Physiological responses to "all-out" and even-paced cycling intervals

Background: Endurance cyclists typically devote ~20% of their training regimens to performing low-volume high-intensity interval training which is associated with large physiological and performance benefits. The relationship between intensity and duration is important during high-intensity interval training as both can profoundly influence metabolic energy expenditure, fatigue development and subsequent adaptations. Purpose: Within the literature, most interval training is delivered using either an "all-out" or even-paced approach; however, to the author’s knowledge no study has yet compared the metabolic stress, perceived exertion and fatigue resulting from such intervals. Therefore, this study compared the physiological and perceptual responses to matched mechanical work interval bouts using “all-out” and two different even-paced methodologies (i.e. computer- and athlete-controlled). Methods: In a randomised design, 15 male trained cyclists (age: 39 ± 8 years, body mass: 79.4 ± 8.2kg, VO2max: 59.8 ± 6.5 ml•kg-1•min-1, peak power: 436 ± 27 W) performed one incremental maximal exercise test, one familiarisation session and three experimental high-intensity interval sessions implementing one of three pacing strategies; (i) “all-out”, (ii) computer-controlled and (iii) athlete-controlled. All experimental sessions were work- matched and consisted of three 3-minute intervals with three minutes of recovery. A 4 km time trial was completed twenty minutes following each experimental interval session to assess measured levels of latent fatigue. Oxygen consumption, heart rate and perceived exertion, pain and effort were recorded throughout the high-intensity interval sessions with average power output and heart rate measured throughout the 4 km time trial. Results: Overall greater (p<0.001) oxygen consumption was observed in the “all-out” condition (54.1 ± 6.6 ml.kg-1.min-1) compared with the computer- (51.5 ± 5.7 ml.kg-1.min-1) and athlete-controlled conditions (53.0 ± 5.8 ml.kg-1.min-1). Furthermore, the time spent at 85% VO2max was greater (p<0.001) during the “all-out” trial when compared with computer- and athlete-controlled trials. Sessional perceived exertion was greater in the “all-out” trial when compared with the computer- (p<0.001) and athlete-controlled (p<0.05) conditions. Average power output measured during the 4 km time trial was lower (p<0.001) after the “all-out” session compared with both even-pacing strategies. Conclusion: Our findings indicate irrespective of work completed, greater physiological stress was observed within an “all-out” interval training approach when compared with both athlete- and computer- controlled conditions, resulting in greater latent fatigue as measured by 4 km time trial performance. The selections of pacing strategies are likely to play a key role in interval training and should be acknowledged throughout exercise prescription

Reactive and proactive aggression as meaningful distinctions at the variable and person level in primary school-aged children

Reactive and proactive aggression is a dichotomous classification of aggression in adults and children. This distinction has been supported by a number of variable-based and factor analytic studies. Due to high inter-correlations, however, the reactive-proactive aggression distinction may not be entirely useful for understanding how group or individual aggressive behavior varies in children and adolescents. Drawing on a sample of primary school-aged children (N = 242) aged 7-12 years, this study sought to determine whether reactive and proactive aggression could be distinguished at the variable-level and the person-level in children. Exploratory Factor Analysis of data from an aggression instrument measuring both functions and forms of aggression, found a two-factor construct of aggression constituted by a reactive and proactive aggression factor. A person-based analysis was then conducted after classifying children according to the presence of reactive and/or proactive aggression. Discriminant function analysis was used to discern whether classifications on the basis of aggression function produced meaningful distinctions in terms of antisocial traits and emotional valence and intensity measures. Two functions were identified which distinguished children with different combinations of reactive and proactive aggression. Reactive-only aggressive children were defined primarily by high levels of impulsivity, while proactive-only children were defined primarily by higher levels of antisocial traits. Children high in both types of aggression exhibited both the presence of antisocial traits and impulsivity. Contrary to recent findings, this suggests that differences in aggression functions remain meaningful at the person level in children. Implications for interventions are discussed

Treating children with early-onset conduct problems and callous–unemotional traits: an empirical evaluation of KooLKIDS

