Adipose tissue and skeletal muscle are metabolically active tissues that play a central role in whole-body energy homeostasis. The functionality of these tissues, and hence cardiometabolic health, relies on adequate adjustments in perfusion reflecting metabolic demands in different physiological conditions. Acute exercise increases skeletal muscle perfusion, and this response can be enhanced by prolonged exercise training. Yet, whether similar responses occur in adipose tissue remains unclear. Here, we investigated the effect of a single bout of resistance exercise on adipose tissue microvascular perfusion in healthy older females. Moreover, we explored the effects of 8 weeks of aerobic exercise training on the microvascular perfusion response to acute resistance exercise. Study participants (age: 70 ± 4 y; BMI: 24.7 ± 2.8 kg/m2) were assigned to either a supervised aerobic exercise training (3 times/week) or a no training control group. Before and after the intervention period, microvascular blood volume was measured in femoral adipose tissue and the adjacent skeletal muscle using contrast-enhanced ultrasound. More specifically, the measurements were conducted at rest and at t = 10 and t = 40 min after a single resistance exercise session. We found that microvascular blood volume increased in both adipose (3.0 ± 2.5-fold, p < 0.05) and skeletal muscle (4.5 ± 1.9-fold, p = 0.001) tissue after the resistance exercise session. Eight weeks of aerobic exercise training improved adipose tissue microvascular perfusion after acute resistance exercise compared to the control group (time x group, p = 0.033), without significant within-group changes. The present findings indicate that microvascular blood volume in femoral adipose tissue increases after an acute bout of resistance exercise and may be enhanced following exercise training in healthy older females.

PURPOSE:To determine whether high-intensity resistance exercise training with nutritional support (RET) during recovery from total knee arthroplasty induces greater improvements in muscle-related outcomes compared with standard rehabilitation (SR) alone. METHODS:Thirty-three patients (70 ± 6 yr; 28.7 ± 3.1 kg⋅m -2 ) were randomized to receive RET (intervention + regular rehabilitation, n = 18) or SR (regular rehabilitation only, n = 15) for 12 wk, starting 8 wk post-TKA. RET involved supervised, bilateral, high-intensity resistance exercise, 3×/wk, daily supplementation (45 g protein, 5.5 g Vivinal GOS, 800 IU vitamin D, 366 mg calcium), and dietary counseling. Outcomes included bilateral and unilateral leg press one-repetition maximum, DXA-derived appendicular lean mass, computed tomography-derived quadriceps cross-sectional area, 6-min walking test, and 5-times chair-stand test (5CST). Data are mean ± SD, analyzed with two-way repeated-measures ANOVAs, or median [IQR], analyzed with Wilcoxon Signed-Rank test. RESULTS:Bilateral leg press one-repetition maximum improved to a greater extent following RET (131 ± 38 to 174 ± 56 kg; P < 0.001) versus SR (124 ± 36 to 143 ± 49 kg, P = 0.018, P value of interaction [ Pint ] = 0.026). Strength in the nonoperated leg increased in the RET group only (RET: 22% ± 17%, P < 0.001, SR: 6% ± 11%, P = 0.175, Pint = 0.002). Operated leg strength increased similarly between groups (RET: 51% ± 33%, SR: 40% ± 30%, P value of main time effect [ Ptime ] < 0.001, Pint = 0.338), as did appendicular lean mass (RET: 0.5 ± 0.8 kg, SR: 0.3 ± 0.8 kg, Ptime = 0.009, Pint = 0.390), and quadriceps cross-sectional area (operated: RET: 7.8% ± 7.5%, SR: 9.2% ± 5.9%, nonoperated: RET: 4.8% ± 4.5%, SR: 3.8% ± 3.7%, Ptime < 0.001, Pint ≥ 0.557). Six-minute walking test improved more in the SR (428 ± 94 to 513 ± 75 m, P < 0.001) versus RET group (417 ± 69 to 460 ± 72 m, P = 0.002, Pint = 0.034). 5CST only improved significantly following RET (RET: 15.3 [4.2] to 13.2 [3.9] s, P = 0.039, SR: 14.4 [4.0] to 14.4 [5.1] s, P = 0.064). CONCLUSIONS:Compared with standard total knee arthroplasty rehabilitation, high-intensity resistance training with nutritional support induces greater gains in bilateral strength but not muscle mass or physical functioning.

