Similar Anti-Inflammatory Acute Responses from Moderate-Intensity Continuous and High-Intensity Intermittent Exercise

The purpose of this study was to compare the effect of high-intensity intermittent exercise (HIIE) versus volume matched steady state exercise (SSE) on inflammatory and metabolic responses. Eight physically active male subjects completed two experimental sessions, a 5-km run on a treadmill either continuously (70% vVO₂max) or intermittently (1:1 min at vVO₂max). Blood samples were collected at rest, immediately, 30 and 60 minutes after the exercise session. Blood was analyzed for glucose, non-ester fatty acid (NEFA), uric acid, lactate, cortisol, and cytokines (IL-6, IL-10 and TNF-α) levels. The lactate levels exhibited higher values immediately post-exercise than at rest (HIIE 1.34 ± 0.24 to 7.11 ± 2.85, and SSE 1.35 ± 0.14 to 4.06±1.60 mmol·L^-1, p < 0.05), but HIIE promoted higher values than SSE (p < 0.05); the NEFA levels were higher immediately post-exercise than at rest only in the SSE condition (0.71 ± 0.04 to 0.82±0.09 mEq/L, respectively, p < 0.05), yet, SSE promoted higher values than HIIE immediately after exercise (HIIE 0.72±0.03 vs SSE 0.82±0.09 mEq·L^-1, p < 0.05). Glucose and uric acid levels did not show changes under the different conditions (p > 0.05). Cortisol, IL-6, IL-10 and TNF-α levels showed time-dependent changes under the different conditions (p < 0.05), however, the area under the curve of TNF-α in the SSE were higher than HIIE (p < 0.05), and the area under the curve of IL-6 in the HIIE showed higher values than SSE (p < 0.05). In addition, both exercise conditions promote increased IL-10 levels and IL-10/TNF-α ratio (p < 0.05). In conclusion, our results demonstrated that both exercise protocols, when volume is matched, promote similar inflammatory responses, leading to an anti-inflammatory status; however, the metabolic responses are different.

Key points

• Metabolic contribution of both exercise, HIIE and SSE, was different.
• Both protocols leading to an anti-inflammatory status.
• HIIE induce a higher energy expenditure take into account total session duration.

Key words: High intensity intermittent exercise, steady state exercise, metabolism, inflammation, energy expenditure, cytokines     

Maximal Fat Oxidation: Comparison between Treadmill,Elliptical and Rowing Exercises

Fat oxidation during exercise is associated with cardio-metabolic benefits, but the extent of which whole-body exercise modality elicits the greatest fat oxidation remains unclear. We investigated the effects of treadmill, elliptical and rowing exercise on fat oxidation in healthy individuals. Nine healthy males participated in three, peak oxygen consumption tests, on a treadmill, elliptical and rowing ergometer. Indirect calorimetry was used to assess maximal oxygen consumption (V̇O_2peak), maximal fat oxidation (MFO) rates, and the exercise intensity MFO occurred (Fat_max). Mixed venous blood was collected to assess lactate and blood gases concentrations. While V̇O_2peak was similar between exercise modalities, MFO rates were higher on the treadmill (mean ± SD; 0.61 ± 0.06 g·min^-1) compared to both the elliptical (0.41 ± 0.08 g·min^-1, p = 0.022) and the rower (0.40 ± 0.08 g·min^-1, p = 0.017). Fat_max values were also significantly higher on the treadmill (56.0 ± 6.2 %V̇O_2peak) compared to both the elliptical (36.8 ± 5.4 %V̇O_2peak, p = 0.049) and rower (31.6 ± 5.0 %V̇O_2peak, p = 0.021). Post-exercise blood lactate concentrations were also significantly lower following treadmill exercise (p = 0.021). Exercising on a treadmill maximizes fat oxidation to a greater extent than elliptical and rowing exercises, and remains an important exercise modality to improve fat oxidation, and consequently, cardio-metabolic health.Key points

• The ability to oxidize fat has been associated with improved oxidative enzymes activity and mitochondrial biogenesis.
• The present study examined the effects of treadmill, elliptical, and rower exercises on maximal fat oxidation rates (MFO), the intensity were MFO was observed (Fat_max) and on fat oxidation curves in healthy and young participants.
• Both MFO and Fat_max were higher during treadmill exercise. Multiple linear mixed-effects regression analyses further revealed an effect of exercise modality on fat oxidation curves.
• Adequate selection of exercise modality during training may have a meaningful impact on substrate oxidation. Treadmill exercise should be considered in training design for those looking to maintain or improve metabolic profiling.

