Lower Limb Lean Mass Research Articles

Five days of bed rest in young and old adults: Retainment of skeletal muscle mass with neuromuscular electrical stimulation.

The consequences of short-term disuse are well known, but effective countermeasures remain elusive. This study investigated the effects of neuromuscular electrical stimulation (NMES) during 5 days of bed rest on retaining lower limb muscle mass and muscle function in healthy young and old participants. One leg received NMES of the quadriceps muscle (3 × 30min/day) (NMES), and the other served as a control (CON). Isometric quadriceps strength (MVC), rate of force development (RFD), lower limb lean mass, and muscle thickness were assessed pre-and post-intervention. Muscle thickness remained unaltered with NMES in young and increased in old following bed rest, while it decreased in CON legs. In old participants, mid-thigh lean mass (MTLM) was preserved with NMES while decreased in CON legs. In the young, only a tendency to change with bed rest was detected for MTLM. MVC and early-phase RFD decreased in young and old, irrespective of NMES. In contrast, late-phase RFD was retained in young participants with NMES, while it decreased in young CON legs, and in the old, irrespective of NMES. NMES during short-term bed rest preserved muscle thickness but not maximal muscle strength. While young and old adults demonstrated similar adaptive responses in preventing the loss of skeletal muscle thickness, RFD was retained in the young only.

Body composition in male lifelong trained strength, sprint and endurance athletes and healthy age-matched controls.

Aging involves many physiological processes that lead to decreases in muscle mass and increases in fat mass. While regular exercise can counteract such negative body composition outcomes, masters athletes maintain high levels of exercise throughout their lives. This provides a unique model to assess the impact of inherent aging. The present study compared lean mass and fat mass in young and masters athletes from different sports to age-matched non-athletic individuals. Participants included young (20-39 years, n = 109) and older (70-89 years, n = 147) competitive male athletes, and 147 healthy age-matched controls (young = 53, older = 94 males). Athletes were separated into strength (e.g., weightlifters, powerlifters), sprint (e.g., sprint runners, jumpers) and endurance (e.g., long-distance runners, cross-country skiers) athletic disciplines. Body composition was assessed by dual-energy x-ray absorptiometry (DXA). Upper and lower limb lean mass was combined for appendicular lean mass as well as appendicular lean mass index (ALMI; kg/m2). Individuals' scores were assessed against established cut-offs for low muscle mass, obesity, and sarcopenic obesity to determine prevalence in each group. ALMI was greater in young strength (0.81-2.36 kg/m2, ∼15% and 1.24-2.74 kg/m2, ∼19%) and sprint (95% CI = 0.51-1.61 kg/m2, ∼11% and 0.96-1.97 kg/m2, ∼15%) athletes than in endurance and controls, respectively (all P < 0.001). In masters athletes, only strength athletes had greater ALMI than endurance athletes, but both older strength and sprint athletes had greater ALMI than older controls (0.42-1.27 kg/m2, ∼9% and 0.73-1.67 kg/m2, ∼13%, respectively, both P < 0.001). Fat mass was significantly lower in sprint and endurance athletes compared to strength athletes and controls in both age-groups. Sarcopenic obesity was identified in one young (2%) and eighteen (19%) older controls, while only two older endurance athletes (3%) and one older strength athlete (2%) were identified. Lifelong competitive sport participation leads to lower prevalence of sarcopenic obesity than a recreationally active lifestyle. This is achieved in strength athletes by emphasizing muscle mass, while sprint and endurance athletes demonstrate low fat mass levels. However, all older athlete groups showed higher fat mass than the young groups, suggesting that exercise alone may not be sufficient to manage fat mass.

Are there differences in anaerobic relative muscle power between upper and lower limbs in adolescent swimmers: A blinded study

Success in speed swimming depends on the efficiency of the anaerobic system for the production of cellular energy, especially during muscle power production. In the adolescent athletes much is unknown with regards to the relationships between relative power of upper and lower limbs with speed swimming performance. The aim the present study was to identify differences in relative muscle power of upper and lower limbs in adolescent swimmers and relate these to speed swimming performances. Sixty adolescents, of both sexes (50% female, 50% male, 30 swimmers and 30 controls), were recruited. The relative upper limb power (ULP[W/kg]) was assessed by a medicine ball test and the relative lower limbs power (LLP[W/kg]) by a jump test on a jumping platform. Lean mass of the upper and lower limbs was assessed by dual-energy X-ray absorptiometry (DXA) (g). Sport performance was assessed during national level competition (50-m swimming time [in seconds]). Biological maturation (BM) was indexed by years from attainment of peak height velocity. ULP(W/kg) was higher than LLP(W/kg) in both groups (p ​< ​0.05). Upper and lower limb lean mass (g) correlated significantly with ULP(W/kg) and LLP(W/kg) in both groups (p ​< ​0.05). ULP(W/kg) and LLP(W/kg) correlated with 50-m swimming performance (s), in both sexes (p ​< ​0.05). Advanced BM was associated with ULP(W/kg) and LLP(W/kg) in both groups (p ​< ​0.05), and with 50-m swimming performance (s) in both sexes (p ​< ​0.05). We concluded that ULP(W/kg) is higher than LLP (W/kg) in adolescent swimmers. Upper and lower limb lean mass and BM were both positively associated with increased ULP (W/kg) and LLP (W/kg).

