Sex differences in the rate of fatigue development and recovery.

BACKGROUND: Many musculoskeletal injuries in the workplace have been attributed to the repetitive loading of muscle and soft tissues. It is not disputed that muscular fatigue is a risk factor for musculoskeletal injury, however the disparity between gender with respect to muscular fatigability and rate of recovery is not well understood. Current health and safety guidelines do not account for sex differences in fatiguability and may be predisposing one gender to greater risk. The purpose of this study was to quantify the sex differences in fatigue development and recovery rate of lower and upper body musculature after repeated bouts of sustained isometric contractions. METHODS: Twenty-seven healthy males (n = 12) and females (n = 15) underwent bilateral localized fatigue of either the knee extensors (male: n = 8; female: n = 8), elbow flexors (male: n = 8; female: n = 10), or both muscle groups. The fatigue protocol consisted of ten 30-second sub-maximal isometric contractions. The changes in maximum voluntary contraction (MVC), electrically evoked twitches, and motor unit activation (MUA) were assessed along with the ability to control the sustained contractions (SLP) during the fatigue protocol using a mixed four-factor repeated measures ANOVA (gender x side x muscle x time) design with significance set at p < 0.05. RESULTS: There was a significant loss of MVC, MUA, and evoked twitch amplitude from pre- to post-fatigue in both the arms and legs. Males had greater relative loss of isometric force, a higher rate of fatigue development, and were less capable of maintaining the fatiguing contractions in the legs when compared to the females. CONCLUSION: The nature of the induced fatigue was a combination of central and peripheral fatigue that did not fully recover over a 45-minute period. The results appear to reflect sex differences that are peripheral, and partially support the muscle mass hypothesis for explaining differences in muscular fatigue.

A light-weight cooling vest enhances performance of athletes in the heat.

During the 1990s, emphasis on the health and safety of people who exercise in hot, humid conditions increased and many organizations became aware of the need for protection against heat-related disorders. A practical, pre-cooling strategy applicable to several sporting codes, which is low cost, easy to use, light-weight and which enhances cooling of the human body prior to and following exercise, was developed and tested. Eight males and eight females participated in a maximal oxygen consumption (VO2max) test and four trials: a control (without cooling) and wearing each of three different cooling vests (A, B, C). Vests were worn during the rest, stretch, warm-up (50% VO2max) and recovery stages of the protocol, but not during the 30 min run (70% VO2max). Core and skin temperatures during exercise were reduced (by approximately 0.5 degrees C, rectal; 0.1-1.4 degrees C, abdominal skin temperature) and sweat rates were lower (by approximately 10-23%). Endurance times for running at 95% of VO2max were increased by up to 49 s. Perceptions of the thermal state and skin wetness showed changes to greater levels of satisfaction. Physiological and sensory responses were related to design features of the vests.

Local cold acclimation of the hand impairs thermal responses of the finger without improving hand neuromuscular function.

AIM: To investigate the effects of cold acclimation on the thermal response and neuromuscular function of the hand. METHODS: Ten healthy subjects [three female, seven male, age (mean +/- SD): 27.9 +/- 7.9 years] immersed their right hand in 8 degrees C water for 30 min, 5 days a week for 3 weeks. On the first and the last day, neuromuscular function of the first dorsal interosseus (FDI) muscle was tested. RESULTS: There was no significant change in maximal voluntary contraction strength or evoked contractile characteristics of the FDI after cold acclimation. Minimum finger temperature decreased significantly from 10.6 +/- 1.2 to 9.3 +/- 0.8 degrees C after 3 weeks (P < 0.01), with most of the decrease occurring after a single exposure. Mean finger temperature dropped significantly from 14.2 +/- 1.9 to 11.7 +/- 1.4 degrees C following cold acclimation (P < 0.05), with 90% of this adaptation occurring after 5 days. Onset time of cold-induced vasodilatation increased from 446 +/- 171 to 736 +/- 384 s (P < 0.05) and the amplitude decreased from 5.3 +/- 3.2 to 2.5 +/- 2.1 degrees C (P < 0.05). This was significantly different from the control group, who immersed their right hand on the first and last days only. CONCLUSION: These data suggest that cold acclimation does not enhance hand temperature or function but may put the hands at a greater risk of cold injury when exposed to the cold.

