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.     

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.     

The influence of acetaminophen on repeated sprint cycling performance

Introduction

The aim of this study was to investigate the effect of acetaminophen on repeated sprint cycling performance.

Methods

Nine recreationally active male participants completed a graded exercise test, a familiarisation set of Wingate Anaerobic Tests (WAnTs) and two experimental sets of WAnTs (8 × 30 s sprints, 2 min active rest intervals). In the experimental WAnTs, participants ingested either 1.5 g acetaminophen or a placebo in a double-blind, randomised, crossover design. During the WAnT trials, participants provided ratings of perceived pain 20 s into each sprint. Mean and peak power output and heart rate were recorded immediately following each sprint, and percentage decrement in mean power output was subsequently calculated.

Results

Participants cycled at a significantly greater mean power output over the course of 8 WAnTs (p < 0.05) following the ingestion of acetaminophen (391 ± 74 vs. 372 ± 90 W), due to a significantly greater mean power output during sprints 6, 7 and 8 (p < 0.05). Percentage decrements in mean power output were also significantly reduced (p < 0.05) following acetaminophen ingestion (17 ± 14 vs. 24 ± 17 %). No significant differences in peak power output, perceived pain or heart rate were observed between conditions.

Conclusion

Acetaminophen may have improved performance through the reduction of pain for a given work rate, thereby enabling participants to exercise closer to a true physiological limit. These results suggest that exercise may be regulated by pain perception, and that an increased pain tolerance can improve exercise performance.     

Reducing the volume of sprint interval training does not diminish maximal and submaximal performance gains in healthy men

Purpose

The present study examined the effect of reducing sprint interval training (SIT) work-interval duration on increases in maximal and submaximal performance.

Methods

Subjects (n = 36) were assigned to one of three training groups: endurance training (ET; 60 min per session for weeks 1–2, increasing to 75 min per session for weeks 3–4), or sprint interval training consisting of either repeated 30 (SIT 30) or 15 (SIT 15) second all-out intervals (starting with 4 bouts per session for weeks 1–2, increasing to 6 intervals per session for weeks 3–4). Training consisted of cycling 3 times per week for 4 weeks.

Results

While there was a significant main effect of training on \(\dot{V}{\text{O}}_{{{\text{2peak}}}}\) such that \(\dot{V}{\text{O}}_{{{\text{2peak}}}}\) was elevated post-training, no significant difference was observed in the improvements observed between groups (ET ~13 %, SIT 30–4 %, SIT 15–8 %). A significant main effect of training was observed such that lactate threshold and critical power were higher during post-testing across all groups (p < 0.05). There was a main effect of training (p < 0.05) on Wingate peak power with no differences observed between groups at post-training.

Conclusions

Together, these results indicate that reducing SIT work-interval duration from 30 to 15 s had no impact on training-induced increases in aerobic or anaerobic power, or on increases in lactate threshold (absolute) and critical power.     

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.     

Weight Perception and Dietary Intake among Chinese Youth, 2004–2009

Background

Little is known on the extent of weight misperception and its relation with dietary intake among Chinese youth.

Purpose

The study aimed to investigate extent and correlates of weight misperception and its relation with dietary intake among Chinese youth.

Method

Data pertaining to Chinese youth, 6–17 years of age, from the 2004–2009 China Health and Nutrition Survey (N?=?3,923) were analyzed using STATA version 12.1. The heights and weights of the participants were measured by well-trained health workers at the participants' homes or a local clinic following the reference protocol recommended by the World Health Organization. The dietary intake data of the participants were collected on three consecutive days at both the household and individual levels.

Results

Of the children 6–11 years of age, 18.9 % were underweight and 15.3 % were overweight. Among the children 12–17 years of age, 18.3 % were underweight and 8.1 % were overweight. Less than 60 % of Chinese youth accurately estimated their weight status. Nutrition knowledge was positively related to a perception of being overweight (adjusted odds ratio [AOR]?=?1.98, p?=?.007) among children 12–17 years of age. A perception of being overweight was positively associated with fat and protein intake among children 6–11 years of age (p?<?.05).

Conclusions

A discrepancy exists between the actual and perceived weight status of Chinese youth. Efforts are needed in China to promote accurate weight perception, healthy weight, and eating behaviors.     

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.     

Operating lung volumes are affected by exercise mode but not trunk and hip angle during maximal exercise

Introduction

Despite VO_2peak being, generally, greater while running compared to cycling, ventilation (V _E) during maximal exercise is less while running compared to cycling. Differences in operating lung volumes (OLV) between maximal running and cycling could be one explanation for previously observed differences in V _E and this could be due to differences in body position e.g., trunk/hip angle during exercise.

