A cross-sectional study of the relationship between physical activity, diet quality, and high-sensitivity C-reactive protein in US adults.

BACKGROUND AND AIMS: High-sensitivity C-reactive protein (hs-CRP) is associated with many diseases, especially cardiovascular disease (CVD). Research into the independent and integrated relationships of physical activity and diet quality with hs-CRP across sex-specific cohorts is lacking. METHODS AND RESULTS: National Health and Nutrition Examination Survey data (2015-2018) was used to examine the relationship between physical activity and diet quality with hs-CRP and hs-CRP classified CVD risk using multiple multinormal logistic regression adjusted for covariates including demographics. Physical activity was measured using a self-reported survey and further categorized to those who met (MPAR) or did not meet (NPAR) national recommendations. Diet quality was measured using the Healthy Eating Index-2015, and further categorized to higher (HDQ) and lower (LDQ) diet quality. hs-CRP was also categorized as low, average, and high CVD risk using established cut-points. Physical activity was inversely related to hs-CRP in males (p < 0.001) whereas diet quality was inversely related to hs-CRP in females (p = 0.031). Compared to those with NPAR and LDQ, the hs-CRP for males with NPAR and HDQ and females with MPAR and HDQ was 1.18 mg/L and 0.75 mg/L lower respectively. Although, diet quality was inversely associated with high CVD risk in both sexes (p < 0.05), the lowest proportion of high and average CVD risk was observed in males and females with MPAR and HDQ. CONCLUSION: Physical activity and diet-quality lowered CVD risk regardless of sex. However, the independent effects of physical activity and diet quality on hs-CPR differs between sexes.

Acute and Chronic Effects of Static Stretching on Intramuscular Hamstring Stiffness.

Passive hamstring stiffness varies proximo-distally, resulting in inhomogeneous tissue strain during stretching that may affect localized adaptations and risk of muscle injuries. The purpose of the present study was to determine the acute and chronic effects of static stretching (SS) on intramuscular hamstring stiffness. Thirty healthy active participants had acute changes in passive biceps femoris (BF), semimembranosus (SM), and semitendinosus (ST) stiffness measured at 25% (proximal), 50% (middle), and 75% (distal) muscle length, using shear-wave elastography, immediately after SS. Participants then completed 4 weeks of either a SS intervention (n = 15) or no intervention (CON, n = 15) with stiffness measured before and after the interventions. The acute and chronic effects of SS were compared between anatomical regions and between regions on the basis of their relative stiffness pre-intervention. Acutely, SS decreased stiffness throughout the BF and SM (p ≤ 0.05) but not the ST (p = 0.326). However, a regional effect of stretching was observed for SM and ST with greater reduction in stiffness occurring in stiffer muscular regions (p = 0.001-0.013). Chronically, SS increased BF and ST (p < 0.05), but not SM (p = 0.422) stiffness compared with CON, but no regional effect of stretching was observed in any muscle (p = 0.361-0.833). SS resulted in contrasting acute and chronic effects, acutely decreasing stiffness in stiffer regions while chronically increasing stiffness. These results indicate that the acute effects of SS vary along the muscle's length on the basis of the relative stiffness of the muscle and that acute changes in stiffness from SS are unrelated to chronic adaptations.

Intramuscular Hamstring Stiffness Affects Anatomically Modeled Localized Muscle Strain During Passive Hip Flexion.

ABSTRACT: Rehbein, CO, McDougle, JM, Peñailillo, L, and Earp, JE. Intramuscular hamstring stiffness affects anatomically modeled localized muscle strain during passive hip flexion. J Strength Cond Res XX(X): 000-000, 2024-Hamstring strain injuries occur when localized tissue strain capacity is exceeded. Localized strain may be affected by intramuscular variation in stiffness, but research in this area is lacking. The purpose of this study was to determine the effects of intramuscular hamstring stiffness on localized muscle strain during passive hip flexion. Twenty-eight (age 25.0 ± 4.9 years) healthy women (n = 15) and men (n = 13) had biceps femoris, semitendinosus, and semimembranosus stiffness measured proximally, medially, and distally during passive hip flexion and extension using shear-wave elastography. Anthropometric and stiffness measurements were entered into an anatomical model of equivalent springs to estimate localized tissue strain and differentiate between the relative contribution to passive strain from each muscular region. In shortened and stretched positions, stiffness was lowest proximally for all muscles (Cohen's d = 0.66-0.79, p < 0.001). In addition, relative strain contribution was greater proximally (37.5-39.4%) compared with middle (31.74-32.2%) or distal (28.6-30.3%) regions (p < 0.001), with proximal contribution to strain increasing with greater hip flexion. Our results suggest that intramuscular variations in passive hamstring stiffness contribute to inhomogeneous strain throughout the muscle during passive hip flexion. Given the prevalence of proximal stretch-pattern strain injuries, variation in intramuscular stiffness may contribute to risk for such injuries.

