The effect of crank rate on physiological responses and exercise efficiency using a range of submaximal workloads during arm crank ergometry

Optimal and freely chosen paddling rate during moderate kayak ergometry

Moderate paddling, as in long distance kayaking, constitutes an endurance activity, which shares energetic aspects with activities such as long distance running and road cycling. The aim of the present study was to investigate whether in moderate paddling there is a U-shaped relationship between oxygen uptake and stroke rate, and also whether elite kayakers apply a freely chosen stroke rate, which is energetically optimal. Eleven young male elite kayakers performed moderate kayak ergometry at preset target stroke rates of 65, 75, and 90 strokes min^-1, and at a freely chosen stroke rate, while physiological responses including oxygen uptake were measured. The results showed that considering average values calculated across all participants, there was an approximately U-shaped relationship between oxygen uptake and target stroke rate with a minimum at 75 strokes min^-1. The freely chosen stroke rate was 67.0 ± 6.1 strokes min^-1. Thus, the freely chosen stroke rate, for the group in total, appeared to be lower and require higher oxygen uptake as compared to the energetically optimal preset target stroke rate. Eight out of 11 participants had a higher oxygen uptake (5.1% ± 6.7%, p = 0.028, across all participants) at their freely chosen stroke rate than at the preset target stroke rate, which resulted in the lowest oxygen uptake. In conclusion, an approximately U-shaped relationship between oxygen uptake and stroke rate for young elite kayakers during moderate ergometer kayaking was found. Additionally, the freely chosen stroke rate was systematically lower and, consequently, required higher oxygen uptake than the preset stroke rate, which resulted in the lowest oxygen uptake.

Oxygen uptake during upper body and lower body Wingate anaerobic tests

The aim of this study was to determine the aerobic contribution to upper body and lower body Wingate Anaerobic tests (WAnT). Eight nonspecifically trained males volunteered to take part in this study. Participants undertook incremental exercise tests for peak oxygen uptake and two 30-s WAnT (habituation and experimental) for both the upper and lower body. The resistive loadings used were 0.040 and 0.075 kg·kg body mass−1, respectively. Peak power output (PPO) and mean power output (MPO) were calculated for each WAnT. The aerobic contribution of each WAnT was assessed using breath by breath expired gas analysis. Peak oxygen uptake was lower for the upper body when compared with the lower body (P = 0.001). Similarly, PPO and MPO were greater for the lower body (both P < 0.001). Absolute oxygen uptake during the upper body WAnT was lower than for the lower body (P = 0.013), whereas relative oxygen uptake (% peak oxygen uptake) was similar (P = 0.997). The mean aerobic contribution for the upper body WAnT (43.5% ± 29.3%) was greater than for the lower body (29.4% ± 15.8%; P < 0.001). The greater aerobic contribution to the WAnT observed for the upper body in comparison with the lower body is likely due to methodological differences in upper and lower body WAnT protocols and potentially differences in anaerobic power production and exercise efficiency. The results of this study suggest that differences may exist for the aerobic contribution of upper and lower body Wingate anaerobic tests.

The effects of an increasing versus constant crank rate on peak physiological responses during incremental arm crank ergometry

We examined the effects of concomitant increases in crank rate and power output on incremental arm crank ergometry. Ten healthy males undertook three incremental upper body exercise tests to volitional exhaustion. The first test determined peak minute power. The subsequent tests involved arm cranking at an initial workload of 40% peak minute power with further increases of 10% peak minute power every 2 min. One involved a constant crank rate of 70 rev · min(-1), the other an initial crank rate of 50 rev · min(-1) increasing by 10 rev · min(-1) every 2 min. Fingertip capillary blood samples were analysed for blood lactate at rest and exhaustion. Local (working muscles) and cardiorespiratory ratings of perceived exertion (RPE) were recorded at the end of each exercise stage. Heart rate and expired gas were monitored continuously. No differences were observed in peak physiological responses or peak minute power achieved during either protocol. Blood lactate concentration tended to be greater for the constant crank rate protocol (P = 0.06). Test duration was shorter for the increasing than for the constant crank rate protocol. The relationship between local RPE and heart rate differed between tests. The results of this study show that increasing cadence during incremental arm crank ergometry provides a valid assessment of peak responses over a shorter duration but alters the heart rate-local RPE relationship.