Purpose

We asked whether OLV differed between maximal running and cycling and if this difference was due to trunk/hip angle during exercise.

Methods

Eighteen men performed three graded maximal exercise tests; one while running, one while cycling in the drop position (i.e., extreme hip flexion), and one while cycling upright (i.e., seated with thorax upright). Resting flow-volume characteristics were measured in each body position to be used during exercise. Tidal flow-volume loops were measured throughout the exercise.

Results

V _E during maximal running (148.8 ± 18.9 L min^?1) tended to be lower than during cycling in the drop position (158.5 ± 24.7 L min^?1; p = 0.07) and in the upright position (158.5 ± 23.7 L min^?1; p = 0.06). End-inspiratory and end-expiratory lung volumes (EILV, EELV) were significantly larger during drop cycling compared to running (87.1 ± 4.1 and 35.8 ± 6.2 vs. 83.9 ± 6.0 and 33.0 ± 5.7 % FVC), but only EILV was larger during upright cycling compared to running (88.2 ± 3.5 % FVC). OLV and V _E did not differ between cycling positions.

Conclusion

Since OLV are altered by exercise mode, but cycling position did not have a significant impact on OLV, we conclude that trunk/hip angle is likely not the primary factor determining OLV during maximal exercise.     

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.     

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.     

Left atrial functional changes following short-term exercise training

Background

Exercise-induced adaptations of the human atria remain understudied, particularly early in the training process. We examined the effects of short-term high-intensity interval training (HIT) and continuous moderate-intensity training (CMT) on left atrial (LA) systolic and diastolic function, relative to left ventricular (LV) function in young, healthy men, by speckle tracking echocardiography (STE).

Methods

Fourteen untrained men (mean age = 25 ± 4 years) were randomized to HIT or CMT, and assessed before and after six training sessions over a 12-day period. HIT included 8-12 intervals of cycling for 60 s at 95–100 % of maximal aerobic power (VO_2MAX), interspersed by 75 s of cycling at 10 % VO_2MAX. CMT consisted of 90–120 min of cycling at 65 % VO_2MAX.

Results

VO_2MAX increased following HIT and CMT by 11.5 and 5.5 %, respectively (p < 0.05). Calculated plasma volume expanded 11 % following HIT and 10 % following CMT (p < 0.005). Resting LV volumes and ejection fraction were unaltered following training. Peak atrial longitudinal strain increased following HIT (41.8 ± 5.2 %–47.1 ± 3.7 %, p < 0.01) and CMT (38.5 ± 4.6 %–41.7 ± 6.0 %, p < 0.01). Atrial systolic strain rate increased following HIT (1.6 ± 0.2 %/s–2.0 ± 0.3 %/s, p < 0.01) and CMT (1.6 ± 0.2 %/s–1.9 ± 0.2 %/s, p < 0.01).

Conclusions

LA function assessed by STE improves rapidly during short-term intensive exercise training.     

Energy expenditure and substrate oxidation during and after eccentric cycling

Purpose

This study compared concentric cycling (CONC) and two bouts of eccentric cycling (ECC1, ECC2) for substrate utilisation and resting energy expenditure (REE).

Methods

Ten men (28 ± 8 years) performed each cycling bout for 30 min at 60 % of maximal concentric power output, with 2 weeks between bouts. Fat and carbohydrate (CHO) utilisation were assessed during and after cycling, and REE was measured before and 2 days after CONC, and before, 2 and 4 days after ECC1 and ECC2, using indirect calorimetry. An oral glucose tolerance test was performed before and 1 day after CONC, and before and 1 and 3 days after ECC1 and ECC2, and both peak and area-under-the-curve (AUC) of the glucose concentration were compared between bouts.

Results

Energy expenditure and CHO utilisation during cycling were 36 and 42 % less in ECC1, and 40 and 52 % less in ECC2, than CONC (P < 0.05). Fat utilisation was greater during ECC1 (72 %) and ECC2 (85 %) than CONC, and 48 % greater during ECC2 than ECC1 (P < 0.05). Post-exercise energy expenditure and fat utilisation were less for ECC1 than CONC (30 and 52 %, respectively), but similar between CONC and ECC2. REE did not change from baseline after any bouts. Peak and AUC glucose concentration decreased 3 days after ECC1, but no changes were evident after CONC or ECC2.

Conclusion

These results show greater fat utilisation during eccentric than concentric cycling at the same workload, and greater fat oxidation during and after secondary eccentric cycling bout without glucose uptake impairment.     

Pacing strategies during repeated maximal voluntary contractions

Purpose

Pacing strategies have been reported to occur during continuous cyclical exercises. However, currently no studies have examined if pacing takes place during repeated maximal voluntary muscle contractions (MVCs). Accordingly, the purpose of this study was to examine if informing subjects on the number of MVCs they would perform would affect force and root mean squared electromyography (EMG), during similar fatiguing protocols.

