Effect of training on maximum oxygen intake and on anaerobic metabolism in man

Two-Day Cardiopulmonary Exercise Testing in Females with a Severe Grade of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Comparison with Patients with Mild and Moderate Disease

Introduction: Effort intolerance along with a prolonged recovery from exercise and post-exertional exacerbation of symptoms are characteristic features of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The gold standard to measure the degree of physical activity intolerance is cardiopulmonary exercise testing (CPET). Multiple studies have shown that peak oxygen consumption is reduced in the majority of ME/CFS patients, and that a 2-day CPET protocol further discriminates between ME/CFS patients and sedentary controls. Limited information is present on ME/CFS patients with a severe form of the disease. Therefore, the aim of this study was to compare the effects of a 2-day CPET protocol in female ME/CFS patients with a severe grade of the disease to mildly and moderately affected ME/CFS patients. Methods and results: We studied 82 female patients who had undergone a 2-day CPET protocol. Measures of oxygen consumption (VO₂), heart rate (HR) and workload both at peak exercise and at the ventilatory threshold (VT) were collected. ME/CFS disease severity was graded according to the International Consensus Criteria. Thirty-one patients were clinically graded as having mild disease, 31 with moderate and 20 with severe disease. Baseline characteristics did not differ between the 3 groups. Within each severity group, all analyzed CPET parameters (peak VO₂, VO₂ at VT, peak workload and the workload at VT) decreased significantly from day-1 to day-2 (p-Value between 0.003 and <0.0001). The magnitude of the change in CPET parameters from day-1 to day-2 was similar between mild, moderate, and severe groups, except for the difference in peak workload between mild and severe patients (p = 0.019). The peak workload decreases from day-1 to day-2 was largest in the severe ME/CFS group (−19 (11) %). Conclusion: This relatively large 2-day CPET protocol study confirms previous findings of the reduction of various exercise variables in ME/CFS patients on day-2 testing. This is the first study to demonstrate that disease severity negatively influences exercise capacity in female ME/CFS patients. Finally, this study shows that the deterioration in peak workload from day-1 to day-2 is largest in the severe ME/CFS patient group.

Methods to determine aerobic endurance

Physiological testing of elite athletes requires the correct identification and assessment of sports-specific underlying factors. It is now recognised that performance in long-distance events is determined by maximal oxygen uptake (V(2 max)), energy cost of exercise and the maximal fractional utilisation of V(2 max) in any realised performance or as a corollary a set percentage of V(2 max) that could be endured as long as possible. This later ability is defined as endurance, and more precisely aerobic endurance, since V(2 max) sets the upper limit of aerobic pathway. It should be distinguished from endurance ability or endurance performance, which are synonymous with performance in long-distance events. The present review examines methods available in the literature to assess aerobic endurance. They are numerous and can be classified into two categories, namely direct and indirect methods. Direct methods bring together all indices that allow either a complete or a partial representation of the power-duration relationship, while indirect methods revolve around the determination of the so-called anaerobic threshold (AT). With regard to direct methods, performance in a series of tests provides a more complete and presumably more valid description of the power-duration relationship than performance in a single test, even if both approaches are well correlated with each other. However, the question remains open to determine which systems model should be employed among the several available in the literature, and how to use them in the prescription of training intensities. As for indirect methods, there is quantitative accumulation of data supporting the utilisation of the AT to assess aerobic endurance and to prescribe training intensities. However, it appears that: there is no unique intensity corresponding to the AT, since criteria available in the literature provide inconsistent results; and the non-invasive determination of the AT using ventilatory and heart rate data instead of blood lactate concentration ([La(-)](b)) is not valid. Added to the fact that the AT may not represent the optimal training intensity for elite athletes, it raises doubt on the usefulness of this theory without questioning, however, the usefulness of the whole [La(-)](b)-power curve to assess aerobic endurance and predict performance in long-distance events.