BACKGROUND:Sufficient high-quality protein intake is required to prevent sarcopenia in older adults. Plant-based proteins have been reported to have lower anabolic properties when compared with animal-based proteins. Whether the lower quality of plant-based protein can be improved, thereby resulting in an anabolic response noninferior to an equivalent amount of animal-based protein, remains to be established in older adults. OBJECTIVES:To compare postprandial muscle protein synthesis rates following ingestion of a single bolus of a soy- and pea-derived protein blend (PLANT), with a soy-pea protein blend fortified with free leucine (PLANT+LEU), or whey protein (WHEY) in older males. METHODS:In this randomly assigned, double-blind, parallel-group design, 45 healthy older males [aged 69 ± 5 y, BMI (in kg·m‒2) 26.2 ± 3.2] were selected to ingest a 20 g protein blend combining 12 g soy plus 8 g pea protein (PLANT), 20 g of the soy-pea protein blend fortified with 2 g leucine (PLANT+LEU), or 20 g WHEY. Primed continuous L-[ring-13C6]-phenylalanine infusions were applied, with blood and muscle sampling ≤4 h after protein ingestion to assess plasma amino acid profiles and muscle protein synthesis rates. RESULTS:WHEY increased plasma essential amino acid concentrations more than PLANT and PLANT+LEU over the 4 h postprandial period (Incremental area under the curve: 135 ± 20 compared with 99 ± 21 compared with 105 ± 21 mmol·240 min·L‒1, respectively; P < 0.001). Plasma peak leucine concentrations were higher after PLANT+LEU ingestion compared with PLANT and WHEY (567 ± 74 μmol·L‒1 compared with 310 ± 49 μmol·L‒1 compared with 471 ± 74 μmol·L‒1, respectively; P < 0.001). Postprandial muscle protein synthesis rates averaged 0.034 ± 0.010 %·h‒1, 0.035 ± 0.012 %·h‒1, and 0.034 ± 0.010 %·h‒1 following PLANT, PLANT+LEU, and WHEY ingestion, respectively (treatment P = 0.828), and were not increased when compared with postabsorptive values. CONCLUSIONS:Ingestion of 20 g of protein alone, independent of its quality, is not enough to increase muscle protein synthesis rates in older males. More work is needed to define the preferred combination of both protein quality and quantity to stimulate muscle protein synthesis in an older population. This trial was registered at clinicaltrials.gov as NCT05711095.