Key words: Substrate oxidation, indirect calorimetry, exercise modality, metabolism     

Lactate Kinetics After Intermittent and Continuous Exercise Training

The purpose of this study was to assess, the effects of continuous and intermittent exercise training on lactate kinetic parameters and maximal aerobic speed (MAS) using field tests. Twenty-four male sport students were equally divided into continuous (CT) and intermittent (IT) physically trained groups. Another six participants acted as non-trained controls (CG). The trained participants practiced 6-days per week for 6 weeks. Before and after training, all participants completed an incremental exercise test to assess their MAS, and a 30- second supra-maximal exercise followed by 30 minutes of active recovery to determine the individual blood lactate recovery curve. It was found that exercise training has significantly increased MAS (p < 0.001), the lactate exchange and removal abilities as well as the lactate concentrations at the beginning of the recovery ([La]-(0)); for both CT and IT groups; this was accompanied by a significant reduction of the time to lactate-peak. Nevertheless, the improvement in MAS was significantly higher (p < 0.001) post-intermittent (15.1 % ± 2.4) than post-continuous (10.3 % ± 3.2) training. The lactate-exchange and removal abilities were also significantly higher for IT than for CT-group (P<0.05). Moreover, IT-group showed a significantly shorter half-time of the blood lactate (t-½-[La]) than CT-group (7.2 ± 0.5 min vs 7.7 ± 0.3 min, respectively) (p < 0.05). However, no significant differences were observed in peak blood lactate concentration ([La]_peak), time to reach [La]_peak (t-[La]_peak), and [La]-(0) between the two physically-trained groups. We conclude that both continuous and intermittent training exercises were equally effective in improving t-[La]_peak and [La]_peak, although intermittent training was more beneficial in elevating MAS and in raising the lactate exchange (γ₁) and removal (γ₂) indexes.

Key points

• Coaches and athletes need to be aware of the potentiality positive effects of exercise intensity.
• Improvements in physical fitness are associated with a concomitant increase in the lactate removal ability.
• In order to reduce lactate accumulation and increase maximal aerobic speed maximally, interval training method, with work speeds equal to 90% - 100% of MAS, may be the effective way when compared with continuous training method.

Key words: Biexponential mathematical model, recovery, supra-maximal exercise.     

Cardiovascular response to peak voluntary exercise in males with cervical spinal cord injury

Context/Objective: Traumatic damage to the cervical spinal cord is usually associated with a disruption of the autonomic nervous system (ANS) and impaired cardiovascular control both during and following exercise. The magnitude of the cardiovascular dysfunction remains unclear. The aim of the current study was to compare cardiovascular responses to peak voluntary exercise in individuals with tetraplegia and able-bodied participants.

Design: A case-control study.

Subjects: Twenty males with cervical spinal cord injury (SCI) as the Tetra group and 27 able-bodied males as the Control group were included in the study.

Outcome Measures: Blood pressure (BP) response one minute after the peak exercise, peak heart rate (HR_peak), and peak oxygen consumption (VO_2peak) on an arm crank ergometer were measured. In the second part of the study, 17 individuals of the Control group completed the Tetra group's workload protocol with the same parameters recorded.

Results: There was no increase in BP in response to the exercise in the Tetra group. Able-bodied individuals exhibited significantly increased post-exercise systolic BP after the maximal graded exercise test (123±16%) and after completion of the Tetra group's workload protocol (114±11%) as compared to pre-exercise. The Tetra group VO_2peak was 59% and the HR_peak was 73% of the Control group VO_2peak and HR_peak, respectively.

Conclusions: BP did not increase following maximal arm crank exercise in males with a cervical SCI unlike the increases observed in the Control group. Some males in the Tetra group appeared to be at risk of severe hypotension following high intensity exercise, which can limit the ability to progressive increase and maintain high intensity exercise.     

Lung Diffusion Capacity can Predict Maximal Exercise in Apparently Healthy Heavy Smokers

Chronic exposure to tobacco smoking may damage lung and heart function. The aim of this study was to assess maximal exercise capacity and its relationship with lung function in apparently healthy smokers. We recruited 15 heavy smokers (age 47 years ± 7, BMI 25 kg/m² ± 3, pack/years 32 ± 9) without any cardiovascular or pulmonary signs and symptoms. Fifteen healthy non smoking subjects were enrolled as a control group. All subjects underwent pulmonary function tests, electrocardiograms at rest and graded cycle exercise tests. In smokers and controls, resting lung and cardiac function parameters were in the normal range, apart from diffusing lung capacity (TLCO) values which were significantly lower in smokers (p < 0.05). As compared to controls, smokers presented lower maximal exercise capacity with lower values at peak of exercise of oxygen uptake (peak VO₂), workload, oxygen uptake/watt ratio and oxygen pulse (p < 0.05) and higher dyspnoea perception (p < 0.05). Moreover, peak VO₂, maximal workload and oxygen pulse at peak exercise were related to and predicted by TLCO (p < 0. 05). Our study confirms that maximal exercise capacity is reduced in apparently healthy heavy smokers, and shows that TLCO explains some of the variance in maximal exercise.

