Purpose: Heart rate variability (HRV) has gained acceptance as a key marker of cardiovascular health. We compared HRV responses after continuous moderate-intensity exercise (CMIE) and high-intensity interval exercise (HIIE) matched for intensity and duration in individuals with midspectrum chronic kidney disease (CKD). Methods: Twenty men and women (age 62.0 ± 10 yrs.) diagnosed with CKD stages G3a and G3b participated in a 2 (condition) x 4 (time point) repeated cross-over measures design study. HRV time-domain indices were based on the standard deviation of all NN intervals (SDNN) and the square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD) and frequency domain. High-frequency (HF), low-frequency (LF), total power (TP) were examined. CMIE consisted of treadmill walking for 30 minutes at a 2% incline and speed corresponding to 60%-65% of reserve volume of oxygen (VO2R). HIIE included five intervals of 3 minutes at 90% of VO2R and 2 minutes at 20% VO2R intervals. Conditions were designed to be of the same average intensity (60% to 65% of VO2R) and caloric expenditure (~144 kcal). Results: Immediately following exercise SDNN, RMSSD, HF, LF, and TP were significantly lower compared to before exercise (p <.05). HRV responses were not different between conditions and conditions X time (p >.05). Conclusions: Thirty minutes of either CMIE or HIIE decreased HRV indices, pointing to an autonomic imbalance favoring vagal mediation. HRV's responses regarding HIIE were no different from CMIE, therefore, from an autonomic function point of view this similarity may be useful for CKD exercise prescription and programming.
Purpose: Morning priming exercise and caffeine intake have been previously suggested as an effective strategy to increase within-day performance and readiness. However, the concurrent effect of both strategies is unknown. The present research aimed to map the within-day time course of recovery and performance of countermovement jump (CMJ) outcomes, kinetics, and strategy and readiness after priming alone and in combination with caffeine. Methods: Eleven participants performed a control, a priming exercise (Priming) and a priming with concurrent caffeine intake (PrimingCaf) in a double-blind randomized, crossover design. CMJ metrics were assessed before, post, and 2 h, 4 h, and 6 h after each condition while readiness was assessed at 6 h. Results: Perceived physical, mental performance capability and activation balance were higher at 6 h after Priming and PrimingCaf conditions. Immediate reductions in jump height (5.45 to 6.25%; p < .046), concentric peak velocity (2.40 to 2.59%; p < .041) and reactive strength index-modified (RSImod) (9.06 to 9.23% p < .051) after Priming and PrimingCaf were observed, being recovered at 2 h (p > .99). Concentric impulse was restored in PrimingCaf (p > .754; d = -0.03 to-0.08) despite lower concentric mean force/BM (p < .662; d = -0.18 to -0.26) as concentric duration was increased (p > .513; d = 0.15 to 0.21). Individual analysis revealed that some participants benefit from both strategies as they showed increases in jump height over the smallest worthwhile change while others did not. Conclusions: Psychological readiness was increased after both priming conditions at 6 h; however, it seems necessary to consider individual changes to achieve the positive effects of the priming or the priming in combination with caffeine on jumping outcomes.
Introduction: The aim of this study was to examine differences between a control warm-up and an Electric Muscle Stimulation (EMS)-induced warm-up in off-road cyclists when examining anaerobic performance measures from a repeated Wingate test (WAnT). Methods: Twelve trained off-road cyclists completed a randomized crossover study (age: 31 ± 10 years, height: 176.79 ± 6.09 cm, body mass: 74.57 ± 4.77 kg). Participants completed two randomized, separate testing sessions involving a control warm-up and an EMS warm-up before undergoing the repeated WAnT, which was used to collect anaerobic performance and physiolo- gical measures during both sessions. High-frequency EMS was applied to the knee extensor muscles for 4 min after a standardized warm-up during the EMS session. Results: Analysis revealed that there were no significant differences between mean power output, peak power output, and percentage decrement between the two sessions. The EMS session resulted in significantly lower average HR values and significantly lower differences in pre-to-post-test blood lactate values when compared to the control session. Discussion: According to the results of this study, an acute application of EMS is not a useful tool for off-road cyclists to improve power output or maintain anaerobic capacity. Hence, its use before competition is questionable.
Purpose: Metabolic equivalents for youth (METy) are derived using the estimated basal metabolic rate (BMR). However, is unknown whether this METy can be different when measured resting energy expenditure (REE) is used. The purposes of this article are to: (a) To determine whether there is equivalence between METy values calculated using measured REE (METy-mea) and METy using predicted BMR (METy-est). (b) To determine whether METy values of different activities are dependent on age, sex, and body composition. Methods: A cross-sectional study with a sample of 122 Mexican children (5-11 years old) was conducted. With indirect calorimetry, energy expenditure was measured at rest and during 16 sedentary- to vigorous-intensity physical activities. METy were obtained in two forms: METy-mea and METy-est. Equivalence testing was used to compare METy-mea and METy-est. To examine the individual-level agreement, Bland-Altman plots were graphed, and intra-class correlation coefficients (ICC) were calculated. Linear regression models were estimated having METy as the outcome. Results: For 15 activities, there was equivalence between METy-mea and METy-est (t > 2.05, p < 0.050). However, at the individual-level, for 7 activities the agreement between METy-eREE and METy-mREE was inadequate (ICC<0.75). In the Bland-Altman plots was evident that in 8 activities METy-est was biased compared to METy-mea, METy-est had more correlations with body mass index and body fat. Conclusions: In conclusion, at group-level, for most activities METy-mea and METy-est were equivalent. However, at the individual level, METy-est of many activities is not a valid estimate of METy-mea. METy-est of many physical activities were dependent on adiposity, which could be an artifact introduced when BMR is predicted.