The influence of whole-body vs. torso pre-cooling on physiological strain and performance of high-intensity exercise in the heat.

Little research has been reported examining the effects of pre-cooling on high-intensity exercise performance, particularly when combined with strategies to keep the working muscle warm. This study used nine active males to determine the effects of pre-cooling the torso and thighs (LC), pre-cooling the torso (ice-vest in 3 degrees C air) while keeping the thighs warm (LW), or no cooling (CON: 31 degrees C air), on physiological strain and high-intensity (45-s) exercise performance (33 degrees C, 60% rh). Furthermore, we sought to determine whether performance after pre-cooling was influenced by a short exercise warm-up. The 45-s test was performed at different (P<0.05) mean core temperature [(rectal+oesophageal)/2] [CON: 37.3+/-0.3 (S.D.), LW: 37.1+/-0.3, LC: 36.8+/-0.4 degrees C] and mean skin temperature (CON: 34.6+/-0.6, LW: 29.0+/-1.0, LC: 27.2+/-1.2 degrees C) between all conditions. Forearm blood flow prior to exercise was also lower in LC (3.1+/-2.0 ml 100 ml tissue(-1) x min(-1)) than CON (8.2+/-2.5, P=0.01) but not LW (4.3+/-2.6, P=0.46). After an exercise warm-up, muscle temperature (Tm) was not significantly different between conditions (CON: 37.3+/-1.5, LW: 37.3+/-1.2, LC: 36.6+/-0.7 degrees C, P=0.16) but when warm-up was excluded, T(m) was lower in LC (34.5+/-1.9 degrees C, P=0.02) than in CON (37.3+/-1.0) and LW (37.1+/-0.9). Even when a warm-up was performed, torso+thigh pre-cooling decreased both peak (-3.4+/-3.8%, P=0.04) and mean power output (-4.1+/-3.8%, P=0.01) relative to the control, but this effect was markedly larger when warm-up was excluded (peak power -7.7+/-2.5%, P=0.01; mean power -7.6+/-1.2%, P=0.01). Torso-only pre-cooling did not reduce peak or mean power, either with or without warm-up. These data indicate that pre-cooling does not improve 45-s high-intensity exercise performance, and can impair performance if the working muscles are cooled. A short exercise warm-up largely removes any detrimental effects of a cold muscle on performance by increasing Tm.

Effect of pre-cooling, with and without thigh cooling, on strain and endurance exercise performance in the heat.

Body cooling before exercise (i.e. pre-cooling) reduces physiological strain in humans during endurance exercise in temperate and warm environments, usually improving performance. This study examined the effectiveness of pre-cooling humans by ice-vest and cold (3 degrees C) air, with (LC) and without (LW) leg cooling, in reducing heat strain and improving endurance performance in the heat (35 degrees C, 60% RH). Nine habitually-active males completed three trials, involving pre-cooling (LC and LW) or no pre-cooling (CON: 34 degrees C air) before 35-min cycle exercise: 20 min at approximately 65% VO2peak then a 15-min work-performance trial. At exercise onset, mean core (Tc, from oesophagus and rectum) and skin temperatures, forearm blood flow (FBF), heart rate (HR), and ratings of exertion, body temperature and thermal discomfort were lower in LW and LC than CON (P<0.05). They remained lower at 20 min [e.g. Tc: CON 38.4+/-0.2 (+/-S.E.), LW 37.9+/-0.1, and LC 37.8+/-0.1 degrees C; HR: 177+/-3, 163+/-3 and 167+/-3 b.p.m.), except that FBF was equivalent (P=0.10) between CON (15.5+/-1.6) and LW (13.6+/-1.0 ml.100 ml tissue(-1) x min(-1)). Subsequent power output was higher in LW (2.95+/-0.24) and LC (2.91+/-0.25) than in CON (2.52+/-0.28 W kg(-1), P=0.00, N=8), yet final Tc remained lower. Pre-cooling by ice-vest and cold air effectively reduced physiological and psychophysical strain and improved endurance performance in the heat, irrespective of whether thighs were warmed or cooled.

