ECSS Paris 2023: GSSI
INTRODUCTION: Collagen ingestion has been suggested to stimulate muscle connective protein remodeling. However, ingestion of a single bolus of collagen peptides does not seem to further augment post-exercise muscle connective protein synthesis rates. It has been hypothesized that the proposed benefits of collagen ingestion on post-exercise muscle connective protein remodeling are more evident when assessed over a more prolonged period of post-exercise recovery. METHODS: In a randomized, double-blind, parallel design, 20 recreationally active male adults (age: 24±4 y; BMI: 24±4 kg/m2) were allocated to ingest either 4 boluses of hydrolyzed collagen (40, 20, 20 and 20 g; COLL, n=10) or a non-caloric placebo (PLA, n=10) distributed throughout 8 hours of post-exercise recovery from a single bout of unilateral leg resistance-type exercise. Participants received primed continuous L-[ring-13C6]-phenylalanine infusions with blood and muscle biopsy samples collected frequently to assess muscle connective protein synthesis rates at rest and during 8 hours of post-exercise recovery. Time-dependent variables were analyzed by two-way repeated measures ANOVA with time as within-subject factor and treatment as between-subject factor. Non-time-dependent variables were compared between treatment groups by an independent t-test. A statistical level of P<0.05 was accepted. All data were analyzed in SPSS and are expressed as mean±SD. RESULTS: Collagen ingestion increased the availability of circulating essential and non-essential amino acids (all P<0.001). Plasma leucine concentrations increased within 30 min after the ingestion of the initial bolus of collagen (P<0.001) and remained higher throughout the entire recovery period compared to placebo (with average values at 161±13 vs 116±14 µmol/L, respectively; P<0.001). Collagen ingestion strongly increased post-prandial hydroxyproline (iAUC 162±26 vs -1±1 mmol/L x 480 min), proline (iAUC 225±40 vs -14±4 mmol/L x 480 min), and glycine (iAUC 320±85 vs -7±5 mmol/L x 480 min) availability when compared to placebo (all P<0.001). Collagen ingestion resulted in higher muscle connective protein synthesis rates in both the rested (0.069±0.017 vs 0.052±0.011 %/h; P=0.018), and exercised leg (0.094±0.024 vs 0.058±0.009 %/h; P<0.001) when compared to the placebo ingestion. CONCLUSION: Collagen ingestion during 8 hours of post-exercise recovery increases plasma amino acid availability, with a sustained increase in circulating proline and glycine concentrations. The increase in plasma amino acid availability stimulates muscle connective protein synthesis rates both at rest and during recovery from exercise, which may support connective tissue remodeling in healthy active males.
Read CV Jeremias KaiserECSS Paris 2023: GSSI
INTRODUCTION: Ketogenic diets (KD) have been proposed to enhance endurance performance by increasing fat oxidation and reducing carbohydrate dependence. However, their effects on muscle glycogen availability and high-intensity performance remain controversial, particularly after short-term adaptation. Therefore, the aim of this study was to investigate the effects of 10-day KD adaptation on (1) metabolic and physiological adaptation during moderate-intensity endurance exercise and (2) subsequent high-intensity endurance performance. METHODS: Twenty-four trained endurance athletes (29.7 ± 3.8 years; VO₂max 59.1 ± 6.3 mL·kg⁻¹·min⁻¹) completed a 7-day standardized diet before being randomized to a ketogenic diet (KD; <5% CHO, 2.0 g/kg/day protein) or control diet (CD; >55% CHO, 2.0 g/kg/day protein) for 10 days, while maintaining habitual training. Body composition was assessed by DXA and BIA pre- and post-intervention. After an overnight fast, participants performed a 2-h cycling bout at 55% peak power output. VO₂, respiratory quotient, and substrate oxidation were measured intermittently (5 min every 15 min) via indirect calorimetry. Vastus lateralis biopsies were obtained pre- and post-exercise to quantify muscle glycogen. Time to exhaustion (TTE) was subsequently assessed using an incremental protocol (starting at 75% VO₂ peak, +5% every 5 min). Data were analyzed using two-way RM ANOVA. RESULTS: KD significantly reduced body mass (−2.1 ± 1.9 kg, p<0.001), primarily due to decreases in total (−1.15 ± 0.79 kg, p<0.001) and intracellular water (−0.64 ± 0.14 kg, p<0.001). Pre-exercise muscle glycogen was markedly lower following KD (254 ± 68 vs 530 ± 140 mmol·kg⁻¹ d.w., p< 0.001). Although net glycogen utilization during exercise was reduced in KD, post-exercise glycogen concentrations remained significantly lower than pre-diet values (142 ± 71 vs 250 ± 120 mmol·kg⁻¹ d.w., p<0.001). KD increased mean fat oxidation during exercise compared to pre-diet values (1.07 ± 0.19 vs 0.55 ± 0.15 g·min⁻¹, p<0.001). However, this shift in substrate utilization was accompanied by a higher oxygen cost (+141 ± 42 mL·min⁻¹, p<0.05), reduced gross efficiency (−0.75%, p<0.05), and increased mean heart rate (+10 ± 5 bpm, p<0.01). Time to exhaustion was also significantly reduced following KD (−221 ± 103 s, p<0.05), indicating impaired high-intensity endurance performance. No significant changes were observed in the control group. CONCLUSION: A 10-day ketogenic diet enhances fat oxidation but substantially reduces muscle glycogen availability and increases the oxygen cost of exercise. These metabolic changes impair exercise efficiency and compromise high-intensity endurance performance, suggesting that short-term KD adaptation may be insufficient to support performance when high-intensity efforts are required.
