Daily blood flow restriction does not preserve muscle mass and strength during 2 weeks of bed rest.

We measured the impact of blood flow restriction on muscle protein synthesis rates, muscle mass and strength during 2 weeks of strict bed rest. Twelve healthy, male adults (age: 24 ± 3 years, body mass index: 23.7 ± 3.1 kg/m2 ) were subjected to 14 days of strict bed rest with unilateral blood flow restriction performed three times daily in three 5 min cycles (200 mmHg). Participants consumed deuterium oxide and we collected blood and saliva samples throughout 2 weeks of bed rest. Before and immediately after bed rest, lean body mass (dual-energy X-ray absorptiometry scan) and thigh muscle volume (magnetic resonance imaging scan) were assessed in both the blood flow restricted (BFR) and control (CON) leg. Muscle biopsies were collected and unilateral muscle strength (one-repetition maximum; 1RM) was assessed for both legs before and after the bed rest period. Bed rest resulted in 1.8 ± 1.0 kg lean body mass loss (P < 0.001). Thigh muscle volume declined from 7.1 ± 1.1 to 6.7 ± 1.0 L in CON and from 7.0 ± 1.1 to 6.7 ± 1.0 L in BFR (P < 0.001), with no differences between treatments (P = 0.497). In addition, 1RM leg extension strength decreased from 60.2 ± 10.6 to 54.8 ± 10.9 kg in CON and from 59.2 ± 12.1 to 52.9 ± 12.0 kg in BFR (P = 0.014), with no differences between treatments (P = 0.594). Muscle protein synthesis rates during bed rest did not differ between the BFR and CON leg (1.11 ± 0.12 vs. 1.08 ± 0.13%/day, respectively; P = 0.302). Two weeks of bed rest substantially reduces skeletal muscle mass and strength. Blood flow restriction during bed rest does not modulate daily muscle protein synthesis rates and does not preserve muscle mass or strength. KEY POINTS: Bed rest, often necessary for recovery from illness or injury, leads to the loss of muscle mass and strength. It has been postulated that blood flow restriction may attenuate the loss of muscle mass and strength during bed rest. We investigated the effect of blood flow restriction on muscle protein synthesis rates, muscle mass and strength during 2 weeks of strict bed rest. Blood flow restriction applied during bed rest does not modulate daily muscle protein synthesis rates and does not preserve muscle mass or strength. Blood flow restriction is not effective in preventing muscle atrophy during a prolonged period of bed rest.

The muscle protein synthetic response following corn protein ingestion does not differ from milk protein in healthy, young adults.

Plant-derived proteins are generally believed to possess lesser anabolic properties when compared with animal-derived proteins. This is, at least partly, attributed to the lower leucine content of most plant-derived proteins. Corn protein has a leucine content that is highest among most plant-derived proteins and it even exceeds the levels observed in animal-derived proteins such as whey protein. Therefore, this study aimed to compare muscle protein synthesis rates following the ingestion of 30 g corn protein and a 30 g blend of corn plus milk protein with 30 g milk protein. In a randomized, double blind, parallel-group design, 36 healthy young males (26 ± 4 y) received primed continuous L-[ring-13C6]-phenylalanine infusions and ingested 30 g corn protein (CORN), 30 g milk protein (MILK), or a 30 g proteinblend with 15 g corn plus 15 g milk protein (CORN + MILK). Blood and muscle biopsies were collected for 5 h following protein ingestion to assess post-prandial plasma amino acid profiles and myofibrillar protein synthesis rates. The results show that Ingestion of protein increased myofibrillar protein synthesis rates from basal post-absorptive values in all treatments(P < 0.001). Post-prandial myofibrillar protein synthesis rates did not differ between CORN vs MILK (0.053 ± 0.013 vs 0.053 ± 0.013%∙h-1, respectively; t-test P = 0.90), or between CORN + MILK vs MILK (0.052 ± 0.024 vs 0.053 ± 0.013%∙h-1, respectively; t-test P = 0.92). Ingestion of 30 g corn protein, 30 g milk protein, or a blend of 15 g corn plus 15 g milk protein robustly increases muscle protein synthesis rates in young males. The muscle protein synthetic response to the ingestion of 30 g corn-derived protein does not differ from the ingestion of an equivalent amount of milk protein in healthy, young males. Clinical Trial Registry number. NTR6548 (registration date: 27-06-2017) https://www.trialregister.nl/ .

Post-prandial muscle protein synthesis rates following the ingestion of pea-derived protein do not differ from ingesting an equivalent amount of milk-derived protein in healthy, young males.

