Effects of Bilateral or Unilateral Plyometric Training of Lower Limbs on the Bilateral Deficit During Explosive Efforts.

OBJECTIVES: Bilateral Deficit (BLD) occurs when the force generated by both limbs together is smaller than the sum of the forces developed separately by the two limbs. BLD may be modulated by physical training. Here, were investigated the effects of unilateral or bilateral plyometric training on BLD and neuromuscular activation during lower limb explosive extensions. METHODS: Fourteen young males were randomized into the unilateral (UL_) or bilateral (BL_) training group. Plyometric training (20 sessions, 2 days/week) was performed on a sled ergometer, and consisted of UL or BL consecutive, plyometric lower limb extensions (3-to-5 sets; 8-to-10 repetitions). Before and after training, maximal explosive efforts with both lower limbs or with each limb separately were assessed. Electromyography of representative lower limb muscles was measured. RESULTS: BL_training significantly and largely decreased BLD (p=0.003, effect size=1.63). This was accompanied by the reversion from deficit to facilitation of the electromyography amplitude of knee extensors during bilateral efforts (p=0.007). Conversely, UL_training had negligible effects on BLD (p=0.781). Also, both groups showed similar improvements in their maximal explosive power generated after training. CONCLUSIONS: Bilateral plyometric training can mitigate BLD, and should be considered for training protocols focused on improving bilateral lower limb motor performance.

Effects of 24-week Polarized Training vs. Threshold Training in Obese Male Adults.

The combination of high volume of moderate-intensity continuous training with a low volume of high-intensity interval training improved body composition and physical capacities in individuals with obesity. However, polarized training (POL) has never been used in adult men with obesity. Thus, the purpose of this study was to investigate changes in body composition and physical capacities induced by a 24-week POL or threshold (THR) program in obese male adults. Twenty male patients (mean age 39.8±6.3 yrs; mean body mass index [BMI] 31.6±2.7 kg∙m-2) participated in this study (n: 10 POL, n: 10 THR). After 24-week, body mass (BM) and fat mass (FM) decreased by -3.20±3.10 kg (P<0.05) and -3.80±2.80 kg (P<0.05), respectively, similarly in both groups. Maximal oxygen uptake ( ̇VO2max) and ̇VO2 at respiratory compensation point (RCP) increased in the POL group (+8.5±12.2 and+9.0±17.0%, P<0.05) and in the THR group (+4.24±8.64 and+4.0±6.70%, P<0.05), as well ̇VO2 at gas exchange threshold (GET) increased similarly in both groups (+12.8±12.0%, P<0.05). POL and THR were equally effective in improving body composition and physical capacities in obese subjects. Future studies are needed to determine whether adherence to the training program can be improved by adding a running competition compared with a group without competition at the end of the training program.

Sarcopenia parameters in active older adults - an eight-year longitudinal study.

BACKGROUD: Sarcopenia is a common skeletal muscle syndrome that is common in older adults but can be mitigated by adequate and regular physical activity. The development and severity of sarcopenia is favored by several factors, the most influential of which are a sedentary lifestyle and physical inactivity. The aim of this observational longitudinal cohort study was to evaluate changes in sarcopenia parameters, based on the EWGSOP2 definition in a population of active older adults after eight years. It was hypothesized that selected active older adults would perform better on sarcopenia tests than the average population. METHODS: The 52 active older adults (22 men and 30 women, mean age: 68.4 ± 5.6 years at the time of their first evaluation) participated in the study at two time points eight-years apart. Three sarcopenia parameters were assessed at both time points: Muscle strength (handgrip test), skeletal muscle mass index, and physical performance (gait speed), these parameters were used to diagnose sarcop0enia according to the EWGSOP2 definition. Additional motor tests were also performed at follow-up measurements to assess participants' overall fitness. Participants self-reported physical activity and sedentary behavior using General Physical Activity Questionnaire at baseline and at follow-up measurements. RESULTS: In the first measurements we did not detect signs of sarcopenia in any individual, but after 8 years, we detected signs of sarcopenia in 7 participants. After eight years, we detected decline in ; muscle strength (-10.2%; p < .001), muscle mass index (-5.4%; p < .001), and physical performance measured with gait speed (-28.6%; p < .001). Similarly, self-reported physical activity and sedentary behavior declined, too (-25.0%; p = .030 and - 48.5%; p < .001, respectively). CONCLUSIONS: Despite expected lower scores on tests of sarcopenia parameters due to age-related decline, participants performed better on motor tests than reported in similar studies. Nevertheless, the prevalence of sarcopenia was consistent with most of the published literature. TRIAL REGISTRATION: The clinical trial protocol was registered on ClinicalTrials.gov, identifier: NCT04899531.