Sex and race/ethnicity specific reference predictive equations for abdominal adiposity indices using anthropometry in US adults.

BACKGROUND AND AIMS: Abdominal adiposity indices have stronger associations with cardiometabolic risk factors compared to anthropometric measures but are rarely used in large scale studies due to the cost and efficiency. The aim of this study is to establish sex and race/ethnicity specific reference equations using anthropometric measures. METHODS AND RESULTS: A secondary data analysis (n = 6589) of healthy adults was conducted using data from National Health and Nutrition Examination Survey 2011-2018. Variables included in the analyses were anthropometric measures (height; weight; waist circumference, WC) and abdominal adiposity indices (android percent fat; android to gynoid ratio, A/G ratio; visceral adipose tissue area, VATA; visceral to subcutaneous adipose area ratio, VSR). Multivariable prediction models were developed using quantile regression. Bland-Altman was used for external validation of prediction models. Reference equations to estimate android percent fat, A/G ratio, VATA and VSR from anthropometric measurements were developed using a randomly selected subsample of 4613. These reference equations for four abdominal adiposity indices were then cross-validated in the remaining subsample of 1976. The measured and predicted android percent fat, A/G ratio, VATA and VSR were not statistically different (p > 0.05) except for the A/G ratio in Asian males and VSR in White females. The results of Bland-Altman further revealed that ≥93% of predicted abdominal adiposity indices fell within the limits of agreement (±1.96 standard deviation). CONCLUSION: The sex and race/ethnicity specific reference equations for abdominal adiposity indices established using anthropometrics in the present study have strong predictive ability in US healthy adults.

Eccentric Cycling Is an Alternative to Nordic Hamstring Exercise to Increase the Neuromuscular Function of Knee Flexors in Untrained Men.

ABSTRACT: Valdes, O, Inzulza, S, Collao, N, Garcia-Vicencio, S, Tufano, JJ, Earp, J, Venegas, M, and Peñailillo, L. Eccentric cycling is an alternative to Nordic hamstring exercise to increase the neuromuscular function of knee flexors in untrained men. J Strength Cond Res 37(11): 2158-2166, 2023-Nordic hamstring exercise (NHE) has been proposed to reduce knee flexor (KF) injuries. However, submaximal alternatives to NHE are necessary for the clinical or weaker population. The aim of this study was to compare the effects of Nordic hamstring training (NHT) and eccentric cycling (ECC) training on the neuromuscular function of the KF. Twenty healthy men (27.7 ± 3.5 years) were randomly assigned into 2 groups that performed 10 training sessions (2-3 sessions·week-1) of either NHT (n = 10) or ECC (n = 10). Maximal voluntary isometric contraction of the KF and knee extensor (KE) muscles (MVICKF and MVICKE) was measured, and the hamstring/quadriceps strength (H/Q) ratio was calculated. Furthermore, changes in NHE maximum reaction force (NHE-MRFKF), NHE break-point angle (NHE-BPA), and muscle activity of the semitendinosus (STEMG) and biceps femoris (BFEMG) during the NHE after the interventions were compared. Although no group × time effects were observed (p = 0.09-0.70), but time effects were found for all variables. Pairwise comparisons revealed that MVICKF (+16.9%; p = 0.02), H/Q ratio (+11.8%; p = 0.01), NHE-MRFKF (+19.8%; p = 0.005), and NHE-BPA (+30.8%; p = 0.001) increased after ECC, whereas NHE-MRFKF (+9.7%; p = 0.003), NHE-BPA (+35.5%; p = 0.0002), and STEMG (+33.7%; p = 0.02) increased after NHT. A group × time effect was observed (p = 0.003) in BFEMG, revealing an increase only after ECC (+41.1%; p < 0.0001). Similar neuromuscular adaptations were found after both training modalities. Therefore, ECC provides similar adaptations as NHT and may serve as an alternative form of KF training for those unable to perform NHE.