PURPOSE: Plant-derived proteins have received considerable attention as an alternative to animal-derived proteins. However, plant-derived proteins are considered to have less anabolic properties when compared with animal-derived proteins. The lower muscle protein synthesis rates following ingestion of plant- compared with animal-derived protein have been attributed to the lower essential amino acid content of plant-derived proteins and/or their specific amino acid deficiencies. This study aimed to compare post-prandial muscle protein synthesis rates following the ingestion of 30 g pea-derived protein with 30 g milk-derived protein in healthy, young males. METHODS: In a randomized, double-blind, parallel-group design, 24 young males (24 ± 3 y) received a primed continuous L-[ring-13C6]-phenylalanine infusion after which they ingested 30 g pea (PEA) or 30 g milk-derived protein (MILK). Blood and muscle biopsies were collected frequently for 5 h to assess post-prandial plasma amino acid profiles and subsequent post-prandial muscle protein synthesis rates. RESULTS: MILK increased plasma essential amino acid concentrations more than PEA over the 5 h post-prandial period (incremental area under curve 151 ± 31 vs 102 ± 15 mmol∙300 min∙L-1, respectively; P < 0.001). Ingestion of both MILK and PEA showed a robust muscle protein synthetic response with no significant differences between treatments (0.053 ± 0.013 and 0.053 ± 0.017%∙h-1, respectively; P = 0.96). CONCLUSION: Post-prandial muscle protein synthesis rates following the ingestion of 30 g pea-derived protein do not differ from the response following ingestion of an equivalent amount of milk-derived protein. International Clinical Trials Registry Platform (NTR6548; 27-06-2017).

Type II Muscle Fiber Capillarization Is an Important Determinant of Post-Exercise Microvascular Perfusion in Older Adults.

INTRODUCTION: Microvascular perfusion is essential for post-exercise skeletal muscle recovery to ensure adequate delivery of nutrients and growth factors. This study assessed the relationship between various indices of muscle fiber capillarization and microvascular perfusion assessed by contrast-enhanced ultrasound (CEUS) at rest and during recovery from a bout of resistance exercise in older adults. METHODS: Sixteen older adults (72 ± 6 y, 5/11 male/female) participated in an experimental test day during which a muscle biopsy was collected from the vastus lateralis and microvascular perfusion was determined by CEUS at rest and at 10 and 40 min following a bout of resistance exercise. Immunohistochemistry was performed on muscle tissue samples to determine various indices of both mixed and fiber-type-specific muscle fiber capillarization. RESULTS: Microvascular blood volume at t = 10 min was higher compared with rest and t = 40 min (27.2 ± 4.7 vs. 3.9 ± 4.0 and 7.0 ± 4.9 AU, respectively, both p < 0.001). Microvascular blood volume at t = 40 min was higher compared with rest (p < 0.001). No associations were observed between different indices of mixed muscle fiber capillarization and microvascular blood volume at rest and following exercise. A moderate (r = 0.59, p < 0.05) and strong (r = 0.81, p < 0.001) correlation was observed between type II muscle fiber capillary-to-fiber ratio and the microvascular blood volume increase from rest to t = 10 and t = 40 min, respectively. In addition, type II muscle fiber capillary contacts and capillary-to-fiber perimeter exchange index were strongly correlated with the microvascular blood volume increase from rest to t = 40 min (r = 0.66, p < 0.01 and r = 0.64, p < 0.01, respectively). CONCLUSION: Resistance exercise strongly increases microvascular blood volume for at least 40 min after exercise cessation in older adults. This resistance exercise-induced increase in microvascular blood volume is strongly associated with type II muscle fiber capillarization in older adults.

Becoming a World Champion Powerlifter at 71 Years of Age: It Is Never Too Late to Start Exercising.

This case study assessed body composition, muscle strength, cardiorespiratory fitness, and metabolic health of the present female world champion powerlifter in the 70+ age category who started resistance exercise training at 63 years of age with no prior experience with structured exercise training. Measures of body composition (magnetic resonance imaging, computed tomography, and dual-energy X-ray absorptiometry scanning, leg volume); strength (one-repetition maximum leg press and extension, maximum voluntary contraction, and handgrip strength); physical function (short physical performance battery); cardiorespiratory fitness (peak oxygen consumption); and metabolic health (oral glucose tolerance test) were assessed. In addition, a muscle biopsy was collected to assess muscle fiber type distribution and cross-sectional area (CSA). Where possible, data were compared with previously (un)published sex- and age-matched data using z scores. Skeletal muscle mass index was calculated by dividing limb muscle mass by height squared. Data from the control groups are expressed as mean ± 95% confidence interval. Our participant (age: 71 years; body mass: 64.5 kg; body mass index: 27.6 kg/m2) reported a good bone mineral density of 1.09 g/cm2 (T score between -1 and +1) and very low values of abdominal and organ body fat (i.e., between 20% and 70% lower compared with a reference group of postmenopausal women). In addition, she showed a 33% greater skeletal muscle mass index when compared with healthy, older female control subjects (7.9 vs. 5.9 [5.7-6.2] kg/m2; n = 61) as well as 37% greater muscle quadriceps CSA (63.8 vs. 46.6 [44.5-48.7] cm2; n = 48) and 46% greater Type II muscle fiber CSA (4,536 vs. 3,097 [2,707-3,488] µm2; n = 19). Absolute leg press muscle strength was 36% greater (190 vs. 140 [132-147] kg; n = 30) and handgrip strength was 33% greater (33 vs. 25 [23-26] kg; n = 48) when compared with healthy, age-matched controls. In conclusion, even for resistance exercise naïve individuals, starting exercise at an advanced age can lead to improvements in body composition and muscle strength allowing older adults to reduce the risk for developing metabolic syndrome, live independently, and even compete at a world class level.

Muscle Mass and Strength Gains Following Resistance Exercise Training in Older Adults 65-75 Years and Older Adults Above 85 Years.