Background & aims Healing after total hip arthroplasty (THA) involves remodelling of collagenous tissues, such as bone. While collagen protein supplementation has been suggested to modulate bone metabolism, the effects following THA are yet to be investigated. Therefore, we aimed to characterize changes in biomarkers of bone metabolism following THA and to assess the potential modulating effects of collagen protein supplementation. Methods In this randomized, double-blinded, placebo-controlled trial, 39 older adults (71±6 y; 27.4±3.6 kg/m2) consumed either hydrolysed collagen protein (15 g protein; HC group) or an energy-matched placebo supplement (maltodextrin; 15 g carbohydrates; PLA group) for 14 days following THA. Procollagen type 1 N-terminal propeptide (P1NP) and C-terminal telopeptide of type 1 collagen (CTX-1) concentrations were assessed in blood samples obtained before surgery (pre-surgery), immediately following surgery (t=0), and one (t=1), four (t=4), and fifteen (t=15) days post-surgery. Patient-reported outcome measures (PROMs) were assessed at pre-surgery, t=4, and t=15. Data are shown as mean±SD and were analysed using 2-way repeated measures ANOVA. Results P1NP concentrations decreased from pre-surgery (HC: 53±18, PLA: 58±21 ng/mL) to t=1 (HC: 21±11, PLA: 25±10 ng/mL), subsequently peaking at t=15 (HC: 160±44, PLA: 154±55 ng/mL), with no group differences (P-time<0.001, P-interaction=0.588). CTX-1 showed a steady increase from pre-surgery (HC: 0.50±0.16, PLA: 0.50±0.23 ng/mL) throughout the follow-up period, also peaking at t=15 (HC: 0.66±0.19, PLA: 0.71±0.25 ng/mL) with no group differences (P-time<0.001, P-interaction=0.168). While most PROMs improved over time similarly in both groups, pain at rest declined significantly in the HC group only (HC: 6±3 to 2±2, P<0.001; PLA: 4±3 to 3±2, P=0.054; P-interaction=0.007). Conclusion Bone turnover markers greatly increase following total hip arthroplasty, but this is not modulated by daily collagen supplementation. Clinical trial registry This trial was registered on 20 July 2021 at the Dutch Trial Register (NL9608) and is available at https://onderzoekmetmensen.nl/nl/trial/27884.

The present study assessed the effects of aerobic exercise training (AER) on blood glucose regulation in healthy older adults, and whether these effects depend on baseline glucose regulation. Thirty-four healthy older adults (71 ± 4 y) were randomized to perform 8 weeks of AER (n = 17) or no exercise (CON, n = 17). A five-point oral glucose tolerance test was performed at baseline and post-intervention to assess plasma glucose and insulin concentrations. Glucose regulation was assessed by Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), Hepatic Insulin Resistance Index (HIRI), Muscle Insulin Sensitivity Index (MISI), and Matsuda index. Two-factor repeated measures ANOVAs were performed on the full cohort and on a subgroup (CON: n = 10, AER: n = 9) with Matsuda index ≤5. Full Cohort Analyses: a significant interaction effect (P < 0.05) was observed only for HIRI (P = 0.025), which worsened in CON (+151 ± 232, P = 0.016) but not AER (-32 ± 221, P = 0.557). Subgroup Analyses: significant interaction effects were observed for hepatic glucose regulation (P ≤ 0.013), which worsened in CON (HOMA-IR: +0.5 ± 0.6, P = 0.085; HIRI: +249 ± 253, P = 0.006), but tended to improve in AER (HOMA-IR: -0.6 ± 1.2, P = 0.051; HIRI: -133 ± 241, P = 0.125). A significant interaction effect was observed for Matsuda index (P = 0.004), which increased in AER (from 3.2 ± 1.1 to 4.8 ± 2.1, P = 0.002), but remained unchanged in CON (from 3.8 ± 0.9 to 3.5 ± 1.4, P = 0.401). A trend toward an interaction effect was noted for MISI (AER: from 0.12 ± 0.07 to 0.19 ± 0.16; CON: from 0.18 ± 0.11 to 0.16 ± 0.06, P = 0.082). Aerobic exercise training improves blood glucose regulation in healthy older adults, with greater impact in those with a more compromised blood glucose regulation (based on Matsuda index ≤5).

