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Biomedical subjects

E C Rhodes

Publications and source records attributed to E C Rhodes.

36 records · Page 2Linked to original sources
PubMed1995

Maximal and ventilatory threshold responses to treadmill and water immersion running.

This study compared the metabolic responses of 13 endurance runners, familiar with nonweight-bearing water immersion (WI) running, at ventilatory threshold (Tvent) and maximal effort (VO2max) for both treadmill and WI running performance. Oxygen consumption (VO2), ventilation (VE), heart-rate (HR), VE/VO2, respiratory exchange ratio (RER), perceived exertion (RPE), and stride frequency (SF) were measured at Tvent and VO2max. Paired t-tests revealed higher VO2max (59.7 vs 54.6 ml.kg.-1min-1), HRmax (190 vs 175 bpm), RERmax (1.20 vs 1.10), VO2 at Tvent (46.3 vs 42.8 ml.kg.-1min-1), HR at Tvent (165 vs 152 bpm) for treadmill versus WI running, respectively. Treadmill and WI VEmax (109.0 vs 105.8 l.min-1), RPEmax (20), VE at Tvent (66.4 vs 65.7 l.min-1), RER at Tvent (0.99 vs 0.98), RPE at Tvent (13 vs 12) were similar, as were blood lactate [BLa] values obtained at 30 s (10.4 vs 9.8 mmol.l-1) and 5 min (9.7 vs 9.2 mmol.l-1) post-test. SF values over time were higher on the treadmill. The lower WI VO2max with similar peak [BLa] and lower SF values suggests that the active musculature and muscle recruitment patterns differ in WI running due to the high viscosity friction of water, and the nonweight-bearing nature of WI running.

Adult↗
PubMed1995

Applied physiology of ice hockey.

Today's elite hockey players are physically bigger and have improved levels of physiological fitness when compared with their predecessors. Correspondingly, previous ice hockey studies that have become widely referenced may have little relevance to current players and the way the game is presently played. A great need exists to apply exercise science to the game of ice hockey. Although much has been written about the physiology of ice hockey, there is little information based on well controlled studies. Particularly, there is a paucity of knowledge concerning optimal training schedules, training specificity, recovery profiles and seasonal detraining. Moreover, the reports that do exist have attempted to make comparisons across all levels of skill and talent. Thus, fundamental questions remain as to actual physiological exercise response and specialised training programmes for ice hockey players, particularly at the elite level. There is a demand for new properly designed experiments to find answers pertaining to the appropriate training methods for today's ice hockey players. Future research directions should consider the relationships between performance and such variables as neuromuscular skills, strength, power, peripheral adaptations, travel, hydration, detraining and sport-specific training programmes. Incidence and severity of injury among ice hockey players in relation to fatigue and fitness must also be investigated. Much of the information currently used in ice hockey will remain speculative and anecdotal until these studies are conducted.

Adaptation, Physiological↗
PubMed1993

Relationship between the lactate and ventilatory thresholds during prolonged exercise.

The anaerobic threshold is commonly measured by either blood lactate (lactate threshold) or ventilatory gases (ventilatory threshold); however, the relationship between these 2 methods is not conclusive. The lactate threshold has been characterised at either a fixed or variable blood lactate concentration (BLa). Recent studies have indicated a specific blood lactate concentration for each individual which considers the interindividual variations in lactate kinetics (individual anaerobic threshold), following either a continuous, exponential pattern or a discontinuous, threshold-like response. The ventilatory threshold is assessed using a variety of ventilatory parameters, many of which exhibit a threshold-like response during progressive exercise. Despite the apparent causal relationship between the stimulation of the ventilatory chemoreceptors and ultimately the ventilatory response and the accumulation of protons in the circulating blood, evidence does exist which refutes such a connection. Such evidence supporting a coincidental relationship examines no significant change in ventilation with significant increases in blood lactate concentration. Conversely, evidence from patients with McArdle's disease indicates that although no lactic acid is produced, these individuals do experience a threshold-like ventilatory response during incremental exercise. The ability to perform at the anaerobic threshold is now recognised as an integral component of endurance events. Several studies have concluded that the ventilatory threshold is highly correlated with endurance performance, in distances ranging from 26 miles (41.6 km) [r = -0.94] to 5 and 10 km (r = -0.945). The lactate threshold, in particular the individual anaerobic threshold, has been examined from a performance standpoint. Much of the literature supports the individual anaerobic threshold as the exercise intensity at which performance is maximal and able to be sustained for at least 50 minutes. With the variety of techniques utilised in assessing the anaerobic threshold, caution should be taken in interpretation of the results as the different protocols may elicit a variety of responses during incremental exercise. Furthermore, it is essential to account for the individual's unique response to such exercise.