High-intensity interval training: optimizing oxygen consumption and time to exhaustion taking advantage of the exponential reconstitution behaviour of D'.

PURPOSE: Accumulating the time near maximum aerobic power [Formula: see text] is considered to be the most effective way to improve aerobic capacity. The aims of this study were: (1) to verify whether postponing the first recovery interval improves time to exhaustion during a high-intensity interval training (HIIT) test, and (2) to verify whether a HIIT protocol with decreasing interval duration (HIDIT) is more effective in accumulating time near [Formula: see text] compared with two classical protocols with short intervals (SIHIIT) and long intervals (LIHIIT). METHODS: Nine active males (35 ± 11 years, [Formula: see text] 52 ± 5 mL·min-1·kg-1) performed a graded exercise test on an athletic track. Critical velocity and D' were estimated from three to five high-intensity trials to exhaustion. Then, the subjects performed three trials with a single recovery interval after 30 s (Rec30s), after 3 min (Rec3min) and after exhaustion (RecTlim) to verify whether postponing the first recovery interval enhances the time to exhaustion. Finally, the subjects performed the three HIIT protocols mentioned above. RESULTS: The time to exhaustion was significantly greater in RecTlim (464 ± 67 s) than in Rec3min (388 ± 48 s) (p < 0.0078) and Rec30s (308 ± 44 s) (p > 0.0001). Additionally, it was significantly greater in Rec3min than in Rec30s (p = 0.0247). Furthermore, the time accumulated near [Formula: see text] was significantly longer in HIDIT (998 ± 129 s) than in SIHIIT (678 ± 116 s) (p = 0.003) and LIHIIT (673 ± 115 s) (p < 0.031). CONCLUSIONS: During the trials, postponing the first recovery interval was effective in improving the time to exhaustion. Moreover, HIDIT was effective in prolonging the time near [Formula: see text].

Do poles really "save the legs" during uphill pole walking at different intensities?

PURPOSE: In sky- and trail-running competitions, many athletes use poles. The aims of this study were to investigate whether the use of poles affects the force exerted on the ground at the feet (Ffoot), cardiorespiratory variables and maximal performance during uphill walking. METHODS: Fifteen male trail runners completed four testing sessions on different days. On the first two days, they performed two incremental uphill treadmill walking tests to exhaustion with (PWincr) and without poles (Wincr). On the following days, they performed submaximal and maximal tests with (PW80 and PWmax) and without (W80 and Wmax) poles on an outdoor trail course. We measured cardiorespiratory parameters, the rating of perceived exertion, the axial poling force and Ffoot. RESULTS: When walking on the treadmill, we found that poles reduced maximum Ffoot (- 2.8 ± 6.4%, p = 0.03) and average Ffoot (- 2.4 ± 3.3%, p = 0.0089). However, when outdoors, we found pole effect only for average Ffoot (p = 0.0051), which was lower when walking with poles (- 2.6 ± 3.9%, p = 0.0306 during submaximal trial and - 5.21 ± 5.51%, p = 0.0096 during maximal trial). We found no effects of poles on cardiorespiratory parameters across all tested conditions. Performance was faster in PWmax than in Wmax (+ 2.5 ± 3.4%, p = 0.025). CONCLUSION: The use of poles reduces the foot force both on the treadmill and outdoors at submaximal and maximal intensities. It is, therefore, reasonable to conclude that the use of poles "saves the legs" during uphill without affecting the metabolic cost.

Effects of 12-week combined training versus high intensity interval training on cardiorespiratory fitness, body composition and fat metabolism in obese male adults.

