We assessed the accuracy and inter-sessional reliability of traditional (manual) compared to automatic (AutoHR) heart rate (HR) clamping methods during submaximal intensity continuous cycling. On separate occasions, thirteen males cycled at an HR corresponding to 80% of the ventilatory threshold for 18 min. Cycling power output was adjusted using either manual or AutoHR methods, encompassing three trials per method. For the manual method, cycling power output was adjusted every 30 s by 0, 5 or 10 W at the experimenter\'s discretion. Conversely, AutoHR automatically adjusted power output based on the difference between target and actual HR. Participants\' HR was measured at 1 Hz. Root-mean square error (RMSE) and intraclass correlation coefficients (ICC) were calculated from the difference between measured and target HR to represent accuracy and reliability of each method. The RMSE for the manual method (3.2 ± 2.6 bpm) was significantly higher compared to AutoHR (2.8 ± 2.3 bpm) (p < 0.01, r = 0.13); inter-day ICC were 0.92 and 0.89 for manual adjustment and AutoHR, respectively. Automatic methods to clamp HR are more accurate than manual approaches during submaximal intensity continuous cycling and can be easily implemented for uniform HR control in individual and group training sessions at minimal cost.

This study aimed to investigate the effect of maturity status on force-velocity relationships in a ballistic lower limb (BLL) test in high-level soccer adolescents and young adults. The population was 61 adolescents (13.0-17.9 years) and 23 young adults (18.0-26.2 years). Subjects completed the BLL test on a ballistic ergometer equipped with two force plates and a linear encoder. Following Samozino\'s method, maximal power output (Pmax), force (F0) and velocity (v0) were determined. An allometric model was applied to Pmax and F0 with body mass (BM) and fat-free mass (FFM). Significant effects of maturity status were found for absolute Pmax, F0, relative Pmax to BM and FFM, relative F0 to FFM and F0 allometrically scaled to BM and FFM (p = 0.02 to p < 0.001; η = 0.10 to η = 0.49). There was no significant effect for Pmax allometrically scaled to BM and FFM, F0 relative to BM and v0. Body dimensions explain group differences in Pmax whereas for F0, qualitative factors explain the differences between the groups. As maturity status and body dimensions influence Pmax, these factors should be considered when assessing explosive short efforts. This could help to better identify potential athletic talent and adapt training content.

BACKGROUND: Critical illness requiring invasive mechanical ventilation can precipitate important functional disability, contributing to multidimensional morbidity following admission to an intensive care unit (ICU). Early in-bed cycle ergometry added to usual physiotherapy may mitigate ICU-acquired physical function impairment.
METHODS: We randomly assigned 360 adult ICU patients undergoing invasive mechanical ventilation to receive 30 minutes of early in-bed Cycling + Usual physiotherapy (n=178) or Usual physiotherapy alone (n=182). The primary outcome was the Physical Function ICU Test-scored (PFIT-s) at 3 days after discharge from the ICU (the score ranges from 0 to 10, with higher scores indicating better function).
RESULTS: Cycling began within a median (interquartile range) of 2 (1 to 3) days of starting mechanical ventilation; patients received 3 (2 to 5) cycling sessions for a mean (±standard deviation) of 27.2 ± 6.6 minutes. In both groups, patients started Usual physiotherapy within 2 (2 to 4) days of mechanical ventilation and received 4 (2 to 7) Usual physiotherapy sessions. The duration of Usual physiotherapy was 23.7 ± 15.1 minutes in the Cycling + Usual physiotherapy group and 29.1 ± 13.2 minutes in the Usual physiotherapy group. No serious adverse events occurred in either group. Among survivors, the PFIT-s at 3 days after discharge from the ICU was 7.7 ± 1.7 in the Cycling + Usual physiotherapy group and 7.5 ± 1.7 in the Usual physiotherapy group (absolute difference, 0.23 points; 95% confidence interval, -0.19 to 0.65; P=0.29).
CONCLUSIONS: Among adults receiving mechanical ventilation in the ICU, adding early in-bed Cycling to usual physiotherapy did not improve physical function at 3 days after discharge from the ICU compared with Usual physiotherapy alone. Cycling did not cause any serious adverse events. (Funded by the Canadian Institutes of Health Research and others; ClinicalTrials.gov numbers, NCT03471247 [full randomized clinical trial] and NCT02377830 [CYCLE Vanguard 46-patient internal pilot].).

