Age difference in efficiency of locomotion and maximal power output in well-trained triathletes

Purpose

The aim of this study was to examine the influence of age on cycling efficiency and sprint power output in well-trained endurance masters athletes.

Methods

The investigation was conducted on 60 healthy well-trained triathletes separated into six separate groups (n = 10) depending on age: 20–29 years old; 30–39 years old; 40–49 years old; 50–59 years old; 60–69 years old; 70 years old. Each participant attended the laboratory on three separate occasions to perform (1) an incremental cycling test, (2) maximal peak sprint power test, involving three 5-s sprint efforts (3) and a 10-min sub-maximal cycling test for determination of cycling efficiency.

Results

Cycling efficiency decreased beyond 50 years (50–59 years compared with 20–29 years: ?7.3 ± 1.8 %; p < 0.05) and continued to decrease beyond 60 years (60–69 years compared with 50–59 years: ?10.7 ± 2.4 %; p < 0.05), no further decrease was observed after 70 years. A continuous impairment in maximal sprint power output was observed after the age of 50 years leading to an overall decrease of 36 % between 20–29 years and >70 years. Significant positive relationships were observed between maximal sprint power output and both cycling efficiency (r ² = 0.64, p < 0.05) and maximal aerobic power (r ² = 0.42 and p < 0.05).

Conclusion

The present data indicates a significant effect of ageing on cycling efficiency and maximal sprint power output after 50 years and a significant relationship was found between these two parameters.     

Co-ingestion of caffeine and carbohydrate after meal does not improve performance at high-intensity intermittent sprints with short recovery times

Purpose

To determine the effects of co-ingesting caffeine (CAF) and carbohydrate (CHO) on high-intensity intermittent sprints (HIS) performance and physiological responses.

Methods

Twelve active males underwent 4 interventions at least 7 days apart in a randomized, double-blind, placebo-controlled, balanced trial. A meal contained 65 % CHO was provided 2 h before the HIS test. Participants ingested the placebo (PLA) or CAF (6 mg kg^?1 BW) 1 h before taking an HIS test, and ingested a PLA or CHO solution (0.8 g kg^?1 BW) before undergoing the testing protocol. The HIS protocol comprised ten sets of 5 × 4-s sprints on a cycle ergometer with a 2-min recovery between each set.

Results

There was no significant difference between peak power output and mean power output between trials (p > 0.05). Compared with PLA, CAF + CHO resulted in a 5.2 % reduction in total work, corresponding to a 24.7–25.7 % increase in fatigue at the end stage of the HIS. The administration of CAF + CHO supplementation also resulted in an 11.1 % increase in blood lactate, and elevated blood glucose concentrations throughout HIS testing compared with PLA (p < 0.05). Cortisol concentrations also increased with CAF + CHO intake compared with PLA; however, there was no significant effect of CAF + CHO supplementation on testosterone concentrations.

Conclusion

Co-ingestion of CAF and CHO did not improve high-intensity sprint cycling performance or reduce fatigue in active males. Moreover, combined CAF and CHO supplementation might facilitate catabolism during prolonged high-intensity intermittent exercise.     

The influence of aerobic fitness on the recovery of peak power output

Purpose

The aims of this study were to evaluate the recovery kinetics of peak power output (PPO) following a maximal sprint, and to evaluate the influence of aerobic fitness on that recovery process.

Methods

On separate occasions, 16 well-trained men (age: 21 ± 3 years; height: 1.84 ± 0.05 m; and body mass: 78.8 ± 7.8 kg) performed a 30 s maximal sprint on a cycle ergometer, followed by a predetermined stationary rest period (5, 10, 20, 40, 80, and 160 s) and a subsequent 5 s sprint to determine PPO recovery kinetics. On another occasion, \({\dot V}{{\rm O}_{2}}\) was monitored during recovery from a 30 s sprint to provide a comparison with the recovery of PPO. Finally, subjects completed a \({\dot V}{{\rm O}_{2{\rm max}}}\) test to evaluate the influence of aerobic fitness on the recovery of PPO.