Methods

Thirty well-trained male subjects completed three fatiguing protocols in a randomized order. In the control condition participants were informed they would perform 12 MVCs, and then completed all 12. In the unknown condition they were not told how many MVCs they would perform, but were stopped after 12. Lastly, in the deception condition they were initially told they would perform only 6 MVCs, but after the 6 contractions they were asked to perform a few more repetitions and were stopped after 12.

Results

Compared to the unknown condition, subjects demonstrated greater forces (p < 0.05, ES = 0.35–1.14, 2–7.5 %) and biceps EMG (p < 0.05, ES = 0.6, 6 %) in the deception condition during the first six MVCs. Additionally, under all conditions subjects applied greater forces in the last repetition (#12) relative to the previous one (#11) (p < 0.06, ES = 0.36–0.5, 2.8–3.8 %).

Conclusions

The anticipation of performing a certain number of MVCs led the subjects to utilize different pacing strategies. The results also question the assumption that subjects followed the instruction to exert maximal effort during repeated MVCs.     

Latent cytomegalovirus infection and innate immune function following a 75 km cycling time trial

Purpose

This study compared the acute immune response, inflammation, and lipid peroxidation to a 75 km cycling time trial in male athletes testing positive or negative for latent cytomegalovirus (CMV) infection.

Design

Trained cyclists (N = 20) were tested for CMV serostatus, and cycled 75 km on a mountainous course using indoor trainers with continuous workload monitoring. Pre-, post-, and 1 h post-exercise blood samples were analyzed for total blood leukocyte counts, blood granulocyte (GR) and monocyte (MO) phagocytosis (PHAG) and oxidative burst activity (OBA), four plasma cytokines, and plasma F₂-isoprostanes.

Results

Forty percent of the subjects tested positive for CMV. No differences in subject characteristics were found between CMV_pos and CMV_neg groups. Mean power (57.3 ± 1.6, 59.4 ± 1.8 % maximal Watts, p = 0.803), heart rate (87.0 ± 1.0, 86.5 ± 1.3 % maximal heart rate, p = 0.376), and total time (2.56 ± 0.08, 2.60 ± 0.08 h, p = 0.744) to complete the 75 km cycling time trial did not differ between CMV_pos and CMV_neg groups. Whereas exercise induced significant changes in total blood leukocyte counts, GR and MO-PHAG, four plasma cytokines, and plasma F₂-isoprostanes (p < 0.05, ω² > 0.03), these exercise-induced changes did not differ between CMV_pos and CMV_neg groups (p > 0.05, ω² < 0.01).

Conclusions

CMV serostatus does not appear to influence these innate immune responses or markers of inflammation and lipid peroxidation in response to a single bout of heavy exertion.     

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.     

Mild to moderate hypohydration reduces boys’ high-intensity cycling performance in the heat

Purpose

To evaluate the effect of 1 and 2 % hypohydration on high-intensity cycling performance of 10- to 12-year-old boys in the heat.

Methods

In a counterbalanced order, nine boys attended three sessions in which they cycled intermittently (6 × 10-min bouts at 40–45 % $\dot{V}{\text{O}}_{2\hbox{max} }$ ) in a climate chamber. During each session, environmental conditions and water intake were individually adjusted to achieve a target hypohydration level of 0, 1 or 2 %, based on change in body weight (BW). Following 45 min of rest in thermoneutral conditions when the target hypohydration was maintained, each boy re-entered the climate chamber (35 °C and 50–55 % RH) to perform the cycling performance test at 90 % $\dot{V}{\text{O}}_{2\hbox{max} }$ until exhaustion. Heart rate (HR) and rectal temperature (T _re) were recorded continuously throughout each session. Total mechanical work (TMW) was taken as a measure of cycling performance.

Results

Actual hypohydration level at the start of the cycling performance test in each session was: 0.1 ± 0.0 %, 1.1 ± 0.1 % and 2.0 ± 0.1 %. With 2 % hypohydration, TMW (35.5 ± 6.8 kJ) was significantly (p < 0.05) lower than with 0 % hypohydration (49.3 ± 9.8 kJ). When expressed as a percentage of TMW with 0 % hypohydration, TMW was reduced by 15.5 and 23.3 % with 1 and 2 % hypohydration, respectively (p < 0.05 for both). At the start of the cycling performance test, HR was 13 and 15 bpm higher, and T _re was 0.3 °C higher (p < 0.05 for all) with 1 and 2 % hypohydration, respectively, compared with 0 % hypohydration.

Conclusion

Mild (~1 %) to moderate (~2 %) hypohydration reduces high-intensity cycling performance of healthy young boys in the heat.     