Key points

• Chronic exposure to tobacco smoking may damage lung and heart function.
• Smokers present lower diffusion capacity and maximal exercise capacity.
• In smokers maximal exercise capacity can be predicted by resting diffusion lung capacity.

Key words: Tobacco, lung function, exercise capacity, lung diffusion capacity.     

The Effects of Intermittent Exercise on Physiological Outcomes in an Obese Population: Continuous Versus Interval Walking

This study compared the effects of 12 weeks of caloric restriction and interval exercise (INT) and caloric restriction and continuous aerobic exercise (CON) on physiological outcomes in an obese population. Forty-four individuals (BMI ≥ 30 kg·m^-2) were randomised into the INT or CON group. Participant withdrawal resulted in 12 and 14 participants in the INT and CON groups, respectively. All participants were on a strict monitored diet. Exercise involved two 15-min bouts of walking performed on five days per week. Interval exercise consisted of a 2:1 min ratio of low-intensity (40-45% VO_2peak) and high- intensity (70-75% VO_2peak) exercise, while the CON group exercised between 50-55% VO_2peak. Exercise duration and average intensity (%VO_2peak) were similar between groups. There were no significant differences (p > 0.05) between the two groups for any variable assessed apart from very low density lipoprotein (VLDL-C), which significantly decreased over time in the INT group only (p < 0.05, d = 1.03). Caloric restriction and interval exercise compared to caloric restriction and continuous aerobic exercise resulted in similar outcome measures apart from VLDL-C levels, which significantly improved in the INT group only.

Key points

• Twelve weeks of interval exercise and caloric restriction resulted in significant improvement in very low density lipoprotein cholesterol in an obese population, as compared to continuous aerobic exercise and caloric restriction.
• Twelve weeks of either interval exercise or continuous exercise resulted in similar improvements in aerobic fitness in an obese population.

Key words: Interval training, body fat, fitness, metabolism     

Relationship between Fat Oxidation and Lactate Threshold in Athletes and Obese Women and Men

The first aim of this study was to determine the exercise intensity that elicited the highest rate of fat oxidation in sedentary, obese subjects (OB; n=10 men, n=10 women) compared with endurance athletes (AT; n=10 men, n=10 women). The second aim was to investigate the relationship between VO₂ at the intensity eliciting the highest rate of fat oxidation and the corresponding VO₂ at the lactate threshold. Peak oxygen consumption (VO_2peak) was determined in 20 AT and 20 OB using an incremental exercise protocol on a cycle ergometer. Based on their VO_2peak values, subjects completed a protocol requiring them to exercise for 20 min at three different workloads (55, 65 and 75% VO_2peak), randomly assigned on two separate occasions. The oxidation rates of fat and carbohydrate were measured by indirect calorimetry. The highest rates of fat oxidation were at 75 % VO_2peak (AT), and at 65 % VO_2peak (OB). The rate of fat oxidation was significantly higher in AT (18.2 ± 6.1) compared with OB women (10.6 ± 4.5 kJ min^-1·kg^-1) (p < 0.01). There was no significant difference in the rate of fat oxidation for the men (AT 19.7 ± 8.1 vs. OB 17.6 ± 8.2 kJ min^-1·kg^-1). AT reached LT at a significantly (p < 0.01) higher exercise intensity expressed in VO_2peak than obese subjects (AT women 76.4 ± 0.1, men 77.3 ± 0.1 vs. OB women, 49.7 ± 0.1, men 49.5 ± 0.1% VO_2peak). A significant correlation was found between VO₂ at LT and VO₂ (L·min^-1) eliciting the maximal rate of fat oxidation in athletes (women; r = 0.67; p = 0.03; men: r = 0.75; p = 0.01) but not in the obese. In summary, we observed higher rates of fat oxidation at higher relative work rates in AT compared with OB. A significant correlation was found between LT and the exercise intensity eliciting a high rate of fat oxidation in AT (r=0.89; p < 0.01) but not in OB. Cardiorespiratory fitness, defined as VO_2peak, seems to be important in defining the relationship between a high rate of fat oxidation and LT.