Anaerobic Threshold↗
PubMed1992

Police Officer's Physical Abilities Test compared to measures of physical fitness.

This study compared the Police Officer's Physical Abilities Test (POPAT) with selected field and laboratory tests of physical fitness. Ninety-eight volunteer police officers (73 men, 25 women) completed all aspects of the testing. Fifty-five (55)% of the total group passed the POPAT by bettering the 4 min 15 sec "cut" point. Only 16% of the women and 68% of the men passed the overall test. Laboratory tests revealed a rather unfit sample of subjects (mean VO2 max = 42.6 ml.kg.min-1; % body fat = 22.9). Stepwise multiple regression indicated that 55% of the variance on the run component of the test was accounted for by maximal aerobic power and anaerobic capacity. The fight component of POPAT did not correlate highly with standard field tests of strength. Pass/fail aspects of the test were not clearly delineated by selected lab and field tests. It was concluded that POPAT, being a valid, task-specific, job related test, consists of motor abilities and technique as much as generalized fitness parameters.

Adult↗
PubMed1991

Relationship between blood lactate and excess CO2 in elite cyclists.

This study examined the relationship between expired non-metabolic CO2 (exCO2) and the accumulation of blood lactate. Particular emphasis was placed on the ventilatory (exCO2 and VE/VO2) and lactate threshold relationship. A total of 21 elite cyclists (15 males, 6 females) performed a progressive intensity bicycle ergometer test during which ventilatory parameters were monitored on-line at 15-s intervals, and blood lactate sampling occurred at each minute. Transition threshold values were determined for each of the three indices: excess CO2 (TexCO2), VE/VO2 (Tvent) and blood lactate (Tlac). The three threshold values (TexCO2, Tvent, Tlac) all correlated significantly (P less than 0.001) when each was expressed as an absolute VO2 (l min-1). A significant ANOVA (F = 8.41, P less than 0.001) and post-hoc correlated t-tests demonstrated significant differences between the TexCO2 and Tlac (P less than 0.001) and the TexCO2 and Tvent values (P less than 0.025). The Tlac occurred at an average blood lactate concentration of 3.35 mM, while the mean expired excess CO2 volume at the TexCO2 was 14.04 ml kg-1 min-1. Over an 11-min range across the threshold values (TexCO2 and Tlac), which were used as relative points of reference, the expired excess CO2 volume (ml kg-1 min-1) and blood lactate concentration (mM) correlated significantly (r = 0.69, P less than 0.001). Higher individual correlations over the same period of time (r = 0.82-0.96, P less than 0.001) stress the individual nature of this relationship. These results indicate a strong relationship between the three threshold values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

A review of blood lactate and ventilatory methods of detecting transition thresholds.

As far back as the 1930s exercise physiologists recognised the existence of critical levels of work intensity above which lactate accumulation increased drastically and energy production was affected. Investigation of these transition points (thresholds) both invasively and non-invasively has led to much recent controversy. Respiratory exchange variables such as Ve, Ve/VO2, VCO2, excess CO2 and blood lactate have been monitored for simple, double and exponential breakaway points to elucidate these critical work intensities. A number of studies have produced high correlations between endurance performance and anaerobic threshold calculations, further demonstrating the potential existence of critical work intensities. Much of the controversy surrounding these phenomena has centered on mechanisms and nomenclature. The term 'anaerobic threshold' has been severely criticised because in addition to the tissues being oxygen insufficient, an imbalance in the energy systems may have resulted. The anaerobic condition or lactate accumulation may be due to changes in lactate production and removal. Muscle fibre type and the fibre type recruitment patterns may also be important factors in threshold transitions. Further examination is made in this review of non-invasive measures for determining transition thresholds and protocols for elucidating the critical points.

Anaerobic Threshold↗
PubMed1989

Jet-lag and human performance.

The desynchronisation of an athlete's physiological and psychological cycles has adverse effects on his/her performance. The primary cause of dysrhythmia in an athlete is jet-lag, which is a rapid displacement across the earth's time zones and is often experienced while competing in international events and in continental leagues. General symptoms which arise from dysynchronization include malaise, appetite loss, tiredness during the day and disturbed sleep. The specific symptoms resulting from jet-lag are characterised as phase shifts in physiological and psychological cycles. These phase shifts occur in body temperature, ability to mobilise energy substrates, excretion of water and metabolites, arousal levels, sleep/wake cycles and reaction time. The severity of these adverse effects and therefore the time required for resynchronization depends on the ability to preset the bodily rhythms prior to flying, the number of time zones crossed, the direction of flight, the type of individual (introvert/extrovert), age, social interaction and activity, diet plan and prescribed use of chronobiotic drugs.