Resistance exercise training (RET) can be applied effectively to increase muscle mass and function in older adults (65-75 years). However, it has been speculated that older adults above 85 years are less responsive to the benefits of RET. This study compares the impact of RET on muscle mass and function in healthy older adults 65-75 years versus older adults above 85 years. We subjected 17 healthy older adults 65-75 years (OLDER 65-75, n = 13/4 [female/male]; 68 ± 2 years; 26.9 ± 2.3 kg/m2) and 12 healthy older adults above 85 years (OLDER 85+, n = 7/5 [female/male]; 87 ± 3 years; 26.0 ± 3.6 kg/m2) to 12 weeks of whole-body RET (three times per week). Prior to, and after 6 and 12 weeks of training, quadriceps and lumbar spine vertebra 3 muscle cross-sectional area (computed tomography scan), whole-body lean mass (dual-energy X-ray absorptiometry scan), strength (one-repetition maximum test), and physical performance (timed up and go and short physical performance battery) were assessed. Twelve weeks of RET resulted in a 10% ± 4% and 11% ± 5% increase in quadriceps cross-sectional area (from 46.5 ± 10.7 to 51.1 ± 12.1 cm2, and from 38.9 ± 6.1 to 43.1 ± 8.0 cm2, respectively; p < .001; η2 = .67); a 2% ± 3% and 2% ± 3% increase in whole-body lean mass (p = .001; η2 = .22); and a 38% ± 20% and 46% ± 14% increase in one-repetition maximum leg extension strength (p < .001; η2 = .77) in the OLDER 65-75 and OLDER 85+ groups, respectively. No differences in the responses to RET were observed between groups (Time × Group, all p > .60; all η2 ≤ .012). Physical performance on the short physical performance battery and timed up and go improved (both p < .01; η2 ≥ .22), with no differences between groups (Time × Group, p > .015; η2 ≤ .07). Prolonged RET increases muscle mass, strength, and physical performance in the aging population, with no differences between 65-75 years and 85+ years older adults.

Acute Quark Ingestion Increases Muscle Protein Synthesis Rates at Rest with a Further Increase after Exercise in Young and Older Adult Males in a Parallel-Group Intervention Trial.

BACKGROUND: Ingestion of protein concentrates or isolates increases muscle protein synthesis rates in young and older adults. There is far less information available on the anabolic response following the ingestion of dairy wholefoods, which are commonly consumed in a normal diet. OBJECTIVES: This study investigates whether ingestion of 30 g protein provided as quark increases muscle protein synthesis rates at rest and whether muscle protein synthesis rates are further increased after resistance exercise in young and older adult males. METHODS: In this parallel-group intervention trial, 14 young (18-35 y) and 15 older (65-85 y) adult males ingested 30 g protein provided as quark after a single-legged bout of resistance exercise on leg press and leg extension machines. Primed, continuous intravenous L-[ring-13C6]-phenylalanine infusions were combined with the collection of blood and muscle tissue samples to assess postabsorptive and 4-h postprandial muscle protein synthesis rates at rest and during recovery from exercise. Data represent means ± SDs; η2 was used to measure the effect size. RESULTS: Plasma total amino acid and leucine concentrations increased after quark ingestion in both groups (both time: P < 0.001; η2 > 0.8), with no differences between groups (time × group: P = 0.127 and P = 0.172, respectively; η2<0.1). Muscle protein synthesis rates increased following quark ingestion at rest in both young (from 0.030 ± 0.011 to 0.051 ± 0.011 %·h-1) and older adult males (from 0.036 ± 0.011 to 0.062 ± 0.013 %·h-1), with a further increase in the exercised leg (to 0.071 ± 0.023 %·h-1 and to 0.078 ± 0.019 %·h-1, respectively; condition: P < 0.001; η2 = 0.716), with no differences between groups (condition × group: P = 0.747; η2 = 0.011). CONCLUSIONS: Quark ingestion increases muscle protein synthesis rates at rest with a further increase following exercise in both young and older adult males. The postprandial muscle protein synthetic response following quark ingestion does not differ between healthy young and older adult males when an ample amount of protein is ingested. This trial was registered at the Dutch Trial register, which is accessible via trialsearch.who.int www.trialregister.nl as NL8403.

Vicia faba Peptide Network Supplementation Does Not Differ From Milk Protein in Modulating Changes in Muscle Size During Short-Term Immobilization and Subsequent Remobilization, but Increases Muscle Protein Synthesis Rates During Remobilization in Healthy Young Men.