Are substrate use during exercise and mitochondrial respiratory capacity decreased in arm and leg muscle in type 2 diabetes?

AIM/HYPOTHESIS

The aim of the study was to investigate mitochondrial function, fibre type distribution and substrate oxidation in arm and leg muscle during exercise in patients with type 2 diabetes and in obese and lean controls.

METHODS

Indirect calorimetry was used to calculate fat and carbohydrate oxidation during both progressive arm-cranking and leg-cycling exercises. Muscle biopsies from arm and leg were obtained. Fibre type, as well as O(2) flux capacity of saponin-permeabilised muscle fibres were measured, the latter by high resolution respirometry, in patients with type 2 diabetes, age- and BMI-matched obese controls, and age-matched lean controls.

RESULTS

Fat oxidation was similar in the groups during either arm or leg exercise. During leg exercise at higher intensities, but not during arm exercise, carbohydrate oxidation was lower in patients with type 2 diabetes compared with the other groups. In patients with type 2 diabetes, ADP-stimulated state 3 respiration per mg muscle with parallel electron input from complex I+II was lower in m. vastus lateralis compared with obese and lean controls, whereas no differences between groups were present in m. deltoideus. A higher percentage of type IIX fibres was seen in m. vastus lateralis in patients with type 2 diabetes compared with obese and lean controls, whereas no difference was found in the deltoid muscle.

CONCLUSIONS/INTERPRETATION

This study demonstrates similar O(2) flux capacity, fibre type distribution and carbohydrate oxidation in arm muscle in the groups despite the presence of attenuated values in leg muscle in patients with type 2 diabetes compared with obese and lean controls.

The influence of crank configuration on muscle activity and torque production during arm crank ergometry

This study investigated the effect of crank configuration on muscle activity and torque production during submaximal arm crank ergometry. Thirteen non-specifically trained male participants volunteered. During the research trials they completed a warm-up at 15W before two 3-min exercise stages were completed at 50 and 100W; subjects used either a synchronous or asynchronous pattern of cranking. During the final 30-s of each submaximal exercise stage electromyographic and torque production data were collected. After the data had been processed each parameter was analysed using separate 2-way ANOVA tests with repeated measures. The activity of all muscles increased in line with external workload, although a shift in the temporal pattern of muscle activity was noted between crank configurations. Patterns of torque production during asynchronous and synchronous cranking were distinct. Furthermore, peak, minimum and delta (peak-minimum) torque values were different (P<0.05) between crank configurations at both workloads. For example, at 100W, peak torque using synchronous [19.6 (4.3) Nm] cranking was higher (P<0.05) compared to asynchronous [16.8 (1.6) Nm] cranking. In contrast minimum torque was lower (P<0.05) at 100 W using synchronous [4.8 (1.7)Nm] compared to asynchronous [7.3 (1.2)Nm] cranking. There was a distinct bilateral asymmetry in torque production during asynchronous cranking with the dominant transmitting significantly more force to the crank arm. Taken together, these preliminary data demonstrate the complex nature of muscle activity during arm crank ergometry performed with an asynchronous or synchronous crank set-up. Further work is required to determine how muscle activity (EMG activity) and associated patterns of torque production influence physiological responses and functional capacity during arm crank ergometry.

The effects of cadence and power output upon physiological and biomechanical responses to incremental arm-crank ergometry