Background: /Objectives: A weekly combination of a high volume of moderate-intensity continuous training (MICT) with a low volume of high-intensity interval training (HIIT) provides important improvements in body composition and physical capacities in individuals with obesity. However, previous studies did not determine the weekly proportions of HIIT and MICT a priori. This study aimed to investigate changes in body composition, physical capacities and the fat oxidation rate in obese male adults by comparing a combination of MICT and HIIT, called combined training (COMB), with HIIT for a 12-week period. Methods: Thirty-four obese male adults (mean age: 39.4 ± 7.0 y; mean body mass index [BMI] 34.0 ± 4.2 kg m-2) participated in this study (n = 18 for COMB, n = 16 HIIT), attending âˆ¼ 36 training sessions. The COMB group performed 3 repetitions of 2 min at 95% of peak oxygen uptake (V'O2 peak) (e.g., HIIT ≤20%), followed by 30 min at 60% of VO2 peak (e.g., MICT ≥80%). The HIIT group performed 5-7 repetitions of 2 min at 95% of VO2 peak. At baseline (PRE) and at the end of the training period (POST), body composition, VO2 peak, and the fat oxidation rate were measured. The two training programs were equivalent in caloric expenditure. Results: At POST, body mass (BM) and fat mass (FM) decreased by a mean of 3.09 ± 3.21 kg and 3.90 ± 2.40 kg, respectively (P < 0.05), in both groups and V'O2 peak increased in both groups by a mean of 0.47 ± 0.34 L min-1 (P < 0.05). The maximal fat oxidation rate increased similarly in both groups from 0.32 ± 0.05 to 0.36 ± 0.06 g min-1 (P < 0.05). Conclusion: COMB training represents a viable alternative to HIIT to improve anthropometric characteristics, physical capacities and fat oxidation in obese male adults.

Association of protein-energy partitioning with body weight and body composition changes in adolescents with severe obesity.

BACKGROUND/OBJECTIVES: Body composition and protein-energy partitioning changes are important factors of body weight regulation, but have not been studied in the context of clinical obesity treatment setting. Thus, the aim of the present study was to investigate the pattern of body weight loss, body composition, and energy partitioning changes during a 9-month multidisciplinary weight loss program and 4-month follow up and to test the associations among these changes in adolescents with severe obesity. SUBJECTS/METHODS: Twenty-five adolescents (14.1 ± 1.5 years old; 13 girls) with severe obesity joined a pediatric obesity center for a 9-month inpatient multidisciplinary weight loss program. All participants performed body composition assessment (i.e. fat mass-FM, and fat-free mass-FFM) and completed a 36-h session in indirect calorimetric chamber before the start (T0), at the end of the intervention (T1) and 4 months follow-up to the intervention (T2). The protein-energy partitioning (P ratio) was calculated as urinary nitrogen loss/total energy expenditure over 24 hours. INTERVENTIONS: 9-month individualized multidisciplinary weight loss program consisting of lifestyle education, psychological support, physical activity, and dietary intervention. RESULTS: Initial P ratio was positively associated with changes in body weight from T0 to T1 (p = 0.038). The changes in FFM/FM were negatively associated with body weight changes in boys (p = 0.006) from T0 to T1 and in girls (p < 0.001) from T1 to T2. Urinary nitrogen excretion (p < 0.001) and total energy expenditure (p < 0.001) significantly decreased during the weight loss program while the P ratio did not significantly change. CONCLUSION: The present results suggest that baseline and changes in energy partitioning may be associated with changes in body weight in adolescents with severe obesity. In addition, sexual dimorphism in these patterns of change suggest the need for specific dietary and physical activity strategies in boys and girls to optimize body weight loss and to prevent or slow weight regain.

Effects of NMES-elicited versus voluntary low-level conditioning contractions on explosive knee extensions.

OBJECTIVES: Electrically-induced or voluntary conditioning-contractions (CC) can be used to affect contractile properties of a subsequent explosive contraction (EC). Here, we aimed at comparing the effect of neuromuscular-electrical-stimulation (NMES) vs voluntary CC performed prior to explosive contractions of the knee extensors. METHODS: A 10 sec NMES CC (100Hz, 1000µs, 10% MVC), or a voluntary contraction (VOL CC) mimicking the NMES CC, preceded an isometric EC of the knee extensors. Explosive contraction was performed with the goal to reach the target (70% MVC) as quickly as possible. RESULTS: All the parameters related with the explosive contractions' muscle-output were similar between protocols (difference ranging from 0.23%, Mean Torque; to 5.8%, Time to Target), except for the Time to Peak Torque, which was lower when preceded by NMES (11.1%, p=0.019). Interestingly, the RTD 0-50 ms_EC was 37.3% higher after the NMES compared with the VOL CC protocol. CONCLUSION: Explosive contraction was potentiated by an NMES CC as compared with a voluntary CC. This may be due to a reduction in descending drive following VOL CC, which has been shown to occur even with low-level voluntary efforts. These findings could be used to improve rehabilitation or training protocols that include conditioning contractions.