Effects of isometric loading intensity on patellar tendon microvascular response.

Acute increases in tendon blood flow and oxygenation after stress (i.e., hyperemic response) can enhance tendon recovery. While loading intensity is a fundamental part of resistance training programs, its effects on tendon's hyperemic response are unknown. This study aimed to compare acute changes in total (total hemoglobin [THb]) and oxygenated hemoglobin (HbO2 ) concentrations in the patellar tendon after isometric exercise at different intensities. Thirteen participants performed 8 (5 s) isometric knee extensions at 25%, 50%, and 75% maximal load (maximal voluntarily isometric contraction [MVIC]), separated by 20 min recovery, prescribed in randomized and counterbalanced order. Changes in patellar tendon THb, HbO2 and deoxygenated hemoglobin (HHb) in response to exercise at each intensity were measured using near-infrared spectroscopy. Post-exercise, HbO2 increased with 50% ( η p 2  = 0.305, f = 5.26, p < 0.01) and 75% ( η p 2  = 0.245, f = 4.56, p < 0.01) but not 25% ( η p 2  = 0.088, f = 1.16, p = 0.339) MVIC, while THb increased in 50% ( η p 2  = 0.305, f = 5.26, p = 0.01) but not 25% ( η p 2  = 0.067, f = 0.865, p = 0.51) or 75% ( η p 2  = 0.126, f = 1.729, p = 0.14) MVIC. Additionally, increasing load from 25% to 50% MVIC resulted in greater THb (f = 2.459, p = 0.43), HbO2 (f = 3.389, p = 0.13) and HHb (f = 0.320, p = 0.01) post-exercise responses, but no differences were observed between 50% and 75% MVIC (THb: f = 0.748, p = 0.59; HbO2 : f = 0.825, p = 0.54; HHb: f = 0.713, p = 0.62). Our results suggest there is a loading threshold at ~50% MVIC at which the tendon hyperemic response is fully achieved. Training above this intensity is not expected to provide any additional change to the tendon microvascular response. Therefore, moderate loading seems to be sufficient to fully elicit the patellar tendon hyperemic response that's believed to stimulate tendon healing.

Total Body and Extracellular Water Measures Are Unrelated to Cramp Sensitivity in Euhydrated Cramp-Prone Individuals.

ABSTRACT: Earp, JE, Stearns, RL, Agostinucci, J, Lepley, AS, and Ward-Ritacco, CL. Total body and extracellular water measures are unrelated to cramp sensitivity in euhydrated cramp-prone individuals. J Strength Cond Res 36(9): 2653-2656, 2022-Spectral bioelectrical impedance analysis (BIA) is a valid and noninvasive tool for measuring total body water (TBW), intracellular water (ICW), and extracellular water (ECW). As altered hydration and electrolyte imbalance have been proposed as one of 2 etiologies for exercise-associated muscle cramps (EAMC), the purpose of this study was to determine if distribution of body water is related to cramp sensitivity in similarly hydrated cramp-prone individuals. To this end, 11 euhydrated subjects who regularly experience EAMC had their relative TBW, ICW, and ECW assessed using 8-pole spectral BIA. Subjects' cramp sensitivity was then assessed by electrically stimulating the tibial nerve at increasing frequencies until a muscle cramp occurred, allowing for the determination of the threshold frequency (TF) at which the cramp occurred. It was observed that TF was not significantly related to TBW ( r = 0.087, p = 0.368), ICW ( r = 0.105, p = 0.338), ECW ( r = 0.087, p = 0.368), or ECW:TBW ( r = 0.147, p = 0.280). As cramp etiology is poorly understood, these results add to a growing body of literature questioning the role of hydration and electrolyte imbalance in EAMC. Although fluid distribution may be unrelated to TF in those who commonly experience EAMC, additional research is needed to compare those who commonly experience cramps (athletes as well as individuals with specific neuropathies or pharmacologically induced cramps) with those who do not experience cramps and to determine if acute shifts in body water compartmentalization are related to changes in cramp sensitivity.

Comparing Acceleration and Change of Direction Ability Between Backpedal and Cross-over Run Techniques for Use in American Football.

