Active Muscle Mass Research Articles

Anthropometric and bioimpedansometric predictors of postoperative complications in patients with gastric and cardioesophageal junction cancers

BACKGROUND: Among the most common intra-abdominal complications of surgical treatment of gastric and cardioesophageal junction cancers are acute postoperative pancreatitis and abdominal abscesses.
 AIM: Identification and study of anthropometric and bioimpedansometric predictors of the complicated course of the postoperative period in patients with gastric and cardioesophageal junction cancers.
 MATERIAL AND METHODS: 250 patients with gastric and cardioesophageal junction cancers, 123 men and 127 women, were examined. All subjects underwent radical surgical treatment. In the postoperative period, postoperative complications were recorded in 40 patients. All subjects underwent anthropometric and bioimpedance examination. Height and body weight, transverse diameter of the chest, width of the shoulders and pelvis, waist and hip circumference, and body morphotype were determined. Bioimpedansometric examination was carried out before surgery and in the postoperative period using a domestic hardware and software complex with determination of the body component composition and the phase angle value. The phase angle of impedance reflected the metabolic rate in the body. The results were statistically processed using descriptive statistics methods. The Shapiro–Francia, Kolmogorov–Smirnov tests, Student's t-test, Mann–Whitney test, and the logistic regression method were used. Differences were considered statistically significant at p 0.05.
 RESULTS: Women of the gynecomorphic body type were characterized by a significant decrease in the relative values of active cellular and skeletal muscle mass (p=0.001; p=0.001), and the phase angle value until 12–14 days after surgery (p=0.001). Men of the andromorphic body type were characterized by a significant decrease in the relative values of active cell mass (p=0.001) and the phase angle until 12–14 days after surgery (p=0.001). In women of a gynecomorphic morphotype, the likelihood of postoperative complications was 4 times higher than in women of an andromorphic morphotype (p=0.001). Representatives of the mesomorphic body morphotype of both sexes were characterized by stable bioimpedance measurements during the entire postoperative period.
 CONCLUSION: Low values of the phase angle in men and women, as well as the classic gynecomorphic body type in women can be used in oncoabdominal surgery as predictors of a high risk postoperative complications developing in patients with gastric and cardioesophageal junction cancers.

The Improvement in Exercise Performance during Reduced Muscle Mass Exercise is Associated with an Increase in Femoral Blood Flow in Older and Younger Endurance-Trained Athletes.

This study investigated whether the improved performance observed with maximal self-paced single-leg (SL), compared with double-leg (DL) cycling, is associated with enhanced femoral blood flow and/or altered tissue oxygenation. The hyperaemic response to exercise was assessed in younger and older athletes. Power output was measured in 12 older (65 ± 4 y) and 12 younger (35 ± 5 y) endurance-trained individuals performing 2 x 3 min maximal self-paced exercise using SL and DL cycling. Blood flow (BF) in the femoral artery was assessed using Doppler ultrasound and muscle oxygenation was measured using near-infrared spectroscopy on the vastus lateralis. SL cycling elicited a greater power output (295 ± 83 vs 265 ± 70 W, P < 0.001) and peak femoral BF (1749.1 ± 533.3 vs 1329.7 ± 391.7 ml/min, P < 0.001) compared with DL cycling. Older individuals had a lower peak BF in response to exercise (1355.4 ± 385.8 vs 1765.2 ± 559.6 ml/min, P = 0.019) compared with younger individuals. Peak BF in response to exercise was correlated with power output during SL (r = 0.655, P = 0.002) and DL (r = 0.666, P = 0.001) cycling. The greater exercise performance during SL compared with DL cycling may be partly explained by a greater hyperaemic response when reducing active muscle mass. Despite regular endurance training, older athletes had a lower femoral BF in response to maximal self-paced exercise compared with younger athletes.