BACKGROUND: Muscle mass and strength decrease during short periods of immobilization and slowly recover during remobilization. Recent artificial intelligence applications have identified peptides that appear to possess anabolic properties in in vitro assays and murine models. OBJECTIVES: This study aimed to compare the impact of Vicia faba peptide network compared with milk protein supplementation on muscle mass and strength loss during limb immobilization and regain during remobilization. METHODS: Thirty young (24 ± 5 y) men were subjected to 7 d of one-legged knee immobilization followed by 14 d of ambulant recovery. Participants were randomly allocated to ingest either 10 g of the Vicia faba peptide network (NPN_1; n = 15) or an isonitrogenous control (milk protein concentrate; MPC; n = 15) twice daily throughout the study. Single-slice computed tomography scans were performed to assess quadriceps cross-sectional area (CSA). Deuterium oxide ingestion and muscle biopsy sampling were applied to measure myofibrillar protein synthesis rates. RESULTS: Leg immobilization decreased quadriceps CSA (primary outcome) from 81.9 ± 10.6 to 76.5 ± 9.2 cm2 and from 74.8 ± 10.6 to 71.5 ± 9.8 cm2 in the NPN_1 and MPC groups, respectively (P < 0.001). Remobilization partially recovered quadriceps CSA (77.3 ± 9.3 and 72.6 ± 10.0 cm2, respectively; P = 0.009), with no differences between the groups (P > 0.05). During immobilization, myofibrillar protein synthesis rates (secondary outcome) were lower in the immobilized leg (1.07% ± 0.24% and 1.10% ± 0.24%/d, respectively) than in the non-immobilized leg (1.55% ± 0.27% and 1.52% ± 0.20%/d, respectively; P < 0.001), with no differences between the groups (P > 0.05). During remobilization, myofibrillar protein synthesis rates in the immobilized leg were greater with NPN_1 than those with MPC (1.53% ± 0.38% vs. 1.23% ± 0.36%/d, respectively; P = 0.027). CONCLUSION: NPN_1 supplementation does not differ from milk protein in modulating the loss of muscle size during short-term immobilization and the regain during remobilization in young men. NPN_1 supplementation does not differ from milk protein supplementation in modulating the myofibrillar protein synthesis rates during immobilization but further increases myofibrillar protein synthesis rates during remobilization.

The Muscle Protein Synthetic Response to the Ingestion of a Plant-Derived Protein Blend Does Not Differ from an Equivalent Amount of Milk Protein in Healthy Young Males.

BACKGROUND: Plant-derived proteins are considered to have lesser anabolic properties when compared with animal-derived proteins. The attenuated rise in muscle protein synthesis rates following ingestion of plant-derived compared with animal-derived protein has been, at least partly, attributed to deficiencies in specific amino acids such as leucine, lysine, and/or methionine. Combining different plant-derived proteins could provide plant-derived protein blends with a more balanced amino acid profile. OBJECTIVES: This study aimed to compare postprandial muscle protein synthesis rates following the ingestion of 30 g milk protein with a 30 g blend combining wheat, corn, and pea protein in healthy young men. METHODS: In a randomized, double-blind, parallel-group design, 24 young males (aged 24 ± 4 y) received a primed continuous l-[ring-13C6]-phenylalanine infusion after which they ingested 30 g milk protein (MILK) or a 30 g plant-derived protein blend combining 15 g wheat, 7.5 g corn, and 7.5 g pea protein (PLANT-BLEND). Blood and muscle biopsies were collected frequently for 5 h to assess postprandial plasma amino acid profiles (secondary outcome) and subsequent muscle protein synthesis rates (primary outcome). Data were analyzed by 2-factor repeated measures ANOVA and 2-samples t tests. RESULTS: MILK increased plasma essential amino acid concentrations more than PLANT-BLEND over the 5 h postprandial period (incremental AUC = 151 ± 31 compared with 79 ± 12 mmol·300 min·L-1, respectively; P < 0.001). Ingestion of both MILK and PLANT-BLEND increased myofibrillar protein synthesis rates (P < 0.001), with no significant differences between treatments (0.053 ± 0.013%/h and 0.064 ± 0.016%/h, respectively; P = 0.08). CONCLUSIONS: Ingestion of 30 g plant-derived protein blend combining wheat-, corn-, and pea-derived protein increases muscle protein synthesis rates in healthy young males. The muscle protein synthetic response to the ingestion of 30 g of this plant-derived protein blend does not differ from the ingestion of an equivalent amount of a high-quality animal-derived protein.Clinical trial registry number for Nederlands Trial Register: NTR6548 (https://trialsearch.who.int/Trial2.aspx?TrialID=NTR6548).

Higher Muscle Protein Synthesis Rates Following Ingestion of an Omnivorous Meal Compared with an Isocaloric and Isonitrogenous Vegan Meal in Healthy, Older Adults.

BACKGROUND: Plant-derived proteins are considered to have fewer anabolic properties when compared with animal-derived proteins. The anabolic properties of isolated proteins do not necessarily reflect the anabolic response to the ingestion of whole foods. The presence or absence of the various components that constitute the whole-food matrix can strongly impact protein digestion and amino acid absorption and, as such, modulate postprandial muscle protein synthesis rates. So far, no study has compared the anabolic response following ingestion of an omnivorous compared with a vegan meal. OBJECTIVES: This study aimed to compare postprandial muscle protein synthesis rates following ingestion of a whole-food omnivorous meal providing 100 g lean ground beef with an isonitrogenous, isocaloric whole-food vegan meal in healthy, older adults. METHODS: In a randomized, counter-balanced, cross-over design, 16 older (65-85 y) adults (8 males, 8 females) underwent 2 test days. On one day, participants consumed a whole-food omnivorous meal containing beef as the primary source of protein (0.45 g protein/kg body mass; MEAT). On the other day, participants consumed an isonitrogenous and isocaloric whole-food vegan meal (PLANT). Primed continuous L-[ring-13C6]-phenylalanine infusions were applied with blood and muscle biopsies being collected frequently for 6 h to assess postprandial plasma amino acid profiles and muscle protein synthesis rates. Data are presented as means ± standard deviations and were analyzed by 2 way-repeated measures analysis of variance and paired-samples t tests. RESULTS: MEAT increased plasma essential amino acid concentrations more than PLANT over the 6-h postprandial period (incremental area under curve 87 ± 37 compared with 38 ± 54 mmol·6 h/L, respectively; P-interaction < 0.01). Ingestion of MEAT resulted in ∼47% higher postprandial muscle protein synthesis rates when compared with the ingestion of PLANT (0.052 ± 0.023 and 0.035 ± 0.021 %/h, respectively; paired-samples t test: P = 0.037). CONCLUSIONS: Ingestion of a whole-food omnivorous meal containing beef results in greater postprandial muscle protein synthesis rates when compared with the ingestion of an isonitrogenous whole-food vegan meal in healthy, older adults. This study was registered at clinicaltrials.gov as NCT05151887.