ABSTRACT: Angelino, D, McCabe, TJG, and Earp, JE. Comparing acceleration and change of direction ability between backpedal and cross-over run techniques for use in American football. J Strength Cond Res 35(1): 47-55, 2021-In American football, defensive backs guard receivers using either cross-over (CO) run or backpedal (BP) techniques, but the efficacy of these techniques is unknown. The purpose of this study was to compare linear acceleration (LA) and change of direction (CoD) ability when using CO and BP. Collegiate football defensive backs participated in LA (n = 13) and CoD (n = 7) testing. During LA, subjects performed CO, BP, and forward sprints with split times taken between 0-3 and 3-5 yd and ground reaction forces recorded 0 and 3 yd from the start. During CoD testing, subjects performed the CO or BP for 3 yd and then were given a cue to sprint to a gate 5 yd away in 1 of 4 directions (downfield, midfield, sideline, or upfield). In LA, CO was faster than BP between 0-3 yd (Δ -0.20 ± 0.02 seconds, p = 0.000) and 3-5 yd (Δ -0.12 ± 0.02 seconds, p = 0.000). At the start of the movement, CO demonstrated greater propulsive forces (p = 0.017). However, 3 yd from the start, CO demonstrated greater propulsive forces and reduced braking forces (p = 0.000 & 0.003). In CoD, CO was faster than BP when running in the downfield (Δ 0.21 ± 0.05 seconds, p = 0.044) and lateral directions (Δ 0.21 ± 0.08 seconds, p = 0.035), but similar in the upfield direction (Δ 0.01 ± 0.08, p = 0.986). Our results indicate that CO is superior to BP in LA, CoD ability, and movement efficiency and support the use of CO for defensive backs.

Effect of a Neoprene Knee Sleeve on Performance and Muscle Activity in Men and Women During High-Intensity, High-Volume Resistance Training.

ABSTRACT: Hatfield, DL, Stranieri, AM, Vincent, LM, and Earp, JE. Effect of a neoprene knee sleeve on performance and muscle activity in men and women during high-intensity, high-volume resistance training. J Strength Cond Res 35(12): 3300-3307, 2021-The purpose of this study was to assess the effects of a commercially available neoprene knee sleeve (KS) on exercise performance and muscle activity during an exhaustive leg press exercise. Twenty resistance-trained individuals, 11 men {21.0 ± 2.2 years; 77.7 ± 8.7 kg; 1 repetition maximum (1RM/body mass [BM]): 0.30 ± 0.04} and 9 women (22.0 ± 3.5 years; 66.1 ± 9.1 kg; 1RM/BM: 0.30 ± 0.04), all subjects (21.5 ± 2.8 years; 72.5 ± 10.5 kg; 1RM/BM: 0.30 ± 0.04), participated in 3 testing sessions. The second and third sessions were performed using a counterbalanced and randomized design in which subjects exercised with (WS) or without (NS) KSs and performed 6 sets of leg press exercise at 80% of 1RM until failure with a 3-minute rest between sets. Number of repetitions, blood lactate (BL), heart rate (HR), rating of perceived exertion (RPE), and peak and average power were recorded after each set. Surface electromyography (EMG) of the right and left vastus lateralis muscles was also recorded to compare muscle activity between conditions. Significance was set at p ≤ 0.05, and values are presented as mean ± SD. No significant differences were observed in the total number of repetitions for all sets (p = 0.3; WS 75.3 ± 33.7, NS 79.8 ± 34.3) and the number of repetitions per set between conditions (p ≤ 0.05) or between men and women. Similarly, no significance differences (p ≤ 0.05) were observed for BL, HR, RPE, or EMG per set between conditions or between men and women. These results suggest that wearing compressive neoprene KSs has no effect on improving performance and associated variables during high-load, high-volume lower-body resistance training.

Effects of Eccentric Cycling Performed at Long vs. Short Muscle Lengths on Heart Rate, Rate Perceived Effort, and Muscle Damage Markers.

