and 2) this study, % net VO2max was employed as the criterion measure of exercise intensity and a comparison was made between the prediction of % net VO2-MAXby the above two methods. Experiments were performed on nine males (M +/- SD age = 23.7 +/- 2.6 yrs) and consisted of double determinations of resting VO2 and multiple measurements of resting HR under five different conditions. Duplicate determinations of maximal VO2 and HR preceded a third treadmill test consisting of four, 5-minute workloads representing approx 25, 45, 65, and 85% net VO2max. The results demonstrated that the KM's prediction of exercise intensity was not significantly different (P greater than 0.05) from measured intensity at any of the four workloads. Additionally, the % HR max procedure yielded large, significant overpredictions of exercise intensity (29, 22, 16 and 8% overpredictions for the four submaximal intensities, respectively. These results suggest that the KM yields a training HR that reflects exercise intensity within reasonable limits of accuracy.