Key Points

• Within the tested intensities of 55, 65 and 75% VO_2peak athletes reached higher rates of fat oxidation at higher relative work rates compared with obese subjects.
• We found in obese women and men the intensity of the highest rate of fat oxidation at 65% VO_2peak.
• Between the lactate threshold and the intensity eliciting a high rate of fat oxidation a significant correlation was found in athletes but not in obese subjects.

Key words: Exercise intensity, substrate utilization, obesity, lactate threshold     

Reliability Of Arm Wingate Anaerobic Testing In Persons With Complete Paraplegia

Abstract

Background: Accurate, reliable assessment of upper extremity muscular power in persons with paraplegia caused by spinal cord injury (SCI) would provide an objective indication of their ability to generate the forces necessary for the performance of daily activities. Wingate Anaerobic Testing (WAnT) consists of a 30-second sprint test on a cycle ergometer and has been used widely in both athletic and research settings.

Purpose: To examine test-retest reliability of arm WAnT performance in persons with complete SCI and paraplegia.

Methods: Forty-three participants with thoracic-level paraplegia (T2 through T12) performed 2 trials of arm WAnT with 2 to 7 days between each trial. Testing was performed using a Monarch 834E ergometer with participants seated in their wheelchairs. Participants were directed to crank at maximal pace for 30 seconds against a resistance load equivalent to 3.5% of their body mass. The SMI OptoSensor 2000 system was used to determine values of peak power (P_peak), mean power (P_mean), minimum power, and rate of fatigue, which were compared between trials using 1-way analysis of variance for repeated measures. Coeffi cients of determination (r₂) were calculated between trials for P_peak and P_mean.

Results: No significant diffe rence was found between trials for any of the power output variables. Regression analysis ind icat ed that P_peak and P_mean were closely associated between the 2 trials (r₂= 0.92 and 0.94, respectively).

Conclusion: Arm WAnT is a reliable measurement tool for the assessment of upper extremity muscular power in persons with complete paraplegia.     

Longitudinal relationship between wheelchair exercise capacity and life satisfaction in patients with spinal cord injury: A cohort study in the Netherlands

Objective

To examine the relationship between wheelchair exercise capacity and life satisfaction in persons with spinal cord injury from the start of active inpatient rehabilitation up to 5 years after discharge.

Design

Prospective cohort study.

Subjects

Persons with spinal cord injury, aged 18–65 years, and wheelchair dependent at least for long distances.

Method

Measurements at the start of active rehabilitation, after 3 months, at discharge from inpatient rehabilitation, and 1 and 5 years after discharge. A peak wheelchair exercise test was performed to record peak oxygen uptake (VO_2peak) and peak power output (PO_peak). Life satisfaction was measured as current life satisfaction and change of life satisfaction in comparison with life after spinal cord injury. Relationships between (changes in) exercise capacity and (changes in) life satisfaction were analyzed random coefficient analysis, corrected for possible confounders (age, gender, level of lesion, functional status, secondary impairments, pain, and sports activity) if necessary.

Results

Of 225 persons included, 130 attended two or more peak exercise tests, who were include in the analyses. Mean age at start was 39 years, 75% were male, 73% had paraplegia, and 76% had a traumatic lesion. Mean PO_peak increased during the study from 32.9 to 55.9 Watts, mean VO_2peak from 1.02  to 1.38 l/minute, and mean life satisfaction from 5.7 to 7.8. An increase of PO_peak with 10 W was associated with a 0.3-point increase of life satisfaction (P = 0.01). An increase of VO_2peak with 0.1 l/minute was associated with a 0.1-point increase of life satisfaction (P = 0.049).

Conclusion

High(er) wheelchair exercise capacity is related to high(er) life satisfaction in spinal cord injury patients.     

Reproducibility of Outdoor Flat and Uphill Cycling Time Trials and Their Performance Correlates with Peak Power Output in Moderately Trained Cyclists