Differential effects of contracting muscle mass and relative exercise intensity on arterial plasma potassium concentration during and following incremental arm and leg cycling exercise

Whilst arm cycling is commonly used during clinical testing and rehabilitation, the associated changes in arterial plasma K+ concentration ([K+]a) and thus possible risks of associated hyperkalaemia and hypokalaemia are unknown. During exercise, K+ is released from contracting skeletal muscles and simultaneously taken up by inactive muscles, with [K+]a increasing markedly during intense exercise. Hence during exercise [K+]a should be influenced by both the contracting muscle mass and the relative exercise intensity. We therefore investigated the effects of incremental one-arm (1ARM) and two-leg (2LEGS) cycling on [K+]a, and on lactate ([Lac-]), hydrogen ([H+]), adrenaline and noradrenaline. Eight healthy participants performed 1ARM, rested (3.0 ± 0.2 h, mean±SE) then performed 2LEGS, with radial arterial blood sampled at rest, during common submaximal workrates (25, 50 W), peak workrate and 1–30 min post-exercise. During exercise at 50 W, VO2, [K+]a and [Lac-]a were higher during 1ARM than 2LEGS (P < 0.05). In contrast, at peak exercise, 2LEGS (272 ± 15 W) elicited higher VO2, [K+]a, [Lac-]a, [adrenaline]a and [noradrenaline]a than 1ARM (57 ± 4 W) (P < 0.05), with [H+]a elevated only in 2LEGS (P < 0.05). A curvilinear response for [K+]a versus %VO2peak was similar between modes, until diverging close to VO2peak. The slope of the log[K+]a versus %VO2peak regression was higher in 2LEGS (P < 0.01), indicating greater [K+]a throughout exercise utilising a larger muscle mass, and similarly for [Lac-]a. In conclusion, during exercise utilising a smaller contracting muscle mass, [K+]a and [Lac-]a were greater at the same absolute submaximal work rate compared to utilising a large muscle mass. Whilst responses were similar between modes when expressed against relative exercise intensity, [K+]a and [Lac-]a were higher during exercise with a large muscle mass. Hence, for submaximal exercise, the relative intensity is more important in determining [K+]a and [Lac-]a, but the size of the contracting muscle mass still exerts a positive effect, whilst during peak exercise, the size of the active muscle mass was more important in determining [K+]a and [Lac-]a. Furthermore, arm cycling did not induce marked disturbances in [K+]a during or after exercise, suggesting minimal associated myocardial risks and thus supporting its safe use in clinical and aged populations.

Reliability of Anaerobic Contributions during a Single Exhaustive Knee-extensor Exercise.

The total anaerobic contribution (AC[La-]+PCr) is a valid and reliable methodology. However, the active muscle mass plays an important role in the AC[La-]+PCr determination, which might influence its reliability. Thus, this study aimed to investigate the effects of two exhaustive intensities on the reliability of the AC[La-]+PCr during a one-legged knee extension (1L-KE) exercise. Thirteen physically active males were submitted to a graded exercise to determine the peak power output (PPO) in the 1L-KE. Then, two constant-load exercises were conducted to task failure at 100% (TTF100) and 110% (TTF110) of PPO, and the exercises were repeated on a third day. The blood lactate accumulation and the oxygen uptake after exercise were used to estimate the anaerobic lactic and alactic contributions, respectively. Higher values of AC[La-]+PCr were found after the TTF100 compared to TTF110 (p=0.042). In addition, no significant differences (p=0.432), low systematic error (80.9 mL), and a significant ICC (0.71; p=0.004) were found for AC[La-]+PCr in the TTF100. However, an elevated coefficient of variation was found (13.7%). In conclusion, we suggest the use of the exhaustive efforts performed at 100% of the PPO with the 1L-KE model, but its elevated individual variability must be carefully considered in future studies.

Диагностика нутритивных нарушений у детей после перенесенной черепно-мозговой травмы (обзор современных рекомендаций)