Results

Despite following similar time courses (F = 0.36, p = 0.558), and being well described by double-exponential models, the kinetic parameters of PPO and \({\dot V}{{\rm O}_{2}}\) in recovery were significantly different (p < 0.05). There was no significant relationship (r = 0.15; p = 0.578) between \({\dot V}{\rm O}_{2{\rm max}}\) and the time to achieve 50 % recovery of PPO. Moreover, there was no difference (p = 0.61) between the recovery kinetics of participants classified according to their \({\dot V}{\rm O}_{2{\rm max}}\) (59.4 ± 1.3 vs 48.5 ± 2.2 ml·kg^?1·min^?1).

Conclusion

Despite similar overall recovery kinetics, \({\dot V}{{\rm O}_{2}}\) and PPO show differences in key model parameters. Moreover, the recovery of PPO does not appear to be affected by aerobic fitness.     

Glucocorticoids improve high-intensity exercise performance in humans

Purpose

It was investigated whether oral dexamethasone (DEX) administration improves exercise performance by reducing the initial rate of muscle fatigue development during dynamic exercise.

Methods

Using a double-blinded placebo controlled randomized crossover design, subjects ingested either 2 × 2 mg of DEX or placebo for five consecutive days. Muscle function was investigated using one-legged kicking exercise and whole body performance was evaluated using a 20-m shuttle run and a 30-m sprint test.

Results

One-legged dynamic knee-extensor exercise time to exhaustion was 29 ± 35 % (mean ± SD) longer (P < 0.05) in DEX compared to Placebo. Likewise, total running distance in the shuttle run test was 19 ± 23 % longer (P < 0.05), whereas 30-m sprint performance was unaltered. During the initial 75 s of dynamic leg extensions, peak force and rate of force development determined from an electrically evoked twitch declined in a similar way in DEX and placebo. Similarly, the EMG root mean square was similar with DEX and placebo treatment.

Conclusion

Short-term dexamethasone administration increases high-intensity one-legged kicking time to exhaustion and 20-m shuttle run performance, although sprint ability and the initial loss of muscular force generating capacity are similar after DEX and placebo.     

The effect of arm training on thermoregulatory responses and calf volume during upper body exercise

Purpose

The smaller muscle mass of the upper body compared to the lower body may elicit a smaller thermoregulatory stimulus during exercise and thus produce novel training-induced thermoregulatory adaptations. Therefore, the principal aim of the study was to examine the effect of arm training on thermoregulatory responses during submaximal exercise.

Methods

Thirteen healthy male participants (Mean ± SD age 27.8 ± 5.0 years, body mass 74.8 ± 9.5 kg) took part in 8 weeks of arm crank ergometry training. Thermoregulatory and calf blood flow responses were measured during 30 min of arm cranking at 60 % peak power (W _peak) pre-, and post-training and post-training at the same absolute intensity as pre-training. Core temperature and skin temperatures were measured, along with heat flow at the calf, thigh, upper arm and chest. Calf blood flow using venous occlusion plethysmography was performed pre- and post-exercise and calf volume was determined during exercise.

Results

The upper body training reduced aural temperature (0.1 ± 0.3 °C) and heat storage (0.3 ± 0.2 J g^?1) at a given power output as a result of increased whole body sweating and heat flow. Arm crank training produced a smaller change in calf volume post-training at the same absolute exercise intensity (?1.2 ± 0.8 % compared to ?2.2 ± 0.9 % pre-training; P < 0.05) suggesting reduced leg vasoconstriction.

Conclusion

Training improved the main markers of aerobic fitness. However, the results of this study suggest arm crank training additionally elicits physiological responses specific to the lower body which may aid thermoregulation.     

Influence of acute exercise of varying intensity and duration on postprandial oxidative stress

Introduction

Aerobic exercise can reduce postprandial lipemia, and possibly oxidative stress, when performed prior to a lipid-rich meal.

Purpose

To compare the impact of acute exercise on postprandial oxidative stress.