BACKGROUND:Industrial processing and storage of milk products can strongly increase protein glycation level. Previously, we have reported that a high protein glycation level impairs protein digestion, thereby compromising lysine bioavailability. The lower postprandial lysine availability may restrict the anabolic properties of a high glycated protein. OBJECTIVES:The objective of this study was to assess the impact of milk protein glycation on postprandial plasma amino acid availability and subsequent postprandial muscle protein synthesis rates during recovery from a single bout of resistance-type exercise. METHODS:Forty-five recreationally active, healthy young males participated in this double-blinded, randomized parallel study. After performing a single bout of whole-body resistance-type exercise, subjects ingested 20 g milk protein with either a low (4%; LOW-GLYC) or high (47%; HIGH-GLYC) glycation level or a noncaloric placebo (PLA). Continuous intravenous infusion of L-[ring-13C6]-phenylalanine was combined with the collection of blood and muscle tissue samples during a 6-h postprandial period to assess plasma amino acid concentrations and muscle protein synthesis rates. RESULTS:Protein ingestion increased plasma total and essential amino acid concentrations compared with placebo (time × treatment interaction: P < 0.001), with no differences between the low and high glycated milk protein. Plasma lysine availability, assessed over the full 6 h postprandial period, was substantially lower following ingestion of the protein with the high versus low glycation level (-5 ± 7 compared with 10 ± 9 mmol · L-1 · 360 min, respectively, P < 0.001). Postprandial muscle protein synthesis rates did not differ between treatments (0.059 ± 0.016, 0.061 ± 0.012, and 0.061 ± 0.018 % · h-1, in LOW-GLYC, HIGH-GLYC and PLA, respectively, P = 0.939). CONCLUSIONS:Ingestion of protein with a higher glycation level attenuates postprandial plasma lysine availability. Milk protein glycation does not modulate postprandial muscle protein synthesis rates during recovery from resistance exercise in healthy, young males. This trial was registered at the Dutch Trial Register as NL8690; https://onderzoekmetmensen.nl/nl/trial/49398.

Background The polyphenol oleuropein activates mitochondrial calcium import, which increases pyruvate dehydrogenase (PDH) activity. Preclinically, this increase in PDH activity following oleuropein supplementation resulted in improved mitochondrial bioenergetics and fatigue resistance. Objectives This study aimed to examine the effects of acute and chronic oleuropein supplementation on muscle energy metabolism, whole-body substrate metabolism, strength, and fatigue resistance in older males. Methods In a randomized, double-blind, placebo-controlled trial, 40 healthy older males (60 ± 5y) received either placebo (PLA) or 100 mg oleuropein from 250 mg olive leaf extract (OLE) supplementation daily for 36 d. On day 1 and day 36, muscle and blood samples were collected, and indirect calorimetry was performed before and ≤120 min following supplement intake. Leg strength and fatigue were measured before and after 29 d of supplementation. Results were analyzed using analysis of covariance or robust analysis of covariance. Results OLE ingestion on day 1 and day 36 increased plasma oleuropein metabolites (P < 0.001). On day 1, no differences were observed in muscle PDH activity, mitochondrial respiration, or whole-body substrate metabolism 120 min after acute OLE ingestion. Ribonucleic acid sequencing revealed upregulation of oxidative phosphorylation gene pathways (false discovery rate < 0.05), whereas PDH-Serine293-phosphorylation was higher after acute OLE compared with PLA ingestion (P = 0.015). Following chronic supplementation, fractional PDH activity was ∼25% greater in OLE compared with PLA (49 ± 14 compared with 38 ± 10%; P = 0.016) with no differences in absolute PDH activity and PDH-Serine293-phosphorylation between groups. Mitochondrial respiration and protein content, whole-body substrate metabolism, leg strength, and fatigue resistance were not different between OLE and PLA. Plasma low-density lipoprotein cholesterol was lower after chronic OLE compared with PLA (P = 0.043), with no differences in other blood metabolic markers. Conclusions Chronic OLE supplementation resulted in higher skeletal muscle fractional PDH activity in healthy, older males, which may impact resting energy metabolism. Acute or chronic oleuropein supplementation does not modulate skeletal muscle mitochondrial respiration, muscle strength, muscle fatigue, or whole-body substrate metabolism.This trial was registered at clinicaltrials.gov as NCT05217433.