The aim of this study was to examine the effects of cadence and power output on physiological and biomechanical responses to incremental arm-crank ergometry (ACE). Ten male subjects (mean ± SD age, 30.4 ±5.4 y; height, 1.78 ±0.07 m; mass, 86.1 ±14.2 kg) undertook 3 incremental ACE protocols to determine peak oxygen uptake (VO2 peak; mean of 3 tests: 3.07 ± 0.17 L·min–1) at randomly assigned cadences of 50, 70, or 90 r·min–1. Heart rate and expired air were continually monitored. Central (RPE-C) and local (RPE-L) ratings of perceived exertion were recorded at volitional exhaustion. Joint angles and trunk rotation were analysed during each exercise stage. During submaximal power outputs of 50, 70, and 90 W, oxygen consumption (VO2) was lowest for 50 r·min–1 and highest for 90 r·min–1 (p < 0.01). VO2 peak was lowest during 50 r·min–1 (2.79 ±0.45 L·min–1; p < 0.05) when compared with both 70 r·min–1 and 90 r·min–1 (3.16 ±0.58, 3.24 ±0.49 L·min–1, respectively; p > 0.05). The difference between RPE-L and RPE-C at volitional exhaustion was greatest during 50 r·min–1 (2.9 ± 1.6) when compared with 90 r·min–1 (0.9 ± 1.9, p < 0.05). At VO2 peak, shoulder range of motion (ROM) and trunk rotation were greater for 50  and 70 r·min–1 when compared with 90 r·min–1 (p < 0.05). During submaximal power outputs, shoulder angle and trunk rotation were greatest at 50 r·min–1 when compared with 90 r·min–1 (p < 0.05). VO2 was inversely related to both trunk rotation and shoulder ROM during submaximal power outputs. The results of this study suggest that the greater forces required at lower cadences to produce a given power output resulted in greater joint angles and range of shoulder and trunk movement. Greater isometric contractions for torso stabilization and increased cost of breathing possibly from respiratory–locomotor coupling may have contributed increased oxygen consumption at higher cadences.

Effect of different intensities of active recovery on sprint swimming performance

Active recovery reduces blood lactate concentration faster than passive recovery and, when the proper intensity is applied, a positive effect on performance is expected. The purpose of the study was to investigate the effect of different intensities of active recovery on performance during repeated sprint swimming. Nine male well-trained swimmers performed 8 repetitions of 25 m sprints (8 x 25 m) interspersed with 45 s intervals, followed by a 50 m sprint test 6 min later. During the 45 s and 6 min interval periods, swimmers either rested passively (PAS) or swam at an intensity corresponding to 50% (ACT50) and 60% (ACT60) of their individual 100 m velocity. Blood lactate was higher during PAS compared with ACT50 and ACT60 trials (p < 0.05), whereas plasma ammonia and glycerol concentration were not different between trials (p > 0.05). Mean performance time for the 8 x 25 m sprints was better in the PAS compared with the ACT50 and ACT60 trials (PAS: 13.10 +/- 0.07 vs. ACT50: 13.43 +/- 0.10 and ACT60: 13.47 +/- 0.10s, p < 0.05). The first 25 m sprint was not different across trials (p > 0.05), but performance decreased after sprint 2 during active recovery trials (ACT50 and ACT60) compared with the passive recovery (PAS) trial (p < 0.05). Performance time for the 50 m sprint performed 6 min after the 8 x 25 m sprints was no different between trials (p > 0.05). These results indicate that active recovery at intensities corresponding to 50% and 60% of the 100 m velocity during repeated swimming sprints decreases performance. Active recovery reduces blood lactate concentration, but does not affect performance on a 50 m sprint when 6 min recovery is provided. Passive recovery is advised during short-interval repeated sprint training in well-trained swimmers.

The effect of crank rate strategy on peak aerobic power and peak physiological responses during arm crank ergometry

The main aim of this study was to determine whether the use of an imposed or freely chosen crank rate would influence submaximal and peak physiological responses during arm crank ergometry. Fifteen physically active men participated in the study. Their mean age, height, and body mass were 25.9 (s = 6.2) years, 1.80 (s = 0.10) m, and 78.4 (s = 6.1) kg, respectively. The participants performed two incremental peak oxygen consumption (VO(2peak)) tests using an electronically braked ergometer. One test was performed using an imposed crank rate of 80 rev x min(-1), whereas in the other the participants used spontaneously chosen crank rates. The order in which the tests were performed was randomized, and they were separated by at least 2 days. Respiratory data were collected using an on-line gas analysis system, and fingertip capillary blood samples ( approximately 20 microl) were collected for the determination of blood lactate concentration. Heart rate was also recorded throughout the tests. Time to exhaustion was measured and peak aerobic power calculated. Submaximal data were analysed using separate two-way repeated-measures analyses of variance, while differences in peak values were analysed using separate paired t-tests. Variations in spontaneously chosen crank rate were assessed using a one-way analysis of variance with repeated measures. Agreement between the crank rate strategies for the assessment of peak values was examined by calculating intra-class correlation coefficients (ICC) and 95% limits of agreement (95% LoA). While considerable between-participant variations in spontaneously chosen crank rate were observed, the mean value was not different (P > 0.05) from the imposed crank rate of 80 rev x min(-1) at any point. No differences (P > 0.05) were observed for submaximal data between crank strategies. Furthermore, mean peak minute power [158 (s = 20) vs. 158 (s = 18) W], time to exhaustion [739 (s = 118) vs. 727 (s = 111) s], and VO(2peak)[3.09 (s = 0.38) vs. 3.04 (s = 0.34) l x min(-1)] were similar for the imposed and spontaneously chosen crank rates, respectively. However, the agreement for the assessment of VO(2peak) (ICC = 0.78; 95% LoA = 0.04 +/- 0.50 l x min(-1)) between the cranking strategies was considered unacceptable. Our results suggest that either an imposed or spontaneously chosen crank rate strategy can be used to examine physiological responses during arm crank ergometry, although it is recommended that the two crank strategies should not be used interchangeably.