Twist2-expressing cells reside in human skeletal muscle and are responsive to aging and resistance exercise training.

Skeletal muscle is maintained and repaired by sub-laminar, Pax7-expressing satellite cells. However, recent mouse investigations have described a second myogenic progenitor population that resides within the myofiber interstitium and expresses the transcription factor Twist2. Twist2-expressing cells exclusively repair and maintain type IIx/b muscle fibers. Currently, it is unknown if Twist2-expressing cells are present in human skeletal muscle and if they function as myogenic progenitors. Here, we perform a combination of single-cell RNA sequencing analysis and immunofluorescence staining to demonstrate the identity and localization of Twist2-expressing cells in human skeletal muscle. Twist2-expressing cells were identified to be anatomically and transcriptionally comparable to fibro-adipogenic progenitors (FAPs) and lack expression of typical satellite cell markers such as Pax7. Comparative analysis revealed that human and mouse Twist2-expressing cells were highly transcriptionally analogous and resided within the same anatomical structures in vivo. Examination of young and aged skeletal muscle biopsy samples revealed that Twist2-positive cells are more prevalent in aged muscle and increase following 12-weeks of resistance exercise training (RET) in humans. However, the quantity of Twist2-positive cells was not correlated with indices of muscle mass or muscle fiber cross-sectional area (CSA) in young or older muscle, and their abundance was surprisingly, negatively correlated with CSA and myonuclear domain size following RET. Taken together, we have identified cells expressing Twist2 in human skeletal muscle which are responsive to aging and exercise. Further examination of their myogenic potential is warranted.

The Postprandial Plasma Amino Acid Response Does Not Differ Following the Ingestion of a Solid Versus a Liquid Milk Protein Product in Healthy Adult Females.

Dietary protein digestion and amino acid absorption rates are modulated by numerous factors such as the food matrix. It has been speculated that protein ingested in liquid form is more rapidly digested and absorbed when compared with ingestion in solid form. Here, we assessed the postprandial plasma amino acid availability following ingestion of a single bolus of protein provided in either liquid or solid form. Twelve healthy, young females were included in this randomized cross-over study. On two separate test days, participants ingested 20-g milk protein concentrate in solid form (protein bar) or in liquid form (protein drink). Products were composed of matched ingredients and, thereby, had the same macro- and micronutrient composition. On both test days, arterialized blood samples were collected at regular time intervals for up to 4 hr following protein ingestion to assess the postprandial rise in plasma amino acid concentrations. Protein ingestion robustly elevated circulating plasma amino acid concentrations (p < .001), with no significant differences between treatments (p = .088). The incremental area under the curve of the postprandial rise in total plasma amino acid concentrations did not differ following bar versus drink consumption (160 ± 73 vs. 160 ± 71 mmol·L-1·240 min-1, respectively; 95% confidence interval [-37, 37]; Cohen's dz = 0.003; p = .992). Ingestion of protein in liquid or solid form does not modulate postprandial amino acid availability in healthy, female adults. Any differences in protein digestion and amino acid absorption due to differences in food matrix are not attributed to the protein being consumed as a bar or as a drink.

Raw Eggs To Support Postexercise Recovery in Healthy Young Men: Did Rocky Get It Right or Wrong?