Methods

We compared aerobic and anaerobic exercise bouts of different intensities and durations on postprandial blood triglycerides (TAG), oxidative stress biomarkers (malondialdehyde, hydrogen peroxide, advanced oxidation protein products), and antioxidant status (trolox equivalent antioxidant capacity, superoxide dismutase, catalase, glutathione peroxidase). Twelve trained men (21–35 years) underwent four conditions: (1) No exercise rest; (2) 60-min aerobic exercise at 70 % heart rate reserve; (3) five 60-s sprints at 100 % max capacity; and (4) ten 15-s sprints at 200 % max capacity. All exercise bouts were performed on a cycle ergometer. A high-fat meal was consumed 1 h after exercise cessation. Blood samples were collected pre-meal and 2 and 4 h post-meal and analyzed for TAG, oxidative stress biomarkers, and antioxidant status.

Results

No significant interaction or condition effects were noted for any variable (p > 0.05), with acute exercise having little to no effect on the magnitude of postprandial oxidative stress.

Conclusion

In a sample of healthy, well-trained men, neither aerobic nor anaerobic exercise attenuates postprandial oxidative stress in response to a high-fat meal.     

Effect of age and combined sprint and strength training on plasma catecholamine responses to a Wingate-test

Purpose

The purpose of this research is to study the effects of aging and combined training (sprint and strength) on catecholamine responses [adrenaline (A) and noradrenaline (NA)].

Methods

Thirty-two male subjects voluntarily participated in this study. They were randomly divided into four groups: A young trained group (age 21.4 ± 1.2 years, YT, n = 8), a young control group (age 21.9 ± 1.9 years, YC, n = 8), a middle-aged trained group (age 40.8 ± 2.8 years, AT, n = 8) and a middle-aged control group (age 40.4 ± 2.0 years, AC, n = 8). YT and AT participated in a high intensity sprint and strength training program (HISST) for 13 weeks. All the participants realized the Wingate-test before (P1) and after (P2) HISST. Plasma A and NA concentrations were determined at rest (A ₀, NA₀) and at the end of exercise (A _max, NA_max).

Results

At P1, a significant difference (p < 0.05) in terms of age was observed for NA₀ and A ₀ between YT and AT and between control groups YC and AC. This age effect disappeared after training when compared YT and AT. After HISST, A _max increased significantly (p < 0.05) in YT and AT (from 3.08 ± 0.17 to 3.23 ± 0.34 nmol l^?1 in YT and from 3.23 ± 0.52 to 4.59 ± 0.10 nmol l^?1 in AT). However, NA_max increased significantly (p < 0.05) in AT only (from 3.34 ± 0.31 to 3.75 ± 0.60 nmol l^?1). A _max was highly increased in AT compared to YT (4.59 ± 0.10 vs. 3.23 ± 0.34 nmol l^?1), respectively.

Conclusion

The combined training (sprint and strength) appeared to reduce the age effect of the catecholamine response both at rest and in response to exercise.     

External muscle heating during warm-up does not provide added performance benefit above external heating in the recovery period alone

Purpose

Having previously shown the use of passive external heating between warm-up completion and sprint cycling to have had a positive effect on muscle temperature (T _m) and maximal sprint performance, we sought to determine whether adding passive heating during active warm up was of further benefit.

Methods

Ten trained male cyclists completed a standardised 15 min sprint based warm-up on a cycle ergometer, followed by 30 min passive recovery before completing a 30 s maximal sprint test. Warm up was completed either with or without additional external passive heating. During recovery, external passive leg heating was used in both standard warm-up (CONHOT) and heated warm-up (HOTHOT) conditions, for control, a standard tracksuit was worn (CON).

Results

T _m declined exponentially during CON, CONHOT and HOTHOT reduced the exponential decline during recovery. Peak (11.1 %, 1561 ± 258 W and 1542 ± 223 W), relative (10.6 % 21.0 ± 2.2 W kg^–1 and 20.9 ± 1.8 W kg^–1) and mean (4.1 %, 734 ± 126 W and 729 ± 125 W) power were all improved with CONHOT and HOTHOT, respectively compared to CON (1,397 ± 239 W; 18.9 ± 3.0 W kg^–1 and 701 ± 109 W). There was no additional benefit of HOTHOT on T _m or sprint performance compared to CONHOT.