Children with early-onset conduct problems (EOCP) and callous–unemotional (CU) traits are highly resistant to treatment and cost society significantly more than their healthy counterparts. Employing a multiple baseline design, 13 males (9.0–10.2\ua0years of age) with a history of school suspensions were sequentially introduced to KooLKIDS, a school-based interactive multimedia intervention for young children with EOCP and CU. Teacher and child self-report data revealed significant reductions for the group in proactive and reactive aggression, and antisocial traits. Significant changes in the desired direction were also found on measures of emotion regulation. When the data were analyzed for each individual child, however, the magnitude of any effects for behaviour change varied greatly. KooLKIDS offers potential for treating children with EOCP and CU and hence preventing progression towards more serious antisocial behaviour

Validity of the Wahoo KICKR power trainer and reliability of a 4 km cycle time trial

Purpose: To assess the validity of power and the reliability of a 4 km cycle time trial (TT) using the Wahoo KICKR Power Trainer. Methods: The Wahoo KICKR power output was assessed using a dynamic calibration rig (DCR) over power outputs of 100-600 W at cadences of 80, 90 and 100 rpm. Twelve trained male cyclists (mean ± SD; age: 34.0 ± 6.5 years, height: 178.4 ± 6.2 cm, body mass: 76.8 ± 9.6 kg) completed three 4 km TTs on the Wahoo KICKR, each separated by a minimum of two and a maximum of three days. Mean power (W), cadence (rpm), speed (km.h-1), heart rate (bpm) and total time (s) were recorded for each TT while ratings of effort (0-10) and sessional ratings of perceived exertion (6-20) were collected immediately and 10 mins post each TT. Results: Bias for differences in power (%) recorded by the Wahoo KICKR to the DCR was 0.8% (95%LOA -4.0- 5.6%) (Figure 1). Average ICC between trials (2-1, 3-2, 3-1) for power was 0.95 (95%CI 0.89-0.98), cadence 0.80 (95 %CI 0.60- 0.92), speed 0.70 (95%CI 0.46- 0.88), heart rate 0.93 (95%CI 0.85- 0.98) and total time 0.75 (95%CI 0.53-0.90). Coefficient of variation was 2.9%, 4.5%, 3.7%, 1.5%, 3.6% for power, cadence, speed, heart rate and total time, respectively (Table 2). Results: sIgA concentrations (µg.ml¯ٰ) before and after the treadmill were [mean 595, s = 64.6 and mean 841, s = 76.3] and before and after the bike were [mean 593.9, s = 51.1 and 778.8 s = 99.3]. sIgA secretion rates (µg.min¯ٰ) before and after the treadmill were [mean 396.2, s = 73.7 and 223 s = 99.6] and before and after the bike were [mean 284.1, s = 74.3 and 216.6, s = 29.5]. Saliva flow rates (µl.min¯ٰ) before and after the treadmill were [mean 657.8, s = 92.2 and 289.3, s = 56.6] and before and after the bike were [mean 487.2, s = 123.3 and 319.5, s = 66.5]. The results indicated that sIgA secretion rate (P \u3c 0.028) and saliva flow rate (P \u3c 0.01) were significantly decreased following the 2 hour treadmill protocol but not the 2 hour bike protocol. sIgA concentration was also significantly elevated following the treadmill (P \u3c 0.01), with no significant increase following the bike protocol. Conclusion: These results suggest that when compared to a DCR, the Wahoo KICKR Power Trainer displays a small mean bias across all measures of power, with caution to be applied at the lower ranges of power output (\u3c200 W). When completed on the Wahoo KICKR Power Trainer, a 4 km TT in trained cyclists is highly reproducible

The influence of considering individual resistance training variables as a whole on muscle strength: A systematic review and meta-analysis protocol.