“Impact of aging on maximal oxygen uptake adjusted for lower limb lean mass, total body mass, and absolute values in runners”

Performance in endurance sports decreases with aging, which has been primarily attributed to cardiovascular and musculoskeletal aging; however, there is still no clear information on the factors that are most affected by aging. The aim of this study was to compare two groups of runners (< 50 and > 50 years of age) according to their absolute, weight-adjusted maximal oxygen uptake (V̇O2max), lower limb lean mass-adjusted V̇O2max, ventilatory threshold, and respiratory compensation point (RCP). A total of 78 male recreational long-distance runners were divided into Group 1 (38.12 ± 6.87 years) and Group 2 (57.55 ± 6.14 years). Participants were evaluated for body composition, V̇O2max, VT, and RCP. Group 1 showed higher absolute and body mass-adjusted V̇O2max (4.60 ± 0.57 l·min−1 and 61.95 ± 8.25 ml·kg−1·min−1, respectively) than Group 2 (3.77 ± 0.56 l·min−1 and 51.50 ± 10.22 ml·kg−1·min−1, respectively), indicating a significant difference (p < 0.001, d = − 1.46 and p < 0.001, d = − 1.16). Correspondingly, Group 1 showed a significantly higher lower limb lean mass–adjusted V̇O2max (251.72 ± 29.60 ml·kgLM−1·min−1) than Group 2 (226.36 ± 43.94 ml·kgLM−1·min−1) (p = 0.008, d = − 0.71). VT (%V̇O2max) (p = 0.19, d = 0.19) and RCP (%V̇O2max) (p = 0.24, d = 0.22) did not differ between the groups. These findings suggest that both variables that are limited by central or peripheral conditions are negatively affected by aging, but the magnitude of the effect is higher in variables limited by central conditions. These results contribute to our understanding of how aging affects master runners.

Sex Differences in Maximal Oxygen Uptake Adjusted for Skeletal Muscle Mass in Amateur Endurance Athletes: A Cross Sectional Study.

Male athletes tend to outperform female athletes in several endurance sports. Maximum cardiac output can be estimated by maximal oxygen consumption (V˙O2max), and it has been established that men present V˙O2max values about 20% higher than women. Although sex differences in V˙O2max have already been well studied, few studies have assessed sex differences with regard to muscle oxidative capacity. The aim of this study was to compare aerobic muscle quality, accessed by V˙O2max and adjusted by lower limb lean mass, between male and female amateur triathletes. The study also aimed to compare sex differences according to V˙O2 submaximal values assessed at ventilatory thresholds. A total of 57 participants (23 women and 34 men), who had been training for Olympic-distance triathlon races, underwent body composition evaluation by dual-energy X-ray absorptiometry and performed a cardiorespiratory maximal test on a treadmill. Male athletes had significantly higher V˙O2max, both absolutely and when adjusted to body mass. Conversely, when V˙O2max was adjusted for lean mass, there was no significant difference between sexes. The same was observed at submaximal exercise intensities. In conclusion, differences in V˙O2max adjusted to body mass but not lean mass may explain, at least in part, sex differences in performance in triathlons, marathons, cycling, and other endurance sports.

Relationship between Lower-Limb Bioelectrical Impedance Indicators of Hydration Status and Muscle Function in Aged Population: A Cross-Sectional Study