BACKGROUND: Egg protein is ingested during recovery from exercise to facilitate the postexercise increase in muscle protein synthesis rates and, as such, to support the skeletal muscle adaptive response to exercise training. The impact of cooking egg protein on postexercise muscle protein synthesis is unknown. OBJECTIVES: We sought to compare the impact of ingesting unboiled (raw) compared with boiled eggs during postexercise recovery on postprandial myofibrillar protein synthesis rates. METHODS: In a parallel design, 45 healthy, resistance-trained young men (age: 24 y; 95% CI: 23, 25 y) were randomly assigned to ingest 5 raw eggs (∼30 g protein), 5 boiled eggs (∼30 g protein), or a control breakfast (∼5 g protein) during recovery from a single session of whole-body resistance-type exercise. Primed continuous l-[ring-13C6]-phenylalanine infusions were applied, with frequent blood sampling. Muscle biopsies were collected immediately after cessation of resistance exercise and at 2 and 5 h into the postexercise recovery period. Primary (myofibrillar protein synthesis rates) and secondary (plasma amino acid concentrations) outcomes were analyzed using repeated-measures (time × group) ANOVA. RESULTS: Ingestion of eggs significantly increased plasma essential amino acid (EAA) concentrations, with 20% higher peak concentrations following ingestion of boiled compared with raw eggs (time × group: P < 0.001). Myofibrillar protein synthesis rates were significantly increased during the postexercise period when compared with basal, postabsorptive values in all groups (2-4-fold increase: P < 0.001). Postprandial myofibrillar protein synthesis rates were 20% higher after ingesting raw eggs [0.067%/h; 95% CI: 0.056, 0.077%/h; effect size (Cohen d): 0.63], and 18% higher after ingesting boiled eggs (0.065%/h; 95% CI: 0.058, 0.073%/h; effect size: 0.69) when compared with the control breakfast (0.056%/h; 95% CI: 0.048, 0.063%/h), with no significant differences between groups (time × group: P = 0.077). CONCLUSIONS: The ingestion of raw, as opposed to boiled, eggs attenuates the postprandial rise in circulating EAA concentrations. However, postexercise muscle protein synthesis rates do not differ after ingestion of 5 raw compared with 5 boiled eggs in healthy young men. This trial was registered at the Nederlands Trial Register as NL6506 (www.trialregister.nl).

Cheese Ingestion Increases Muscle Protein Synthesis Rates Both at Rest and During Recovery from Exercise in Healthy, Young Males: A Randomized Parallel-Group Trial.

BACKGROUND: Protein ingestion increases muscle protein synthesis rates. The food matrix in which protein is provided can strongly modulate the postprandial muscle protein synthetic response. So far, the muscle protein synthetic response to the ingestion of whole foods remains largely unexplored. OBJECTIVES: To compare the impact of ingesting 30 g protein provided as milk protein or cheese on postprandial plasma amino acid concentrations and muscle protein synthesis rates at rest and during recovery from exercise in vivo in young males. METHODS: In this randomized, parallel-group intervention trial, 20 healthy males aged 18-35 y ingested 30 g protein provided as cheese or milk protein concentrate following a single-legged resistance-type exercise session consisting of 12 sets of leg press and leg extension exercises. Primed, continuous intravenous L-[ring-13C6]-phenylalanine infusions were combined with the collection of blood and muscle tissue samples to assess postabsorptive and 4-h postprandial muscle protein synthesis rates at rest and during recovery from exercise. Data were analyzed using repeated measures Time × Group (× Leg) ANOVA. RESULTS: Plasma total amino acid concentrations increased after protein ingestion (Time: P < 0.001), with 38% higher peak concentrations following milk protein than cheese ingestion (Time × Group: P < 0.001). Muscle protein synthesis rates increased following both cheese and milk protein ingestion from 0.037 ± 0.014 to 0.055 ± 0.018%·h-1 and 0.034 ± 0.008 to 0.056 ± 0.010%·h-1 at rest and even more following exercise from 0.031 ± 0.010 to 0.067 ± 0.013%·h-1 and 0.030 ± 0.008 to 0.063 ± 0.010%·h-1, respectively (Time: all P < 0.05; Time × Leg: P = 0.002), with no differences between cheese and milk protein ingestion (Time × Group: both P > 0.05). CONCLUSION: Cheese ingestion increases muscle protein synthesis rates both at rest and during recovery from exercise. The postprandial muscle protein synthetic response to the ingestion of cheese or milk protein does not differ when 30 g protein is ingested at rest or during recovery from exercise in healthy, young males.

Cheese Ingestion Increases Muscle Protein Synthesis Rates Both at Rest and During Recovery from Exercise in Healthy, Young Males: A Randomized Parallel-Group Trial.

BACKGROUND: Protein ingestion increases muscle protein synthesis rates. The food matrix in which protein is provided can strongly modulate the postprandial muscle protein synthetic response. So far, the muscle protein synthetic response to the ingestion of whole foods remains largely unexplored. OBJECTIVES: To compare the impact of ingesting 30 g protein provided as milk protein or cheese on postprandial plasma amino acid concentrations and muscle protein synthesis rates at rest and during recovery from exercise in vivo in young males. METHODS: In this randomized, parallel-group intervention trial, 20 healthy males aged 18-35 y ingested 30 g protein provided as cheese or milk protein concentrate following a single-legged resistance-type exercise session consisting of 12 sets of leg press and leg extension exercises. Primed, continuous intravenous L-[ring-13C6]-phenylalanine infusions were combined with the collection of blood and muscle tissue samples to assess postabsorptive and 4-h postprandial muscle protein synthesis rates at rest and during recovery from exercise. Data were analyzed using repeated measures Time × Group (× Leg) ANOVA. RESULTS: Plasma total amino acid concentrations increased after protein ingestion (Time: P < 0.001), with 38% higher peak concentrations following milk protein than cheese ingestion (Time × Group: P < 0.001). Muscle protein synthesis rates increased following both cheese and milk protein ingestion from 0.037 ± 0.014 to 0.055 ± 0.018%·h-1 and 0.034 ± 0.008 to 0.056 ± 0.010%·h-1 at rest and even more following exercise from 0.031 ± 0.010 to 0.067 ± 0.013%·h-1 and 0.030 ± 0.008 to 0.063 ± 0.010%·h-1, respectively (Time: all P < 0.05; Time × Leg: P = 0.002), with no differences between cheese and milk protein ingestion (Time × Group: both P > 0.05). CONCLUSION: Cheese ingestion increases muscle protein synthesis rates both at rest and during recovery from exercise. The postprandial muscle protein synthetic response to the ingestion of cheese or milk protein does not differ when 30 g protein is ingested at rest or during recovery from exercise in healthy, young males.