Physical fitness reference standards in Italian children.

Physical fitness in childhood is considered a marker of current and future health. For this reason, there is a need for a simple but reliable test to assess the different components of physical fitness even at school during physical education lessons. However, standard values are required to correctly interpret the results of such tests. Hence, this study aimed to generate sex- and age-specific normative percentile values for health-related physical fitness in Italian children. To this aim, 30,472 children aged 6-11 years from the Friuli Venezia-Giulia region (Italy) were examined. The fitness test battery included the Léger test (cardiorespiratory), the shuttle test (agility), standing long jumps, frontal throws of a basketball (lower and upper limb strength), the sit-and-reach test (flexibility), and the standing balance test. Sex- and age-percentile curves were determined using the General Additive Model for Location Scale and Shape (GAMLSS).Conclusion: The reference standards are provided as 1st, 3rd, 10th, 25th, 50th, 75th, 90th, 97th, and 99th percentiles in the form of both tables and charts and are roughly comparable with those of other European children. What is Known: • Physical fitness in childhood is considered a marker of current and future health; • Several tests have been developed to assess physical fitness in children; • There are general European reference standards for a series of tests of the main fitness components for children. What is New: • The present study provides specific reference standards for a series of tests that are indicative of the main fitness components and easily applied in children, particularly those in the Italian population; • Standing balance test and basketball frontal throw test references in a wide sample of children; • The performance of children in the present study was roughly comparable to that of other European children.

Effects of NMES pulse width and intensity on muscle mechanical output and oxygen extraction in able-bodied and paraplegic individuals.

PURPOSE: Neuromuscular Electrical Stimulation (NMES) is commonly used in neuromuscular rehabilitation protocols, and its parameters selection substantially affects the characteristics of muscle activation. Here, we investigated the effects of short pulse width (200 µs) and higher intensity (short-high) NMES or long pulse width (1000 µs) and lower intensity (long-low) NMES on muscle mechanical output and fractional oxygen extraction. Muscle contractions were elicited with 100 Hz stimulation frequency, and the initial torque output was matched by adjusting stimulation intensity. METHODS: Fourteen able-bodied and six spinal cord-injured (SCI) individuals participated in the study. The NMES protocol (75 isometric contractions, 1-s on-3-s off) targeting the knee extensors was performed with long-low or short-high NMES applied over the midline between anterior superior iliac spine and patella protrusion in two different days. Muscle work was estimated by torque-time integral, contractile properties by rate of torque development and half-relaxation time, and vastus lateralis fractional oxygen extraction was assessed by Near-Infrared Spectroscopy (NIRS). RESULTS: Torque-time integral elicited by the two NMES paradigms was similar throughout the stimulation protocol, with differences ranging between 1.4% (p = 0.877; able-bodied, mid-part of the protocol) and 9.9% (p = 0.147; SCI, mid-part of the protocol). Contractile properties were also comparable in the two NMES paradigms. However, long-low NMES resulted in higher fractional oxygen extraction in able-bodied (+ 36%; p = 0.006). CONCLUSION: Long-low and short-high NMES recruited quadriceps femoris motor units that demonstrated similar contractile and fatigability properties. However, long-low NMES conceivably resulted in the preferential recruitment of vastus lateralis muscle fibers as detected by NIRS.

Effects of 3-month high-intensity interval training vs. moderate endurance training and 4-month follow-up on fat metabolism, cardiorespiratory function and mitochondrial respiration in obese adults.