Resistance exercise training is an effective treatment strategy to counteract the age-related loss of muscle mass and strength in older adults. However, there is a large inter-individual variation in muscle fiber hypertrophy following resistance exercise training. It has been hypothesized that a less than optimal muscle fiber capillarization and perfusion capacity may compromise muscle hypertrophy during resistance exercise training in older adults. We assessed whether 8 weeks of aerobic exercise preconditioning, to improve muscle fiber capillarization and perfusion capacity, augments the gains in muscle mass and strength during subsequent resistance exercise training in older adults. In total, 34 healthy older males and females (71 years standard deviation (SD) ± 5 years) participated in 12 weeks of progressive resistance exercise training, preceded by either 8 weeks of aerobic preconditioning (AER, n = 17) through cycle-ergometer endurance training, or a no exercise control condition (CON, n = 17). Muscle strength (one repetition maximum (1RM)) and muscle fiber characteristics (histochemistry) were assessed at baseline, following 8 weeks of AER or CON, and after 12 weeks of resistance exercise training. Femoral artery blood flow and vastus lateralis muscle microvascular perfusion kinetics were assessed at baseline and following 8 weeks of AER or CON intervention. Thigh muscle volume (magnetic resonance imaging scan) was assessed before and after the 12 weeks of resistance exercise training. Aerobic exercise preconditioning increased type I (+ 19 ± 19

BACKGROUND:Protein ingestion during recovery from exercise can further increase muscle protein synthesis rates. Plant-derived proteins are generally believed to have lesser anabolic properties than animal-derived proteins. To our knowledge, no studies have compared the impact of plant-derived with that of animal-derived protein ingestion on postexercise muscle protein synthesis rates in healthy, young females. OBJECTIVES:This study compared muscle protein synthesis rates following the ingestion of 20 g native canola protein, 20 g whey protein, or a noncaloric placebo during recovery from a single bout of resistance exercise in healthy, young females. METHODS:In this randomly assigned, parallel group, double-blind placebo-controlled design, 36 healthy young (age, 23 ± 4 y; BMI, 22.7 ± 2.2 kg/m2) females performed 8 sets of lower-body resistance exercise at 80% of their predetermined 1-repetition maximum after which they ingested 20 g native canola protein isolate, 20 g whey protein isolate, or a noncaloric placebo. Primed continuous L-[ring-13C6]-phenylalanine infusions were applied with frequent sampling of blood and muscle tissue to assess postprandial plasma amino acid profiles and 5-h postexercise muscle protein synthesis rates. Data are presented as mean ± SD. RESULTS:Plasma essential amino acid concentrations strongly increased following ingestion of both whey and canola protein when compared with the placebo treatment (peak: 2113 ± 354, 1249 ± 173, and 780 ± 60 μmol/L, respectively; P < 0.001) with greater postprandial plasma essential amino acid availability following whey than after canola protein ingestion (incremental AUC, 158 ± 50 and 90 ± 23 mmol/L × 5 h; P < 0.001). No significant differences in postexercise muscle protein synthesis rates were observed following the ingestion of whey protein isolate, canola protein isolate, and placebo (0.071 ± 0.015, 0.069 ± 0.016, and 0.061 ± 0.013%/h, respectively; treatment; P = 0.200). CONCLUSIONS:A single session of resistance exercise strongly increases muscle protein synthesis rates in young females. Ingestion of 20 g whey or native canola protein does not further augment muscle protein synthesis rates during the early stages of postexercise recovery in healthy, young females. This trial was registered at clinicaltrials.gov as NCT05664269.

