Biology subjects

Horwath, O.

Publications and source records attributed to Horwath, O..

4 recordsLinked to original sources

bioRxiv2025

Comparable Strength and Hypertrophic Adaptations to Low-Load and High-Load Resistance Exercise Training in Trained Individuals: Many Roads Lead to Rome

The muscular and myocellular adaptations to low-load resistance exercise training (LL-RET) remain incompletely understood, particularly in the trained state. The primary aim of this study was to examine adaptations to an LL-RET regimen and compare these to a high-load training regimen (HL-RET). Fourteen resistance-trained males and females (26.4 {+/-} 4.4 years) participated in a 9-week RET program (twice per week). Using a within-subject design, each individual trained one leg with HL-RET (3-5 repetitions), and the other with LL-RET (20-25 repetitions), all sets performed to volitional failure. Pre- and post-intervention, muscle endurance, maximal strength, and muscle thickness using ultrasound was assessed. Muscle biopsies were analyzed for fiber type composition, fiber cross-sectional area (fCSA), and satellite cell- and myonuclear content using immunofluorescence. The training regimens led to comparable increases in maximal strength in multi-joint movements (21%), but not in single-joint movements were HL-RET was superior. LL-RET induced superior improvements in local muscle endurance (9% vs -2.7%, p=0.013). Regardless of training regimen, muscle thickness increased by [~]7.4% at the mid-thigh site and [~]8.5% at the distal site pre-to post-intervention. However, no changes were observed in fiber type composition or fCSA. Satellite cell content increased by [~]25% in type I fibers, independent of training regimen, but no changes were noted in myonuclear content. Here we novelly show that LL-RET can replicate many aspects of HL-RET leading to similar increases in both muscle hypertrophy and strength. Our study thus supports the notion that comparable adaptations to RET can be achieved using distinct loading regimens. New and noteworthyThis study compared two distinct resistance exercise loading strategies (3-5 RM vs. 20-25 RM) in trained individuals, evaluating both muscular and myocellular adaptations. Our findings demonstrate that low-load resistance exercise training (LL-RET) is an effective alternative to traditional high-load strategies for increasing strength and muscle size. These results highlight that skeletal muscle growth can be achieved through various external stressors, offering valuable insights for individuals seeking hypertrophy but unable to tolerate high loads.

physiology↗

bioRxiv2025

A glucosinolate-rich beverage lowers blood lactate concentrations during submaximal exercise

Glucosinolate-rich broccoli sprouts combined with intense exercise training for 7 days have been shown to reduce blood lactate concentrations during exercise, attenuate hypoglycemic events, improve physical performance, and reduce markers of oxidative stress. This study aimed to investigate the acute, dose-dependent effects of glucosinolate-rich red kale sprouts (GRS) on blood lactate and blood glucose following the ingestion of three different doses. Fifteen healthy participants consumed 37.5 g or 75 g of GRS or an isocaloric placebo blended into a beverage on three separate occasions. The participants cycled on an ergometer at three submaximal work rates before and three hours after ingestion. Measurements of oxygen uptake, substrate-level oxidation, blood lactate, blood glucose, and ratings of perceived exertion were taken before and after each cycling interval. The intake of glucosinolate-rich sprouts acutely decreased blood lactate levels during submaximal cycling and increased blood glucose levels at rest. The largest reduction in blood lactate was observed at the 37.5 g dose compared to placebo, where the concentration was 0.4 {+/-} 0.2 mM lower at work rate close to threshold (p = 0.003). For the 75 g dose, the reduction in blood lactate was 0.25 {+/-} 0.1 mM (p = 0.02). No significant effects were seen in the lowest work rate. The mean resting glucose level was 3.9 {+/-} 0.1 mM following placebo, compared to 4.3 {+/-} 0.1 mM after intake of either 37.5 g or 75 g dose (p < 0.01, respectively). These findings suggest that glucosinolate-rich broccoli sprouts have a lactate-lowering effect during submaximal efforts, which may have important implications for supplementation for improving endurance performance.

physiology↗

bioRxiv2024

Endurance exercise with reduced muscle glycogen content influences substrate utilization and attenuates acute mTORC1- and autophagic signaling in human type I and type II muscle fibers