The influence of training on endurance and blood lactate concentration during submaximal exercise

The purpose of this study was to examine the effect of short-term training on maximum oxygen uptake (VO2 max) and two different measures of endurance performance. Endurance was determined for 15 female subjects (7 training, 8 control) as (1) exercise time to exhaustion at 80% VO2 max (T80%) and (2) the highest relative exercise intensity tolerable during a 30-minute test (T30 min), before and after a 6-week training period. In addition, VO2 max and the work rate equivalent to a blood lactate concentration of 4 mmol.l-1 (OBLA) were determined. Maximum oxygen uptake increased by 24% (p less than 0.01) for the training group (TG) and 7% (p less than 0.01) for the control group (CG). Cumulative average work rate (CAWR) during T30 min increased by 25% for the TG while there was no change for the CG. No significant difference was found pre- and post-training in the %VO2 max (estimated from CAWR) at which the TG and CG performed T30 min. Exercise time to exhaustion on T80% increased by 347% (p less than 0.01) and 16% (NS) for the TG and the CG respectively. Good correlations were found between VO2 max and CAWR (W) (pre-training r = 0.84; post-training r = 0.83), OBLA (W) and CAWR (W) (pre-training r = 0.89; post-training r = 0.88) and change in endurance time and the change in submaximal blood lactate concentration (r = 0.70, p less than 0.01). The results of this study suggest that the ability to sustain a high relative exercise intensity is not enhanced following short-term training.

The effects of maximum steady state pace training on running performance

Maximum aerobic power (VO2 max), maximum anaerobic power (AP max), submaximal exercise heart rate (HRsub), and performance times for distances of 15m, 600 m, 3.22 km, and 10 km were evaluated in 12 male runners prior to and after 7 weeks of a running programme at each individual's maximum steady-state (MSS) pace. MSS pace, a running speed at which blood lactate is believed to equal 2.2 mmol . l-1, was calculated from weekly 3.22 km runs utilising the regression equation of LaFontaine et al (1981). During the training period, the mean MSS pace increased 11.3% from 3.76 to 4.19 m.s.-1. Body weight and maximal exercise heart rate were unaffected by MSS training. However, MSS training was associated with increases (p less than 0.05) in absolute VO2 max (8.9%) and VO2 max relative to body weight (8.1%), absolute AP max (3.7%) and AP max, relative to body weight (4.3%); decreases in resting HR (5.4%) and HRsub (6.9%); and decreases in performance times for runs of 15m (1.8%), 600 m (4.4%), 3.22 km (9.6%), and 10 km (12.1%). MSS paces determined prior to the pre- and post-training 10 km races were significantly related to the pre-training (r = 0.98) and post-training 10 km (r = 0.95) performance paces. Pretraining MSS pace, maximal aerobic power, and performance times for the 3.22 km and 10 km distances were highly related to improvements in MSS pace and performance times for the 3.22 km and 10 km runs. Our findings indicate that training at MSS pace is an effective method to increase maximal aerobic and anaerobic power, and decrease performance times for short- and middle-distance running events. Pre-training running performance may predict the magnitude of improvement due to MSS pace training.

Longitudinal associations between anaerobic threshold and distance running performance

Longitudinal alterations in anaerobic threshold (AT) and distance running performance were assessed three times within a 4-month period of intensive training, using 20 male, trained middle-distance runners (19-23 yr). A major effect of the high intensity regular intensive training together with 60- to 90-min AT level running training (2 d X wk-1) was a significant increase in the amount of O2 uptake corresponding to AT (VO2 AT; ml O2 X min-1 X kg-1) and in maximal oxygen uptake (VO2max; ml O2 X min-1 X kg-1). Both VO2 AT and VO2max showed significant correlations (r = -0.69 to -0.92 and r = -0.60 to -0.85, respectively) with the 10,000 m run time in every test. However, further analyses of the data indicate that increasing VO2 AT (r = -0.63, P less than 0.05) rather than VO2max (r = -0.15) could result in improving the 10,000 m race performance to a larger extent, and that the absolute amount of change (delta) in the 10,000 m run time is best accounted for by a combination of delta VO2 AT and delta 5,000 m run time. Our data suggest that, among runners not previously trained over long distances, training-induced alterations in AT in response to regular intensive training together with AT level running training may contribute significantly to the enhancement of AT and endurance running performance, probably together with an increase in muscle respiratory capacity.