Effect of daily versus intermittent exposure on heat acclimation.

In order to compare the effectiveness of a daily to an intermittent acclimation protocol, 14 competitive rowers (mean +/- SD VO2peak = 48 +/- 7 ml x kg x min(-1)) were randomly assigned to either a consecutive (10 consecutive days) or intermittent acclimation group (10 sessions over 3 weeks). For every heat exposure, subjects in each group exercised for 30 min at 70% VO2peak in an environmental chamber set at 38 degrees C and 70% relative humidity. Acclimation state was monitored by measuring heart rate (HR), rectal and skin temperature (Tre and Tsk), ratings of perceived exertion (RPE) and whole body sweat rate (SR) during each heat exposure. Final exercise Tre decreased significantly by 0.6 +/- 0.7 degrees C with intermittent heat exposure but the decrease was significantly larger (p < 0.05) with consecutive day heat exposure (1.0 +/- 0.1 degrees C). Final exercise HR also decreased significantly by 13 +/- 12 bpm (p < 0.05) in the consecutive group, and non-significantly by 5 +/- 13 bpm in the intermittent group. RPE decreased with daily (5 +/- 1, p < 0.05) but did not significantly decrease with intermittent heat exposure (1 +/- 3). Similarly, Tsk significantly decreased with consecutive (0.4 +/- 0.2 degrees C, p < 0.05) but not intermittent exposure (0.2 +/- 0.3 degrees C) and SR did not change in either group. Minimal adaptation occurs with intermittent heat exposure and it appears that daily heat exposure is the most effective acclimation strategy.

Indices of lactate threshold and their relationship with 10-km running velocity.

PURPOSE: The object of this study was to determine the relationship of three measures of running velocity at lactate threshold (LT) with 10-km running velocity. The methods used to determine LT velocity (m.s(-1)) during submaximal treadmill running were: 1) LT(1), the velocity preceding two consecutive increases in blood lactate > or = 1 mmol.L(-1); 2) LT(D), the velocity associated with the maximum perpendicular distance between the nonlinear regression line and the straight line formed by the two end data points of the blood lactate profile; and 3) LT(4), the velocity corresponding to a blood lactate concentration of 4 mmol.L(-1). METHODS: Thirty competitive and recreational runners (11 female and 19 male) undertook two 10-km time trials (7 d apart), three treadmill familiarization sessions over the following 21 d, and then completed an incremental submaximal treadmill run. From blood lactate samples taken during the submaximal run, mean LT velocity (+/- SD) at LT(1) (3.76 +/- 0.57), LT(D) (3.79 +/- 0.58), and LT(4) (4.11 +/- 0.64) was determined. Pearson product moment correlation analysis revealed a strong relationship between all mean LT speeds and mean 10-km running velocity (3.77 +/- 0.57), with the strongest relationship observed for LT(D) (r = 0.86, P < 0.001). Correlations by gender between LT(D) and 10-km velocity were r = 0.84 (female) and r = 0.78 (male). Male subjects had significantly higher LT velocities than female subjects using all methods (P < 0.001), and velocity at LT(4) was significantly faster than 10-km velocity and velocity at LT(1) and LT(D) (P < 0.001). CONCLUSION: Of the methods measured, LT(D) appears to be the most sensitive and valid measure of LT velocity and may be of benefit in monitoring the training program of 10-km distance runners.

Running economy is impaired following a single bout of resistance exercise.