Examinations of the effect of resistance training (RT) on muscle strength have attempted to determine differences between prescriptions, mostly examining individual training variables. The broad interaction of variables does not appear to be completely considered, nor has a dose-response function been determined. This registered (doi.org/10.17605/OSF.IO/EH94V) systematic review with meta-analysis aims to determine if the interaction of individual training variables to derive RT dose, dosing, and dosage can influence muscle strength and determine if an optimal prescription range exists for developing muscle strength. To derive RT dose, the following calculation will be implemented: number of sets × number of repetitions × number of exercises × exercise intensity, while RT dosing factors in frequency and RT dosage considers program duration. A keyword search strategy utilising interchangeable terms for population (adult), intervention (resistance training), and outcomes (strength) will be conducted across three databases (CINAHL, MEDLINE, and SPORTDiscus). Novel to the field of exercise prescription, an analytical approach to determine the dose-response function for continuous outcomes will be used. The pooled standardised mean differences for muscle strength will be estimated using DerSimonian and Laird random effects method. Linear and non-linear dose-response relationships will be estimated by fitting fixed effects and random effects models using the one-stage approach to evaluate if there is a relationship between exercise dose, dosing and dosage and the effect on muscle strength. Maximised log-likelihood and the Akaike Information Criteria will be used to compare alternative best fitting models. Meta regressions will investigate between-study variances and a funnel plot and Egger's test will assess publication bias. The results from this study will identify if an optimal prescription range for dose, dosing and dosage exists to develop muscle strength

Reliability of power settings of the wahoo KICKR power trainer after 60 hours of use

Purpose: To assess the reliability of power-output measurements of a Wahoo KICKR Power Trainer (KICKR) on 2 separate occasions separated by 14 mo of regular use (?1 h/wk). Methods: Using the KICKR to set power outputs, powers of 100–600 W in increments of 50 W were assessed at cadences of 80, 90, and 100 rpm that were controlled and validated by a dynamic calibration rig. Results: A small ratio bias of 1.002 (95% limits of agreement [LoA] 0.992–1.011) was observed over 100–600 W at 80–100 rpm between trials 1 and 2. Similar ratio biases with acceptable limits of agreement were observed at 80 rpm (1.003 [95% LoA 0.987–1.018]), 90 rpm (1.000 [0.996–1.005]), and 100 rpm (1.002 [0.997–1.007]). The intraclass correlation coefficient with 95% confidence interval (CI) for mean power between trials was 1.00 (95% CI 1.00–1.00) with a typical error (TE) of 3.1 W and 1.6% observed between trials 1 and 2. Conclusion: When assessed at 2 separate time points 14 mo apart, the KICKR has acceptable reliability for combined power outputs of 100–600 W at 80–100 rpm, reporting overall small ratio biases with acceptable LoA and low TE. Coaches and sport scientists should feel confident in the power output measured by the KICKR over an extended period of time when performing laboratory training and performance assessments

Validity of power settings of the Wahoo KICKR Power Trainer

Purpose: To assess the validity of power output settings of the Wahoo KICKR Power Trainer (KICKR) using a dynamic calibration rig (CALRIG) over a range of power outputs and cadences. Methods: Using the KICKR to set power outputs, powers of 100–999 W were assessed at cadences (controlled by the CALRIG) of 80, 90, 100, 110, and 120 rpm. Results: The KICKR displayed accurate measurements of power of 250–700 W at cadences of 80–120 rpm with a bias of –1.1% (95% limits of agreement [LoA] –3.6% to 1.4%). A larger mean bias in power was observed across the full range of power tested, 100–999 W (4.2%, 95% LoA –20.1% to 28.6%), due to larger biases of 100–200 and 750–999 W (4.5%, 95% LoA –2.3% to 11.3%, and 13.0%, 95% LoA –24.4% to 50.3%), respectively. Conclusions: Compared with a CALRIG, the KICKR has acceptable accuracy reporting a small mean bias and narrow LoA in the measurement of power output of 250–700 W at cadences of 80–120 rpm. Caution should be applied by coaches and sports scientists when using the KICKR at power outputs of750 W due to the greater variability in recorded power

Intestinal damage following short-duration exercise at the same relative intensity is similar in temperate and hot environments