PURPOSE: The purpose of this study was to investigate, in obese adults, changes in body composition, physical capacities, fat oxidation and ex vivo mitochondrial respiration induced by a 3-month either moderate-intensity continuous training (MICT) or high-intensity interval training (HIIT); afterwards, the patients were followed for four months. METHODS: Thirty-two patients (mean age 39 years; mean body mass index [BMI] 36 kg∙m-2) participated in this study attending ~ 34 sessions of training. At baseline (PRE), at the end of the program (POST) and after follow-up, body composition, peak O2 uptake (V'O2peak) and fat oxidation rate were measured. Vastus lateralis biopsies for the evaluation of mitochondrial respiration were performed only at PRE and POST. RESULTS: At POST, body mass (BM) and fat mass (FM) decreased (- 6 and - 14%, respectively, P < 0.05) in MICT and HIIT; V'O2peak increased in both groups (+ 6 and + 16%, respectively, P < 0.05). Maximal fat oxidation rate increased only after HIIT (P < 0.001). Maximal ADP-stimulated mitochondrial respiration normalized by citrate synthase increased (P < 0.05) by 67% and 36% in MICT and HIIT, respectively, without significant difference. After follow-up, BM and FM were still lower (- 4 and - 20%, respectively, P < 0.050) compared with baseline in both groups. Only after HIIT, V'O2peak (+ 8%) and maximal fat oxidation rate were still higher (P < 0.05). CONCLUSIONS: HIIT was more effective in improving and maintaining V'O2peak and fat oxidation. These results may be relevant for an appropriate prescription of training programs designed to optimize aerobic fitness in obese subjects.

Do poles save energy during steep uphill walking?

PURPOSE: In trail running and in uphill races many athletes use poles. However, there are few data about pole walking on steep uphill. The aim of this study was to compare the energy expenditure during uphill walking with (PW) and without (W) poles at different slopes. METHODS: Fourteen mountain running athletes walked on a treadmill in two conditions (PW and W) for 5 min at seven different angles (10.1°, 15.5°, 19.8°, 25.4°, 29.8°, 35.5° and 38.9°). We measured cardiorespiratory parameters, blood lactate concentration (BLa) and rating of perceived exertion (RPE). Then, we calculated the vertical cost of transport (CoTvert). Using video analysis, we measured stride frequency (SF) and stride length (SL). RESULTS: Compared to W, CoTvert during PW was lower at 25.4°, 29.8° and 35.5° PW ([Formula: see text] 2.55 ± 3.97%; [Formula: see text] 2.79 ± 3.88% and [Formula: see text] 2.00 ± 3.41%, p < 0.05). RPE was significantly lower during PW at 15.5°, 19.8°, 29.8°, 35.5° and 38.9° ([Formula: see text] 14.4 ± 18.3%; [Formula: see text] 16.2 ± 15.2%; [Formula: see text] 16.6 ± 16.9%; [Formula: see text] 17.9 ± 18.7% and [Formula: see text] 18.5 ± 17.8%, p < 0.01). There was no effect of pole use on BLa. However, BLa was numerically lower with poles at every incline except for 10.1°. On average, SF for PW was lower than for W ([Formula: see text] 6.7 ± 5.8%, p = 0.006) and SL was longer in PW than in W (+ 8.6 ± 4.5%, p = 0.008). CONCLUSIONS: PW on steep inclines was only slightly more economical than W, but the substantially lower RPE during PW suggests that poles may delay fatigue effects during a prolonged effort. We advocate for the use of poles during steep uphill walking, although the energetic savings are small.

Metabolic and muscular factors limiting aerobic exercise in obese subjects.

PURPOSE: The aim of the present study was to understand the role of central (cardiovascular O2 delivery) and peripheral factors (muscle level) in limiting the maximal aerobic performance in obese (OB) subjects. METHODS: Fifteen OB (mean age ± SD 25 ± 7 years; BMI 43 ± 7 kg/m2) and 13 lean sedentary subjects (CTRL, age 27 ± 7 years; BMI 22 ± 3 kg/m2) participated in this study. Oxygen uptake (VO2), hearth rate (HR) and cardiac output (CO) were measured during cycle ergometer (CE) and knee extension (KE) incremental tests. Maximal voluntary contractions (MVCs) of knee extensor muscles were performed before and immediately after the two tests. RESULTS: VO2peak, HR peak and CO peak were significantly higher in CE than KE (+ 126%, + 33% and + 46%, respectively, p < 0.001), both in OB and CTRL subjects, without differences between the two subgroups. Maximal work rate was lower in OB than CTRL (191 ± 38 vs 226 ± 39 W, p < 0.05) in CE, while it was similar between the two subgroups in KE. Although CE and KE determined a reduction of MVC in both subgroups, MVC resulted less decreased after CE than KE exercises (- 14 vs - 32%, p < 0.001) in OB, while MVC decrements were similar after the two exercises in CTRL (- 26% vs - 30%, p > 0.05, for CE and KE, respectively). CONCLUSIONS: The lower muscle fatigue observed in OB after CE compared to KE test suggests that central factors could be the most important limiting factor during cycling in OB.