The purpose of this study was to determine whether a low-volume high-intensity resistance training session influenced running economy during a subsequent aerobic treadmill run. Nine well trained distance runners (mean +/- SD; VO2max, 66.6 +/- 10.2 ml x kg(-1) x min(-1); weight, 65.8 +/- 10.2 kg; height, 173.4 +/- 7.8 cm; age 20 +/- 1.1 years) with resistance training experience performed treadmill running at two different speeds (0.56 m x sec(-1) and 0.20 m x sec(-1) below speed corresponding to lactate equilibrium) either rested or 1, 8 or 24 hours after a 50-minute whole body resistance training session. Running economy was assessed using open circuit spirometry while heart rate was recorded telemetrically. The contractile properties of the quadriceps femoris were also determined following each resistance training session and prior to each treadmill run using percutaneous electrical stimulation. Submaximal oxygen consumption was significantly increased one hour (2.6 +/- 2.3%, p= 0.007), and eight hours (1.6 +/- 2.5%, p= 0.032), but not 24 hours after resistance training. No significant differences were found in exercising heart rate, ventilation, respiratory exchange ratio, ratings of perceived exertion, or running mechanics. Peak twitch torque, time to peak torque, and half relaxation time of the quadriceps femoris were significantly reduced immediately following resistance training while peak twitch torque was also lower one hour following resistance training. Running economy following a resistance training session is impaired for up to 8 hours. This change was not paralleled by a concomitant change in exercising heart rate. The mechanism responsible for increased oxygen consumption following resistance training may be related to impairment of the force generating capacity of skeletal muscle, as there was a significant decrement in the contractile properties of the quadriceps femoris following resistance training.

Effect of precooling on high intensity cycling performance.

OBJECTIVE: To examine the effects of precooling skin and core temperature on a 70 second cycling power test performed in a warm and humid environment (29 degrees C, 80% relative humidity). METHODS: Thirteen male national and international level representative cyclists (mean (SD) age 24.1 (4.1) years; height 181.5 (6.2) cm; weight 75.5 (6.4) kg; maximal oxygen uptake (VO2peak) 66.1 (7.0) ml/kg/min) were tested in random order after either 30 minutes of precooling using cold water immersion or under control conditions (no precooling). Tests were separated by a minimum of two days. The protocol consisted of a 10 minute warm up at 60% of VO2peak followed by three minutes of stretching. This was immediately followed by the 70 second power test which was performed on a standard road bicycle equipped with 172.5 mm powermeter cranks and mounted on a stationary ergometer. RESULTS: Mean power output for the 70 second performance test after precooling was significantly (p<0.005) increased by 3.3 (2.7)% from 581 (57) W to 603 (60) W. Precooling also significantly (p<0.05) decreased core, mean body, and upper and lower body skin temperature; however, by the start of the performance test, lower body skin temperature was no different from control. After precooling, heart rate was also significantly lower than control throughout the warm up (p<0.05). Ratings of perceived exertion were significantly higher than the control condition at the start of the warm up after precooling, but lower than the control condition by the end of the warm up (p<0.05). No differences in blood lactate concentration were detected between conditions. CONCLUSIONS: Precooling improves short term cycling performance, possibly by initiating skin vasoconstriction which may increase blood availability to the working muscles. Future research is required to determine the physiological basis for the ergogenic effects of precooling on high intensity exercise.

Biofeedback and relaxation techniques improves running economy in sub-elite long distance runners.

PURPOSE: The purpose of this investigation was to determine whether a psychophysiological intervention of biofeedback and relaxation could decrease the submaximal oxygen consumption (VO2submax) during treadmill running and improve running economy for a group of trained long distance runners. METHODS: Before and after a 6-wk control phase, seven long distance runners were tested for running economy, peak oxygen consumption (VO2peak), peak running velocity, and stretch-shortening cycle efficiency. These runners then participated in a 6-wk training program in which they learned and practiced relaxation techniques and ran on the treadmill at a velocity eliciting 70% of peak running velocity for 10 min while biofeedback of heart rate (HR), ventilation (VE), and VO2 was presented to them. RESULTS: Data indicated that participants were able to lower their VO2, HR, and VE at lactate threshold by 7.3%, 2.5%, and 9.2%, respectively, using relaxation techniques (P<0.05). Post-tests of lactate threshold, VO2peak, peak running velocity, and stretch-shortening cycle efficiency showed that these changes did not occur as a result of a training effect. CONCLUSION: It was concluded that the improvements in running economy occurred as a result of the psychophysiological intervention.