Circadian Rhythm↗
PubMed1987

Correlation between ventilatory threshold and endurance capability in marathon runners.

The purpose of the study was to develop an index of endurance capability [i.e., "the ability to sustain a high fractional utilization of maximal oxygen uptake (VO2max) for a prolonged period of time"]. The index was based on the linear reduction of fractional utilization of VO2max with total running time greater than 7 min plotted on a log scale. The endurance index estimated from VO2max, running efficiency and the marathon performance of 18 male runners (30 +/- 7 yr old; VO2max = 66 +/- 5 ml.kg-1.min-1) ranged between -4.07 and -9.96% VO2max.1 nt-1 (mean +/- SD = -6.40 +/- 1.50) and was not related to VO2max (r = 0.107) or speed in the marathon race (r = 0.354). However, the endurance index was closely related (r = 0.853) to the fractional utilization of VO2max at ventilatory threshold (breakaway of the excess CO2 elimination curve) which occurred at 76.1 +/- 5.5% VO2max in response to a graded treadmill test. These results indicate that: (i) running time on long distance races is not, per se, an adequate measure of endurance capability because of the major contribution of VO2max to long distance running performance; (ii) the endurance index expressed as %VO2max.1n t-1 is an objective and independent index of endurance capability; and (iii) runners with a high endurance capability tend to hyperventilate at higher relative workload during a graded treadmill test.

Adult↗
PubMed1986

Physiological profiles of the Canadian Olympic Soccer Team.

Physiological profiles of elite athletes are becoming increasingly important both for the sport scientist and coach, primarily to effectively develop training programs and to use as a motivational tool in the pursuit of excellence. Descriptive profiles were developed on 16 aspirants of the Canadian Olympic Soccer team during their training program at U.B.C. Selected strength measures were obtained from a Cybex II isokinetic dynamometer at 30 degrees sec-1. Metabolic variables were derived utilizing a Beckman metabolic cart interfaced with a Hewlitt Packard 3052A data acquisition system. Protocols involved were the following: VO2max (initial velocity 8.05 km X h-1, greater than 0.805 km X min-1); Anaerobic speed test (AST) (20% grade, 12.8 km X h-1). the nonlinear increase in excess CO2 was utilized to determine the anaerobic threshold (AT). (Table: see text). Recommendations emphasized maintenance of low body fat, increasing maximal aerobic power by approximately 10% and creating a hams/quads ratio of 60%. Also, a nutritional survey and periodic evaluation of iron status is necessary for the athletes.

Adult↗
PubMed1986

The relationship of individual anaerobic thresholds to total, alactic and lactic oxygen debts after a set treadmill run.

This study investigated the relationship of individual anaerobic thresholds to oxygen debt. Anaerobic threshold speed (VTAM) was determined for 21 male university students using a continuous ramp treadmill protocol. The onset of anaerobiosis was determined by visual inspection of excess CO2 elimination. The following week, all subjects ran at the treadmill speed 3.3 m.sec-1 for 10 minutes (this speed split the group into two halves). Recovery oxygen consumption was monitored after this run. Application of double exponential equations by computer and subsequent integration was used to calculate total, alactic, and lactic oxygen debts. Subjects who ran above their VTAM (group L-VTAM) had significantly (p less than .05) higher total, lactic and alactic debts compared to subjects who ran below their VTAM (group H-VTAM). The total debt demonstrated a significant (p less than .05) negative correlation (r = .77) to VTAM in group L-VTAM. This appears to be due to increasing lactic debt, that was also significantly (p less than .05) negatively correlated (r = -.73) to VTAM. Group H-VTAM did not exhibit this characteristic. This study demonstrates that VTAM, as determined by excess CO2 elimination, is a critical factor in determining oxygen debt and therefore, work above this point (which results in the onset of metabolic acidosis) may limit the optimal running speed for a given distance.

Acid-Base Equilibrium↗
PubMed1985

Submaximal exercise responses of tetraplegics and paraplegics.

This study describes responses of 21 wheelchair users to a continuous, increasing work rate test to exhaustion on a wheelchair ergometer. Heart rate, ventilation, O2 uptake, respiratory exchange ratio, ventilation equivalent for O2, and O2 pulse were determined for each minute. Subjects were divided into tetraplegic (n = 8), high-lesion paraplegic (n = 6), and low-lesion paraplegic (n = 7) groups. Linear regression analyses, with O2 uptake as the independent variable, were used to determine the strength of relationships within each group and differences between groups in slopes and intercepts of regression equations. All variables were significantly (P less than 0.05) related to O2 uptake (r = 0.42-0.94). The only significant difference between the high- and low-lesion paraplegic groups was for heart rate intercept, as the heart rate for the low-lesion group tended to be lower at any given O2 uptake. Tetraplegics had a higher intercept and/or slope for ventilation equivalent, ventilation, and respiratory exchange ratio and lower intercepts for heart rate and O2 pulse. These differences in responses to a progressive exercise task are logically related to the differences in maximal O2 uptake, functional muscle mass, and vasomotor and cardiac control of the groups.