Background: Thigh muscle strength capacities are major modifiable risk factors for knee and thigh muscle injuries. Therefore, their valid assessment is essential. Most isokinetic knee tests are conducted in a seated position and rely on dynamometer-based data. However, their accuracy is doubtful because axis alignment is erroneous. Purpose: This study investigated if hip angle (flexed vs. extended) and assessment method (dynamometer-based vs. camera-based) affect isokinetic outcome parameters. Methods: Sixteen healthy male participants (27 years, 184 cm, 80 kg) performed discrete isokinetic tests of the knee flexors and extensors (60°/s) while their kinematics were captured (100 fps). Results: Both assessment methods revealed very strong linear relationships (94% ≤ R2 ≤ 98%) although peak moments (d ≤ 0.87), contractional work (d ≤ 1.26), and functional knee flexor:extensor ratios (d ≤ 0.81) significantly differed. Seated knee flexor tests demonstrated the largest knee trajectory center's misalignment (x = 4.0 cm, z = -2.5 cm; 1.37 ≤ d ≤ 4.74). Conclusion: Hip-angle induced kinematic changes did not affect the relation between the lever arms, thus causing highly proportional deviations of kinetic parameters. The assessment method altered the magnitude, but not the message of isokinetic knee tests, which should be preferentially performed with extended hip joint to improve axis alignment. Knowledge of these kinetic and kinematic interactions assists practitioners and scientists with isokinetic tests and/or rehabilitation training to ensure reasonable interpretations of gathered isokinetic outcomes.
Purpose: The purpose of this study was to explore how parent involvement influenced the effectiveness of a movement intervention targeting gross motor skills and physical activity behavior in preschool-aged boys and girls. Methods: Parents received training at monthly school-based sessions and online to implement the movement intervention once per month at school and once per week at home across 6 months (N = 104; Mage = 48.30 months, SD = 6.90). Children completed the Test of Gross Motor Development-3 at baseline and wore physical activity trackers 24/7 for six weeks during the intervention. COVID-19 disrupted the intervention and prevented immediate post testing. Children (N = 60; Mage = 60.86 months, SD = 6.57) who returned to the center one year later completed gross motor skill retention testing. Results: For each additional school-based session attended by the parents (up to six), children's locomotor and manipulative skills were 1.87 and 1.95 points higher, respectively, at the start of the following academic year. For physical activity, each session increase in attendance at the school-based component of the intervention resulted in an additional 1455 steps in average weekly step count. Conclusion: Increased parent engagement demonstrated greater change in gross motor skills and larger acute physical activity responses. Understanding barriers that impact the level of parental intervention engagement (i.e., dose) also provides insight into why some children learn and others do not within a parent-led intervention. Although the implementation and results of this study were impacted by COVID, these data can help researchers optimize future intervention strategies.
Purpose: The purpose of this study was to investigate the effects of Bio-Electro-Magnetic-Energy-Regulation (BEMER) on recovery and performance parameters in anaerobic exercise compared to active and passive recovery. Method: Fifteen recreationally active participants completed four sessions separated by 2-5 days between each session. The first visit involved one Wingate Anaerobic Test (WAnT; 30-s cycling sprint on a Monark ergometer) to familiarize participants with testing procedures. The three subsequent sessions involved four repeated WAnTs. Each sprint was followed by 4 min of either passive recovery (laying supine), active recovery (pedaling at 50 rpm at 20% of sprint workload), or BEMER recovery (laying supine on the BEMER body pad at intensity level "5-Plus."). The same recovery method was used within each testing session, and recovery method order was randomized across participants. Results: There was no difference in peak power, average power, fatigue index, or average work performed between recovery conditions. Active recovery resulted in a statistically significant decrease in ratings of pain intensity (M = -0.767, SD = 0.928) and pain unpleasantness (M = -0.608, SD = 0.915), from the first minute to the fourth minute of recovery, compared to both BEMER (Intensity: M = 0.675, SD = 0.745, Unpleasantness: M = 1.125, SD = 0.862) and passive (Intensity: M = 0.542, SD = 0.774, Unpleasantness: M = 1.018, SD = 0.872) recoveries, where pain ratings increased. Conclusions: Although no recovery method resulted in increased performance, active recovery led to a more comfortable exercise experience while still allowing comparable exercise performance.
Purpose: It has been hypothesized that sports injury risk is explained by muscle metabolism. The objective was to evaluate the muscle oxygen saturation slopes (ΔSmO2 slopes) and muscle oxygenation asymmetry (MO2Asy) at rest and to study their associations with injuries during the pre-season. Methods: A total of 16 male and 10 female footballers participated in this study. Injuries were diagnosed and classified by level of severity during the pre-season. The workload was also evaluated using the rate of perceived exertion × training time, from which the accumulated loads. The SmO2 was measured at rest in the gastrocnemius muscle using the arterial occlusion method in the dominant and non-dominant legs. The repeated measures ANOVA, relative risk, and binary logistic regression were applied to assess the probability of injury with SmO2 and workload. Results: Higher MO2Asy and ΔSmO2 Slope 2 were found among footballer who suffered high-severity injuries and those who presented no injuries. In addition, an MO2Asy greater than 15% and an increase in accumulated load were variables that explained a greater probability of injury. Conclusion: This study presents the new concept of muscle oxygenation asymmetry in sports science and its possible application in injury prevention through the measurement of SmO2 at rest.
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