Conclusion

External heating during an active warm up does not provide additional physiological or performance benefit. As noted previously, external heating is capable of reducing the rate of decline in T _m after an active warm-up, improving subsequent sprint cycling performance.     

Pain sensitivity is normalized after a repeated bout of eccentric exercise

Purpose

The purpose of this study was to investigate the effect of repeated bouts of eccentric exercise on the nociceptive withdrawal reflex (NWR) threshold, a measure of sensitivity in the spinal nociceptive system.

Methods

Sixteen healthy students (age 25.7 ± 0.6 years, BMI 24.8 ± 1 kg m^?2) participated in this randomized, controlled, crossover study. Two identical bouts of high-intensity eccentric exercises were performed on the tibialis anterior muscle 7 days apart. Control sessions involving no exercise were performed 4 weeks apart the exercise sessions. Pressure pain thresholds (PPT) and the NWR threshold were recorded before, immediately after, and 1 day after both bouts of exercise.

Results

Pressure pain thresholds decreased significantly at two of the muscle belly sites on the day after initial bout compared with baseline. NWR threshold decreased by 25 ± 4 % immediately after initial bout and by 30 ± 5 % the next day (p < 0.05) as an indication of generalized pain hypersensitivity. On the contrary, no changes were found in both pain thresholds after second bout of eccentric exercise indicating that both localized and generalized pain sensitivity were normalized.

Conclusion

In conclusion, this study for the first time documented that an initial bout of unaccustomed high-intensity eccentric exercise, which results in muscle soreness can induce central sensitization. A repeated bout of exercise, however, facilitates inherent protective spinal mechanisms against the development of muscle soreness.     

Maximal strength,power, and aerobic endurance adaptations to concurrent strength and sprint interval training

Purpose

This study was designed to examine whether concurrent sprint interval and strength training (CT) would result in compromised strength development when compared to strength training (ST) alone. In addition, maximal oxygen consumption (VO₂max) and time to exhaustion (TTE) were measured to determine if sprint interval training (SIT) would augment aerobic performance.

Methods

Fourteen recreationally active men completed the study. ST (n = 7) was performed 2 days/week and CT (n = 7) was performed 4 days/week for 12 weeks. CT was separated by 24 h to reduce the influence of acute fatigue. Body composition was analyzed pre- and post-intervention. Anaerobic power, one-repetition maximum (1RM) lower- and upper-body strength, VO₂max and TTE were analyzed pre-, mid-, and post-training. Training intensity for ST was set at 85 % 1RM and SIT trained using a modified Wingate protocol, adjusted to 20 s.

Results

Upper- and lower-body strength improved significantly after training (p < 0.001) with no difference between the groups (p > 0.05). VO₂max increased 40.9 ± 8.4 to 42.3 ± 7.1 ml/kg/min (p < 0.05) for CT, whereas ST remained unchanged. A significant difference in VO₂max (p < 0.05) was observed between groups post-intervention (CT: 42.3 ± 7.1 vs. ST: 36.0 ± 3.0 ml/kg/min). A main effect for time and group was observed in TTE (p < 0.05). A significant main effect for time was observed in average power (p < 0.05).

Conclusion

Preliminary findings suggest that performing concurrent sprint interval and strength training does not attenuate the strength response when compared to ST alone, while also improves aerobic performance measures, such as VO₂max at the same time.     