Background: Reduced Intracellular Water (ICW) has been related to poor muscle strength and functional capacity in aged populations. We aimed to evaluate hydration status and intracellular hydration of lower-limb lean mass in aged population and the relationship with thigh muscle function. Methods: Design and population: Cross-sectional study of community-dwelling ≥70 year old subjects. Measurements: Lower-limb hydration status was assessed by bioimpedance analysis and thigh muscle function was assessed by isokinetic evaluation. Frailty was established according to Fried criteria, sarcopenia according to EWGSOP-2 criteria, and physical performance according to the Timed Up-and-Go (TUG) test. Results: Assessed were 117 individuals (mean age 75.0 years, 50.4% women). Women had lower Fat-Free Mass (FFM), Total Body Water (TBW), and Phase Angle (PhA) values than men. Age was negatively correlated with ICW (r=-0.187; p=0.045), the ICW/FFM ratio (r=-0.192; p=0.039), and PhA (r=-0.311; p&lt;0.001). Extension and flexion strength and power of the knee were positively correlated with Total Water (TW) (L), FFM (kg), and the protein compartment (kg) of the lower-limb in both men and women, but not with TW as percentage of weight, ICW as percentage of TW, and the TW/FFM and ICW/FFM ratios, while the TUG test was negatively correlated with ICW as a percentage of TW. Conclusion: Knee flexion and extension strength, power, and work increase as thigh FFM, TBW, and protein compartment values increase. No correlation was observed between intracellular hydration and muscle function, but correlation was observed with performance. As plausible hypotheses, further studies are required to test for these correlations.

Total and regional body composition are related with aerobic fitness performance in elite futsal players

Body composition (i.e., fat and lean mass profile) has been related to aerobic performance, an essential capacity for futsal athletes. The present study aimed to verify the relationship between total and regional body composition (percentage of fat and lean mass) with aerobic performance in elite futsal players. Male professional futsal athletes (n = 44) from two Brazilian National Futsal League teams and athletes representing the National team participated in this study. Body composition was evaluated using DXA (Dual-Energy X-ray Absorptiometry) and aerobic fitness by ergospirometry. There was a negative (p < 0.05) correlation between maximum oxygen uptake and maximal velocity reached with total body (r = −0.53; r = −0.58), trunk (r = −0.52; r = −0.56) and lower-limb (r = −0.46; r = −0.55) fat mass percentage. Lower-limb lean mass percentage had a positive (p < 0.05) correlation with maximum oxygen uptake (r = 0.46) and maximal velocity (r = 0.55). In conclusion, total and regional body composition present a relationship with aerobic performance in professional futsal players.

Higher thyroid hormone has a negative association with lower limb lean body mass in euthyroid older adults: Analysis from the Baltimore Longitudinal study of aging.

Background: Hyperthyroidism is associated with lower lean body mass, as a result of catabolic actions of thyroid hormone. Therefore, higher thyroid hormone levels could be a factor in the development of sarcopenia and age associated functional decline. The relationship between thyroid hormone and muscle mass in ambulatory, euthyroid older adults is not known. Method: We used mixed-effects models to estimate the cross-sectional relationships (accounting for inter-person variability) between thyroid axis hormone measures and lower limb composition or sarcopenia at visits in the Baltimore Longitudinal Study of Aging (BLSA) at which DEXA scans were available and both thyrotropin (TSH) and free thyroxine (FT4) were in the reference range. Analyses were adjusted for levothyroxine use, age, race, sex, BMI, smoking, alcohol intake, cholesterol, and systolic blood pressure. Results: 1442 euthyroid participants (median age 68, 50% female, and 69% white) contributed to 5306 visits from 2003 to 2019. FT4 was negatively associated with lower limb lean mass (beta: 88.49; 95% Confidence Interval (CI): 122.78, -54.20; p < 0.001) and positively associated with sarcopenia (OR: 1.11%, 95% CI: 1.01, 1.22) in the whole cohort. Additionally, higher FT4 was associated with lower leg lean mass (beta: 66.79; 95% CI: 102.24, -31.33; p < 0.001) and sarcopenia (OR:1.09%, 95% CI:1.01, 1.18) in older adults, but not in younger adults alone. Conclusion: In euthyroid older adults, higher FT4 is associated with lower leg lean mass and higher odds of sarcopenia. Understanding the relationship between thyroid hormone and sarcopenia is needed to improve clinical decision-making and avoid functional decline from excess thyroid hormone use in older adults.

The association between muscle mass quantity and its quality in physically active older women

In this study, the authors aim to determine whether lower limb strength is related to lower limb lean mass and whether this relationship is affected by lower limb functionality in physically active older women. Twenty-six women underwent measures of knee muscles strength and lean mass of lower limbs. Bilateral strength of the knee flexors and extensors was measured by an isokinetic dynamometer. The concentric peak torque was measured at an angular velocity of 60°/s. Lean mass of the lower limbs was measured by bio-impedance analysis. Pearson’s correlation analysis revealed significant association between the strength of the knee flexors and lean mass on non-dominant limb only (r = .427, p = .03). Researchers revealed that strategies aiming to prevent lean mass and muscle strength losses should be specifically targeted to individual muscles or muscle groups, even in physically active older women. To improve overall mobility, the strengthening of larger muscle such as hamstring is crucial.

Effect of Whey Protein Supplementation in Postmenopausal Women: A Systematic Review and Meta-Analysis.