Do changing patterns of heat and humidity influence thermoregulation and endurance performance?

The purpose of this project was to determine whether changing patterns of temperature and humidity, as expected in the morning versus afternoon, had a differential effect on thermoregulation and endurance performance. Eight male distance runners each participated in two heat pattern tests consisting of two hours treadmill running at 70%-maximum oxygen consumption. The mean heat load for each test was identical (22.2 degrees C wet bulb temperature) but either dry bulb temperature increased (24 to 27.5 degrees C) or decreased (27.5 to 24 degrees C) over the course of the two hour heat stress test. Whole body sweat rate was 10.7% higher (p<0.05) and there was greater plasma volume loss (2.7 versus 1.6%, p<0.05) in the cooling versus warming pattern test. Mean skin and body temperature changed in a significantly different (p<0.05) manner between the two patterns and closely followed ambient dry bulb temperature change. The thermoregulatory variables of heart rate and rectal temperature were not affected and performance did not differ between pattern tests. Ratings of perceived exertion (RPE) and oxygen consumption were also not significantly different between cooling and warming test. In summary, although some minor differences were noted, thermal homeostasis was maintained equally well during either warming or cooling for wet bulb temperatures between 24 and 27 degrees C. The mean heat load is therefore more important than changing patterns of temperature and humidity in determining an individual's physiological response to exercise in a warm environment.

The relationship of strength and muscle balance to shoulder pain and impingement syndrome in elite quadriplegic wheelchair rugby players.

Wheelchair athletes are susceptible to injuries related to overuse of the shoulder, in particular shoulder impingement syndrome. The present study examined the relationship of shoulder pain to demographic details, isokinetic strength and muscle balance in 8 elite quadriplegic rugby players. Demographic data were collected using personal interviews and each subject was clinically examined for signs of impingement syndrome by a physician. In addition each subject underwent bilateral isokinetic strength testing of the shoulder at 60 and 180 deg/s for abduction/adduction and internal/external rotation. A series of step-wise multiple discriminant analysis successfully predicted clinical symptoms from demographic, muscular strength and balance data. In particular, there was a significant deficit in adductor strength and this was related to shoulder pain and wasting of the scapular muscles. This strength deficit may be due to the high level of spinal lesions in the quadriplegic population. The level of spinal lesion may contribute to the aetiology of shoulder pathology in quadriplegia, and differentiate it from that observed in able-bodied athletes who exhibit weak abductors.

The effect of warm-up intensity on range of motion and anaerobic performance.

Although there is a paucity of scientific support for the benefits of warm-up, athletes commonly warm up prior to activity with the intention of improving performance and reducing the incidence of injuries. The purpose of this study was to examine the role of warm-up intensity on both range of motion (ROM) and anaerobic performance. Nine males (age = 21.7 +/- 1.6 years, height = 1.77 +/- 0.04 m, weight = 80.2 +/- 6.8 kg, and VO2max = 60.4 +/- 5.4 ml/kg/min) completed four trials. Each trial consisted of hip, knee, and ankle ROM evaluation using an electronic inclinometer and an anaerobic capacity test on the treadmill (time to fatigue at 13 km/hr and 20% grade). Subjects underwent no warm-up or a warm-up of 15 minutes running at 60, 70 or 80% VO2max followed by a series of lower limb stretches. Intensity of warm-up had little effect on ROM, since ankle dorsiflexion and hip extension significantly increased in all warm-up conditions, hip flexion significantly increased only after the 80% VO2max warm-up, and knee flexion did not change after any warm-up. Heart rate and body temperature were significantly increased (p < 0.05) prior to anaerobic performance for each of the warm-up conditions, but anaerobic performance improved significantly only after warm-up at 60% VO2max (10%) and 70% VO2max (13%). A 15-minute warm-up at an intensity of 60-70% VO2max is therefore recommended to improve ROM and enhance subsequent anaerobic performance.