(195 WORDS)It has been suggested that different nutritional stimuli are required to augment myofibrillar versus muscle connective protein synthesis rates. To study such different aspects of skeletal muscle remodeling, researchers often isolate myofibrillar or connective protein fractions from muscle tissue samples. However, the composition of these muscle protein fractions remains poorly defined. Here, we evaluated the amino acid profiles and protein compositions of the myofibrillar and muscle connective protein fractions within skeletal muscle tissue. The muscle connective protein fraction was shown to contain ∼70% of the total mixed muscle collagen content, with 4.4 ± 0.9% collagen relative to total protein content. This was 3-4 fold greater than the collagen content in mixed muscle tissue (1.2 ± 0.2%; p < 0.05). Myofibrillar proteins, such as actin and myosin, accounted for 39% of the myofibrillar protein fraction and 32% of the muscle connective protein fraction. The muscle connective protein fraction contained a higher proportion (42%) of key scaffolding proteins compared to the myofibrillar protein fraction (11%). In conclusion, the muscle connective protein fraction contains an enriched proportion of collagen among a large proportion of intra- and extracellular scaffolding and cell adhesion proteins, all of which are far less abundant in the myofibrillar protein fraction.

PURPOSE:Cold-water immersion lowers muscle protein synthesis rates during postexercise recovery. Whether this effect can be explained by lower muscle microvascular perfusion and a subsequent decline in postprandial amino acid incorporation into muscle tissue after cooling is currently unknown. METHODS:Twelve young males (24 ± 4 yr) performed a single resistance exercise session followed by water immersion for 20 min with one leg immersed in cold water (8°C: COLD) and the contralateral leg in thermoneutral water (30°C: CON). After immersion, a beverage was ingested containing 20 g free amino acids, 0.25 g L-[ring- 13 C 6 ]-phenylalanine, and 45 g carbohydrates. Microvascular perfusion of the vastus lateralis muscle was assessed for both legs using contrast-enhanced ultrasound at rest, immediately after exercise and water immersion, and at t = 60 and t = 180 min after beverage ingestion. A muscle biopsy sample ( vastus lateralis ) was collected from both legs ( t = 240 min) to determine amino acid tracer incorporation. RESULTS:Microvascular blood volume was significantly lower in the COLD versus CON leg immediately after water immersion (1.24 ± 0.82 vs 3.13 ± 1.64 video intensity, respectively, P < 0.001) and remained lower at t = 60 and t = 180 min after beverage ingestion (0.90 ± 0.84 vs 1.53 ± 0.98, and 2.10 ± 2.53 vs 2.77 ± 2.81 video intensity, respectively, both P < 0.05). Exogenous amino acid incorporation into muscle protein was lower in the COLD versus CON leg (0.011 ± 0.004 vs 0.016 ± 0.005 mole percent excess, respectively, P < 0.001). The difference in postprandial amino acid incorporation into muscle protein between the COLD and the CON legs was strongly associated with the difference in microvascular blood volume between the two legs during recovery ( r = 0.65, P < 0.05). CONCLUSIONS:Cold-water immersion during postexercise recovery greatly reduces muscle microvascular perfusion and blunts postprandial amino acid incorporation in muscle.

BACKGROUND:Industrial processing and storage of milk products can strongly increase protein glycation level. Previously, we have reported that ingestion of highly glycated milk protein attenuates the postprandial rise in plasma lysine concentrations compared to the ingestion of an equivalent amount of milk protein with a low glycation level. Whether the attenuated increase in plasma lysine availability is attributed to compromised protein digestion and subsequent lysine absorption remains to be established. OBJECTIVES:The present study combined stable-isotope methodology with the ingestion of specifically produced, intrinsically labeled protein to assess protein digestion and amino acid absorption following ingestion of milk protein with a high versus low glycation level in vivo in humans. METHODS:Fifteen recreationally active, healthy young males participated in this double-blinded, randomized cross-over study. Subjects ingested 40 g intrinsically L-[1-13C]-lysine-labeled milk protein with either a low (3%) or high (50%) glycation level. Continuous intravenous infusion of L-[4,4,5,5-2H4]-lysine was combined with frequent blood sample collection during a 6-h postprandial period to evaluate dietary protein-derived lysine release into the circulation. RESULTS:Postprandial plasma lysine concentrations were lower following the ingestion of milk protein with a high versus low glycation level (time × treatment effect: P = 0.002; ƞ2 = 0.214), resulting in a 23 mmol/L x 360 min (95% confidence interval [CI]: 13, 32) lower incremental area under the curve (0 ± 12 vs 23 ± 11 mmol/L x 360 min, respectively, P < 0.001). The postprandial release of milk protein-derived lysine into the circulation was attenuated following ingestion of the protein with the high versus low glycation level (time × treatment effect: P < 0.001; ƞ2 = 0.640) and was 31% (95% CI: 26, 36) lower over the full 6-h postprandial period (18 ± 4 vs 49 ± 10% of the ingested lysine, respectively, P < 0.001). CONCLUSIONS:A high level of milk protein glycation strongly reduces postprandial plasma lysine availability in vivo in humans. Industrial processing and storage of (milk) protein products can strongly modulate protein bioavailability and, as such, lower the nutritional value of a protein source. This trial was registered at www. CLINICALTRIALS:gov as NCT05479916.