Blood lactate. Implications for training and sports performance

The blood lactate response to exercise has interested physiologists for over fifty years, but has more recently become as routine a variable to measure in many exercise laboratories as is heart rate. This rising popularity is probably due to: the ease of sampling and improved accuracy afforded by recently developed micro-assay methods and/or automated lactate analysers; and the predictive and evaluative power associated with the lactate response to exercise. Several studies suggest that the strong relationship between exercise performance and lactate-related variables can be attributed to a reflection by lactate during exercise of not only the functional capacity of the central circulatory apparati to transport oxygen to exercising muscles, but also the peripheral capacity of the musculature to utilise this oxygen. For example, several studies contrast the relationship between VO2max and endurance running performance with that between a lactate variable and the same running performance. In every study, the lactate variable is more highly correlated with performance. Similarly, prescribing training intensity as a function of the lactate concentration elicited by the training may prove to be a means of obtaining a more homogeneous adaptation to training in a group of athletes or subjects than is obtained by setting intensity as a function of maximal heart rate or % VO2max. A review of the recent literature shows that the lactate response to supramaximal exercise is a sensitive indicator of adaptation to 'sprint training' and is correlated with supramaximal exercise performance. This review also describes the possible applications of lactate measurements to enhance the rate of recovery from high intensity exercise. Although the lactate response to exercise is reproducible under standardised conditions it can be influenced by the site of blood sampling, ambient temperature, changes in the body's acid-base balance prior to exercise, prior exercise, dietary manipulations, or pharmacological interpretation.

Reproducibility of aerobic and anaerobic thresholds in 20-50 year old men

The reproducibility of the aerobic (AerT) and the anaerobic (AnT) threshold was studied in 33 men aged 20-50 years. They completed two maximal exercise tests on a bicycle ergometer. The thresholds, as VO2 (1 X min-1), were determined visually by two investigators using both the blood lactate and the respiratory indices. The respiratory variables were measured with a computerized breath-by-breath method; samples of venous blood were drawn every 2nd min and analysed enzymatically for lactate. The reproducibility of the AerT (r = 0.94) and of the AnT (r = 0.96) were equally good. The AnT can be determined either from blood lactate concentrations (AnTLa) or from ventilatory and gas exchange response (AnTr) during a 2-min incremental exercise test. They both also showed similar reproducibility: r = 0.93 for the AnTLa and r = 0.95 for the AnTr. The work rate and the measured physiological variables at the AerT and AnT, except for the blood lactacte concentration, were very reproducible. Age did not affect the reproducibility of the thresholds. The poor reproducibility of blood lactate concentration of the AnT confirmed our previous opinion that the fixed blood lactate levels of 2 and 4 mmol X 1(-1) are poor indicators of AerT and AnT.

Fitness facilitates sleep

Eight army recruits were studied at the start, middle, and end of their initial 18-week training programme. At each point the subjects were studied for four consecutive nights in the sleep laboratory. Their sleep was characterized by the means of the recordings on the last two nights. Within 2 days of the sleep recordings (but never on the same day) each subject spent 2 non-consecutive days in the exercise laboratory. On the 1st day a maximum oxygen consumption (VO2 max) measurement was performed on a treadmill and on the 2nd day a 24-min progressive exercise bicycle ergometer test was carried out with simultaneous venous sampling (for lactic acid measurements) and oxygen consumption recordings from which the lactate turn point (LTP) was calculated. LTP was used as a measure of fitness. Approximately 1 week after the above measures lean muscle mass as calculated by total body potassium estimation was obtained for each subject. Slow wave sleep (SWS) as a percentage of total sleep time increased significantly between the start and the measurements at 9 and 18 weeks, being 21.9%, 29.9%, and 28.5% respectively. Anaerobic threshold increased significantly (P less than 0.05) over the first 9 weeks and continued to increase to the end of the training period (P less than 0.001) using VO2 when lactate level was 2 mmol/l as a percentage of VO2 max. With increase in fitness, sleep onset latency and wake time during sleep decreased and sleep efficiency improved. The results suggest that as fitness increases sleep quality improves.

Effect of physical conditioning on blood lactate disappearance after supramaximal exercise

The purpose of this study was to investigate the effect of physical conditioning on the rate of blood lactate disappearance during recovery from supramaximal exercise. The rate of blood lactate disappearance was determined in 11 female and 4 male subjects before and after a 6-week conditioning programme. Blood samples were taken during the 30 minutes following supramaximal exercise during both passive (resting) and active recoveries. Pre-test active recovery was performed at 25% VO2 max; post-test active recovery was performed at both the same absolute and relative intensities (% VO2 max) as during the pre-test. Eight of the subjects trained 4 days/week for 6 weeks with high-intensity interval bicycle ergometer exercise, and 7 subjects served as controls. The conditioning programme significantly (p less than .05) increased VO2 max by 6.7 ml/kg.min (15%) and work capacity on the cycle ergometer by 2.8 minutes (27%). Physical conditioning did not affect significantly (p less than .05) the rate of blood lactate disappearance measured during passive recovery or during active recovery at the same absolute intensity, but increased significantly (p less than .05) the rate of blood lactate disappearance during active recovery performed at the same relative exercise intensity. The increased disappearance rate following conditioning was attributed to the higher absolute intensity of recovery work performed.