The impact of high-intensity intermittent exercise on resting metabolic rate in healthy males

Introduction

High-intensity intermittent exercise training (HIT) may favourably alter body composition despite low training volumes and predicted energy expenditure (EE).

Purpose

To characterise the acute impact of two common HIT protocols on EE and post-exercise oxygen consumption (11 h EPOC).

Methods

Oxygen consumption (l min^?1), respiratory exchange ratio (RER) and EE were measured in nine healthy, lean males over 12 h under three conditions: control (CON), HIT1 (10 × 1 min high-intensity cycling bouts followed by 1 min rest) and HIT2 (10 × 4 min high-intensity cycling bouts followed by 2 min rest).

Results

Total exercise period EE during HIT1 (1,151 ± 205 kJ) (mean ± SD) was significantly lower than HIT2 (2,788 ± 322 kJ; p < 0.001). EE within the 60 min after exercise was significantly albeit marginally higher after HIT1 (388 ± 44 kJ; p = 0.02) and HIT2 (389 ± 39 kJ; p = 0.01) compared with CON (329 ± 39 kJ), with no difference between exercise conditions (p = 0.778). RER during this period was significantly lower in HIT1 (0.78 ± 0.06; p = 0.011) and HIT2 (0.76 ± 0.04; p = 0.004) compared with CON (0.87 ± 0.06). During the ‘slow phase’ of EPOC (1.25–9.75 h), there were no significant differences in EE (p = 0.07) or RER (p = 0.173) between trials.

Conclusions

Single HIT sessions notably increases EE during exertion; however, the influence on metabolic rate post-exercise is transient and relatively minor.     

Physiological factors to predict on traditional rowing performance

The purpose of this study was to determine the best prediction factors of traditional rowing performance in traditional elite (ER) and amateur (AR) rowers. Average power during the 20-min all-out test (W _20 min), average power output which elicited a blood lactate concentration of 4 mmol l^?1 $ \left( {W_{{4\;{\text{mmol}}\;{\text{l}}^{ - 1} }} } \right), $ power output in 10 maximal strokes (W _10 strokes), maximal strength and muscle power output during a bench pull (BP) and anthropometric values were all measured for 46 trained male rowers aged 21–30 with 8–15 years of rowing training experience. The ER group showed greater body mass (5%, p < 0.05), greater fat free body mass (5%, p < 0.05), greater 1RM_BP (13%, p < 0.001), longer training experience (43%, p < 0.001), and a shorter time in the 2,000 m test (4%, p < 0.05) than the AR group. The ER group showed higher power output values in W _10 strokes (9%, p < 0.01), W _20 min (15.4%, p < 0.01) and $ W_{{4\;{\text{mmol}}\;{\text{l}}^{ - 1} }} $ (17.8%, p < 0.01) compared with the AR group. Significant relationships were observed between $ W_{{4\;{\text{mmol}}\;{\text{l}}^{ - 1} }} $ and W _20 min (r = 0.65 and 0.80; p < 0.01 in ER and AR, respectively). The indices for rowing performance suggested that W _20 min, $ W_{{4\;{\text{mmol}}\;{\text{l}}^{ - 1} }} , $ W _10 strokes and 1RM_BP were the most important predictors of traditional rowing performance in elite and amateur rowers.     

Quadriceps rate of force development affects gait and function in people with knee osteoarthritis

Objective

Quadriceps weakness exists in people with knee osteoarthritis (OA), but other muscle factors like rate of force development (RFD) may also be affected by knee OA. The purpose of this study was to determine if people with knee OA have deficits in quadriceps RFD, determine if quadriceps RFD would improve predicting knee joint power absorption and generation during free and fast walking, and determine if RFD would improve predicting functional outcomes.

Methods

26 subjects with knee OA and 23 healthy control subjects performed maximal voluntary isometric strength (MVIC) and RFD measures of the quadriceps. Subjects also underwent a 3-D motion analysis of both self-selected free and self-selected fast walking speeds. Joint kinetics were calculated from inverse dynamics.

Results

RFD was not different by group (p = 0.763), however, the OA subjects generated the highest peak RFD at a lower % MVIC (p = 0.008). Controls walked significantly faster at both free and fast walking speeds (p = 0.001, p = 0.029). Knee angles at heel strike and peak knee extension were lower (p = 0.004, p = 0.027) in the OA group. During fast walking knee power generation was higher in controls (p = 0.028). MVIC and force of highest peak RFD predicted KOOS–ADL score in the OA subjects, but only MVIC predicted stair climbing time.

Conclusions

The submaximal force at which peak RFD occurs plays a significant role in knee joint power as well as functional measures in the OA subjects, providing further evidence that factors other than maximal strength are also important in people with knee OA.