The aims of the present study were firstly to examine the reproducibility of outdoor flat and uphill cycling time trials (TT), and secondly to assess the relationship between peak power output (W_peak) obtained in the laboratory and outdoor cycling performance in moderately trained cyclists. Eight competitive male cyclists first performed a progressive cycle ergometer test in the laboratory to determine W_peak (W). Thereafter, they performed three 36 km TT (TT₃₆) on a flat course on separate days and at the same time of the day. On a different day, they also performed three 1.4 km uphill TT (TT_1.4) in a single day. The coefficient of variation (CV) values across three TT₃₆ and TT_1.4 ranged from 1.1 - 1.4% and 2.6 - 2.9%, for performance time (min) and mean power (W), respectively. The correlation between absolute W_peak (W) obtained in the laboratory and mean power during TT₃₆ and TT_1.4 was 0.90 (p < 0.01) and 0.98 (p < 0.01), respectively. Absolute W_peak (W) correlated significantly with performance time in TT₃₆ (r = -0.72, p < 0.05) but not in TT_1.4 (r = -0.52, p > 0.05). The correlation between relative W_peak (W·kg^-1) and performance time in TT₃₆ and TT_1.4 was r = -0.65 (p > 0.05) and r = -0.91 (p < 0.01), respectively. In conclusion, under stable environmental conditions, performance time and mean power are highly reproducible in moderately trained cyclists during outdoor cycling TT. Laboratory determined absolute W_peak (W) may predict cycling performance on a flat course but relative W_peak (W·kg^-1) is a better predictor of performance during uphill cycling.

Key Points

• Under stable environmental conditions, performance time and mean power are highly reproducible in moderately trained cyclists during outdoor flat and uphill cycling time trials.
• Laboratory determined peak power output (W_peak) (W) may predict cycling performance on a flat course.
• Laboratory determined relative W_peak (W·kg^-1) is a better predictor of performance during uphill cycling

Key Words: Field-based, reliability, performance time, mean power, heart rate, PowerTap powermeter     

Physiological Responses to 90 s All Out Isokinetic Sprint Cycling in Boys and Men

The purpose of this study was to compare the VO₂ kinetic and mechanical power responses of boys and men to all out 90 s sprint cycle exercise. Eight boys (14.6 ± 0.3 y) and eight men (33.8 ± 6.5 y) volunteered to participate and completed a ramp test (to determine VO_2peak and ventilatory threshold, VT) and then on subsequent days, two 90 s all out cycle sprints on an isokinetic cycle ergometer. During each test, breath-by-breath pulmonary gas exchange and power output were measured. Parameters from the power output profiles were derived from the average response of the two tests including peak power (PP, highest power output in 1 s), end power (EP_60-90, power over the last 30 s), and mean power over the 90 s (MP₉₀). Independent pairwise and dependent t-tests were used to compare the data from tests between adults and boys subject groups. Significant differences between adults and boys were found for absolute PP (881.4 ± 60.7 vs 533.6 ± 50.7 W), EP_60-90 (288.6 ± 25.7 vs 134.3 ± 17.6 W) and MP₉₀ (434.5 ± 27.4 vs 238.4 ± 17.3 W, p =0.001) respectively. Relative to body mass significant differences between adults and boys were found for EP_60-90, MP₉₀ and total work (p < 0.002). The boys attained 90 s VO₂ values that were closer to VO_2peak than their adult counterparts (93.3 ± 2.6 vs 84.9 ± 2.3 %, p = 0.03). They also demonstrated faster VO₂ kinetics (10.8 ± 1.5 vs 17.6 ± 1.0 s, p < 0.01). In conclusion, during all out 90 s cycle sprinting boys were able to attain VO₂ values that were closer to VO_2peak and a faster time constant than adult men. These findings provide insight into the contribution and speed of response of the aerobic system during an ‘anaerobic’ test.

Key Points

• The results of this study confirm the significant contributions of the aerobic energy systems during so called ‘anaerobic tests’.
• Boys were able to attain VO₂ values from an all out 90 s sprint cycle that were closer to their aerobic VO₂ peak test than adults. More detailed studies are required to investigate the limiting factors that prevent VO₂ peak being reached in an all out sprint cycle.
• All out tests of a duration > 30 s and coupled with gas and power analyses offer paediatric physiologists considerable scope to examine the contributions of the anaerobic and aerobic energy systems until more ethically viable methods are found.