No gender-specific differences in mechanical efficiency during arm or leg exercise relative to ventilatory threshold

The purpose of this study was to determine economy and mechanical efficiency in men and women during both arm cranking (AC) and leg cycling (LC) at 70%, 85%, 100%, and 115% of mode-specific ventilatory threshold (T(vent)). Recreationally active men (n=9) and women (n=9) with similar values for %VO2peak at T(vent) served as subjects. All subjects performed 5 min of exercise at each intensity of 70%, 85%, 100%, and 115% of T(vent) for both AC and LC. Economy was expressed as W/L/min. Gross efficiency (GE) was determined as the ratio of work accomplished to total energy expended (%). Delta efficiency (DE) was determined as the ratio of delta work accomplished to delta energy expended (%). Economy and efficiency during LC were greater than during AC in men and women. During AC or LC exercise, no sex differences were found in either economy (P=0.93 for AC, 0.98 for LC), GE (P=0.88 for AC, 0.75 for LC), or DE (P=0.57 for AC, 0.51 for LC). These findings indicate that men and women show similar economy and efficiency during both AC and LC exercise when subjects have similar %VO2peak at Tvent.

Influence of crank rate on the slow component of pulmonary O2 uptake during heavy arm-crank exercise

The principal aim of this study was to examine the influence of variations in crank rate on the slow component of the pulmonary oxygen uptake ([Formula: see text]O2) response to heavy-intensity arm-crank ergometry (ACE). We hypothesized that, for the same external work rate, a higher crank rate would elicit a greater amplitude of the [Formula: see text]O2 "slow component". Eleven healthy males (mean (± SD) age, 25 (±6) y; body mass, 89.1 (±10.7) kg; ACE [Formula: see text]O2 peak, 3.36 (±0.47) L·min-1) volunteered to participate. The subjects initially completed an incremental exercise test for the determination of [Formula: see text]O2 peak and peak power on an electrically braked arm ergometer. Subsequently, they completed "step" transitions from an unloaded baseline to a work rate requiring 70% of peak power: 2 at a crank rate of 50 r·min-1 (LO) and 2 at a crank rate of 90 r·min-1 (HI). Pulmonary gas exchange was measured on a breath-by-breath basis and [Formula: see text]O2 kinetics were evaluated from the mean response to each condition using non-linear regression techniques. In contradiction to our hypothesis, the [Formula: see text]O2 slow component was significantly greater at 50 r·min-1 than at 90 r·min-1 (LO: 0.60 ± 0.30 vs. HI: 0.47 ± 0.21 L·min-1; p < 0.05). The mean value for the localized rating of perceived exertion was also higher at 50 r·min-1 than at 90 r·min-1 (LO: 16.7 ± 1.4 vs. HI: 15.2 ± 1.3; p < 0.05), but there was no significant difference in end-exercise blood lactate concentration. It is possible that differences in muscle tension development and blood flow resulted in a greater contribution of "low-efficiency" type II muscle fibres to force production at the lower crank rate in ACE, and that this was linked to the greater [Formula: see text]O2 slow component. However, other factors such as greater isometric contraction of the muscles of the trunk and legs at the lower crank rate might also be implicated.Key words: O2 kinetics, [Formula: see text]O2 slow component, fibre recruitment, oxygen uptake.