Canola protein is a rapeseed-derived protein that contains all essential amino acids in proportions that meet the WHO amino acid scoring requirements, making it an interesting protein for human food applications. It is currently unknown whether canola protein processing modulates postprandial plasma amino acid bioavailability in vivo in humans. This study compared postprandial plasma amino acid profiles following the ingestion of unprocessed (native) canola, processed canola, and whey protein isolate in healthy, young, females. In a randomized, clinical, cross-over design, 15 healthy young females (25 ± 3 y) participated in four test days on which they consumed 20 g protein as either native canola, enzyme processed or heat processed canola protein, or 20 g whey protein. Blood samples were collected for 5 h following protein ingestion to assess plasma amino acid concentrations. Ingestion of native canola protein resulted in lower increases in plasma total amino acid (TAA) concentrations compared to whey protein (3191 ± 794 vs. 4429 ± 84 µmol∙L− 1, P < 0.001). Canola protein processing resulted in greater peak plasma total amino acids concentrations, reaching statistical significance for enzyme (3599 ± 687 µmol∙L− 1, P = 0.045) but not heat (3565 ± 722 µmol∙L− 1, P = 0.166) treated compared to native canola protein. Plasma total amino acid availability, expressed as incremental area under the curve over a 5 h postprandial period, did not differ between treatments and averaged 163 ± 81, 171 ± 76, 194 ± 82, and 207 ± 85 mmol∙300 min∙L− 1 following ingestion of native, enzyme- and heat processed canola, and whey protein, respectively (P > 0.05). Ingestion of whey protein allows for a more rapid postprandial rise in circulating essential and non-essential amino acids and greater postprandial plasma total amino acid availability when compared to the ingestion of native canola protein. Ingestion of enzyme- or heat processed canola protein accelerates the postprandial rise in circulating amino acids but does not further augment overall plasma amino acid availability throughout a 5 h postprandial period when compared to the ingestion of native canola protein.

Biomedical research frequently employs null hypothesis testing to determine whether an observed difference in a sample is likely to exist in the broader population. Null hypothesis testing generally assumes that differences between groups or interventions are non-existent, unless proven otherwise. Because biomedical studies with human subjects are often limited by financial and logistical resources, they tend to have low statistical power, i.e. a low probability of statistically confirming a true difference. As a result, small but potentially clinically important differences may be overseen or ignored simply due to the absence of a statistically significant difference. This absence is often misinterpreted as 'equivalence' of treatments. In this educational paper, we will use practical examples related to the effects of exercise and nutrition on muscle protein metabolism to illustrate the most important determinants of statistical power, as well as their implications for both investigators and readers of scientific articles. Changes in muscle mass occur at a relatively slow rate, making it practically challenging to detect differences between treatment groups in a long-term setting. One way to make it 'easier' to differentiate between groups and hence increase statistical power is to have a sufficiently long study duration to allow treatment effects to become apparent. This is especially relevant when comparing treatments with relatively small expected differences such as the effect of modest changes in daily protein intake. Secondly, one could try to minimize the variance and response heterogeneity within groups, for example by using strict inclusion criteria and standardization protocols (e.g., meal provision), by using cross-over designs, or even within-subject designs where two interventions are compared simultaneously (e.g., studying an exercised limb vs a contralateral control limb) although this might limit the generalizability of the findings (e.g. such single-limb exercise training is not common in practice). In terms of data interpretation, investigators should obviously refrain from drawing strong conclusions from underpowered studies. Yet, such studies still provide valuable data for meta-analyses. Finally, because muscle protein synthesis rates are highly responsive to anabolic stimuli, acute metabolic studies are more sensitive to detect potentially clinically relevant differences in the anabolic response between treatments. Apart from further elaborating on these topics, this educational article encourages readers to more critically question null findings and scientists to more clearly discuss limitations that may have compromised statistical power.