(1) Background: Whey protein (WP) in combination with resistance training (RT) is beneficial in improving sarcopenic obesity and its damaging effects in older adults, while the difference between men and women should be considered while interpreting results. This review aims to investigate WP’s efficacy on postmenopausal women with or without RT; (2) Material and Methods: We searched electronic databases including PubMed, EMBASE, and the Cochrane Library from inception to August 2021 for randomized controlled trials that included comparison groups to evaluate WP’s efficacy in women aged 55 years and above. The outcomes included body composition, muscular strength, functional capacity, and dietary intake. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were used to estimate the effect of WP. We also performed subgroup analysis with or without RT; (3) Results: We included 14 studies in the systematic review and 10 studies in the meta-analysis. Subgroup analyses showed RT was a major confounder for muscle strength, lean mass, and dietary protein intake (PI). In the RT subgroup, WP supplementation had a significant positive effect on biceps curl strength (BC) (SMD: 0.6805, 95% CI: 0.176, 1.185, I2: 0%), and lower limb lean-mass (LLLM) (SMD: 1.103, 95% CI: 0.632, 1.574, I2: 14%). In the subgroup without RT, a significant negative effect on PI (SMD: −0.4225, 95% CI: −0.774, −0.071, I2: 47%) was observed, while no significant effect on muscle strength or lean mass was revealed. WP supplementation did not show a significantly different effect on fat mass or body weight loss in both the subgroups; (4) Conclusions: In postmenopausal women, WP supplementation only in combination with RT enhances BC and LLLM compared to placebo controls. Without RT, WP has no significant benefit on muscle strength or lean mass.

Relationship between neuromuscular profile and total volume of resisted sprint training in male professional soccer players

PurposeThis 11-week study aimed to correlate the neuromuscular profile and the total volume of resisted sprint training (RST) under different velocity loss (VL) magnitudes in male professional soccer players.MethodsSeventeen soccer players (age 25.8 ± 4.3 years; height 180.0 ± 8.6 cm; weight 77.7 ± 9.7 kg) were randomly allocated into two training groups, who trained at distinct percentages of VL: 10% of VL (G10, n = 8) or 20% of VL (G20, n = 9). The velocity-based sled training consisted of 20 m resisted sprints executed with a progressive loading increase (45–65% of body-mass). Sprint times (10 m and 20 m), vertical jump height [countermovement jump (CMJ) and squat jump (SJ)], knee flexion and extension peak torque, as well as isometric rate of torque development, and lower limb lean mass were correlated with the total volume of RST performed by G10 and G20 groups.ResultsThe G10 performed 31% less repetitions and total RST distance than G20 (p = 0.002). Significant negative Pearson’s correlations (large-to-very large) were observed between total volume performed by G10 and CMJ height [r = − 0.85, confidence interval at 95% (95% CI) = − 0.98 to − 0.58, p = 0.02, Cohen’s D effect size (ES) = 0.41] as well as SJ height (r = − 0.90, 95% CI − 0.99 to − 0.66, p = 0.005, ES = 0.80), and knee extension concentric peak torque (r = − 0.69, 95% CI − 0.99 0.91, p = 0.05, ES = 0.03). No further correlation was found (p > 0.05).ConclusionsWhen lower magnitudes of VL were used during training sessions (10%), the stronger and more powerful players performed lower volume of RST. Interestingly, this relationship is not confirmed when higher magnitudes of VL (20%) are prescribed (greater fatigue incidence).

Body Composition In Covid-19 Survivors

Body composition analysis gives insight into distributions of muscle, fat, bone, and water, and differences in health and disease. Infection with the SARS COVID-19 virus results in both acute symptoms and well documented long-term symptoms occurring in ~50% of patients (Long COVID) including sustained changes in pain, fatigue, cognition, physical activity, and neurologic function. PURPOSE: To determine whether people who were infected with COVID-19 have altered body composition compared with those who had not contracted COVID-19. METHODS: 24 COVID-19 survivor-control pairs (n = 48, males 14, females 34) matched for age, sex, body mass index (BMI), and 2-13 months post infection (8.04 ± 0.71 months), aged 19-69 yrs (38.6 ± 2.6 yrs, 46 Caucasian, 2 Asian), participated in this study. Body composition was measured by two trained technicians with dual energy x-ray absorptiometry (DXA, Hologic Horizon A) and with bioelectrical impedance analysis (BIA, Tanita MC780-U, quad polar, multifrequency) performed on the same day. Data are expressed as Mean ± SEM. Body fat percentage was measured from BIA and for DXA calculated from lean body and bone mass. Correlations between DXA and BIA were performed. RESULTS: Body composition (lean, bone, fat, visceral adipose) did not differ between those with COVID-19 when compared to BMI/age/sex matched controls. Total lean body mass (LBM: 50.5 ± 1.7 vs 49.4 ± 1.6 kg, p = 0.64), total % body fat (27.0 ± 1.8 vs 26.3 ± 1.7%, p = 0.76), lower limb lean mass (LLLM: 16.8 ± 0.6 vs 16.9 ± 0.5 kg, p = 0.97), and visceral adipose tissue (0.3 ± 0.036 vs 0.3 ± 0.041 kg, p = 0.94) were similar between groups. BIA measures of body composition were significantly correlated with DXA measures for the 48 subjects for LBM (r = 0.98, r2 = 0.95), total % body fat (r = 0.95, r2 = 0.90), and LLLM (r = 0.92, r2 = 0.84). CONCLUSION: COVID-19 survivors (2-13 months post infection) did not have different percent body fat, LBM or LLLM relative to controls when matched for BMI, age, and sex. BIA technology, which is portable, had high agreement with DXA for body fat percent and lean muscle mass and potentially could be a useful tool in assessing body composition in the community.