Peñailillo, L, Aedo, C, Cartagena, M, Contreras, A, Reyes, A, Ramirez-Campillo, R, Earp, JE, and Zbinden-Foncea, H. Effects of eccentric cycling performed at long vs. short muscle lengths on heart rate, rate perceived effort, and muscle damage markers. J Strength Cond Res 34(10): 2895-2902, 2020-It is possible that the magnitude of muscle damage in eccentric cycling is dependent on seat position that could affect the muscle length changes during eccentric contractions. However, no previous study has investigated the effect of seat position on muscle damage and metabolic demand in eccentric exercise. Thus, this study compared 2 seating positions; seat forward in which knee extensor muscles were stretched longer (LONG) and seat back in which the muscles were stretched shorter (SHORT). Young men performed 30 minutes of eccentric cycling at 80% of maximal concentric power output at either LONG (n = 10) or SHORT (n = 10) condition. Heart rate and rate perceived effort (RPE) during exercise, changes in maximal voluntary isometric contraction (MVC) strength of the knee extensors, muscle soreness assessed by a visual analog scale (VAS), and pressure-pain threshold (PPT) before, immediately after, and 24-72 hours after exercise were compared between conditions. Heart rate and RPE were significantly greater in LONG than SHORT group (9.5 and 19.0%, respectively). Post-exercise reduction in MVC was 8.4-14.0% greater in LONG than SHORT group from immediately after to 48 hours after exercise. In addition, VAS was greater in LONG than SHORT group from 48 to 72 hours after exercise, and vastus medialis PPT was greater in SHORT than LONG group from 24 to 72 hours after exercise (p < 0.05). These results suggest that muscle damage and metabolic demand are greater when seat is set back than forward. Thus, when prescribing eccentric cycling to individuals who are unaccustomed to eccentric cycling, it is better to set the seat far from the pedals.

Electrolyte beverage consumption alters electrically induced cramping threshold.

BACKGROUND: Recent investigations have questioned the role of hydration and electrolytes in cramp susceptibility and thus the efficacy of consuming electrolyte-rich carbohydrate beverages (EB) to control/prevent cramping. METHODS: Nine euhydrated, cramp-prone participants had their cramp susceptibility assessed by measuring the nerve stimulation threshold frequency at which cramping occurs (TF) before and after consumption of an EB (kCal: 120, Na: 840 mg, K: 320 mg, Mg: 5 mg) and placebo beverage (PB: kCal: 5, Na: 35 mg). Cramp intensity was assessed using a verbal pain scale and poststimulation electromyography (EMG). RESULTS: TF was greater in EB (14.86 ± 7.47 Hz) than PB (14.00 ± 5.03 Hz; P = .038) and reported pain was lower in EB (2.0 ± 0.6) than PB (2.7 ± 0.8; P = .025) while EMG was similar (P = .646). DISCUSSION: EB consumption decreased cramp susceptibility and pain but did not prevent cramping in any participants. These results suggest that electrolyte consumption independent of hydration can influence cramp susceptibility in young people.

Age-specific trends in health-related quality of life among US adults: findings from National Health and Nutrition Examination Survey, 2001-2016.

PURPOSE: Health-related quality of life (HRQoL) is an important indicator of population health, yet no age-specific trend analyses in HRQoL have been conducted with a nationally representative sample since 2004. Therefore, to address this gap, an age-specific trend analysis of HRQoL was conducted using National Health and Nutrition Examination Surveys (NHANES) data. METHODS: NHANES 2001-2016 data (8 cycles) were examined to evaluate trends in HRQoL by age group (young adults: 21-39, middle-aged: 40-64, older adults: 65+). HRQoL was assessed by self-reported health (SRH) and number of physically unhealthy, mentally unhealthy, and inactive days to due to physical or mental health in the past 30 days. Multiple linear or logistic regression analyses explored trends in HRQoL by age group, adjusting for demographics over time. RESULTS: Analysis revealed increasing fair/poor SRH over time for the entire sample (ß = 0.34, 95% CI 0.08, 0.60, p = 0.011). However, age-specific analysis identified a bi-annual increase in fair/poor SRH only among young adults (ß = 0.49, 95% CI 0.22, 0.76, p < 0.001) and a decrease among older adults (ß = - 0.60, 95% CI - 1.14, - 0.06, p = 0.03). Closer inspection revealed increasing fair/poor SRH increased among young women (ß = 0.52, 95% CI 0.11, 0.93, p = 0.013) and young men (ß = 0.46, 95% CI 0.04, 0.88, p = 0.03) but decreased among older women (ß = - 0.81, 95% CI - 1.59, - 0.03, p = 0.042) over time. Analyses also determined that there was a trend for a decreasing number of physically unhealthy days among young adults (p < 0.001), although no trends were observed for the other HRQoL items. CONCLUSIONS: Although there was a significant trend over time for increasing fair/poor SRH when considering the entire sample, this trend was not consistent between age groups or sexes. Given increasing fair/poor SRH among young adults, there is a need to understand and address factors relating to HRQoL among this age group.