Traumatic brain injury (TBI) is one of the main causes of disability and mortality in the population, and in young people it ranks first. Children after TBI, in addition to neurological problems, have a number of somatic ones, such as malnutrition, dysphagia, and motor disorders of the gastrointestinal tract. Hypercatabolism causes the formation of malnutrition and loss of a significant part of muscle mass in these patients. Gastrointestinal problems limit adequate nutrition. In combination with neurological disorders – motor disorders, long-term immobilization, epilepsy – this can lead to the development of sarcopenia. The presence of sarcopenia, in turn, reduces the rehabilitation potential and directly affects the restoration and acquisition of motor functions. Therefore, it is important to assess and correct nutritional status in children with TBI not only in the acute period, but also during the early restorative treatment. The purpose — to analyze the available literature on the features of assessing nutritional status in children after traumatic brain injury. Results. Children after TBI are prone to immobilization, which leads to loss of muscle mass and bone mineral density, as well as an increase in fat mass. According to the guidelines of the European Society of Pediatric Gastroenterologists, Hepatologists and Nutritionists (ESPGHAN), it is recommended to assess the nutritional status of children with neurological diseases using anthropometry, body composition, and some laboratory parameters. To date, a universal marker of nutritional status disorders in children with neurological diseases in general and with TBI in particular has not been identified. The clinical recommendations «Traumatic brain injury in children» (2022) indicate that such routine laboratory markers of nutrition assessment as total protein, serum albumin, prealbumin, retinol-binding protein, as well as anthropometry have not proven their effectiveness in assessing the state of muscle mass. The «gold standard» in determining the body composition is the bioimpedansometry method, which allows assessing the content of active cell mass, muscle mass, fat and fat-free mass, the total water content. To achieve optimal anthropometric parameters, body composition and rehabilitation prognosis, it is recommended to use indirect calorimetry instead of equations to calculate the resting energy expenditure. Conclusion. The current Federal Clinical Guidelines for the Treatment of Children with TBI (2022) do not have an algorithm and a clear approach to assessing nutritional status and prescribing nutritional support for children of this vulnerable group. To assess the nutritional status, regardless of the level of the hospital, it is recommended to use anthropometry with dynamic control. To assess the body composition it is recommended to use bioimpedansometry, if it is unavailable — mid-upper arm circumference using MUAC tapes, as well as caliperometry. It is also recommended to assess the level of trace elements, with dynamic control at 6 months or annually.

Single-leg cycling to maintain and improve function in healthy and clinical populations.

Exercise with reduced muscle mass facilitates greater muscle-specific adaptations than training with larger muscle mass. The smaller active muscle mass can demand a greater portion of cardiac output which allows muscle(s) to perform greater work and subsequently elicit robust physiological adaptations that improve health and fitness. One reduced active muscle mass exercise that can promote greater positive physiological adaptations is single-leg cycling (SLC). Specifically, SLC confines the cycling exercise to a smaller muscle mass resulting in greater limb specific blood flow (i.e., blood flow is no longer "shared" by both legs) which allows the individual to exercise at a greater limb specific intensity or for a longer duration. Numerous reports describing the use of SLC have established cardiovascular and/or metabolic benefits of this exercise modality for healthy adults, athletes, and individuals living with chronic diseases. SLC has served as a valuable research tool for understanding central and peripheral factors to phenomena such as oxygen uptake and exercise tolerance (i.e., V̇O2peak and V̇O2 slow component). Together, these examples highlight the breadth of applications of SLC to promote, maintain, and study health. Accordingly, the purpose of this review was to describe: 1) acute physiological responses to SLC, 2) long-term adaptations to SLC in populations ranging from endurance athletes to middle aged adults, to individuals living with chronic disease (COPD, heart failure, organ transplant), and 3) various methods utilized to safely perform SLC. A discussion is also included on clinical application and exercise prescription of SLC for the maintenance and/or improvement of health.

Literature Review On Factors Influencing Milk Consumption Behaviour Among Adults

Introduction:Milk and dairy products are good sources of high-quality protein. Protein is important during weight loss and subsequent weight maintenance due to the high satiating effect which helps to prevent over-consumption of energy and thereby reduces body fat stores. Furthermore, dairy protein is a good source of essential amino acids for muscle protein synthesis and thus helps to maintain metabolically active muscle mass during weight loss. Regarding milk consumption, it is important to find the association between personal, environmental, and behaviour factors with consuming milk. Objective: The aim of the study is to identify factors influencing milk consumption behaviour among adults. Methods: This study is based on the literature review and on different case studies from different parts of the world to try to fulfill the main scope of factors influencing milk consumption. Results: Based on this review, environmental factors were found to be the main influences on milk consumption behaviour, followed by personal factors and behaviour factors. Conclusion : This review is also expected to enrich the documentation on the influencing of milk consumption behaviour among adults

Development of body composition, lower body physical characteristics and clubhead speed in skilled junior golfers.