Knee osteoarthritis is associated with deficits in muscle strength, muscle mass, and physical functioning. These muscle-related deficits are acutely exacerbated following total knee arthroplasty (TKA) and persist long after surgery, despite the application of standardized rehabilitation programs that include physical/functional training. Resistance exercise training (RET) has been shown to be a highly effective strategy to improve muscle-related outcomes in healthy as well as clinical populations. However, the use of RET in traditional rehabilitation programs after TKA is limited. In this narrative review, we provide an updated view on whether adding RET to the standard rehabilitation (SR) in the recovery period (up to 1 year) after TKA leads to greater improvements in muscle-related outcomes when compared to SR alone. Overall, research findings clearly indicate that both muscle strength and muscle mass can be improved to a greater extent with RET-based rehabilitation compared to SR. Additionally, measures of physical functioning that rely on quadriceps strength and balance (e.g., stair climbing, chair standing, etc.) also appear to benefit more from a RET-based program compared to SR, especially in patients with low levels of physical functioning. Importantly though, for RET to be optimally effective, it should be performed at 70%-80% of the one-repetition maximum, with 3-4 sets per exercise, with a minimum of 3 times per week for 8 weeks. Based upon this narrative review, we recommend that such high-intensity progressive RET should be incorporated into standard programs during rehabilitation after TKA.

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- 13 C 6 ]-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).

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-C-13(6)]-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 mmol6 h/L, respectively; P-interaction < 0.01). Ingestion of MEAT resulted in similar to 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.

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.

BackgroundCOPD is a disease characterised by skeletal muscle dysfunction. A spatial relationship exists between satellite cells and muscle fibre capillaries, which has been suggested to be of major importance for satellite cell function. In the present study we compared the spatial relationship between satellite cells and capillaries in patients with COPD and age-matched healthy older adults.MethodsMuscle biopsies were obtained from thevastus lateralisof n=18 patients with COPD (8 female, 10 male; age 66±5 years, mild-to-severe airflow obstruction) and n=18 age-, sex- and body mass index-matched healthy control adults (8 female, 10 male; age 68±5 years). Immunohistochemistry was used to assess type I/II muscle fibre size, distribution, myonuclear content, satellite cell number and fibre capillarisation. In addition, type I/II muscle fibre satellite cell distance to its nearest capillary was assessed.ResultsThe percentage of type II muscle fibres was significantly greater in patients with COPD (62±10%) compared with controls (50±12%, p<0.05). Muscle fibre capillarisation was significantly lower in patients with COPD compared with controls (p<0.05). While satellite cell content was not different between groups, type I and type II satellite cell distance to its nearest capillary was significantly greater in patients with COPD (type I: 21.3±4.8 µm; type II: 26.7±9.3 µm) compared with controls (type I: 16.1±3.5 µm; type II: 22.7±5.8 µm; p<0.05).ConclusionSatellite cells are located at a greater distance from their nearest capillary in patients with COPD compared with age-matched controls. This increased distance could play a role in impaired satellite cell function in patients with COPD.