The relationship between lower-limb body composition with isokinetic performance in futsal players: Body composition and performance in futsal players

BACKGROUND: Optimal neuromuscular performance is essential for futsal athletes and it has been linked to body composition. AIM: The present study aimed to verify the relationship between absolute (total amount; kg) and relative (percentage; %) lower-limb and thigh lean and fat mass with isometric and dynamic maximal strength in professional futsal players. METHOD: Sixteen male elite futsal athletes participated in this study. Unilateral lower-limb and thigh lean and fat mass were evaluated using DXA (Dual-Energy X-ray Absorptiometry) and strength performance using unilateral isokinetic concentric-eccentric knee extension (KE) and flexion (KF) peak torque (PT), KE and KF isometric PT at 30° and 70°, and hamstrings-to-quadriceps ratios (H:Q). RESULTS: Unilateral lower-limb lean mass amount showed a significant positive correlation with concentric and isometric KE PT (60°/s: r=0.58; 30°: r=0.55; 70°: r=0.65), and with concentric (60°/s: r=0.61), eccentric (60°/s: r=0.67) and isometric (30°:r=0.79; 70°: r=0.70) KF PT. No significant relationship between lower-limb lean and fat mass percentage with isokinetic performance was verified. Thigh lean mass amount had a significant positive correlation with concentric and isometric KE PT (60°/s:r=0.52; 30°: r=0.51; 70°: r=0.84) and also with concentric (60°/s: r=0.75) and eccentric KF PT (60°/s:r=0.54), while thigh fat mass amount was only associated with eccentric KF PT (r=0.54). No significant correlation between lower-limb and thigh body composition with H:Q ratios was observed. CONCLUSION: In conclusion, contrary to the relative (%) values, absolute (kg) lower-limb and thigh fat and lean mass present a significant correlation with dynamic and isometric KE and KF performance in futsal players.

Adolescent female handball players present greater bone mass content than soccer players: A cross-sectional study.

Osteoporosis is a systemic disease affecting half of women over the age of 50years. Considering that almost 90% of peak of bone mass is achieved until the second decade of life, ensuring a maximal bone mineral content acquisition may compensate for age-associated bone loss. Among several other factors, physical activity has been recommended to improve bone mass acquisition. However, it is unknown whether athletes involved with sports with different impact loading characteristics differ in regards to bone mass measurements. To compare the bone mass content, bone mass density and lean mass of young female soccer players (odd-impact loading exercise), handball players (high-impact loading exercises) and non-athletes. A total of 115 female handball players (15.5±1.3years, 165.2±5.6cm and 61.9±9.3kg) and 142 soccer players (15.5±1.5years, 163.7±6.6cm and 56.5±7.7kg) were evaluated for body composition using a dual-emission X-ray absorptiometry system, and 136 female non-athletes (data from NHANES) (15.1±1.32years, 163.5±5.8cm and 67.2±19.4kg) were considered as the control. Handball players presented higher bone mass content values than soccer players for upper limbs (294.8±40.2g and 270.7±45.7g, p<0.001), lower limbs (1011.6±145.5g and 967.7±144.3g, p=0.035), trunk (911.1±182.5g and 841.6±163.7g, p=0.001), ribs (312.4±69.9g and 272.9±58.0g, p<0.001), spine (245.1±46.8g and 222.0±45.1g, p<0.001) and total bone mass (2708.7±384.1g and 2534.8±386.0g, p<0.001). Moreover, non-athletes presented lower bone mass content for lower limbs (740.6±132.3g, p<0.001), trunk (539.7±98.6g, p<0.001), ribs (138.2±29.9g, p<0.001), pelvis (238.9±54.6g, p<0.001), spine (152.8±26.4g, p<0.001) and total bone mass (1987.5±311.3g, p<0.001) than both handball and soccer players. Handball players also presented higher bone mass density values than soccer players for trunk, ribs and spine (p<0.05) and handball and soccer players presented higher bone mass density than non-athletes for all measurements (p<0.005). Finally, the non-athletes' lower limb lean mass was lower than soccer and handball players values (p<0.05). Adolescent females engaged in handball training for at least one year present higher bone mass contents than those who are engaged in soccer training, which, in turn, present higher bone mass contents than non-athletes. These results might be used by physicians and healthcare providers to justify the choice of a particular sport to enhance bone mass gain in female adolescents.