Increasing temperature and exercise disrupt tight junctions of the gastrointestinal tract although the contribution of environmental temperature to intestinal damage when exercising is unknown. This study investigated the effect of 2 different environmental temperatures on intestinal damage when exercising at the same relative intensity. Twelve men (mean ± SD; body mass, 81.98 ± 7.95 kg; height, 182.6 ± 7.4 cm) completed randomised cycling trials (45 min, 70% maximal oxygen uptake) in 30 °C/40% relative humidity (RH) and 20 °C/40%RH. A subset of participants (n = 5) also completed a seated passive trial (30 °C/40%RH). Rectal temperature and thermal sensation (TSS) were recorded during each trial and venous blood samples collected at pre-and post-trial for the analysis of intestinal fatty acid-binding protein (I-FABP) level as a marker of intestinal damage. Oxygen uptake was similar between 30 °C and 20 °C exercise trials, as intended (p = 0.94). I-FABP increased after exercise at 30 °C (pre-exercise: 585 ± 188 pg·mL −1 ; postexercise: 954 ± 411 pg·mL −1 ) and 20 °C (pre-exercise: 571 ± 175 pg·mL −1 ; postexercise: 852 ± 317 pg·mL −1 ) (p < 0.0001) but the magnitude of damage was similar between temperatures (p = 0.58). There was no significant increase in I-FABP concentration following passive heat exposure (p = 0.59). Rectal temperature increased during exercise trials (p < 0.001), but not the passive trial (p = 0.084). TSS increased more when exercising in 30 °C compared with 20 °C (p < 0.001). There was an increase in TSS during the passive heat trial (p = 0.03). Intestinal damage, as measured by I-FABP, following exercise in the heat was similar to when exercising in a cooler environment at the same relative intensity. Passive heat exposure did not increase I-FABP. It is suggested that when exercising in conditions of compensable heat stress, the increase in intestinal damage is predominantly attributable to the exercise component, rather than environmental conditions

Effects of time of day on pacing in a 4-km time trial in trained cyclists

Context: Time of day has been shown to impact athletic performance, with improved performance observed in the late afternoon–early evening. Diurnal variations in physiological factors may contribute to variations in pacing selection; however, research investigating time-of-day influence on pacing is limited. Purpose: To investigate the influence of time-of-day on pacing selection in a 4-km cycling time trial (TT). Methods: Nineteen trained male cyclists (mean [SD] age 39.0 [10.7] y, height 1.8 [0.1] m, body mass 78.0 [9.4] kg, VO2max 62.1 [8.7] mL·kg−1·min−1) completed a 4-km TT on 5 separate occasions at 08:30, 11:30, 14:30, 17:30, and 20:30. All TTs were completed in a randomized order, separated by a minimum of 2 d and maximum of 7 d. Results: No time-of-day effects were observed in pacing as demonstrated by similar power outputs over 0.5-km intervals (P = .78) or overall mean power output (333.0 [38.9], 339.8 [37.2], 335.5 [31.2], 336.7 [35.2], and 334.9 [35.7] W; P = .45) when TTs were performed at 08:30, 11:30, 14:30, 17:30, and 20:30. Preexercise tympanic temperature demonstrated a time-of-day effect (P < .001), with tympanic temperature higher at 14:30 and 17:30 than at 08:30 and 11:30. Conclusion: While a biological rhythm was present in tympanic temperature, pacing selection and performance when completing a 4-km cycling TT were not influenced by time of day. The findings suggest that well-trained cyclists can maintain a robust pacing strategy for a 4-km TT regardless of time of the day

Acquired and genetic thrombotic risk factors in the athlete

While athletes are often considered the epitome of health due to their physique and lowered potential for metabolic and cardiovascular diseases, they may also be at risk for the onset and development of venous thromboembolism (VTE). In an attempt to achieve and remain competitive, athletes are frequently exposed to numerous athlete-specific risk factors, which may predispose them to VTE through the disruption of factors associated with Virchow's triad (i.e., hypercoagulability, venous stasis, and vessel wall injury). Indeed, hypercoagulability within an athletic population has been well documented to occur due to a combination of multiple factors including exercise, dehydration, and polycythemia. Furthermore, venous stasis within an athletic population may occur as a direct result of prolonged periods of immobilization experienced when undertaking long-distance travels for training and competition, recovery from injury, and overdevelopment of musculature. While all components of Virchow's triad are disrupted, injury to the vessel wall has emerged as the most important factor contributing to thrombosis formation within an athletic population, due to its ability to influence multiple hemostatic mechanisms. Vessel wall injury within an athletic population is often related to repetitive microtrauma to the venous and arterial walls as a direct result of sport-dependent trauma, in addition to high metabolic rates and repetitive blood monitoring. Although disturbances to Virchow's triad may not be detrimental to most individuals, approximately 1 in 1,000 athletes will experience a potentially fatal post-exercise thrombotic incidence. When acquired factors are considered in conjunction with genetic predispositions to hypercoagulability present in some athletes, an overall increased risk for VTE is present