Cold-water immersion blunts and delays increases in circulating testosterone and cytokines post-resistance exercise.

INTRODUCTION: Cold-water immersion (CWI) is often used to promote recovery by reducing exercise-induced muscle damage, soreness, and inflammation. However, recent reports have cautioned that CWI may attenuate the adaptive response to resistance training. PURPOSE: To determine the effect of post resistance-exercise CWI on circulating free testosterone (T) and cytokine (IL-6 and TNF-α) response. METHODS: Using a randomized and counterbalanced repeated-measures design, 11 resistance-trained men completed two workouts (6 sets of 10 repetitions of back squats at 80% of maximum load) a week apart after which they took part in either 15 min of CWI (15 °C) or passive recovery. T, IL-6, and TNFα were measured in blood samples taken before (PRE) and 5 (5POST), 15 (15POST), 30 (30POST), and 60 (60POST) min post-exercise and compared between treatments and over time. RESULTS: For T, a significant interaction effect of condition over time (p = 0.030) as well as greater relative concentrations of T in CON (Δ9.2%) than CWI (Δ-0.5%, p = 0.049) at 30POST were observed. In addition, at 60POST, T dropped below PRE values in CWI (Δ-10.4%, p = 0.028) but not in CON (Δ-1.6%, p = 0.850). A suppressed cytokine response was observed after CWI in IL-6 at 30POST (CWI: Δ4.9%, CON: Δ47.5%, p = 0.041) and TNFα at 15POST (CWI: Δ5.3%, CON: Δ17.0%, p = 0.022). CONCLUSIONS: CWI blunted the T and cytokine response after a bout of resistance exercise. These results indicate that CWI results in an altered anabolic response and may help to explain the previous observation of attenuated hypertrophy when CWI is used after resistance exercise.

Regional Surface Electromyography of the Vastus Lateralis During Strength and Power Exercises.

Neuromuscular activation during and chronic adaptation from exercise are innately linked and both can vary along a muscle's length. During high-force and high-speed exercise, intramuscular hypertrophy follows set patterns that provide the greatest biomechanical advantages. However, it is unknown if muscle activity as recorded by surface electromyography (sEMG) will follow these patterns. The purpose of the present study was to compare vastus lateralis intramuscular sEMG during the heavy squat (HS) and unloaded jump squat (JS) exercises. Ten subjects performed HS with 80% of maximum load and unloaded JS to parallel-depth, while intramuscular peak sEMG and mean sEMG were measured at 33% (proximal), 50% (middle), and 67% (distal) thigh length. Muscle activity was compared between regions and exercises using a 3 × 2 repeated measures ANOVA with Bonferoni post hoc corrections. Peak sEMG was greater proximally in JS than HS (p = 0.033), but similar in the middle and distal regions (p = 0.521, 0.594, respectively), whereas mean sEMG was similar between all regions (p = 0.150-0.979). In addition, a main effect was found in which peak and mean sEMG were greater proximally than the middle and distal regions (p = 0.001, 0.006). Muscle activity measured using sEMG displayed dissimilar patterns to previously observed regional hypertrophy. Specifically, although previous research found greater proximal hypertrophy in JS than HS, in the present study peak sEMG was greater in HS than JS. Furthermore, distally where HS elicited greater hypertrophy than JS, no differences in sEMG were present. Thus, regional sEMG appears not to be a viable tool for predicting differences in regional hypertrophy, most likely due to technological constraints and intramuscular differences in muscle structure.

The influence of loading intensity on muscle-tendon unit behavior during maximal knee extensor stretch shortening cycle exercise.

Tendon stiffness increases as the magnitude and rate of loading increases, according to its viscoelastic properties. Thus, under some loading conditions tendons should become exceptionally stiff and act almost as rigid force transducers. Nonetheless, observations of tendon behavior during multi-joint sprinting and jumping tasks have shown that tendon strain increases whilst muscle strain decreases as the loading intensity increases. The purpose of the current study was to examine the influence of external loading intensity on muscle-tendon unit (MTU) behavior during a high-speed single-joint, stretch-shortening cycle (SSC) knee extension task. Eighteen men (n = 9) and women (n = 9) performed single-leg, maximum intensity SSC knee extensions at loads of 20, 60 and 90% of their one repetition maximum. Vastus lateralis fascicle length (L(f)) and velocity (v(f)) as well as MTU (L(MTU)) and tendinous tissue (L(t)) length were measured using high-speed ultrasonography (96 Hz). Patellar tendon force (F(t)) and rate of force development (RFDt) were estimated using inverse dynamics. Results showed that as loading intensity increased, concentric joint velocity and shortening v f decreased whilst F t and RFDt increased, but no significant differences were observed in eccentric joint velocity or peak L(MTU) or L(f). In addition, the tendon lengthened significantly less at the end of the eccentric phase at heavier loads. This is the first observation that tendon strain decreases significantly during a SSC movement as loading intensity increases in vivo, resulting in a shift in the tendon acting as a power amplifier at light loads to a more rigid force transducer at heavy loads.