Key Words: VO_2peak, anaerobic, kinetics, aerobic, ergometry     

Shaping Physiological Indices,Swimming Technique,and Their Influence on 200m Breaststroke Race in Young Swimmers

The aim of this study was to investigate somatic properties and physiological capacity, and analyze kinematic parameters in the 200 m breaststroke swimming race. Twenty-seven male swimmers participated in the study. They were 15.7±1.98 years old. Their average height was 1.80 ± 0.02 m and lean body mass (LBM) was 62.45 ± 8.29 kg. Physiological exercise capacity was measured in two separate 90 sec. all-out tests, one for the arms and second for legs. During the tests total work of arm cranking (TWAR) and cycling (TWLG) as well as peak of VO₂ for arm (VO_2peakAR) and leg (VO_2peakLG) were measured. The underwater swimmers body movements were recorded during the all-out swimming 200m breaststroke speed test using an underwater camera installed on a portable trolley. The swimming kinematic parameters and propulsive or non-propulsive movement phases of the arms and legs as well as average speed (V200), surface speed (V200surface) and swimming speed in turn zones (V200turns) were extracted. V200surface was significantly related to the percentage of leg propulsion and was shown to have large effect on VO_2peakLG in the Cohen analysis. V200turns depended significantly on the indicators of physiological performance and body structure: TWAR, VO_2peak LG and LBM, LBM, which in turn strongly determined the measured results of TWAR, TWLG, VO_2peakAR and VO_2peakLG. The V200turns and V200surface were strongly associated with V200, 0.92, p < 0.001 and 0.91, p < 0.001 respectively. In each lap of the 200m swimming there was an increased percentage of propulsion of limb movement observed simultaneously with a reduction in the gliding phase in the breaststroke cycles.

Key points

• This study investigated the influence of the selected indicators of somatic properties and physiological capacity as well kinematic and coordination parameters on breaststroke swimming.
• In this observations the body’s functional capacity have an important impact on achieving good breaststroke swimming results, the V₂₀₀ was moderately associated on VO₂peakLG, moreover, separate V₂₀₀turns depended with VO₂peakLG and on LBM and TWAR.
• The speed of surface breaststroke swimming - V₂₀₀surface similarly as V₂₀₀turns had a very strong influence on the end result of V_{200 ,} 0.91, p<0.001 and 0.92, p<0.001 respectively.
• The ability to swim fast on the surface (V₂₀₀surface) was positively and significantly associated with the percentage time of propulsion generation -LP in the breaststroke cycle.

Key words: Breaststroke swimming, physiological indices, lean body mass, kinematic indices     

Effects of Muscle Architecture on Eccentric Exercise Induced Muscle Damage Responses

There is a need to investigate the role of muscle architecture on muscle damage responses induced by exercise. The aim of this study was to determine the effect of muscle architecture and muscle length on eccentric exercise-induced muscle damage responses. Eccentric exercise-induced muscle damage was performed randomly to the elbow flexor (EF), knee extensor (KE), and knee flexor (KF) muscle groups with two week intervals in 12 sedentary male subjects. Before and after each eccentric exercise (immediately after, on the 1^st, 2^nd, 3^rd, and 7^th days) range of motion, delayed onset muscle soreness, creatine kinase activity, myoglobin concentration and isometric peak torque in short and long muscle positions were evaluated. Furthermore, muscle volume and pennation angle of each muscle group was evaluated before initiating the eccentric exercise protocol. Pennation angle and muscle volume was significantly higher and the workload per unit muscle volume was significantly lower in the KE muscles compared with the KF and EF muscles (p < 0.01). EF muscles showed significantly higher pain levels at post-exercise days 1 and 3 compared with the KE (p < 0.01-0.001) and KF (p < 0.01) muscles. The deficits in range of motion were higher in the EF muscles compared to the KE and KF muscles immediately after (day 0, p < 0.01), day 1 (p < 0.05-0.01), and day 3 (p < 0.05) evaluations. The EF muscles represented significantly greater increases in CK and Mb levels at day 1, 3, and 7 than the KE muscles (p < 0.05-0.01). The CK and Mb levels were also significantly higher in the KF muscles compared with the KE muscles (p < 0.05, p < 0.01 respectively). The KF and EF muscles represented higher isometric peak torque deficits in all the post-exercise evaluations at muscle short position (p < 0.05-0.001) compared with the KE muscle after eccentric exercise. Isometric peak torque deficits in muscle lengthened position was significantly higher in EF in all the post-exercise evaluations compared with the KE muscle (p < 0.05-0.01). According to the results of this study it can be concluded that muscle structural differences may be one of the responsible factors for the different muscle damage responses following eccentric exercise in various muscle groups. Key points

• The upper extremity flexor muscles are more affected by eccentric exercise induced muscle damage, either they are in a shortened or lengthened position.
• Loss of peak torque due to eccentric exercise induced muscle damage is observed at different levels in the joint range of motion where the muscles are lengthened or shortened.
• The workload per unit muscle volume during eccentric contraction is higher in muscles having a longitudinal fiber orientation compared to pennate muscles, which is a possible reason for the increased incidence of muscle damage.