Relationships of the anaerobic threshold with the 5 km, 10 km, and 10 mile races

The purpose of present study was to assess the relationship between anaerobic threshold (AT) and performances in three different distance races (i.e., 5 km, 10 km, and 10 mile). AT, VO2 max, and related parameters for 17 young endurance runners aged 16--18 years tested on a treadmill with a discontinuous method. The determination of AT was based upon both gas exchange and blood lactate methods. Performances in the distance races were measured within nearly the same month as the time of experiment. Mean AT-VO2 was 51.0 ml . kg-1 . min-1 (2.837 l . min-1), while VO2 max averaged 64.1 ml . kg-1 . min-1 (3.568 l . min-1). AT-HR and %AT (AT-VO2/VO2 max) were 174.7 beats . min-1 and 79.6%, respectively. The correlations between VO2 max (ml . kg-1 . min-1) and performances in the three distance races were not high (r = -0.645, r = -0.674, r = -0.574), while those between AT-VO2 and performances was r = -0.945, r = -0.839, and r = -0.835, respectively. The latter results indicate that AT-VO2 alone would account for 83.9%, 70.4%, and 69.7% of the variance in the 5 km, 10 km, and 10 mile performances, respectively. Since r = -0.945 (5 km versus AT-VO2) is significantly different from r = -0.645 (5 km versus VO2 max), the 5 km performance appears to be more related to AT-VO2 than VO2 max. It is concluded that individual variance in the middle and long distance races (particularly the 5 km race) is better accounted for by the variance in AT-VO2 expressed as milliliters of oxygen per kilogram of body weight than by differences in VO2 max.

Maximal anaerobic power in national level Indian players

The comparative study of aerobic power in different sports was conducted on 99 National Senior as well as National Junior players specialised in hockey and football, field games; volleyball and basketball, court games. The National Seniors were 27 hockey and 16 volleyball players, whereas, 32 football and 24 basketball players were the National Juniors. The maximal anaerobic power of the players was determined from maximal vertical velocity and body weight by the methods of margaria. The football players have been found to be highest followed by hockey, volleyball and basketball players in vertical velocity. It is observed that field game players are higher than the court game players in vertical velocity and that volleyball players possess higher maximum anaerobic power than football, hockey and basketball players.

Maximal steady state versus state of conditioning

Criteria for the identification of maximal steady state as related to state of conditioning were evaluated. 13 volunteers walker and/or ran during a series of 15 min tests on a treadmill. The speeds ranged from mild to exhaustive. Heart rate was monitored continuously; VO2 was determined from 6 min to 9 min; and venous blood was obtained at 10 min and 15 min for lactate analyses. Max VO2 was established for each subject. Subjects were classified on level of conditioning according to the quantity and quality of their activity record for the previous 6 months. The 10 min heart rate associated with a blood lactate level of 2.2 mM/L (MSSHR) was the best predictor of conditioning. The relative VO2 (% of max VO2) found with a 10 min blood lactate concentration of 2.2 mM/L (RMSSVO2) was almost as accurate as MSSHR in predicting state of conditioning. Changes in blood lactate levels between 10 min and 15 min were not significantly related to conditioning.

Assessment of aerobic and anaerobic capacity of athletes in treadmill running tests

The criteria of max VO2 and max O2D which are traditionally used in studying aerobic and anaerobic work capacity, have the different dimensions. While max VO2 is an index of the power of aerobic energy output, max O2D assesses the capacity of anaerobic sources. For a comprehensive assessment of physical working capacity of athletes, both aerobic and anaerobic capabilities should be represented in three dimensions, i.e. in indexes of power, capacity and efficiency. Experimental procedures have been developed for assessing these three parameters in treadmill running tests. It is proposed to assess anaerobic power by measuring excess CO2, concurrently with determination of max VO2. Maximal aerobic capacity is established as the product of max VO2 by the time of max VO2 maintenance determined in a special test with running at critical speed. The erogmetric criteria derived on the basis of the tests proposed, may be used for systematization of various physical work loads.