Exploring the role of sex in the association of late chronotype on cardiorespiratory fitness.

Circadian rhythms differ between young adult males and females. For example, males tend to be later chronotypes, preferring later timing of sleep and activity, than females. Likewise, there are sex differences in body composition and cardiorespiratory fitness. Few studies have investigated the association between circadian rhythms, cardiorespiratory fitness, and body composition. We sought to determine whether chronotype and circadian phase were associated with cardiorespiratory fitness, body composition, and anthropometric measures in sedentary males and females. Fifty-nine adults participated in the study. Circadian phase and chronotype were measured using dim light melatonin onset (DLMO) and the Morningness-Eveningness Questionnaire (MEQ) score. We used peak oxygen uptake (VO2peak ) results from a maximal graded exercise test to assess cardiorespiratory fitness. Body composition, BMI, and circumferences were collected as markers of adiposity. We observed a sex difference in the association between DLMO and VO2peak . For males, a later DLMO was associated with a lower VO2peak . VO2peak did not vary based on DLMO in females. Later circadian phase was also associated with increased body fat percentage, fat mass index, and abdominal circumference in males, but not females. Collectively, these results suggest that males who are later chronotypes may be at risk of obesity and low cardiorespiratory fitness.

Heart rate recovery as an assessment of cardiorespiratory fitness in young adults.

Background: Cardiorespiratory fitness, typically measured as peak oxygen uptake (VO2peak) during maximal graded exercise testing (GXTmax), is a predictor of morbidity, mortality, and cardiovascular disease. However, measuring VO2peak is costly and inconvenient and thus not widely used in clinical settings. Alternatively, postexercise heart rate recovery (HRRec), which is an index of vagal reactivation, is a valuable assessment of VO2peak in older adults and athletes. However, the validity of HRRec as a clinical indicator of cardiorespiratory fitness in young, sedentary adults, who are a rapidly growing population at risk for developing obesity and cardiovascular disease, has not been fully elucidated. Methods: We investigated the association between cardiorespiratory fitness, measured by VO2peak (mL·kg-1·min-1), and HRRec measures after a GXTmax in 61 young (25.2 ± 6.1 years), sedentary adults (40 females) using 3 methods. We examined the relationship between VO2peak and absolute (b·min-1) and relative (%) HRRec measures at 1, 2, and 3 min post GXTmax, as well as a measure of the slow component HRRec (HRRec 1 min minus HRR 2 min), using Pearson's correlation analysis. Results: VO2peak (36.5 ± 7.9 mL·kg-1·min-1) was not significantly correlated with absolute HRRec at 1 min (r = 0.18), 2 min (r = 0.04) or 3 min (r = 0.01). We also found no significant correlations between VO2peak and relative HRRec at 1 min (r = 0.09), 2 min (r = -0.06) or 3 min (r = -0.10). Lastly, we found no correlation between the measure of the slow component HRRec and VO2peak (r = -0.14). Conclusions: Our results indicate that HRRec measures are not a valid indicator of cardiorespiratory fitness in young, sedentary adults.

Circadian rhythm phase shifts caused by timed exercise vary with chronotype.

BACKGROUNDThe circadian system entrains behavioral and physiological rhythms to environmental cycles, and modern lifestyles disrupt this entrainment. We investigated a timed exercise intervention to phase shift the internal circadian rhythm.METHODSIn 52 young, sedentary adults, dim light melatonin onset (DLMO) was measured before and after 5 days of morning (10 hours after DLMO; n = 26) or evening (20 hours after DLMO; n = 26) exercise. Phase shifts were calculated as the difference in DLMO before and after exercise.RESULTSMorning exercise induced phase advance shifts (0.62 ± 0.18 hours) that were significantly greater than phase shifts from evening exercise (-0.02 ± 0.18 hours; P = 0.01). Chronotype also influenced the effect of timed exercise. For later chronotypes, both morning and evening exercise induced phase advances (0.54 ± 0.29 hours and 0.46 ±0.25 hours, respectively). In contrast, earlier chronotypes had phase advances from morning exercise (0.49 ± 0.25 hours) but had phase delays from evening exercise (-0.41 ± 0.29 hours).CONCLUSIONLate chronotypes - those who experience the most severe circadian misalignment - may benefit from phase advances induced by exercise in the morning or evening, but evening exercise may exacerbate circadian misalignment in early chronotypes. Thus, personalized exercise timing prescription, based on chronotype, could alleviate circadian misalignment in young adults.TRIAL REGISTRATIONTrial registration can be found at www.clinicaltrials.gov (NCT04097886).FUNDINGFunding was supplied by NIH grants UL1TR001998 and TL1TR001997, the Barnstable Brown Diabetes and Obesity Center, the Pediatric Exercise Physiology Laboratory Endowment, the Arvle and Ellen Turner Thacker Research Fund, and the University of Kentucky.