In cholinergic urticaria (CholU), small, itchy wheals are induced by exercise or passive warming and reduced sweating has been reported. Despite the described reduced muscarinic receptor expression, sweat duct obstruction, or sweat allergy, the underlying pathomechanisms are not well understood. To gain further insights, we collected skin biopsies before and after pulse-controlled ergometry and sweat after sauna provocation from CholU patients as well as healthy controls. CholU patients displayed partially severely reduced local sweating, yet total sweat volume was unaltered. However, sweat electrolyte composition was altered, with increased K+ concentration in CholU patients. Formalin-fixed, paraffin-embedded biopsies were stained to explore sweat leakage and tight junction protein expression. Dermcidin staining was not found outside the sweat glands. In the secretory coils of sweat glands, the distribution of claudin-3 and -10b as well as occludin was altered, but the zonula occludens-1 location was unchanged. In all, dermcidin and tight junction protein staining suggests an intact barrier with reduced sweat production capability in CholU patients. For future studies, an ex vivo skin model for quantification of sweat secretion was established, in which sweat secretion could be pharmacologically stimulated or blocked. This ex vivo model will be used to further investigate sweat gland function in CholU patients and decipher the underlying pathomechanism(s).

Magnetic resonance (MR) imaging (MRI) is routinely used to evaluate organ morphology and pathology in the human body at rest or in combination with pharmacological stress as an exercise surrogate. With MR during actual physical exercise, we can assess functional characteristics of tissues and organs under real-life stress conditions. This is particularly relevant in patients with limited exercise capacity or exercise intolerance, and where complaints typically present only during physical activity, such as in neuromuscular disorders, inherited metabolic diseases, and heart failure. This review describes practical and physiological aspects of exercise MR of skeletal muscles, the heart, and the brain. The acute effects of physical exercise on these organs are addressed in the light of various dynamic quantitative MR readouts, including phosphorus-31 MR spectroscopy (31P-MRS) of tissue energy metabolism, phase-contrast MRI of blood flow and muscle contraction, real-time cine MRI of cardiac performance, and arterial spin labeling MRI of muscle and brain perfusion. Exercise MR will help advancing our understanding of underlying mechanisms that contribute to exercise intolerance, which often proceed structural and anatomical changes in disease. Its potential to detect disease-driven alterations in organ function, perfusion, and metabolism under physiological stress renders exercise MR stress testing a powerful noninvasive imaging modality to aid in disease diagnosis and risk stratification. Although not yet integrated in most clinical workflows, and while some applications still require thorough validation, exercise MR has established itself as a comprehensive and versatile modality for characterizing physiology in health and disease in a noninvasive and quantitative way. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 1.

OBJECTIVE: This study aims to identify the optimal method for determining V̇O2max in competitive swimmers in terms of validity and test-retest reliability.
METHODS: Controlled experiment.
METHODS: Twenty competitive swimmers performed four maximal incremental exercise tests: cycling, arm cranking, ergometer swimming, and tethered swimming. Gas analysis was conducted to estimate V̇O2max. Validity was assessed in terms of the amount of variance of the performance on a 1500-m time trial explained by the estimated V̇O2max . Test-retest reliability was evaluated using the intraclass correlation coefficient (ICC).
RESULTS: V̇O2max obtained from tethered swimming, ergometer swimming, and cycling explained a similar amount of variance of the 1500-m performance (R2 = 0.64, 0.64 and 0.65, respectively). However, ergometer swimming yielded significantly lower V̇O2max estimates (40.54 ± 6.55 ml/kg/min) than tethered swimming (54.40 ± 6.21 ml/kg/min) and cycling (54.39 ± 5.63 ml/kg/min). Arm cranking resulted in both a lower explained variance (R2 = 0.41) and a significantly lower V̇O2max (43.14 ± 7.81 ml/kg/min). Tethered swimming showed good reliability (ICC = 0.81).
CONCLUSIONS: Bicycle and tethered swimming tests demonstrated high validity with comparable V̇O2max estimates, explaining a large proportion of differences in endurance performance. Choosing between these two methods involves a trade-off between a higher practical applicability and reliability of the bicycle test and the more sport-specific nature of the tethered swimming test.

Heightened sensation of leg effort contributes importantly to poor exercise tolerance in patient populations. We aim to provide a sex- and age-adjusted frame of reference to judge symptom\'s normalcy across progressively higher exercise intensities during incremental exercise. Two-hundred and seventy-five non-trained subjects (130 men) aged 19-85 prospectively underwent incremental cycle ergometry. After establishing centiles-based norms for Borg leg effort scores (0-10 category-ratio scale) versus work rate, exponential loss function identified the centile that best quantified the symptom\'s severity individually. Peak O2 uptake and work rate (% predicted) were used to threshold gradually higher symptom intensity categories. Leg effort-work rate increased as a function of age; women typically reported higher scores at a given age, particularly in the younger groups (p < 0.05). For instance, \"heavy\" (5) scores at the 95th centile were reported at ~200 W (<40 years) and ~90 W (≥70 years) in men versus ~130 W and ~70 W in women, respectively. The following categories of leg effort severity were associated with progressively lower exercise capacity: ≤50th (\"mild\"), >50th to <75th (\"moderate\"), ≥75th to <95th (\"severe\"), and ≥ 95th (\"very severe\") (p < 0.05). Although most subjects reporting peak scores <5 were in \"mild\" range, higher scores were not predictive of the other categories (p > 0.05). This novel frame of reference for 0-10 Borg leg effort, which considers its cumulative burden across increasingly higher exercise intensities, might prove valuable to judging symptom\'s normalcy, quantifying its severity, and assessing the effects of interventions in clinical populations.