The physical characteristics of golfers have a strong relationship with the clubhead speed (CHS), which is the main indicator of energy produced during a golf swing. However, perennial observations of development in CHS, physical characteristics, and body composition, and their long-term effects on CHS are lacking. Therefore, this study aimed to evaluate the lower body physical characteristics and body composition parameters and their relationship with clubhead speed during one and over a two-year period in junior golfers. Nineteen skilled, male, junior golfers participated in this study. A significant positive relationship (P<0.05) was found between improvement in CHS and increase in the body height (r=0.56), increase in peak power of the countermovement jump (r=0.55), and squat jump (r=0.52). A near-significant positive relationship was found between improvement in CHS and increases in the fat-free mass (r=0.42; P=0.06) and peak torque of the knee extensor at an angular velocity of 60° s-1 (r=0.44; P=0.07). Thus, we recommend that golf coaches work on muscle strengthening and conditioning with their players, focusing on: 1) the increase of the active muscle mass as opposed to the total body mass in relation to the acceleration of CHS; and 2) exercises to develop the muscle power (vertical jumping) and maximum lower limb strength (knee extension).

Long jump: the are body height and body weight good predictors of performance in elite jumpers?

Background: Long jump are cyclic-acyclic movements of maximum intensity. It is a discipline that combines speed and jump in technique, that is, the speed-strength properties of competitors. Speed, agility and explosiveness are of special importance in jumpers. The main goal of the research is to determine the influence of Body height (BH) and Body weight (BW) with the best achieved results of Long jump. Material and methods: In study included 21 top male jumpers (BH=184.19±4.68cm; BW=78.86±6.81kg). Their achieved best results were analyzed. Pearson correlation coefficient was used to determine the relationship between body height and body weight and the results of long jumpers. Univariate model of regression analysis was applied and the relevant coefficients were calculated. The level of acceptance of statistical significance was set to p&lt;0.05. Results: Simple regression analysis did not show a statistically significant effect of Body height on the results in the long jump (BH vs. Long jump R=0.183; p&gt;0.05), while Body weight confirmed a significant inverse relationship with the results of the jump (BW vs. Long jump R= - 0.442; p&lt;0.05). Conclusion: Long jumpers contain a large percentage of active muscle mass that integrates and generates motor explosive abilities for the success of long jumpers, primarily strength and speed, which is confirmed by the results of the study. However, a good jump technique is also necessary, but with optimal body weight, because any increase in weight has a negative effect on the length of the long jump.

Development of postural disorders in schoolchildren

Introduction. Pathologies of the musculoskeletal system have been occupying the leading place in morbidity among schoolchildren for a long time. Our research aim was to examine peculiarities of developing postural disorders in schoolchildren from different age groups. Materials and methods. We examined seventy two primary schoolchildren (their average age was 8.19±0.32 years); 87 middle schoolchildren (12.94±0.24 years); and 54 senior schoolchildren (16.65±0.21 years). These test groups were comparable for gender and social background. The health of the musculoskeletal system was assessed on the base on data of a medical examination and results by laboratory tests (phosphor-calcium metabolism); postural disorders were examined as per surfaces with a computer optical topographer; bone mineral density was determined by ultrasound osteodensitometry; body composition was assessed with bioimpedance analysis (BIA). Results. Pathologies of the musculoskeletal system were detected in 77-83.3% schoolchildren. Each second child in primary and middle school had deforming dorsopathy and each second senior school student had scoliosis. We established a probability of developing scoliosis to be by 5.9 times higher in senior school. Children in primary school predominantly had twisting postural disorders (28.4%) and swayback (11.1%) accompanied with the lower phase angle, a lower share of active muscle mass detected with BIA and osteopenia developing in ¼ cases. 16.1-26.1% of middle schoolchildren had twisting postural disorders and kyphosis, 57.9% children in this age group had lower contents of ionized calcium in blood, 28% had osteopenia and a decrease in fat-free mass detected with BIA. Scoliosis in senior schoolchildren (51.9%) and kyphotic-lordotic back (24.1%) were accompanied with lower contents of phosphor and alkaline phosphatase, developing apparent osteopenia (18.4%) and lower mineral mass. We established the probability of postural disorders developing in three surfaces to be 3.3 times higher among teenagers in senior school. Limitations. The results of the studies can only be extrapolated to the population of 7-17 years children of both genders. Conclusion. We revealed certain peculiarities of developing postural disorders in schoolchildren. They can be used in implementing health-preserving technologies in schools as well as in developing new hygienic and organizational approaches to the conditions of the educational process in schools.