Read CV Davide CharrierECSS Paris 2023: GSSI
INTRODUCTION: Carbohydrate (CHO) ingestion enhances endurance performance, yet current fuelling guidelines are largely derived from male cohorts (1) with elite female athletes markedly underrepresented in CHO-feeding research (2). Recent modelling suggests female marathoners may require higher exogenous CHO intakes (108 ± 22 g·h⁻¹) (3). These projections challenge current sex-specific fuelling policies. Indeed, in elite male marathoners, ingestion of 120 g·h⁻¹ increased whole-body and exogenous CHO oxidation and improved running economy but increased peak gastrointestinal (GI) symptoms of nausea, stomach fullness and abdominal cramps (4). In elite female runners, data at intakes ≥90 g·h⁻¹ do not exist. Therefore, the aim of the present study was to investigate the effects of 60, 90, and 120 g·h⁻¹ of CHO on substrate metabolism, exogenous CHO oxidation, and GI symptoms in elite female marathoners. METHODS: In a double-blind, randomised crossover design, 8 female marathoners (PB 02:40:18 ± 00:06:19) completed three trials after a 24h high CHO (8 g·kg-1) diet and pre-exercise meal (2 g·kg-1). Participants completed three 120-min trials comprising of 15 min at 95% lactate threshold (LT), 90 min at 94% lactate turnpoint (LTP) and a final 15 min at 95% LT. Every 15 minutes, subjects consumed U-13C enriched CHO drinks at rates of 60 (1:0, maltodextrin: fructose), 90 (2:1) or 120 (1:1) g·h⁻¹. CHO and fat oxidation, blood glucose and lactate, running economy and GI symptoms were measured. Data was analysed using a linear mixed effects model, followed by Holm post-hoc analysis. Significance was set at P<0.05. RESULTS: Mean whole-body CHO oxidation (120 g·h⁻¹, 2.51 ± 0.35; 90 g·h⁻¹, 1.83 ± 0.35; 60 g·h⁻¹, 1.53 ± 0.29 g·min⁻¹) and hour-2 exogenous CHO oxidation (120 g·h⁻¹, 1.54 ± 0.10; 90 g·h⁻¹, 1.32 ± 0.10; 60 g·h⁻¹, 0.82 ± 0.13 g·min⁻¹) differed between all trials (P<0.01), such that 120 > 90 > 60 g·h⁻¹. Running economy (mL·kg.km-1) was improved at 120 g·h⁻¹ (214 ± 6) compared to 90 g·h⁻¹ (220 ± 16) and 60 g·h⁻¹ (222 ± 17) (P<0.05). Moderate-to-severe GI symptoms (≥4) occurred across all trials. Peak scores for nausea and abdominal cramps were higher at 90 and 120 g·h⁻¹ compared to 60 g·h⁻¹ (P<0.05). Cumulative GI symptom scores for nausea, and regurgitation were also greater at 120 g·h⁻¹ (P<0.05) compared with 60 g·h⁻¹, while cumulative scores for stomach fullness and abdominal cramps were significantly higher at 120 g·h⁻¹ compared to 90 and 60 g·h⁻¹ (P<0.05). CONCLUSION: We report for the first time that CHO ingestion of 120 g·h⁻¹ confers a metabolic advantage to elite female marathoners by maintaining whole-body CHO oxidation, increasing exogenous CHO oxidation and improving running economy. However, due to the high incidence of GI symptoms, particularly 120 g·h⁻¹, gut training strategies before practical application are warranted.
Read CV Samanvita RavikantiECSS Paris 2023: GSSI