Physical and physiological factors associated with success in the triathlon.

The physiological demands of sequential exercise in swimming, cycling and running are unique and require the triathlete to develop physical and physiological characteristics that are a blend of those seen in endurance swimming, cycling and running specialists. Elite triathletes are generally tall, of average to light weight and have low levels of body fat, a physique which provides the advantages of large leverage and an optimal power to surface area or weight ratio. Triathletes have high maximum oxygen uptake (VO2max) values, but VO2max may be on average marginally lower than values previously observed in endurance specialists. Although VO2max is a predictor of performance in triathletes of mixed abilities, it cannot be used to predict performance within homogenous groups of elite performers. Nevertheless, elite triathletes have significantly higher VO2max values than sub-elite triathletes and high VO2max levels are required for success in triathlons. The ability of the triathlete to exercise at a lower percentage of VO2max for a given submaximal workload may be especially important to triathlon success. This is influenced not only by VO2max itself, but also by anaerobic threshold and economy of movement. Anaerobic threshold, as indicated by either ventilatory threshold or lactate threshold, improves with triathlon training and when measured in the appropriate exercise mode has been related to swim, cycle and run performance in the triathlon. Economy of movement in swimming, cycling and running is also related to triathlon performance, and swimming economy in particular appears to be an area where triathletes could make large improvements. Future research should utilise experimental methodologies to investigate triathlon physiology, in particular, the influence of sequential exercise in different exercise modes on physiological function and examine the influence of different training interventions on triathlon physiology and performance.

The influence of a strength-sprint training sequence on multi-joint power output.

The purpose of this study was to determine whether adaptation to single- versus multi-joint strength training and sprint training was different and whether sequencing strength prior to sprint training was beneficial for increasing power. Thirty-two untrained males were assigned to control (C), sprint-sprint (SS), multi-joint (MJS), or single-joint (SJS) strength-sprint groups. Subjects were tested before training, after 8 wk of strength or sprint training, and after an additional 6 wk of sprint training. By mid-training both SJS and MJS increased 10 repetition maximum strength, but this was not transferable to isometric or isokinetic strength or rate of torque development. SS showed no improvement in these variables. All training groups increased cycle ergometer power output by 8 wk and had similar fiber hypertrophy with no EMG changes. Subsequent sprint training continued to increase maximum power with no further hypertrophy. Tibial nerve conduction velocity increased in all training groups. These results indicate little difference in adaptation to single- and multi-joint strength training. Strength or power improvements caused by training in these models does not transfer to isometric or isokinetic movements. Further, sequenced strength-spring training provided no additional power gain over sprint training alone.

Neuromuscular differences between volleyball players, middle distance runners and untrained controls.

Volleyball players, middle distance runners and non-athletes (n = 10/group) were tested to determine whether neuromuscular differences existed between groups and to clarify the roles of factors involved in maximal power production. The runners were leaner than controls, while the volleyball players were taller, heavier and had larger thigh volumes than the other groups. The volleyball players had higher absolute cycle ergometer power than both middle distance (26%) and control (15%) groups, but differences disappeared when expressed relative to body mass or thigh volume. Volleyball athletes were also stronger than both middle distance (51, 52%) and control subjects (33, 35%) for isokinetic leg extension and plantar flexion respectively (0-4.19 rad.s-1). In leg press they were stronger than middle distance (32%) and control subjects (36%) for only the isometric and 1.05 rad.s-1 contraction. The volleyball players also had higher rates of isometric torque development than the other groups, however nerve conduction velocity did not vary. Vastus lateralis biopsy samples revealed no differences in percent Type II muscle fibers, or fiber cross-sectional area between groups, yet volleyball athletes had larger Type II/I fiber area ratio than controls (15%). Both strength, rate of torque development and power were related to muscle and muscle fiber size variables, but not fiber distribution or nerve conduction velocity. The size of type II muscle fibers seemed to be especially important since this was the only variable related to power when adjusted for body size.