Match-related activity profiles of youth female and male football players during World Cup classification tournaments and their relationship to body composition.

BACKGROUND: The activity profiles of football players during competition can be affected by the athletes' competitive level and sex. However, evidence of this in youth South American athletes is scarce as is the effects of body composition on match activity profiles. Therefore, the present study compared the activity profiles of Chilean under-20 (U20) and under-17 (U17) male and female teams during the World Cup qualification tournaments (WC) using a multicomponent athlete monitoring system and explored the relationships between these profiles and the players' body composition. METHODS: Athlete's body composition was measured as there were total distance, distance covered at different velocities, explosive efforts, sprints, and estimated player load (PL) during the 2018-2019 World Cup Qualifiers. RESULTS: Males had greater muscle and lower fat mass than females and covered 10.8% more total distance with maximal speed being 15.3% faster in match play (P<0.05). However, females covered more distance at higher running speeds and had a greater number of sprints (P<0.05). For males, the U20 club was 3.7% faster and performed 26.3% more explosive efforts than the U17 club (P<0.05). Contrastingly, the female U17 club covered more total distance, more distance at different speeds had more total sprints, greater PL, and muscle mass than the U20 club (P<0.05). Across all athletes, fat mass correlated negatively to total distance (R=-0.39; P=0.001), while muscle mass correlated positively with maximal speed (R=0.72; P=0.001). CONCLUSIONS: Gender, competitive level, and body composition seem to affect match-activity profiles in football players during WC qualifiers.

The relationship between fat distribution and diabetes in US adults by race/ethnicity.

Introduction: This study examined the relationship between fat distribution and diabetes by sex-specific racial/ethnic groups. Methods: A secondary data analysis of National Health and Nutrition Examination Survey 2011-2018 data (n = 11,972) was completed. Key variables examined were visceral adipose tissue area (VATA), subcutaneous fat area (SFA), diabetes prevalence, and race/ethnicity. The association of VATA and SFA and diabetes prevalence was examined separately and simultaneously using multiple logistic regression. Bonferroni corrections were applied to all multiple comparisons between racial/ethnic groups. All analyses were adjusted for demographics and muscle mass. Results: VATA was positively associated with diabetes in both sexes (p < 0.001) and across all racial/ethnic groups (p < 0.05) except Black females. No statistically significant relationships were observed between SFA and diabetes while accounting for VATA with the exception of White females (p = 0.032). When comparing racial/ethnic groups, the relationship between VATA and diabetes was stronger in White and Hispanic females than in Black females (p < 0.005) while the relationship between SFA and diabetes did not differ between any racial/ethnic groups. Conclusion: This study found that VATA is associated with diabetes for both sexes across almost all racial/ethnic groups independent of SFA whereas the only significant relationship between SFA and diabetes, independent of VATA, was observed in White females. The findings indicated that visceral fat was more strongly associated with diabetes than subcutaneous. Additionally, there are health disparities in sex-specific racial/ethnic groups thus further study is warranted.

Leukocyte telomere length is associated with MRI-thigh fat-free muscle volume: data from 16 356 UK Biobank adults.