PlanHab* : hypoxia does not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone.

KEY POINTS: Superposition of hypoxia on 21 day bed rest did not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone. A significant impairment of maximal oxidative performance was identified downstream of cardiovascular O2 delivery, involving both the intramuscular matching between O2 supply and utilization and mitochondrial respiration. These chronic adaptations appear to be relevant in terms of exposure to spaceflights and reduced gravity habitats (Moon or Mars), as characterized by low gravity and hypoxia, in patients with chronic diseases characterized by hypomobility/immobility and hypoxia, as well as in ageing. ABSTRACT: Skeletal muscle oxidative function was evaluated in 11 healthy males (mean ± SD age 27 ± 5 years) prior to (baseline data collection, BDC) and following a 21 day horizontal bed rest (BR), carried out in normoxia ( PIO2  = 133 mmHg; N-BR) and hypoxia ( PIO2  = 90 mmHg; H-BR). H-BR was aimed at simulating reduced gravity habitats. The effects of a 21 day hypoxic ambulatory confinement ( PIO2  = 90 mmHg; H-AMB) were also assessed. Pulmonary O2 uptake ( V̇O2 ), vastus lateralis fractional O2 extraction (changes in deoxygenated haemoglobin + myoglobin concentration, Δ[deoxy(Hb + Mb)]; near-infrared spectroscopy) and femoral artery blood flow (ultrasound Doppler) were evaluated during incremental one-leg knee-extension exercise (reduced constraints to cardiovascular O2 delivery) carried out to voluntary exhaustion in a normoxic environment. Mitochondrial respiration was evaluated ex vivo by high-resolution respirometry in permeabilized vastus lateralis fibres. V̇O2peak decreased (P < 0.05) after N-BR (0.98 ± 0.13 L min-1 ) and H-BR (0.96 ± 0.17 L min-1 ) vs. BDC (1.05 ± 0.14 L min-1 ). In the presence of a decreased (by ∼6-8%) thigh muscle volume, V̇O2peak normalized per unit of muscle mass was not affected by both interventions. Δ[deoxy(Hb + Mb)]peak decreased (P < 0.05) after N-BR (65 ± 13% of limb ischaemia) and H-BR (62 ± 12%) vs. BDC (73 ± 13%). H-AMB did not alter V̇O2peak or Δ[deoxy(Hb + Mb)]peak . An overshoot of Δ[deoxy(Hb + Mb)] was evident during the first minute of unloaded exercise after N-BR and H-BR. Arterial blood flow to the lower limb during both unloaded and peak knee extension was not affected by any intervention. Maximal ADP-stimulated mitochondrial respiration decreased (P < 0.05) after all interventions vs. control. In 21 day N-BR, a significant impairment of oxidative metabolism occurred downstream of cardiovascular O2 delivery, affecting both mitochondrial respiration and presumably the intramuscular matching between O2 supply and utilization. Superposition of H on BR did not worsen the impairment induced by BR alone.

Loss of maximal explosive power of lower limbs after 2 weeks of disuse and incomplete recovery after retraining in older adults.