Acute supra-therapeutic oral terbutaline administration has no ergogenic effect in non-asthmatic athletes

This study aimed to investigate the effects on a possible improvement in aerobic and anaerobic performance of oral terbutaline (TER) at a supra-therapeutic dose in 7 healthy competitive male athletes. On day 1, ventilatory threshold, maximum oxygen uptake $ (\dot{V}O_{2\max }) $ and corresponding power output were measured and used to determine the exercise load on days 2 and 3. On days 2 and 3, 8 mg of TER or placebo were orally administered in a double-blind process to athletes who rested for 3 h, and then performed a battery of tests including a force–velocity exercise test, running sprint and a maximal endurance cycling test at Δ50 % (50 % between VT and $ \dot{V}{\text{O}}_{2\max } $ ). Lactatemia, anaerobic parameters and endurance performance ( $ \dot{V}{\text{O}}_{ 2} ,\dot{V}E $ and time until exhaustion) were raised during the corresponding tests. We found that TER administration did not improve any of the parameters of aerobic performance (p > 0.05). In addition, no change in $ \dot{V}{\text{O}}_{2} $ kinetic parameters was found with TER compared to placebo (p > 0.05). Moreover, no enhancement of the force–velocity relationship was observed during sprint exercises after TER intake (p > 0.05) and, on the contrary, maximal strength decreased significantly after TER intake (p < 0.05) but maximal power remained unchanged (p > 0.05). In conclusion, oral acute administration of TER at a supra-therapeutic dose seems to be without any relevant ergogenic effect on anaerobic and aerobic performances in healthy athletes. However, all participants experienced adverse side effects such as tremors.     

A single-session testing protocol to determine critical power and W′

Purpose

Critical power (CP), and the finite capacity to perform work above CP (W′), can be determined using a 3-min “all-out” cycling test (3MT). This protocol requires two laboratory visits: an incremental exercise test, followed by a 3MT on a separate day. The purpose of this study was to establish whether an incremental exercise test and a 3MT performed during a single laboratory visit can be used to accurately determine CP and W′.

Methods

Twelve participants completed two experimental protocols: (1) Combined protocol: an incremental exercise test followed by a 3MT, with 20 min of recovery between exercise bouts; and (2) Independent protocol: the conventional 3MT protocol, performed on a separate day.

Results

CP determined from the Combined (254 ± 117 W) and Independent (256 ± 118 W) protocols were not different (p = 0.40). Similarly, W′ was not different (p = 0.96) between the Combined (13.7 ± 3.9 kJ) and Independent (13.7 ± 4.5 kJ) protocols. Linear regression revealed a strong level of measurement agreement between the protocols for CP and W′, evidenced by high R ² values (≥0.85) and marginal standard errors of the estimates (CP = 5 W; W′ = 1.81 kJ).

Conclusion

A Combined protocol, consisting of an incremental exercise test followed by a 3MT, provides an accurate and valid method to determine an individual’s CP and, to a lesser extent, W′. Furthermore, this protocol permits the measurement of the gas-exchange threshold and peak O₂ uptake and, consequently, the moderate, heavy, and severe exercise-intensity domains may be defined within a single exercise-testing session.     

Influence of thigh activation on the \dot{V}O2 slow component in boys and men

Purpose

During constant work rate exercise above the lactate threshold (LT), the initial rapid phase of pulmonary oxygen uptake ( \(\dot{V}\) O₂) kinetics is supplemented by an additional \(\dot{V}\) O₂ slow component ( \(\dot{V}\) O_2Sc) which reduces the efficiency of muscular work. The \(\dot{V}\) O_2Sc amplitude has been shown to increase with maturation but the mechanisms are poorly understood. We utilized the transverse relaxation time (T ₂) of muscle protons from magnetic resonance imaging (MRI) to test the hypothesis that a lower \(\dot{V}\) O₂ slow component ( \(\dot{V}\) O_2Sc) amplitude in children would be associated with a reduced muscle recruitment compared to adults.

Methods

Eight boys (mean age 11.4 ± 0.4) and eight men (mean age 25.3 ± 3.3 years) completed repeated step transitions of unloaded-to-very heavy-intensity (U → VH) exercise on a cycle ergometer. MRI scans of the thigh region were acquired at rest and after VH exercise up to the \(\dot{V}\) O_2Sc time delay (ScTD) and after 6 min. T ₂ for each of eight muscles was adjusted in relation to cross-sectional area and then summed to provide the area-weighted ΣT ₂ as an index of thigh recruitment.