Key words: Muscle damage, pennation angle, eccentric exercise, quadriceps muscle, hamstring muscle, biceps brachii muscle     

Longitudinal relationship between wheelchair exercise capacity and life satisfaction in patients with spinal cord injury: A cohort study in the Netherlands

Abstract

Objective

To examine the relationship between wheelchair exercise capacity and life satisfaction in persons with spinal cord injury from the start of active inpatient rehabilitation up to 5 years after discharge.

Design

Prospective cohort study.

Subjects

Persons with spinal cord injury, aged 18–65 years, and wheelchair dependent at least for long distances.

Method

Measurements at the start of active rehabilitation, after 3 months, at discharge from inpatient rehabilitation, and 1 and 5 years after discharge. A peak wheelchair exercise test was performed to record peak oxygen uptake (VO_2peak) and peak power output (PO_peak). Life satisfaction was measured as current life satisfaction and change of life satisfaction in comparison with life after spinal cord injury. Relationships between (changes in) exercise capacity and (changes in) life satisfaction were analyzed random coefficient analysis, corrected for possible confounders (age, gender, level of lesion, functional status, secondary impairments, pain, and sports activity) if necessary.

Results

Of 225 persons included, 130 attended two or more peak exercise tests, who were include in the analyses. Mean age at start was 39 years, 75% were male, 73% had paraplegia, and 76% had a traumatic lesion. Mean PO_peak increased during the study from 32.9 to 55.9 Watts, mean VO_2peak from 1.02 to 1.38 l/minute, and mean life satisfaction from 5.7 to 7.8. An increase of PO_peak with 10 W was associated with a 0.3-point increase of life satisfaction (P = 0.01). An increase of VO_2peak with 0.1 l/minute was associated with a 0.1-point increase of life satisfaction (P = 0.049).

Conclusion

High(er) wheelchair exercise capacity is related to high(er) life satisfaction in spinal cord injury patients.     

The Impact of Short Term Supervised and Home-Based Walking Programmes on Heart Rate Variability in Patients with Peripheral Arterial Disease

The aims of the study were to determine whether heart rate variability (HRV) measured at rest and during exercise could be altered by an exercise training programme designed to increase walking performance in patients with peripheral arterial disease. Forty-four volunteers were randomised into 12 weeks of either: supervised walking training twice weekly for 30 min at 75% VO_2peak (SU), home-based walking training sessions: twice weekly, 30 min per week (HB) or no exercise (CT). HRV measures were calculated from a 5-min resting ECG. Each patient then underwent maximal, graded exercise treadmill testing. All measures were repeated after 12 weeks. The SU group showed significantly (p < 0.001) increased maximal walking time (MWT) but no change in VO_2peak. There were no statistically significant changes in any of the measures of HRV in any group. Effect sizes for change in HRV measures were all very small and in some cases negative. Improved walking performance was not accompanied by central cardiorespiratory or neuroregulatory adaptations in the present study. The lack of any change in HRV was possibly due to either the low intensity or discontinuous nature of exercise undertaken.

Key points

• It is known that exercise can positively influence heart rate variability in some cardiac patients.
• It is known that exercise can increase walking performance in peripheral vascular disease patients.
• Exercise training improved walking performance in peripheral vascular disease patients but HRV was unaltered.
• This may be due to low overall physiological demands on the cardiovascular system or the intermittent nature of the exercise.

Key words: Exercise, ischemia, autonomic nervous system     

Oxygen Uptake Kinetics in Endurance Trained Youth and Adult Cyclists

Previous studies reported faster pulmonary oxygen uptake kinetics at the onset of exercise in untrained youth compared with adults. Whether or not these differences are identical for trained groups have not been examined. The purpose of this study was to compare ˙VO₂ kinetics of youth and adult cyclists at moderate and heavy-intensity exercise. Thirteen adult (age: 23.2 ± 4.8 years; ˙VO_2peak 68.4 ± 6.8 mL·min^-1.kg^-1) and thirteen youth cyclists (age: 14.3 ± 1.5 years; ˙VO_2peak 61.7 ± 4.3 mL·min^-1.kg^-1) completed a series of 6-min square wave exercises at moderate and heavy-intensity exercise at 90 rev·min^-1. A two-way repeated-measure ANOVA was conducted to identify differences between groups and intensities. The time constant, time delay and the mean response time were not significantly different between youth and adult cyclists (p > 0.05). We found significant differences between intensities, with a faster time constant during moderate than heavy-intensity exercise in youth (24.1 ± 7.0 s vs. 31.8 ± 5.6 s; p = 0.004) and adults (22.7 ± 5.6 s vs. 28.6 ± 5.7 s; p < 0.001). The present data suggest that the effect of training history in adult cyclists compensate for the superior primary response of the oxygen uptake kinetics typically seen in youth compared to adults. Furthermore, the ˙VO₂ response is dependent of work rate intensity in trained youth and adult cyclists.Key points

• No differences in the primary response between youth and adult cyclists at moderate and heavy-intensity exercise
• This suggests that adaptations to long-term training have a high potential as an influencing factor on the response of oxygen uptake kinetics
• Oxygen uptake kinetics are influenced by work rate in both youth and adult cyclists with a slower response at higher work rates.