KEY POINTS: Disuse in older adults can critically decrease lower limb muscle power, leading to compromised mobility and overall quality of life. We studied how muscle power and its determinants (muscle mass, single muscle fibre properties and motor control) adapted to 2 weeks of disuse and subsequent 2 weeks of physical training in young and older people. Disuse decreased lower limb muscle power in both groups; however, different adaptations in single muscle fibre properties and co-contraction of leg muscles were observed between young and older individuals. Six physical training sessions performed after disuse promoted the recovery of muscle mass and power. However, they were not sufficient to restore muscle power to pre-disuse values in older individuals, suggesting that further countermeasures are required to counteract the disuse-induced loss of muscle power in older adults. ABSTRACT: Disuse-induced loss of muscle power can be detrimental in older individuals, seriously impairing functional capacity. In this study, we examined the changes in maximal explosive power (MEP) of lower limbs induced by a 14-day disuse (bed-rest, BR) and a subsequent 14-day retraining, to assess whether the impact of disuse was greater in older than in young men, and to analyse the causes of such adaptations. Sixteen older adults (Old: 55-65 years) and seven Young (18-30 years) individuals participated in this study. In a subgroup of eight Old subjects, countermeasures based on cognitive training and protein supplementation were applied. MEP was measured with an explosive ergometer, muscle mass was determined by magnetic resonance, motor control was studied by EMG, and single muscle fibres were analysed in vastus lateralis biopsy samples. MEP was ∼33% lower in Old than in Young individuals, and remained significantly lower (-19%) when normalized by muscle volume. BR significantly affected MEP in Old (-15%) but not in Young. Retraining tended to increase MEP; however, this intervention was not sufficient to restore pre-BR values in Old. Ankle co-contraction increased after BR in Old only, and remained elevated after retraining (+30%). Significant atrophy occurred in slow fibres in Old, and in fast fibres in Young. After retraining, the recovery of muscle fibre thickness was partial. The proposed countermeasures were not sufficient to affect muscle mass and power. The greater impact of disuse and smaller retraining-induced recovery observed in Old highlight the importance of designing suitable rehabilitation protocols for older individuals.

Changes in cardiac and muscle biomarkers following an uphill-only marathon.

The aim of the study was to evaluate changes in cardiac troponin I levels (cTnI) and the main biomarkers of skeletal muscle damage after an uphill-only marathon, along with its relationship with athletes' physiological parameters. Twenty-two runners participated in the "Supermaratona dell'Etna" (43 km, 0-2850 m AMSL). Before and immediately after the race, body mass and hydration status were measured together with blood sampling. At the end of the race, mean cTnI increased significantly in all athletes (mean +900%), and in 52% of them the cTnI values were over the normal range. Mean creatinine and cortisol increased significantly (by 30.5% and 291.4%), while C-reactive protein levels did not change significantly. Then, an uphill-only marathon showed a significant increase in cardiac and skeletal muscle blood biomarkers of injury, and cTnI levels were not significantly correlated with age, body mass index, V̇O2max, training status, ultra-endurance training experience, race time and blood parameters.

Maximal explosive power of the lower limbs before and after 35 days of bed rest under different diet energy intake.

PURPOSE: Microgravity leads to a decline of muscle power especially in the postural muscles of the lower limb. Muscle atrophy primarily contributes to this negative adaptation. Nutritional countermeasures during unloading were shown to possibly mitigate the loss of muscle mass and strength. The aim of this study was to investigate the effects of different diet energy intakes during prolonged inactivity on body composition and lower limbs power output. METHODS: The effects of lower or higher diet energy intake on the decline of maximal explosive power of the lower limbs, as determined on a sledge ergometer before and after 35 days of bed rest, were investigated on two matched groups of young healthy volunteers. Body composition and lean volume of the lower limb were also measured. RESULTS: After bed rest, fat mass increased (+20.5 %) in the higher energy intake group (N = 9), while it decreased (-4.8 %) in the lower energy intake group (N = 10). Also, the loss of body fat-free mass and lean volume of the lower limb was significantly greater in the higher (-4.6 and -10.8 %, respectively) as compared to the lower (-2.4 and -3.7 %, respectively) diet energy intake group. However, the loss of maximal explosive power was similar between the two groups (-25.2 and -29.5 % in the higher and lower energy intake group, respectively; P = 0.440). CONCLUSIONS: The mitigation of loss of muscle mass by means of a moderate caloric diet restriction during prolonged inactivity was not sufficient for reducing the loss of maximal explosive power of the lower limbs.

A 35-day bed rest does not alter the bilateral deficit of the lower limbs during explosive efforts.