Muscle Quality of Knee Extensors Based on Several Types of Force in Multiple Sclerosis Patients with Varying Degrees of Disability.

Background and Objectives: Multiple sclerosis (MS) tends to affect muscle performance, mainly in the lower extremities. The degree of disability is associated with the loss of strength and muscle mass, to varying extents. Muscle quality (MQ) expresses the amount of force produced relative to the activated muscle mass. The purpose of this study was to compare the MQ of the knee extensors in the main manifestations of strength (isometric, dynamic strength, and power) among patients with differing degrees of neurological disability and evolutionary forms of the disease. We also establish reference values for MQ in MS patients (pwMS). Materials and Methods: In total, 250 pwMS were evaluated according to the Expanded Disability Status Scale (EDSS). The maximum dynamic and isometric forces and muscle power manifested a load of 60% of the maximum dynamics of the knee extensors. The lean mass of the thigh and hip was determined by densitometry, and the MQ was calculated for the three types of force evaluated. Results: The pwMS with relapsing remitting MS (RRMS) presented isometric MQ values that were 15.8% better than those of pwMS with primary progressive MS (PPMS) and 13.8% better than those of pwMS with secondary progressive MS (SPMS). For pwMS with SPMS, the dynamic MQ was 16.7% worse than that of patients with RRMS, while the power MQ was 29.5% worse. By degree of disability (<4 >7.5 EDSS score), patients with better MQ had mild EDSS scores, and patients with severe EDSS scores had 24.8%, 25.9%, and 40.3% worse isometric, dynamic, and power MQ scores, respectively, than those with RRMS. Based on these results, reference values for MQ in pwMS were established. Conclusions: The pwMS with different types of MS do not show differences in lean mass or strength but do show differences in MQ. In pwMS with different EDSS grades, there are no differences in lean mass, but there are differences in strength based on MQ, especially power MQ.

Anaerobic Contributions Are Influenced by Active Muscle Mass and The Applied Methodology in Well-Controlled Muscle Group

Anaerobic Contributions Are Influenced by Active Muscle Mass and The Applied Methodology in Well-Controlled Muscle Group

Nutritional Considerations for Para-Cycling Athletes: A Narrative Review.

Para-cycling is a sport including athletes with different disabilities competing on the track and on the roads using bicycles, tandems, tricycles, and handbikes. Scientific literature in this special population is scarce, especially in the field of sports nutrition. This review summarizes the physiological aspects and demands of para-cycling. This information together with the existing literature on nutritional interventions in this population, helps to discuss the nutritional considerations. To date, only a limited amount of recommendations are available for this population. In most para-cycling athletes, a reduction in active muscle mass and consequently a reduction in resting energy expenditure occurs, except for visually impaired athletes. Furthermore, carbohydrate and protein intake and hydration, supplementation, heat, and weight loss need to be tailored to the disability-specific adaptations such as the reduced active muscle mass, neurogenic bladder, and bowel, a reduced metabolic cost during exercise, and a higher risk of micronutrient deficiency.

Зміни центральної гемодинаміки у період раннього відновлення після різних режимів фізичного навантаження

We studied the changes in central hemodynamics in the early recovery period after physical load in 28 young men. Dynamic loading was induced using a modified Martine functional test, static loading - by maintaining on the standing dynamometer DS-200 muscle effort in the amount of 50% of maximum standing force. The change in central hemodynamic para- meters was recorded by tetrapolar thoracic impedance rheo- plethysmogram using a computerized diagnostic complex «Cardio +». Dynamic exercise during early recovery did not lead to a significant increase in heart rate, however, it caused a decrease in the resistance of resistive blood vessels and an increase in pulse blood pressure. The increase in minute blood volume in our study is mainly due to an increase in stroke volume, pointing for high functional reserves of the heart. In the case of static physical activity, the adaptive reactions of central hemodynamics and the course of the processes of early recovery of the circulatory system are radically different from similar indicators during dynamic physical activity. In subjects with a normodynamic type of response of the cardiovascular system to dynamic load, no significant changes in the minute volume of blood flow were registered at a similar volume of active muscle mass static load. In subjects with a normodynamic type of cardiovascular response to dynamic load, no significant changes in cardiac output were observed at a similar static load in terms of active muscle mass. However, during early recovery period, the total peripheral vascular resistance and systolic arterial pressure were increased. The increase in total peripheral resistance may be due to reactive hyperemia in ischemic skeletal muscle caused by increased blood flow to the capillaries after muscle relaxation and delayed outflow into the veins. The significant increase in systolic blood pressure can be explained by the mechanical obstruction of blood flow in the muscle capillaries during prolonged static contraction.