Elastic Resistance Effectiveness on Increasing Strength of Shoulders and Hips.

Picha, KJ, Almaddah, MR, Barker, J, Ciochetty, T, Black, WS, and Uhl, TL. Elastic resistance effectiveness on increasing strength of shoulders and hips. J Strength Cond Res 33(4): 931-943, 2019-Elastic resistance is a common training method used to gain strength. Currently, progression with elastic resistance is based on the perceived exertion of the exercise or completion of targeted repetitions; exact resistance is typically unknown. The objective of this study was to determine whether knowledge of load during elastic resistance exercise will increase strength gains during exercises. Participants were randomized into 2 strength training groups, elastic resistance only and elastic resistance using a load cell (LC) that displays force during exercise. The LC group used a Smart Handle (Patterson Medical Supply, Chicago, IL, USA) to complete all exercises. Each participant completed the same exercises 3 times weekly for 8 weeks. The LC group was provided with a set load for exercises, whereas the elastic resistance only group was not. The participant's strength was tested at baseline and program completion, measuring isometric strength for shoulder abduction (SAb), shoulder external rotation (SER), hip abduction (HAb), and hip extension (HEx). Independent t-tests were used to compare the normalized torques between groups. No significant differences were found between groups. Shoulder strength gains did not differ between groups (SAb p > 0.05; SER p > 0.05). Hip strength gains did not differ between groups (HAb p > 0.05; HEx p > 0.05). Both groups increased strength because of individual supervision, constantly evaluating degree of difficulty associated with exercise and providing feedback while using elastic resistance. Using an LC is as effective as supervised training and could provide value in a clinical setting when patients are working unsupervised.

Recovery Responses to Maximal Exercise in Healthy-Weight Children and Children With Obesity.

PURPOSE: The purpose of this study was to examine differences in heart rate recovery (HRRec) and oxygen consumption recovery (VO2 recovery) between young healthy-weight children and children with obesity following a maximal volitional graded exercise test (GXTmax). METHOD: Twenty healthy-weight children and 13 children with obesity completed body composition testing and performed a GXTmax. Immediately after the GXTmax, HRRec and VO2 recovery were measured each minute for 5 consecutive minutes. RESULTS: There were no statistically significant group differences in HRRec for the 5 min following maximal exercise, Wilks's Lambda = .885, F(4, 28) = 0.911, p = .471, between the healthy-weight children and children with obesity despite statistically significant differences in body fat percentage (BF%; healthy-weight children, 18.5 ± 6.1%; children with obesity, 41.1 ± 6.9%, p < .001) and aerobic capacity relative to body mass (VO2 peak; healthy-weight children, 46.8 ± 8.2 mL/kg/min; children with obesity, 31.9 ± 4.7 mL/kg/min, p < .001). There were statistically significant differences in VO2 recovery for the 5 min following exercise, Wilks's Lambda = .676, F(4, 26) = 3.117, p = .032. There were no statistically significant correlations between HRRec and body mass index (BMI), BF%, VO2peak, or physical activity. CONCLUSIONS: In a healthy pediatric population, obesity alone does not seem to significantly impact HRRec, and because HRRec was not related to obesity status, BMI, or BF%, it should not be used as the sole indicator of aerobic capacity or health status in children. Using more than one recovery variable (i.e., HRRec and VO2 recovery) may provide greater insight into cardiorespiratory fitness in this population.

Physical activity, and not fat mass is a primary predictor of circadian parameters in young men.