Increases in Integrin-ILK-RICTOR-Akt Proteins, Muscle Mass, and Strength after Eccentric Cycling Training.

Recently, it has been suggested that a cellular pathway composed of integrin, integrin-linked kinase (ILK), rapamycin-insensitive companion of mTOR (RICTOR), and Akt may facilitate long-term structural and functional adaptations associated with exercise, independent of the mTORC1 pathway. Therefore, we examined changes in integrin-ILK-RICTOR-Akt protein in vastus lateralis (VL) before and after 8 wk of eccentric cycling training (ECC), which was expected to increase muscle function and VL cross-sectional area (CSA). Eleven men (23 ± 4 yr) completed 24 sessions of ECC with progressive increases in intensity and duration, resulting in a twofold increase in work from the first three (75.4 ± 14.1 kJ) to the last three sessions (150.7 ± 28.4 kJ). Outcome measures included lower limb lean mass, VL CSA, static strength, and peak and average cycling power output. These measures and VL samples were taken before and 4-5 d after the last training session. Significant (P < 0.05) increases in integrin-β1 (1.64-fold) and RICTOR (2.99-fold) protein as well as the phosphorylated-to-total ILK ratio (1.70-fold) were found, but integrin-α7 and Akt did not change. Increases in lower limb, thigh, and trunk lean mass (2.8%-5.3%, P < 0.05) and CSA (13.3% ± 9.0%, P < 0.001) were observed. Static strength (18.1% ± 10.8%) and both peak (8.6% ± 10.5%) and average power output (7.4% ± 8.3%) also increased (P < 0.05). However, no significant correlations were found between the magnitude of increases in protein and the magnitude of increases in CSA, static strength, or power output. In addition to increased muscle mass, strength, and power, we demonstrate that ECC increases integrin-β1 and RICTOR total protein and p-ILK/t-ILK, which may play a role in protection against muscle damage as well as anabolic signaling to induce muscle adaptations.

Muscle function, quality, and relative mass are associated with knee pain trajectory over 10.7 years.

Periarticular muscle plays an important role in the pathogenesis of musculoskeletal pain. We recently reported that pain population consists of distinct subgroups of which the causes and mechanisms may differ. This study aimed to examine the association of lean mass, muscle strength, and quality with 10.7-year pain trajectory. Nine hundred forty-seven participants from a population-based cohort study were analysed. Dual-energy X-ray absorptiometry was used to assess lean and fat mass. Leg strength, knee extensor strength, and lower-limb muscle quality were measured/calculated. Knee pain was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index pain questionnaire. Radiographic knee osteoarthritis was assessed by X-ray. Three distinct pain trajectories were identified: "Minimal pain" (53%), "Mild pain" (34%), and "Moderate pain" (13%). Higher total and lower-limb lean mass were associated with an increased risk of "Mild pain" and "Moderate pain" trajectories relative to the "Minimal pain" trajectory group, but these associations became nonsignificant after further adjustment for fat mass. Total lean mass percentage was associated with a lower risk of "Mild pain" (relative risk ratio [RRR]: 0.95, 95% confidence interval 0.92-0.98) and "Moderate pain" trajectory (RRR: 0.92, 95% confidence interval 0.87-0.96). Greater leg and knee extensor strength and muscle quality were associated with "Mild pain" and "Moderate pain" trajectories (RRR: 0.52-0.65, all P < 0.05). Similar results were found in those with radiographic knee osteoarthritis. Higher lower-limb muscle strength and quality, and relative lean mass, are associated with a reduced risk of severe knee pain trajectories, suggesting that improving muscle function and composition may protect against persistent unfavourable knee pain courses.

COVID-19 era in long-term cardiac rehabilitation programs: how was muscle strenght and lean mass affected in cardiovascular patients?