Results

There were no child/adult differences in the relative \(\dot{V}\) O_2Sc amplitude [Boys 14 ± 7 vs. Men 18 ± 3 %, P = 0.15, effect size (ES) = 0.8] during which the change (?) in area-weighted ΣT ₂ between the ScTD and 6 min was not different between groups (Boys 1.6 ± 1.2 vs. Men 2.3 ± 1.1 ms, P = 0.27, ES = 0.6). A positive and strong correlation was found between the relative \(\dot{V}\) O_2Sc amplitude and the magnitude of the area-weighted ?ΣT ₂ in men (r = 0.92, P = 0.001) but not in boys (r = 0.09, P = 0.84).

Conclusions

This study provides evidence to show that progressive muscle recruitment (as inferred from T ₂ changes) contributes to the development of the \(\dot{V}\) O_2Sc during intense submaximal exercise independent of age.     

Cardiac electrical conduction, autonomic activity and biomarker release during recovery from prolonged strenuous exercise in trained male cyclists

Purpose

Although markers of myocyte injury, electrolyte disturbances and an autonomic imbalance have been reported following exercise, the effect of prolonged strenuous activity on cardiac electrical conduction is not well understood. This study examined atrial and ventricular conduction dynamics during recovery from exercise.

Methods

Electrocardiographic intervals were obtained from eight highly-trained males before, during recovery (15, 30, 45 and 60 min post-exercise) and 24 h after a prolonged bout of strenuous exercise. Time-domain, frequency-domain and non-linear analyses of the RR, PR and QT intervals were analysed to investigate the effect of exercise on autonomic modulation and cardiac electrical conduction. Serum electrolyte and high-sensitivity cardiac troponin T (hs-cTnT) concentrations were measured before exercise, and after 60 min and 24 h of recovery.

Results

The root mean square of the successive differences of RR, PR and QT intervals was significantly reduced during recovery (p < 0.05). Normalised low- and high-frequency power of RR intervals significantly increased and decreased, respectively, during recovery. Approximate entropy of PR and QT intervals, and the QT-variability index significantly increased during recovery. All measures except mean QT interval (pre 422 ± 10 ms vs 24 h post 442 ± 11 ms, p = 0.013) returned to pre-exercise values after 24 h. Serum hs-cTnT was significantly elevated 60 min after exercise (pre 5.2 ± 0.7 ng L^?1 vs 60 min post 27.4 ± 6.2 ng L^?1, p = 0.01) and correlated with exercising heart rate (R ² = 0.89, p < 0.001). Serum electrolyte concentrations were unchanged (p > 0.05).

Conclusion

The results suggest suppressed parasympathetic and/or sustained sympathetic modulation of heart rate during recovery, concomitant with perturbations in atrial and ventricular conduction dynamics. Exercise-induced hs-cTnT release was heart rate dependent.     

Low-volume,high-intensity,aerobic interval exercise for sedentary adults: \dot{V}O2max,cardiac mass,and heart rate recovery

Purpose

The aim of this study was to compare the effects of low-volume, high-intensity aerobic interval training (HAIT) on maximal oxygen consumption ( \(\dot{V}\) O_2max), left ventricular (LV) mass, and heart rate recovery (HRR) with high-volume, moderate-intensity continuous aerobic training (CAT) in sedentary adults.

Methods

Twenty-four healthy but sedentary male adults (aged 29.2 ± 7.2 years) participated in an 8-week, 3-day a week, supervised exercise intervention. They were randomly assigned to either HAIT (18 min, 180 kcal per exercise session) or CAT (45 min, 360 kcal). \(\dot{V}\) O_2max, LV mass (3T-MRI), and HRR at 1 min (HRR-1) and 2 min (HRR-2) after maximal exercise were measured pre- and post-intervention.