Key words: Adolescents, endurance training, exercise physiology, physical performance, trained athletes     

Myoelectric Alterations after Voluntary Induced High - and Low - Frequency Fatigue

The aim of the study was to find whether voluntary induced high- and low-frequency peripheral fatigue exhibit specific alteration in surface EMG signal (SEMG) during evoked and maximum voluntary contractions. Ten male students of physical education performed 60 s long stretch-shortening cycle (SSC) exercise with maximal intensity and 30 s long concentric (CON) exercise with maximal intensity. To verify voluntary induced peripheral fatigue, knee torques during low- (T₂₀) and high-frequency electrical stimulation (T₁₀₀) of relaxed vastus lateralis muscle (VL) were obtained. Contractile properties of the VL were measured with passive twitch and maximal voluntary knee extension test (MVC). Changes in M-waves and SEMG during MVC test were used to evaluate the differences in myoelectrical signals. T₁₀₀/T₂₀ ratio decreased by 10.9 ± 8.4 % (p < 0.01) after the SSC exercise and increased by 35.9 ± 17.5 % (p < 0.001) after the CON exercise. Significant SEMG changes were observed only after the CON exercise where peak to peak time of the M-waves increased by 9.2 ± 13.3 % (p < 0.06), SEMG amplitude during MVC increased by 32.9 ± 21.6 % (p < 0.001) and SEMG power spectrum median frequency decreased by 11.0 ± 10.5 % (p < 0.05). It is concluded that high frequency fatigue wasn''t reflected in SEMG, however the SEMG changes after the CON seemed to reflect metabolic changes due to acidosis.

Key points

• The SSC exercise induced high-frequency fatigue which was not reflected in any SEMG change.
• The CON exercise induced dominantly low-frequency fatigue where only SEMG during MVC changed
• Muscle fibre membrane excitability was not changed due to low- and high-frequency fatigue but mainly reflected metabolic changes.
• Changes in muscle compound action potential did not follow those changes seen after electrically elicited HF and LF fatigue.

Key words: M-wave, stretch-shortening cycle, electrical stimulation, median frequency.     

Change in exercise capacity measured by Cardio-pulmonary Exercise Testing (CPET) in Danish people with cystic fibrosis after initiation of treatment with Lumacaftor/Ivacaftor and Tezacaftor/Ivacaftor

BackgroundSince 2015, when the first cystic fibrosis transmembrane conductance regulator (CFTR) modulators were approved for people with cystic fibrosis (CF) homozygous for F508del-CFTR, studies have shown improved lung function after initiation of the treatment and patients experience improved physical capacity. The aim of this study was to investigate change in exercise capacity after initiation of Lumacaftor/Ivacaftor and Tezacaftor/Ivacaftor treatment (LUM/IVA, TEZ/IVA).MethodsWe performed a single group prospective observational cohort study with follow-up at six and 12 months. The study examined change in exercise capacity in people with CF initiating treatment with LUM/IVA and TEZ/IVA, measured by cardio-pulmonary exercise testing (CPET). Inclusion criteria were people with CF homozygous for F508del-CFTR aged 12 years or older eligible for LUM/IVA and TEZ/IVA treatment from June 2017 until June 2019. Primary outcomes were change in VO_2peak and maximal workload. Secondary outcomes were change in muscle strength, muscle power and body composition in a subgroup of the study population.ResultsA total of 91 patients were included in the analysis. The mean change in VO_2peak and VO_2peak divided by body weight from baseline to 12-months follow-up was 145.7 (91.2;200.2) ml/min and 1.07 (95% CI 0.19;1.95) ml/min/kg, respectively. The mean change in maximal workload between baseline and 12 months was 14.2 Watt (95% CI 9.1;19.2). All improvements in exercise capacity were statistically significant.ConclusionsPatients in this study improved their exercise capacity by a statistically significant increase in VO_2peak and maximal workload 12 months after initiation of treatment with LUM/IVA and TEZ/IVA.