Exercise Test↗
PubMed1983

Maximal exercise responses of tetraplegics and paraplegics.

Eight tetraplegic and 13 paraplegic subjects performed a continuous progressive loading exercise test to exhaustion on a wheelchair ergometer. Their cardiorespiratory responses at maximal O2 uptake were analyzed after initially grouping subjects according to the international system for classification of wheelchair athletes. Analysis of variance provided a basis for regrouping the subjects into tetraplegic (T), high-lesion paraplegic (HLP), and low-lesion paraplegic (LLP) groups and indicated significant differences (P less than 0.05) in maximal power output (24, 47, and 80 W) and O2 uptake (0.97, 1.62, and 2.42 l/min) for T, HLP, and LLP, respectively. T had a significantly lower maximal heart rate (110) compared with the paraplegic values (175 and 190), whereas the HLP, in contrast to the LLP, had a lower maximum ventilation (66 vs. 101 l/min) and a lower O2 pulse (9.3 vs. 12.7 ml/beat). The ventilatory equivalent for O2 was similar in all groups to values for able-bodied subjects in maximal arm crank ergometry, however, suggesting a lack of any respiratory limit to maximal O2 delivery. No differences were noted in respiratory exchange ratio or net efficiency between the groups. In addition to limitations of functional muscle mass, the data suggested that the reduced cardiac capacity of T and HLP may also be linked to their lower maximal exercise capacity and O2 uptake.

Adult↗
PubMed1983

Salbutamol and treadmill performance in non-atopic athletes.

Salbutamol and treadmill performance in non-atopic athletes. Med. Sci. Sports Exerc., Vol. 15, No. 6, pp. 520-522, 1983. Nineteen aerobic, non-atopic, athletes (10 females, 9 males) were studied in a double-blind fashion to determine the effect of a therapeutic dosage of salbutamol on pulmonary function, oxygen consumption (VO2max), heart rate (HR), and anaerobic threshold (AT). A placebo and salbutamol (in aerosol form) were administered in a dosage of two puffs four times per day. Forced vital capacity (FVC), FEV1.0, and mid-maximal expiratory flow were assessed prior to a maximal treadmill run, and at 5, 10, and 15 min of recovery. Resting and maximal HR, VO2max, AT, and VE were determined prior to and immediately after the 1-wk experimental period. Pre-test results showed no evidence of airway obstruction in any athlete. There was no significant change in any pulmonary function variable as a result of salbutamol administration. Maximal oxygen consumption showed a slight, nonsignificant (P greater than 0.05) decrease in both the salbutamol and placebo groups. There was also a similar nonsignificant decrease in pulmonary function in both groups. Resting and maximal HR and AT were unchanged. These results indicate that therapeutic administration of a selective beta-2 agonist does not affect pulmonary function or performance-related variables in non-atopic elite athletes.

Adult↗
PubMedDate not supplied

A critical review of the literature on ratings scales for perceived exertion.

The study of human performance and perceived exertion during physical activity has been an area of considerable interest and research for over 50 years. This review considers the evidence of many investigators who have been researching the physiological basis as well as non-physiological basis for the ratings of perceived exertion. During low levels of activity, physical perception in the working muscles appears to be the primary stimulus for effort perception. When work intensity exceeds the lactate threshold, incremental elevations in blood lactate complement peripheral input from the neuromuscular mechanisms. Once a critical absolute ventilatory threshold is reached, central input also contributes to effort perception. In most instances, peripheral input predominates over central cues, although it has been shown that pronounced central cues may dominate the perception of effort. Central (heart rate, VE, VO2) or local (muscle and blood lactate, adenosine triphosphate, creatine phosphokinase, glycogen) cues highlighted in these studies demonstrate both the complexity of effort perception, and the need for better understanding of the physiological components upon which it is based. Athletes have been shown to have a greater tendency to reduce perceptual ratings than their non-active counterparts. In view of these observations, it is apparent that a theoretical framework based upon physiological and psychological considerations may exist to support the concept of training-induced alterations in perceived exertion. This appears to be particularly true in higher ranges of exercise intensity. Part of the problem in reaching a conclusion on the issue of perceptual ratings trainability centres upon the agreement on what should be recognised as a significant decrement in perceived exertion. It is concluded that there is considerable variation in the findings of the literature and that any reported variations in performance may well be greatly influenced by intersubject variability, the type of exercise, and nutritional status of subject. Further research is required to understand this issue better.

Aerobiosis↗