Funding AcknowledgementsType of funding sources: None.IntroductionExercise prescription is one of the main components of phase III Cardiac Rehabilitation (CR) programs due to its documented prognostic benefits. It has been well established that, when added to aerobic training, resistance training (RT) leads to greater improvements in peripheral muscle strength and muscle mass in patients with cardiovascular disease (CVD). With COVID-19, most centre-based CR programs had to be suspended and CR patients had to readjust their RT program to a home-based model where weight training was more difficult to perform. How COVID-19 Era impacted lean mass and muscle strength in trained CVD patients who were attending long-term CR programs has yet to be discussed.PurposeTo assess upper and lower limb muscle strength and lean mass in CVD patients who had their centre-based CR program suspended due to COVID-19 and compare it with previous assessments.Methods87 CVD patients (mean age 62.9 ± 9.1, 82.8% male), before COVID-19, were attending a phase III centre-based CR program 3x/week and were evaluated annually. After 7 months of suspension, 57.5% (n = 50) patients returned to the face-to-face CR program. Despite all constraints caused by COVID-19, body composition and muscle strength of 35 participants (mean age 64.7 ± 7.9, 88.6% male) were assessed. We compared this assessment with previous years and established three assessment time points: M1) one year before COVID-19 (2018); M2) last assessment before COVID-19 (2019); M3) the assessment 7 months after CR program suspension (last trimester of 2020). Upper limbs strength was measured using a JAMAR dynamometer, 30 second chair stand test (number of repetitions – reps) was used to measure lower limbs strength and dual energy x-ray absorptiometry was used to measure upper and lower limbs lean mass. Repeated measures ANOVA were used.ResultsIntention to treat analysis showed that upper and lower limbs lean mass did not change from M1 to M2 but decreased significantly from M2 to M3 (arms lean mass in M2: 5.68 ± 1.00kg vs M3: 5.52 ± 1.06kg, p = 0.004; legs lean mass in M2: 17.40 ± 2.46kg vs M3: 16.77 ± 2.61kg, p = 0.040). Lower limb strength also decreased significantly from M2 to M3 (M2: 23.31 ± 5.76 reps vs M3: 21.11 ± 5.31 reps, p = 0.014) after remaining stable in the year prior to COVID-19. Upper limb strength improved significantly from M1 to M2 (M1: 39.00 ± 8.64kg vs M2: 40.53 ± 8.77kg, p = 0.034) but did not change significantly from M2 to M3 (M2 vs M3: 41.29 ± 9.13kg, p = 0.517).ConclusionAfter CR centre-based suspension due to COVID-19, we observed a decrease in upper and lower limbs lean mass and lower limb strength in previously trained CVD patients. These results should emphasize the need to promote all efforts to maintain physical activity and RT through alternative effective home-based CR programs when face-to-face models are not available or possible to be implemented.

Increased myocellular lipid and IGFBP-3 expression in a pre-clinical model of pancreatic cancer-related skeletal muscle wasting.

BackgroundSkeletal muscle wasting (SMW) in cancer patients is associated with increased morbidity, mortality, treatment intolerance and discontinuation, and poor quality of life. This is particularly true for patients with pancreatic ductal adenocarcinoma (PDAC), as over 85% experience SMW, which is responsible for ~30% of patient deaths. While the established paradigm to explain SMW posits that muscle catabolism from systemic inflammation and nutritional deficiencies, the cause of death, and the cellular and molecular mechanisms responsible remain to be elucidated. To address this, we investigated the relationship between tumour burden and survival in the KCKO murine PDAC model.MethodsFemale C57BL/6J mice 6–8 weeks of age underwent orthotopic injection with KCKO‐luc tumour cells. Solid tumour was verified on Day 5, post‐tumour inoculation. In vivo, longitudinal lean mass and tumour burden were assessed via dual‐energy X‐ray absorptiometry and IVIS imaging, respectively, and total body weight was assessed, weekly. Animals were sacrificed at a designated end point of ‘failure to thrive’. After sacrifice, lower limb hind muscles were harvested for histology and RNA extraction.ResultsWe found a strong correlation between primary tumour size and survival (r 2 = 0.83, P < 0.0001). A significant decrease in lower limb lean mass was first detected at Day 38 post‐implantation vs. no tumour controls (NTCs) (P < 0.0001). SMW was confirmed by histology, which demonstrated a 38%, 32.7%, and 39.9% decrease in fibre size of extensor digitorum longus, soleus, and tibialis anterior muscles, respectively, in PDAC mice vs. NTC (P < 0.002). Histology also revealed a 67.6% increase in haematopoietic cells within the muscle of PDAC mice when compared with NTC. Bulk RNAseq on muscles from PDAC mice vs. NTC revealed significant increases in c/ebpβ/Δ, il‐1, il‐6, and tnf gene expression. Pathway analyses to identify potential upstream factors revealed increased adipogenic gene expression, including a four‐fold increase in igfbp‐3. Histomorphometry of Oil Red‐O staining for fat content in tibialis anterior muscles demonstrated a 95.5% increase in positively stained fibres from PDAC mice vs. NTC.ConclusionsTogether, these findings support a novel model of PDAC‐associated SMW and mortality in which systemic inflammation leads to inflammatory cell infiltration into skeletal muscle with up‐regulated myocellular lipids.