BackgroundExercising with low muscle glycogen content can improve training adaptation, but the mechanisms underlying the muscular adaptation are still largely unknown. In this study, we measured substrate utilization and cell signaling in different muscle fiber types during exercise and investigated a possible link between these variables. MethodsFive subjects performed a single leg cycling exercise in the evening (day 1) with the purpose of reducing glycogen stores. The following morning (day 2), they performed two-legged cycling at [~]70% of VO2peak for 1h. Muscle biopsies were taken from both legs pre- and post-exercise for enzymatic analyses of glycogen, metabolite concentrations using LC-MS/MS-based quantification, and protein signaling using Western blot in pools of type I or type II fibers. ResultsGlycogen content was 60-65% lower for both fiber types (P<0.01) in the leg that exercised on day 1 (low leg) compared to the other leg with normal level of glycogen (normal leg) before the cycling exercise on day 2. Glycogen utilization during exercise was significantly less in both fiber types in the low compared to the normal leg (P<0.05). In the low leg, there was a 14- and 6-fold increase in long-chain fatty acids conjugated to carnitine in type I and type II fibers, respectively, post-exercise. This increase was 3-4 times larger than in the normal leg (P<0.05). Post-exercise, mTORSer2448 phosphorylation was increased in both fiber types in the normal leg (P<0.05) but remained unchanged in both fiber types in the low leg together with an increase in eEF2Thr56 phosphorylation in type I fibers (P<0.01). Exercise induced a reduction in the autophagy marker LC3B-II in both fiber types and legs, but the post-exercise level was higher in both fiber types in the low leg (P<0.05). Accordingly, the LC3B-II/I ratio decreased only in the normal leg (75% for type I and 87% for type II, P<0.01). ConclusionsStarting an endurance exercise session with low glycogen availability leads to profound changes in substrate utilization in both type I and type II fibers. This may reduce the mTORC1 signaling response, primarily in type I muscle fibers, and attenuate the normally observed reduction in autophagy.

physiology↗

bioRxiv2024

Anabolic sensitivity in healthy, lean, older men is associated with higher expression of amino acid sensors and mTORC1 activators

BackgroundSarcopenia is thought to be underlined by age-associated anabolic resistance and dysregulation of intracellular signalling pathways. However, it is unclear whether these phenomena are driven by ageing per se or other confounding factors. MethodsLean and healthy young (n=10, 22 {+/-} 3 yrs, BMI; 23.4 {+/-} 0.8 kg/m2) and old men (n=10, 70 {+/-} 3 yrs, BMI; 22.7 {+/-} 1.3 kg/m2) performed unilateral resistance exercise followed by intake of essential amino acids (EAA). Muscle biopsies were collected from the rested and the exercised leg before, immediately after, as well as 60 and 180 minutes after EAA intake. Muscle samples were analyzed for amino acid concentrations, muscle protein synthesis (MPS) and associated anabolic signaling. ResultsFollowing exercise, peak plasma levels of EAA and leucine were similar between groups, but the area under the curve was [~]11% and [~]28% lower in Young (p<0.01). Absolute levels of muscle EAA and leucine peaked 60 min after exercise, with [~]15 and [~]21 % higher concentrations in the exercising leg (p<0.01) but with no difference between groups. MPS increased in both the resting ([~] 0.035%{middle dot}h-1 to 0.056%{middle dot}h-1, p<0.05) and exercising leg ([~] 0.035%{middle dot}h-1 to 0.083%{middle dot}h-1, p<0.05) with no difference between groups. Phosphorylation of S6K1Thr389 increased to a similar extent in the exercising leg in both groups but was 2.8-fold higher in the resting leg of Old at the 60 min timepoint (p<0.001). Phosphorylation of 4E-BP1Ser65 increased following EAA intake and exercise, but differences between legs were statistically different only at 180 min (p<0.001). However, phosphorylation of this site was on average 78% greater across all timepoints in Old (p<0.01). Phosphorylation of eEF2Thr56 was reduced ([~] 66 and 39%) in the exercising leg at both timepoints after EAA intake and exercise, with no group differences (p<0.05). However, phosphorylation at this site was reduced by [~] 27% also in the resting leg at 60 min, an effect that was only seen in Old (p<0.01). Total levels of Rheb ([~] 45%), LAT1 ([~] 31%) and Rag B ([~] 31%) were higher in Old (p<0.001). ConclusionLean and healthy old men do not manifest AR as evidenced by potent increases in MPS and mTORC1 signalling following EAA intake and exercise. Maintained anabolic sensitivity with age appears to be a function of a compensatory increase in basal levels of proteins involved in anabolic signalling. Therefore, our results suggest that age per se does not appear to cause AR in human skeletal muscle.

physiology↗