Comparative characteristics of changes in central hemodynamics during early recovery after different exercise regimes

The cardiovascular system is one of the most important functional systems of the body, which determine the level of physical performance of the body. Insufficient study of the response of the circulatory system to the combination of strength training with endurance exercises requires more detailed comparative studies of the impact of dynamic and static loads on the indicators of central hemodynamics. Accordingly, the aim of our study was to study the characteristics of the reaction of the cardiovascular system in the period of early recovery after dosed exercise of a dynamic and static nature. The study examined the response of the central hemodynamics of young men in the period of early recovery after dynamic loading (Martine functional test) and static loading (holding on the stand dynamometer DS-200 force with a power of 50% of maximum standing force). The change in circulatory system parameters was recorded using a tetrapolar thoracic impedance rheoplethysmogram on a computerized diagnostic complex “Cardio +”. It is established that the dynamic load in the period of early recovery does not cause a significant positive chronotropic effect, leads to a decrease in vascular resistance of blood flow, to an increase in pulse blood pressure. The increase in cardiac output is mainly due to the increase in stroke volume, which indicates a fairly high functional reserves of the heart. It is revealed that under conditions of static loading the reaction of central hemodynamics and the course of early recovery are radically different from the changes of indicators under dynamic loading. In persons with a normodynamic type of reaction to dynamic load, there are no significant changes in the minute volume of blood at a similar volume of active muscle mass static load. Meeting the metabolic needs of working skeletal muscles and compensating for the oxygen debt is realized by increasing the total peripheral vascular resistance and increasing systolic blood pressure in the postpartum period. The physiological meaning of this phenomenon is to maintain a sufficient level of venous return of blood to ensure the pumping function of the heart.

Protein Considerations for Athletes With a Spinal Cord Injury.

Athlete participation in the Paralympic games is steadily increasing; prompting research focused on the unique needs of this population. While the Paralympic Games includes a diversity of athletes, athletes with a spinal cord injury (PARA-SCI) represent a subgroup that requires specialized recommendations. Nutritional guidelines designed to optimize performance, in the context of the neurological impairments, are required. This narrative review summarizes the current literature regarding the importance of dietary protein for optimal health and performance. Factors with the potential to affect protein needs in PARA-SCI including loss of active muscle mass, reduced energy expenditure, and secondary complications are examined in detail. Furthermore, we analyze protein intakes in PARA-SCI from the available research to provide context around current practices and trends. In conclusion, we make the case that protein recommendations for able-bodied athletes may not be directly transferable to PARA-SCI. Consequently, PARA-SCI need their own guidelines to maximize performance and ensure long-term health.

Allometric Scaling of Force-velocity Test Output Among Pre-pubertal Basketball Players.

Basketball is characterized by high-intensity episodes predominantly reliant on anaerobic metabolism. The force-velocity test enables individual determination of an optimal braking force and emerged as appropriate to estimate optimal peak power. It has rarely been used in youth basketball. This study aimed to examine the contribution of body size, composition, and biological maturation to interindividual variation in force-velocity test output among pre-pubertal basketball players. The sample consisted of 64 male participants (8.4-12.3 years). Stature, sitting height, body mass and two skinfolds were measured, and leg length estimated. Fat-free mass and lower limb volume were estimated from anthropometry. Age at peak height velocity was predicted from maturity offset. Optimal peak power was correlated with all body size descriptors (correlation: 0.541-0.700). Simple allometric models explained 30-47% of inter-individual variance, with fat-free mass being the best predictor of performance. Whole-body fat-free mass (as a surrogate for active muscle mass) plus the indicator of maturation emerged as the best proportional allometric model (53% explained variance). Even at pre-pubertal ages, the interpretation of the force-velocity test requires assessing the metabolically active component of body mass.