Reliability of measuring isometric and isokinetic peak torque, rate of torque development, integrated electromyography, and tibial nerve conduction velocity.

To determine the reliability of measures used in neuromuscular diagnosis and rehabilitation, 23 adults underwent identical testing on two occasions. Intraclass correlation coefficients (ICC) showed the reliability of peak torque measurement to depend both on the movement tested and velocity of contraction (leg extension ICC = 0.64-0.94, plantar flexion ICC = 0.55-0.76, leg press ICC = 0.72-0.91). Peak rate of torque development (RTD) and the percentage of peak torque at peak RTD were not reliable for any movement (ICC = 0.02-0.28). Mean RTD between 30% and 60% of peak torque was unreliable for leg press (ICC = 0.46), yet fairly reliable for both knee extension (ICC = 0.61) and plantar flexion (ICC = 0.63). Mean integrated electromyography (IEMG) showed fair to good reliability for isometric and 1.05 rad.s-1 leg press (ICC = 0.66, 0.90, respectively), and plantar flexion and leg extension (ICC = 0.75-0.89). Tibial nerve conduction velocity was highly reliable (ICC = 0.89). A range of reliabilities can be expected when measuring these variables, and must be considered when interpreting neuromuscular data.

Physiological predictors of short-course triathlon performance.

The purpose of this study was to investigate if selected physiological variables were related to triathlon performance. Eighteen male and seven female triathletes competed in a short-course triathlon (1-km swim, 30-km cycle, 9-km run) and underwent physiological testing within 14 d. VO2max and ventilatory threshold (VT) were measured on a cycle ergometer, treadmill, and tethered swim apparatus. Leg flexion and extension strength were measured on a Cybex II isokinetic dynamometer. Multiple linear regression did not improve the prediction of triathlon performance over that provided by simple correlations. Swim performance was related to relative swim VO2max in both males (r = -0.48) and females (r = -0.93) as well as the resistance pulled at swim VT (r = -0.81) and absolute leg flexion strength (r = -0.77) in females. No physiological variables were significantly related to cycling time in either gender. Running time was related to relative VO2max (r = -0.88) in females and velocity at run VT in both females (r = -0.88) and males (r = -0.73). Relative swim VO2max (r = -0.98), velocity at run VT (r = -0.89), and absolute leg flexion strength (r = -0.80) were related to overall performance in female triathletes. The only significant predictor of overall triathlon time for males was velocity at run VT (r = -0.78). It therefore appears that in short-course triathletes physiological variables in swimming and running are important to overall performance. Differences in sample size, group variability, and level of performance between males and females may account for the reported differences in the physiological predictors of performance between genders.

The validation of backward extrapolation of submaximal oxygen consumption from the oxygen recovery curve.

The purpose of this study was to determine the validity and practicality of exponential vs linear backward extrapolation of the O2 recovery curve for prediction of exercise oxygen consumption (VO2). Eight men and women, age 20.1, 0.9 years, body mass 66.0, 2.5 kg (mean, SEM), completed seven bouts of cycle ergometer exercise at submaximal power outputs ranging from 50 to 175 W. Respiratory gases were collected from each subject during exercise and recovery. The monoexponential extrapolation of five recovery samples (r2 = 0.85) and linear extrapolation of one recovery sample taken during the first 20-s of recovery (r2 = 0.83) accounted for similar amounts of variance in predicting exercise VO2. The linear regression equation was the most practical predictor, as only one recovery gas sample was necessary and it did not require the complicated mathematical techniques used in exponential regression.