BACKGROUND: Telomere attrition may share common biological mechanisms with bone and muscle loss with aging. Here, we investigated the association between these hallmarks of aging using data from UK Biobank, a large observational study. METHODS: Leukocyte telomere length (LTL as T/S ratio) was measured using a multiplex qPCR assay at baseline (2006-2010). Bone mineral density (whole body and regional; via dual-energy X-ray absorptiometry), trabecular bone score (via lumbar-spine dual-energy X-ray absorptiometry images), fat-free muscle volume (thighs; via magnetic resonance imaging), and muscle fat infiltration (thighs; via magnetic resonance imaging) were measured during the imaging visit (2014-2018). Regression models were used to model LTL against a muscle or bone outcome, unadjusted and adjusted for covariates. RESULTS: A total of 16 356 adults (mean age: 62.8 ± 7.5 years, 50.5% women) were included. In the fully adjusted model, thigh fat-free muscle volume was associated with LTL in the overall sample (adjusted standardized ß (aß) = 0.017, 95% CI 0.009 to 0.026, P < 0.001, per SD increase in LTL), with stronger associations in men (aß = 0.022, 95% CI 0.010 to 0.034, P < 0.001) than in women (aß = 0.013, 95% CI 0.000 to 0.025, P = 0.041) (sex-LTL P = 0.028). The adjusted odds ratio (aOR) for low thigh fat-free muscle volume (body mass index-adjusted, sex-specific bottom 20%) was 0.93 per SD increase in LTL (95% CI 0.89 to 0.96, P < 0.001) in the overall sample, with stronger associations in men (aOR = 0.92, 95% CI 0.87 to 0.99, P = 0.008) than women (aOR = 0.93, 95% CI 0.88 to 0.98, P = 0.009), although the sex difference was not statistically significant in this model (sex-LTL P = 0.37). LTL was not associated with bone mineral density, trabecular bone score, or muscle fat infiltration in the overall or subgroup analyses (P > 0.05). CONCLUSIONS: LTL was consistently associated with thigh fat-free muscle volume in men and women. Future research should investigate moderating effects of lifestyle factors (e.g., physical activity, nutrition, or chronic diseases) in the association between LTL and muscle volume.

Sarcopenia and aortic valve disease.

Valvular heart disease, including calcific or degenerative aortic stenosis (AS), is increasingly prevalent among the older adult population. Over the last few decades, treatment of severe AS has been revolutionised following the development of transcatheter aortic valve replacement (TAVR). Despite improvements in outcomes, older adults with competing comorbidities and geriatric syndromes have suboptimal quality of life outcomes, highlighting the cumulative vulnerability that persists despite valve replacement. Sarcopenia, characterised by loss of muscle strength, mass and function, affects 21%-70% of older adults with AS. Sarcopenia is an independent predictor of short-term and long-term outcomes after TAVR and should be incorporated as a prognostic marker in preprocedural planning. Early diagnosis and treatment of sarcopenia may reduce morbidity and mortality and improve quality of life following TAVR. The adverse effects of sarcopenia can be mitigated through resistance training and optimisation of nutritional status. This is most efficacious when administered before sarcopenia has progressed to advanced stages. Management should be individualised based on the patient's wishes/preferences, care goals and physical capability. Exercise during the preoperative waiting period may be safe and effective in most patients with severe AS. However, future studies are needed to establish the benefits of prehabilitation in improving quality of life outcomes after TAVR procedures.

Whey protein supplementation during resistance training augments lean body mass.

UNLABELLED: Compared to soy, whey protein is higher in leucine, absorbed quicker and results in a more pronounced increase in muscle protein synthesis. OBJECTIVE: To determine whether supplementation with whey promotes greater increases in muscle mass compared to soy or carbohydrate, we randomized non-resistance-trained men and women into groups who consumed daily isocaloric supplements containing carbohydrate (carb; n = 22), whey protein (whey; n = 19), or soy protein (soy; n = 22). METHODS: All subjects completed a supervised, whole-body periodized resistance training program consisting of 96 workouts (~9 months). Body composition was determined at baseline and after 3, 6, and 9 months. Plasma amino acid responses to resistance exercise followed by supplement ingestion were determined at baseline and 9 months. RESULTS: Daily protein intake (including the supplement) for carb, whey, and soy was 1.1, 1.4, and 1.4 g·kg body mass⁻¹, respectively. Lean body mass gains were significantly (p < 0.05) greater in whey (3.3 ± 1.5 kg) than carb (2.3 ± 1.7 kg) and soy (1.8 ± 1.6 kg). Fat mass decreased slightly but there were no differences between groups. Fasting concentrations of leucine were significantly elevated (20%) and postexercise plasma leucine increased more than 2-fold in whey. Fasting leucine concentrations were positively correlated with lean body mass responses. CONCLUSIONS: Despite consuming similar calories and protein during resistance training, daily supplementation with whey was more effective than soy protein or isocaloric carbohydrate control treatment conditions in promoting gains in lean body mass. These results highlight the importance of protein quality as an important determinant of lean body mass responses to resistance training.