Body Composition Matters When Designing and Prescribing HIIT Protocols to Individuals for Health Promotion

Many experimental studies use the quantification of aerobic and anaerobic ability as performance indicators and as injury rehabilitative measures. The measurement of aerobic performance can be quantified by the volume of oxygen consumed while exercising sub-maximally or at maximum capacity or intensity. Recently, high intensity interval training (HIIT) has emerged as a sustainable and effective method for improving cardiorespiratory fitness (CRF). HIIT has been proven to produce equal or greater improvements in cardio respiratory fitness (CRF) when compared to moderate intensity continuous exercise. HIIT has been described as an intermittent exercise period of short intense training bouts interspersed by different recovery periods. Whether using continuous aerobic or intermittent anaerobic training protocols to develop increased exercise capacity, the quantification of the active muscle mass contributing to the measurement outcome is important. Here we suggest that outcome measures should be based on lean tissue mass and not total body composition when examining individual responses to aerobic and anaerobic training protocols.

Local knee heating increases spinal and supraspinal excitability and enhances plantar flexion and dorsiflexion torque production of the ankle in older adults.

Aging is associated with progressive loss of active muscle mass and consequent decreases in resting metabolic rate and body temperature, and slowing of nerve conduction velocities and muscle contractility. These effectors compromise the ability of the elderly to maintain an upright posture during sudden balance perturbation, increase the risk of falls, and lead to self-imposed reduction in physical activity. Short-term superficial acute heating can modulate the neural drive transmission to exercising muscles without any marked change in deep-muscle temperature. To determine whether the short-term (5min) application of local passive knee-surface heating (next-to-skin temperature, ~ 44°C) in healthy older subjects of both sexes (64-74years; eight men/eight women) enhances reflex excitability, we compared the voluntarily and electrically induced ankle muscle torque production and contractile properties with those of healthy younger subjects of both sexes (21-35years, 10 men/10 women). The application of local heating (vs. control) increased the maximal Hoffman reflex (Hmax), the maximal volitional wave (Vsup) amplitude, and the Hmax/Mmax amplitude ratio, and decreased Vsup latency only in older adults. In the older adults (vs. younger adults), the application of local heating (vs. control trial) was accompanied by a significant increase in maximal voluntary peak torque, rate of torque development, and isokinetic peak torque of plantar flexion/dorsiflexion muscle contraction. The spinal and supraspinal reflex excitability of older adults increased during local knee-heating application. The improved motor drive transmission observed in older adults was accompanied by increased voluntarily induced torque production of the ankle muscles during isometric/isokinetic contractions.

Traditional and New Perspectives on Youth Cardiorespiratory Fitness.

ABSTRACTPurposeThis study aimed to review traditional and new perspectives in the interpretation of the development of youth cardiorespiratory fitness (CRF).MethodsWe analyzed data from (i) the literature which for 80 yr has been traditionally based on interpretations of peak oxygen uptake (V˙O2) in ratio with body mass (BM) and (ii) recent multilevel allometric models founded on 994 (475 from girls) determinations of 10- to 16-yr-olds’ peak V˙O2 with measures of age, maturity status, and morphological covariates (BM and fat-free mass), and from 10 to 13 yr, 110 peak V˙O2 determinations of maximum cardiovascular covariates (stroke volume, cardiac output, and arteriovenous oxygen difference).ResultsThe application of ratio scaling of physiological variables requires satisfying specific statistical assumptions that are seldom met. In direct conflict with the ratio-scaled data interpretation of CRF, multilevel allometric modeling shows that with BM controlled, peak V˙O2 increases with age but the effect is smaller in girls than boys. Maturity status exerts a positive effect on peak V˙O2, in addition to those of age and BM. Changes in maximum cardiovascular covariates contribute to explaining the development of CRF, but fat-free mass (as a surrogate for active muscle mass) is the most powerful single influence. With age, maturity status, morphological covariates, and maximum cardiovascular covariates controlled, there remains an unexplained ~4% to ~9% sex difference in peak V˙O2.ConclusionsThe traditional interpretation of peak V˙O2 in ratio with BM is fallacious and leads to spurious correlations with other health-related variables. Studies of the development of CRF require analyses of sex-specific, concurrent changes in age- and maturation-driven morphological and maximum cardiovascular covariates. Multilevel allometric modeling provides a rigorous, flexible, and sensitive method of data analysis.