Results

Changes in \(\dot{V}\) O_2max during the 8-week intervention were significant (P < 0.01) in both groups (HAIT, 8.7 ± 3.2 ml kg^?1 min^?1, 22.4 ± 8.9 %; CAT, 5.5 ± 2.8 ml kg^?1 min^?1, 14.7 ± 9.5 %), while the \(\dot{V}\) O_2max improvement in HAIT was greater (P = 0.02) than in CAT. LV mass in HAIT increased (5.1 ± 8.4 g, 5.7 ± 9.1 %, P = 0.05), but not in CAT (0.9 ± 7.8 g, 1.1 ± 8.4 %, P = 0.71). While changes in HRR-1 were not significant in either group, change in HRR-2 for HAIT (9.5 ± 6.4 bpm, 19.0 ± 16.0 %, P < 0.01) was greater (P = 0.03) than for CAT (1.6 ± 10.9 bpm, 3.9 ± 16.2 %, P = 0.42).

Conclusions

This study suggests that HAIT has potential as a time-efficient training mode to improve cardiorespiratory capacity and autonomic nervous system function in sedentary adults.     

Short-term high-intensity interval and continuous moderate-intensity training improve maximal aerobic power and diastolic filling during exercise

Purpose

This study examined the effects of short-term high-intensity interval training (HIT) and continuous moderate-intensity training (CMT) on cardiac function in young, healthy men.

Methods

Sixteen previously untrained men (mean age of 25.1 ± 4.1 years) were randomly assigned to HIT and CMT (n = 8 each) and assessed before and after six sessions over a 12-day training period. HIT consisted of 8–12 intervals of cycling for 60 s at 95–100 % of pre-training maximal aerobic power ( $\dot{V}$ O_2max), interspersed by 75 s of cycling at 10 % $\dot{V}$ O_2max. CMT involved 90–120 min of cycling at 65 % pre-training $\dot{V}$ O_2max. Left ventricular (LV) function was determined at rest and during submaximal exercise (heart rate ~105 bpm) using two-dimensional and Doppler echocardiography.

Results

Training resulted in increased calculated plasma volume (PV) in both groups, accompanied by improved $\dot{V}$ O_2max in HIT (HIT: from 39.5 ± 7.1 to 43.9 ± 5.5 mL kg^?1 min^?1; CMT: from 39.9 ± 5.9 to 41.7 ± 5.3 mL kg^?1 min^?1; P < 0.001). Resting LV function was not altered. However, increased exercise stroke volume (P = 0.02) and cardiac output (P = 0.02) were observed, secondary to increases in end-diastolic volume (P < 0.001). Numerous Doppler and speckle tracking indices of diastolic function were similarly enhanced during exercise in both training groups and were related to changes in PV.

Conclusion

Short-term HIT and CMT elicit rapid improvements in $\dot{V}$ O_2max and LV filling without global changes in cardiac performance at rest.     

Can a combination of handgrip exercise and prolonged forearm occlusion elicit a maximal brachial artery FMD response?

Introduction

The upper limit of brachial artery (BA) flow-mediated dilation (FMD) has not been thoroughly interrogated, and long duration occlusion + handgrip exercise may create larger shear stress stimuli than previous manipulations.

Purpose

To determine whether novel combinations of occlusion + handgrip exercise can extend the range of FMD stimulus–response relationship characterization and permit identification of a BA-FMD response ceiling.

Methods

Ten healthy subjects performed eight reactive hyperemia (RH) FMD trials: 5, 10, and 15 min of occlusion (5RH, 10RH, 15RH); 5, 10 and 15 min of occlusion + 3-min ischemic exercise (IE) (5IE, 10IE, 15IE); 10 and 15 min of occlusion + 3-min IE + 4-min post-occlusion exercise (PE) (10IEPE, 15IEPE). Shear stress was estimated as shear rate (SR = blood velocity/BA diameter; (ultrasound assessment)) (SR stimulus = area under the curve (AUC) until peak diameter). Data are mean ± SE.