PURPOSE: Bilateral deficit (BLD) occurs when the force (or power) generated by both limbs together is smaller than the sum of the forces (or powers) developed separately by the two limbs. The amount of BLD can be altered by neural adaptations brought about by the repetitive execution of specific motor tasks (training). Prolonged disuse also leads to relevant neural adaptations; however, its effects on BLD are still unknown. Thus, the aim of this study was to investigate the effects of a 35-day bed rest on the BLD of the lower limbs. METHODS: Ten young healthy volunteers performed maximal explosive efforts on a sledge ergometer with both lower limbs or with the right and the left limb separately. Electromyography (EMG) of vastus lateralis, rectus femoris, biceps femoris and gastrocnemius medialis was also measured. RESULTS: Before bed rest, maximal explosive power and peak force were significantly higher in monolateral than bilateral efforts (+18.7 and +31.0 %, respectively). Conversely, peak velocity was 11.9 % greater in bilateral than monolateral efforts. BLD attained a value of 18.1 % and was accompanied by lower EMG amplitude of knee extensors (-17.0 %) and gastrocnemius medialis (-11.7 %) during bilateral efforts. Bed rest led to a ~28.0 % loss in both bilateral and monolateral maximal explosive power. Neither BLD magnitude nor the difference in EMG amplitudes as well as in peak force and velocity between bilateral and monolateral efforts were affected by bed rest. CONCLUSIONS: These results suggest that the neuromuscular factors underlying BLD are unaltered after prolonged disuse.

Factors affecting metabolic cost of transport during a multi-stage running race.

The aim of this study was to investigate: (1) the role of , the fraction of (F) and the metabolic cost of transport (CoT) in determining performance during an ultra-endurance competition and (2) the effects of the race on several biomechanical and morphological parameters of the lower limbs that are likely to affect CoT. Eleven runners (aged 29-54 years) participated in an ultra-endurance competition consisting of three running stages of 25, 55 and 13 km on three consecutive days. Anthropometric characteristics, body composition, morphological properties of the gastrocnemius medialis, maximal explosive power of the lower limb and were determined before the competition. In addition, biomechanics of running and CoT were determined, before and immediately after each running stage. Performance was directly proportional to (r=0.77) and F (r=0.36), and inversely proportional to CoT (r=-0.30). Low CoT values were significantly related to high maximal power of the lower limbs (r=-0.74) and vertical stiffness (r=-0.65) and low footprint index (FPI, r=0.70), step frequency (r=0.62) and external work (r=0.60). About 50% of the increase in CoT during the stages of the competition was accounted for by changes in FPI, which represents a global evaluation of medio-lateral displacement of the foot during the whole stance phase, which in turn is associated with the myotendinous characteristics of the lower limb. Thus, lower CoT values were related to greater muscular power and lower FPI, suggesting that a better ankle stability is likely to achieve better performance in an ultra-endurance running competition.

Analysis of sarcopenic obesity prevalence and diagnostic agreement according to the 2022 ESPEN and EASO Consensus in hospitalized older adults with severe obesity.

Background: Sarcopenic obesity (SO) is a clinical disorder characterized by increased adiposity and decreased muscle mass and function, commonly observed in older adults. However, most of the studies that investigated SO prevalence rates were not based on current standardized diagnostic methods. Thus, this study aims to estimate the prevalence rates of SO and their level of agreement using different instruments proposed by the European Society for Clinical Nutrition and Metabolism (ESPEN) and the European Association for the Study of Obesity (EASO) Consensus, in a sample of hospitalized older adults with severe obesity. Methods: A cross-sectional study with 90 older adults (≥ 60 years) with severe obesity (body mass index ≥ 35 kg/m/²) seeking an in-hospital multidisciplinary body weight reduction program. Skeletal muscle function was assessed using the five-repetition Sit-Stand test (5-SSt) and Handgrip Strength (HGS). Body composition was evaluated by high percentages of fat mass (FM), low appendicular lean mass (ALM/W), and skeletal muscle mass (SMM/W), adjusted to body weight. The stage of SO was assessed on the presence of at least one comorbidity and specific cut-offs were adopted for each step. All analyses were performed according to gender and age range. Results: The prevalence rates of SO in the total sample were 23.3%, 25.5%, 31.1%, and 40.0% considering altered values of 5-SSt+FM+ALM/W, HGS+FM+ALM/W, 5-SSt+FMSSM/W, and HGS+FM+SSM/W, respectively. Higher prevalence rates were observed among female and old elderly subgroups, regardless of the diagnostic combination. There were weak agreements between the muscle function tests (5-SSt versus HGS) using both muscle mass indexes in the total sample and all subgroups. Moderate agreements were observed between muscle mass indexes (SMM/W versus ALM/W) in the total sample, male and younger older adults (using 5-SSt), and strong agreements for men and younger older adults (using HGS). Conclusion: The discrepancies observed between the prevalence rates and their levels of agreement reinforce the need for new studies in similar populations aiming for better standardization of SO assessment.