BACKGROUND: Cardiorespiratory fitness (CRF) is an important indicator of health in childhood and adolescence but longitudinal studies on the development and tracking of CRF from childhood to adolescence are scarce.
OBJECTIVE: The objectives of this study were (1) to assess longitudinal development and track CRF over 10 years from childhood to adolescence, and (2) to examine potential sex differences in the development and tracking of CRF during this period.
METHODS: Participants were Icelandic children born in 1999, measured at the age of 7 (n = 190, 106 girls), 9 (n = 163, 95 girls), 15 (n = 239, 134 girls), and 17 (n = 202, 119 girls). CRF was assessed with a maximal cycle ergometer test and expressed as maximal power output (Max W) and maximal power output relative to lean mass (W/kgLM). Multilevel regression models were used to study the longitudinal development of CRF, and tracking was assessed with Spearman\'s rank correlation, logistic regression, and the percentage of participants remaining in low, moderate, or high CRF categories between measurements.
RESULTS: Max W and W/kgLM increased for both boys and girls up to age 15. Max W plateaued for both boys and girls while W/kgLM plateaued for girls but declined for boys from age 15 to 17. Boys had higher Max W than girls from age 15 and higher W/kgLM from age 9. CRF tracked at low to moderate levels from childhood to adolescence and at high levels in adolescence, with higher values observed for boys than girls.
CONCLUSIONS: Age 15 was a critical time point in the development of CRF, with values starting to plateau for girls and decline for boys. The results support early intervention for improved CRF in later years, with interventions targeting all children, regardless of their CRF level.

We aimed to determine the feasibility, test-retest reliability and long-term stability of a novel method for assessing the force (torque)-velocity (cadence) profile and maximal dynamic force (MDF) during leg-pedaling using a friction-loaded isoinertial cycle ergometer and a high-precision power-meter device. Fifty-two trained male cyclists completed a progressive loading test up to the one-repetition maximum (1RM) on a cycle ergometer. The MDF was defined as the force attained at the cycle performed with the 1RM-load. To examine the test-retest reliability and long-term stability of torque-cadence values, the progressive test was repeated after 72 h and also after 10 weeks of aerobic and strength training. The participants\' MDF averaged 13.4 ± 1.3 N·kg-1, which was attained with an average pedal cadence of 21 ± 3 rpm. Participants\' highest power output value was attained with a cadence of 110 ± 16 rpm (52 ± 5% MDF). The relationship between the MDF and cadence proved to be very strong (R2 = 0.978) and independent of the cyclists\' MDF (p = 0.66). Cadence values derived from this relationship revealed a very high test-retest repeatability (mean SEM = 4 rpm, 3.3%) and long-term stability (SEM = 3 rpm, 2.3%); despite increases in the MDF following the 10-week period. Our findings support the validity, reliability and long-term stability of this method for the assessment of the torque-cadence profile and MDF in cyclists.

OBJECTIVE: Childhood obesity is a major health concern and physical activity is commonly proposed as an intervention strategy to combat the increasing prevalence of overweight and obesity in young people. The aim of this study was to examine the effect of high-intensity, supervised, rowing ergometer training on maximal and submaximal rowing performance in healthy weight and centrally obese adolescents (12-13 yr).
METHODS: Participants were randomized to either 6 wk of supervised rowing ergometry, comprising of 2 sessions per week with each session comprising of 2 × 3-min bouts of high-intensity rowing ergometry ( n = 57), or a control group who continued with their habitual activities ( n = 45). At baseline and follow-up, rowing performance was assessed via a submaximal test and a 3-min maximal test.
RESULTS: Six weeks of rowing ergometer training significantly improved maximal exercise performance; total distance rowed in a 3-min maximal effort improved by 19.7 m (2.7%) (time × group, P = 0.018) and produced a significant reduction in perceived effort in response to a set submaximal load (60 W) (time × group, P = 0.040). At baseline total distance rowed during the 3-min maximal test was significantly affected by body mass (main effect of body mass, P = 0.002), whereby a higher body mass was associated with enhanced rowing performance. However, the pattern of change over time was not different between healthy weight and centrally obese adolescents (time × group × waist centile, P = 0.577).
CONCLUSIONS: A 6-wk high-intensity rowing ergometry training intervention improved maximal rowing performance. This improvement was similar in healthy weight versus overweight and obese adolescents; yet overall overweight and obese adolescents had superior rowing performance compared to their healthy weight counterparts, suggesting that rowing may be an attractive exercise modality for interventions in overweight and obese young people.