Results

There were no differences in SR-AUC among IE and IEPE trials (p > 0.70), however, IE consistently increased the SR-AUC (IE + IEPE trial average 17,845.1 ± 2,023.3 a.u.) vs. the 5RH and 10RH trials (4,943.0 ± 428.4 a.u., 6,800.6 ± 805.9 a.u.) (p < 0.05). The %FMD ranged from 7.3 ± 0.8 % (5RH) to 19.1 ± 2.0 % (15IEPE) (p < 0.001) with no differences among IE and IEPE trials (p > 0.16). FMD increased with increasing SR-AUC (all subjects, all trials: r ² 0.36, p < 0.001)

Conclusions

The stimulus created by brief (5 min) occlusion + ischemic exercise was not significantly enhanced by prolonging occlusion or continuing to exercise post-occlusion. The FMD response did not clearly plateau with increasing stimulus magnitude; however, the FMD capacity was shown to be more than double the FMD magnitude that was elicited with a standard 5-min occlusion test.     

Thermal sensitivity to warmth during rest and exercise: a sex comparison

Purpose

The study aimed to compare thermal sensation in response to a fixed warm stimulus across 31 body locations in resting and active males and females.

Methods

Twelve males (20.6 ± 1.0 years, 78.1 ± 15.6 kg, 180 ± 8.9 cm, 34.4 ± 5.2 ml kg^?1 min^?1) and 12 females (20.6 ± 1.4 years, 62.9 ± 5.5 kg, 167 ± 5.7 cm, 36.5 ± 6.6 ml kg^?1 min^?1) rested in a thermoneutral (22.2 ± 2.2 °C, 35.1 ± 5.8 % RH) room whilst a thermal probe (25 cm²), set at 40 °C was applied in a balanced order to 31 locations across the body. Participants reported their thermal sensation 10 s after initial application. Following this, participants began cycling at 50 % \(\dot{V}{\text{O}}_{{ 2 {\text{max}}}}\) for 20 min, which was then lowered to 30 % \(\dot{V}{\text{O}}_{{ 2 {\text{max}}}}\) and the sensitivity test repeated.

Results

Females had significantly warmer magnitude sensations than males at all locations (4.7 ± 1.8 vs 3.6 ± 2.2, p < 0.05, respectively). Regional differences in thermal sensation were evident but were more prominent for females. Thermal sensation was greatest at the head then the torso and declined towards the extremities. In comparison to rest, exercise caused a significant reduction in thermal sensation for males (?thermal sensation; 0.86 ± 0.3, p < 0.05), but only at select locations in females (0.31 ± 0.56, p > 0.05).

Conclusion

The data provide evidence that the thermal sensation response to warmth varies between genders and between body regions and reduces during exercise. These findings have important implications for clothing design and thermophysiological modelling.     

The effect of an even-pacing strategy on exercise tolerance in well-trained cyclists

Purpose

Previous research has suggested that the optimal pacing strategy for self-paced exercise lasting >4 min is a uniform distribution of work, but this posit is not well established for prolonged endurance events. This study examined the utility of even pacing during 20 km cycling time trials (TTs).

Methods

Fifteen well-trained male cyclists ( $\dot{V}$ O₂max = 4.80 ± 0.38 L min^?1) completed three best effort self-paced (SP) simulated 20 km TTs, followed by two even-paced trials. In one even-paced trial, participants cycled to exhaustion (EP_tlim) at a fixed intensity equivalent to their best SP performance. In the other EP trial, participants were instructed to maintain this target intensity for a distance of 20 km, but the actual intensity was free to vary depending on the effort and cadence of the cyclist (EP-maintained). Cardiorespiratory, blood lactate and perceptual (RPE and affect) measures were assessed throughout.

Results

Nine out of fifteen cyclists failed the EP_tlim task, completing 51–83 % (10.3–15.3 km) of the work done in their SP trial. Failure as a result of even pacing was associated with a faster rise in blood lactate, attainment of a higher relative intensity during SP and a moderate fast starting strategy. This failure was independent of the nature of the even-paced task.

Conclusion

By adopting an uneven, parabolic distribution of work, cyclists in this study were able to achieve an average intensity during self-paced exercise in excess of their maximum sustainable power output. A subsequent matched even-paced bout resulted in cumulative metabolic stress that could not be managed by moment-to-moment changes in power output. These results challenge the notion that strict even pacing is optimal for endurance time trial events.