Ingestion of Free Amino Acids Compared with an Equivalent Amount of Intact Protein Results in More Rapid Amino Acid Absorption and Greater Postprandial Plasma Amino Acid Availability Without Affecting Muscle Protein Synthesis Rates in Young Adults in a Double-Blind Randomized Trial.

BACKGROUND: The rate of protein digestion and amino acid absorption determines the postprandial rise in circulating amino acids and modulates postprandial muscle protein synthesis rates. OBJECTIVE: We sought to compare protein digestion, amino acid absorption kinetics, and the postprandial muscle protein synthetic response following ingestion of intact milk protein or an equivalent amount of free amino acids. METHODS: Twenty-four healthy, young participants (mean ± SD age: 22 ± 3 y and BMI 23 ± 2 kg/m2; sex: 12 male and 12 female participants) received a primed continuous infusion of l-[ring-2H5]-phenylalanine and l-[ring-3,5-2H2]-tyrosine, after which they ingested either 30 g intrinsically l-[1-13C]-phenylalanine-labeled milk protein or an equivalent amount of free amino acids labeled with l-[1-13C]-phenylalanine. Blood samples and muscle biopsies were obtained to assess protein digestion and amino acid absorption kinetics (secondary outcome), whole-body protein net balance (secondary outcome), and mixed muscle protein synthesis rates (primary outcome) throughout the 6-h postprandial period. RESULTS: Postprandial plasma amino acid concentrations increased after ingestion of intact milk protein and free amino acids (both P < 0.001), with a greater increase following ingestion of the free amino acids than following ingestion of intact milk protein (P-time × treatment < 0.001). Exogenous phenylalanine release into plasma, assessed over the 6-h postprandial period, was greater with free amino acid ingestion (76 ± 9%) than with milk protein treatment (59 ± 10%; P < 0.001). Ingestion of free amino acids and intact milk protein increased mixed muscle protein synthesis rates (P-time < 0.001), with no differences between treatments (from 0.037 ± 0.015%/h to 0.053 ± 0.014%/h and 0.039 ± 0.016%/h to 0.051 ± 0.010%/h, respectively; P-time × treatment = 0.629). CONCLUSIONS: Ingestion of a bolus of free amino acids leads to more rapid amino acid absorption and greater postprandial plasma amino acid availability than ingestion of an equivalent amount of intact milk protein. Ingestion of free amino acids may be preferred over ingestion of intact protein in conditions where protein digestion and amino acid absorption are compromised.

Nutritional supplementation to enhance the efficacy of exercise training in older adults: what is the evidence from the latest randomized controlled trials?

PURPOSE OF REVIEW: This review summarizes recent studies that assessed whether nutritional supplementation enhances the efficacy of exercise training in older adults, focusing on the benefits for physical/functional performance of protein, vitamin D, or multi-ingredient supplementation. RECENT FINDINGS: Studies applying long-term exercise training strongly support the benefits of different exercise regimens for muscle strength and function but most studies do not provide direct evidence for protein, vitamin D, or multi-ingredient supplementation to further augment such improvements in older adults. Several methodological limitations are addressed that likely limited the reliability to convincingly establish or refute any additive effects of supplementation. Only when specifically tailored to the population under study, ensuring proper intensity, duration, and adherence to exercise, and aiming for a daily intake of ∼1.5 g protein per kg body mass, and ∼800 IU of vitamin D supplementation, there appears to be some potential to augment the efficacy of long-term exercise training in older adults, with potentially greater benefits in compromised older subpopulations. SUMMARY: There is some support for the efficacy of nutritional supplementation to further augment the beneficial effects of prolonged exercise training in older adults but any intervention needs tailoring of both the exercise and the nutritional intervention towards the intended (sub)population.

Increasing Nitrate-Rich Vegetable Intake Lowers Ambulatory Blood Pressure in (pre)Hypertensive Middle-Aged and Older Adults: A 12-Wk Randomized Controlled Trial.