Circadian rhythms are ≈24 h oscillations in physiology and behavior, and disruptions have been shown to have negative effects on health. Wrist skin temperature has been used by several groups as a valid method of assessing circadian rhythms in humans. We tested the hypothesis that circadian temperature amplitude (TempAmp) and stability (TempStab) would significantly differ among groups of healthy young men of varying adiposities, and that we could identify physiological and behavioral measures that were significantly associated with these temperature parameters. Wrist skin temperatures taken at 10 min intervals for 7 consecutive days were determined in 18 optimal (OGroup), 20 fair (FGroup) and 21 poor (PGroup) %Fat grouped young men and subsequently analyzed using available validated software. Body composition, cardiorespiratory fitness, actigraphy, daily nutritional and sleep data, and fasting lipid, insulin and glucose concentration measures were also determined. Significant changes in TempAmp and TempStab parameters in subjects with a single metabolic syndrome (MetS) risk factor compared to those with no MetS factors was observed. In addition, stepwise multivariate regression analyses showed that 50% of the variance in TempAmp was explained by actigraphy (mean steps taken per day; MSTPD), cardiorespiratory fitness, and late night eating per week (#LNE); and 57% in TempStab by MSTPD, time spent in moderate-to-vigorous activity per day, fat mass, and #LNE. Overwhelmingly, physical activity was the most important measure associated with the differences in circadian rhythm parameters. Further research is warranted to determine the effects of increasing the amount and timing of physical activity on the status of the circadian system in a variety of populations.

Effects of Lumbosacral Manipulation on Isokinetic Strength of the Knee Extensors and Flexors in Healthy Subjects: A Randomized, Controlled, Single-Blind Crossover Trial.

OBJECTIVE: The purpose of this study was to investigate the effect of manual manipulations targeting the lumbar spine and/or sacroiliac joint on concentric knee extension and flexion forces. Torque production was measured during isometric and isokinetic contractions. METHODS: This was a randomized, controlled, single-blind crossover design with 21 asymptomatic, college-aged subjects who had never received spinal manipulation. During 2 separate sessions, subjects' peak torques were recorded while performing maximal voluntary contractions on an isokinetic dynamometer. Isometric knee extension and flexion were recorded at 60° of knee flexion, in addition to isokinetic measurements obtained at 60°/s and 180°/s. Baseline measurements were acquired before either treatment form of lumbosacral manipulation or sham manipulation, followed by identical peak torque measurements within 5 and 20 minutes posttreatment. Data were analyzed with a repeated measures analysis of variance. RESULTS: A statistically significant difference did not occur between the effects of lumbosacral manipulation or the sham manipulation in the percentage changes of knee extension and flexion peak torques at 5 and 20 minutes posttreatment. Similar, nonsignificant results were observed in the overall percentage changes of isometric contractions (spinal manipulation 4.0 ± 9.5 vs sham 1.2 ± 6.3, P = .067), isokinetic contractions at 60°/s (spinal manipulation - 4.0 ± 14.2 vs sham - 0.3 ± 8.2, P = .34), and isokinetic contractions at 180°/s (spinal manipulation - 1.4 ± 13.9 vs sham - 5.5 ± 20.0, P = .18). CONCLUSION: The results of the current study suggest that spinal manipulation does not yield an immediate strength-enhancing effect about the knee in healthy, college-aged subjects when measured with isokinetic dynamometry.

Common forearm fractures in adults.

Fractures of the forearm are common injuries in adults. Proper initial assessment includes a detailed history of the mechanism of injury, a complete examination of the affected arm, and appropriate radiography. Open fractures, joint dislocation or instability, and evidence of neurovascular injury are indications for emergent referral. Fractures demonstrating significant displacement, comminution, or intra-articular involvement may also warrant orthopedic consultation. In the absence of these findings, many forearm fractures can be managed by a primary care physician. Initial management of forearm fractures should follow the PRICE (protection, rest, ice, compression, and elevation) protocol, with the exception of compression, which should be avoided in the acute setting. Distal radius fractures with minimal displacement can be treated with a short arm cast. Isolated ulnar fractures can usually be managed with a short arm cast or a functional forearm brace. Mason type I radial head fractures can be treated with a splint for five to seven days or with a sling as needed for comfort, along with early range-of-motion exercises. Patients with an olecranon fracture are candidates for nonsurgical treatment if the elbow is stable and the extensor mechanism is intact.