Effects of Moderate-to-Heavy Sled Training Using Different Magnitudes of Velocity Loss in Professional Soccer Players.

Grazioli, R, Loturco, I, Lopez, P, Setuain, I, Goulart, J, Veeck, F, Inácio, M, Izquierdo, M, Pinto, RS, and Cadore, EL. Effects of moderate-to-heavy sled training using different magnitudes of velocity loss in professional soccer players. J Strength Cond Res 37(3): 629-635, 2023-This study investigated the effects of a 11-week moderate-to-heavy sled training intervention with different magnitudes of velocity loss on sprint and jump performance, mechanical muscle function, and body composition in professional soccer players. Seventeen players (age 25.8 ± 4.3 years; height 180.0 ± 8.6 cm; mass 77.7 ± 9.7 kg) were randomly allocated into 2 groups, based on different magnitudes of velocity loss: 10% of velocity decrease (G10, n = 8) and 20% of velocity decrease (G20, n = 9). The velocity-based sled training consisted of 20-m resisted sprints with a progressive loading increase from 45 to 65% of body-mass throughout the intervention. Pre-intervention and postintervention sprint and jump performance, hamstring and quadriceps peak torque and isometric rate of torque development, and lower-limb lean mass measured by dual X-ray absorptiometry were assessed and compared. Two-way repeated measures analysis of variance revealed a significant time-effect for decreases in 10- and 20-m sprint times ( p = 0.018 and p = 0.033, respectively), but without a time-group interaction. The G10 showed greater beneficial effects than G20 for both 10-m (-5.5 ± 3.3%, magnitude-based inference [MBI]: possibly vs. -1.7 ± 5.9%, MBI: possibly trivial) and 20-m (-2.5 ± 2.1%, MBI: possibly vs. -1.4 ± 3.7%, MBI: likely trivial) sprint times. Moreover, there was a significant time effect for countermovement jump height and quadriceps isometric peak torque, which decreased significantly after training ( p = 0.019 and p = 0.010, respectively), with no within-group effect of time vs. group interaction for these respective outcomes. The novel velocity-based sled model proposed here, especially under lower magnitudes of velocity loss, was able to significantly improve linear sprint performance in professional soccer players.

Epidural stimulation for cardiovascular function increases lower limb lean mass in individuals with chronic motor complete spinal cord injury.

What is the central question of this study? Spinal cord injury results in paralysis and deleterious neuromuscular and autonomic adaptations. Lumbosacral epidural stimulation can modulate motor and/or autonomic functions. Does long-term epidural stimulation for normalizing cardiovascular function affect leg muscle properties? What is the main finding and its importance? Leg lean mass increased after long-term epidural stimulation for cardiovascular function, which was applied in the sitting position and did not activate the leg muscles. Leg muscle strength and fatigue resistance, assessed in a subgroup of individuals, also increased. These adaptations might support interventions for motor recovery and warrant further mechanistic investigation. Chronic motor complete spinal cord injury (SCI) results in paralysis and deleterious neuromuscular and autonomic adaptations. Paralysed muscles demonstrate atrophy, loss of force and increased fatigability. Also, SCI-induced autonomic impairment results in persistently low resting blood pressure and heart rate, among other features. We previously reported that spinal cord epidural stimulation (scES) optimized for cardiovascular (CV) function (CV-scES), which is applied in sitting position and does not activate the leg muscles, can maintain systolic blood pressure within a normotensive range during quiet sitting and during orthostatic stress. In the present study, dual-energy X-ray absorptiometry collected from six individuals with chronic clinically motor complete SCI demonstrated that 88±11 sessions of CV-scES (7daysweek-1 ; 2hday-1 in four individuals and 5hday-1 in two individuals) over a period of ∼6months significantly increased lower limb lean mass (by 0.67±0.39kg or 9.4±8.1%; P<0.001). Additionally, muscle strength and fatigability data elicited by neuromuscular electrical stimulation in three of these individuals demonstrated a general increase (57±117%) in maximal torque output (between 2 and 44Nm in 14 of the 17 muscle groups tested overall) and torque-time integral during intermittent, fatiguing contractions (63±71%; between 7 and 230% in 16 of the 17 muscle groups tested overall). In contrast, whole-body mass and composition did not change significantly. In conclusion, long-term use of CV-scES can have a significant impact on lower limb muscle properties after chronic motor complete SCI.