BACKGROUND: Emerging evidence suggests that increasing dietary nitrate intake may be an effective approach to improve cardiovascular health. However, the effects of a prolonged elevation of nitrate intake through an increase in vegetable consumption are understudied. OBJECTIVE: Our primary aim was to determine the impact of 12 wk of increased daily consumption of nitrate-rich vegetables or nitrate supplementation on blood pressure (BP) in (pre)hypertensive middle-aged and older adults. METHODS: In a 12-wk randomized, controlled study (Nijmegen, The Netherlands), 77 (pre)hypertensive participants (BP: 144 ± 13/87 ± 7 mmHg, age: 65 ± 10 y) either received an intervention with personalized monitoring and feedback aiming to consume ∼250-300 g nitrate-rich vegetables/d (∼350-400 mg nitrate/d; n = 25), beetroot juice supplementation (400 mg nitrate/d; n = 26), or no intervention (control; n = 26). Before and after intervention, 24-h ambulatory BP was measured. Data were analyzed using repeated measures ANOVA (time × treatment), followed by within-group (paired t-test) and between-group analyses (1-factor ANOVA) where appropriate. RESULTS: The 24-h systolic BP (SBP) (primary outcome) changed significantly (P-interaction time × treatment = 0.017) with an increase in the control group (131 ± 8 compared with 135 ± 10 mmHg; P = 0.036); a strong tendency for a decline in the nitrate-rich vegetable group (129 ± 10 compared with 126 ± 9 mmHg; P = 0.051) which was different from control (P = 0.020); but no change in the beetroot juice group (133 ± 11 compared with 132 ± 12 mmHg; P = 0.56). A significant time × treatment interaction was also found for daytime SBP (secondary outcome, P = 0.011), with a significant decline in the nitrate-rich vegetable group (134 ± 10 compared with 129 ± 9 mmHg; P = 0.006) which was different from control (P = 0.010); but no changes in the beetroot juice (138 ± 12 compared with 137 ± 14 mmHg; P = 0.41) and control group (136 ± 10 compared with 137 ± 11 mmHg; P = 0.08). Diastolic BP (secondary outcome) did not change in any of the groups. CONCLUSIONS: A prolonged dietary intervention focusing on high-nitrate vegetable intake is an effective strategy to lower SBP in (pre)hypertensive middle-aged and older adults. This trial was registered at www.trialregister.nl as NL7814.

No differences in muscle protein synthesis rates following ingestion of wheat protein, milk protein, and their protein blend in healthy, young males.

Plant-derived proteins have been suggested to have less anabolic properties when compared with animal-derived proteins. Whether blends of plant- and animal-derived proteins can compensate for their lesser anabolic potential has not been assessed. The present study compares post-prandial muscle protein synthesis rates following the ingestion of milk protein with wheat protein or a blend of wheat plus milk protein in healthy, young males. In a randomised, double-blind, parallel-group design, 36 males (23 (sd 3) years) received a primed continuous L-[ring-13C6]-phenylalanine infusion after which they ingested 30 g milk protein (MILK), 30 g wheat protein (WHEAT) or a 30 g blend combining 15 g wheat plus 15 g milk protein (WHEAT+MILK). Blood and muscle biopsies were collected frequently for 5 h to assess post-prandial plasma amino acid profiles and subsequent myofibrillar protein synthesis rates. Ingestion of protein increased myofibrillar protein synthesis rates in all treatments (P < 0·001). Post-prandial myofibrillar protein synthesis rates did not differ between MILK v. WHEAT (0·053 (sd 0·013) v. 0·056 (sd 0·012) %·h-1, respectively; t test P = 0·56) or between MILK v. WHEAT+MILK (0·053 (sd 0·013) v. 0·059 (sd 0·025) %·h-1, respectively; t test P = 0·46). In conclusion, ingestion of 30 g milk protein, 30 g wheat protein or a blend of 15 g wheat plus 15 g milk protein increases muscle protein synthesis rates in young males. Furthermore, muscle protein synthesis rates following the ingestion of 30 g milk protein do not differ from rates observed after ingesting 30 g wheat protein or a blend with 15 g milk plus 15 g wheat protein in healthy, young males.

Acute Effects of Dietary Nitrate on Exercise Tolerance, Muscle Oxygenation, and Cardiovascular Function in Patients With Peripheral Arterial Disease.

Previous studies have used supplements to increase dietary nitrate intake in clinical populations. Little is known about whether effects can also be induced through vegetable consumption. Therefore, the aim of this study was to assess the impact of dietary nitrate, through nitrate-rich vegetables (NRV) and beetroot juice (BRJ) supplementation, on plasma nitrate and nitrite concentrations, exercise tolerance, muscle oxygenation, and cardiovascular function in patients with peripheral arterial disease. In a randomized crossover design, 18 patients with peripheral arterial disease (age: 73 ± 8 years) followed a nitrate intake protocol (∼6.5 mmol) through the consumption of NRV, BRJ, and nitrate-depleted BRJ (placebo). Blood samples were taken, blood pressure and arterial stiffness were measured in fasted state and 150 min after intervention. Each intervention was followed by a maximal walking exercise test to determine claudication onset time and peak walking time. Gastrocnemius oxygenation was measured by near-infrared spectroscopy. Blood samples were taken and blood pressure was measured 10 min after exercise. Mean plasma nitrate and nitrite concentrations increased (nitrate; Time × Intervention interaction; p < .001), with the highest concentrations after BRJ (494 ± 110 µmol/L) compared with NRV (202 ± 89 µmol/L) and placebo (80 ± 19 µmol/L; p < .001). Mean claudication onset time and peak walking time did not differ between NRV (413 ± 187 s and 745 ± 220 s, respectively), BRJ (392 ± 154 s and 746 ± 176 s), and placebo (403 ± 176 s and 696 ± 222 s) (p = .762 and p = .165, respectively). Gastrocnemius oxygenation, blood pressure, and arterial stiffness were not affected by the intervention. NRV and BRJ intake markedly increase plasma nitrate and nitrite, but this does not translate to improved exercise tolerance, muscle oxygenation, and/or cardiovascular function.