Impact of voluntary exercise training on the metabolic and behavioral characteristics of the rTg4510 transgenic mouse model of frontotemporal dementia

Frontotemporal dementia (FTD) is a neurodegenerative disorder that affects the frontal and temporal lobes of the brain, primarily in individuals under 65 years of age, and is the second most common form of dementia worldwide. There is no cure for FTD and current treatments offer limited symptomatic relief. Regular physical activity exhibits cognitive and neuroprotective benefits in healthy individuals and in various neurodegenerative diseases, such as Alzheimer's disease, but few studies have examined its efficacy in FTD. Accordingly, we investigated the impact of voluntary exercise training (VET) on the metabolic and behavioral characteristics of the rTg4510 transgenic mouse model of familial FTD. We show that regardless of genotype, VET increased energy expenditure, decreased sleep duration, and improved long-term memory in rTg4510 mice and WT littermates. Moreover, VET appeared to improve hyperactivity, a common feature of FTD, in rTg4510 mice. Although further work is required, these findings provide important insights into the potential benefits of physical activity in FTD.

Sexual Dimorphism in Substrate Metabolism During Exercise

During aerobic exercise, women oxidize significantly more lipids and less carbohydrates than men. This sexual dimorphism in substrate metabolism has been attributed, in part, to the observed differences in epinephrine and glucagon levels between men and women during exercise. To identify the underpinning candidate physiological mechanisms for these sex differences, we developed a sex-specific multi-scale mathematical model that relates cellular metabolism in the organs to whole-body responses during exercise. We conducted simulations to test the hypothesis that sex differences in the exercise-induced changes to epinephrine and glucagon would result in the sexual dimorphism of hepatic metabolic flux rates via the glucagon-to-insulin ratio (GIR). Indeed, model simulations indicate that the shift towards lipid metabolism in the female model is primarily driven by the liver. The female model liver exhibits resistance to GIR-mediated glycogenolysis, which helps maintain hepatic glycogen levels. This decreases arterial glucose levels and promotes the oxidation of free fatty acids. Furthermore, in the female model, skeletal muscle relies on plasma free fatty acids as the primary fuel source, rather than intramyocellular lipids, whereas the opposite holds true for the male model.

Peak performance and cardiometabolic responses of modern US army soldiers during heavy, fatiguing vest-borne load carriage

INTRODUCTION

Physiological limits imposed by vest-borne loads must be defined for optimal performance monitoring of the modern dismounted warfighter.

PURPOSE

To evaluate how weighted vests affect locomotion economy and relative cardiometabolic strain during military load carriage while identifying key physiological predictors of exhaustion limits.

METHODS

Fifteen US Army soldiers (4 women, 11 men; age, 26 ± 8 years; height, 173 ± 10 cm; body mass (BM), 79 ± 16 kg) performed four incremental walking tests with different vest loads (0, 22, 44, or 66% BM). We examined the effects of vest-borne loading on peak walking speed, the physiological costs of transport, and relative work intensity. We then sought to determine which of the cardiometabolic indicators (oxygen uptake, heart rate, respiration rate) was most predictive of task failure.

RESULTS

Peak walking speed significantly decreased with successively heavier vest loads (p < 0.01). Physiological costs per kilometer walked were significantly higher with added vest loads for each measure (p < 0.05). Relative oxygen uptake and heart rate were significantly higher during the loaded trials than the 0% BM trial (p < 0.01) yet not different from one another (p > 0.07). Conversely, respiration rate was significantly higher with the heavier load in every comparison (p < 0.01). Probability modeling revealed heart rate as the best predictor of task failure (marginal R², 0.587, conditional R², 0.791).

CONCLUSION

Heavy vest-borne loads cause exceptional losses in performance capabilities and increased physiological strain during walking. Heart rate provides a useful non-invasive indicator of relative intensity and task failure during military load carriage.

The resting serum metabolome in response to short-term sprint interval training

PURPOSE

To investigate the response of a targeted fraction of (168 metabolites) of the resting serum metabolome to 9 sessions of sprint interval training (SIT).

METHODS

Thirty-four recreationally active males provided resting blood samples before (baseline) and 48-72 h after (post) a short-term (9 sessions) cycle ergometer-based SIT intervention. A targeted analysis of 168 metabolites was performed on serum using liquid chromatography mass spectrometry (LC-MS). 160 distinct metabolites were identified and combined with 4 calculated metabolite sums and 3 calculated metabolite ratios creating a panel of 167 individual factors. Data were analysed using principal component analysis and univariate testing of all factors classified into 5 metabolite subgroups.

RESULTS

SIT improved anaerobic capacity measured by average power output during a Wingate test (p < 0.01; mean difference = 38 W, 95% confidence interval [26, 51]) and aerobic capacity measured by average power output in a 20 min cycling test (p < 0.01; 17 W [12, 23]). Limited separation was discernible in the targeted serum metabolome between baseline and post-intervention when projected on the first and second principal component(s). However, univariate testing identified 11 fatty acids that had lower concentrations (false discovery rate < 0.05) in post-intervention samples.

CONCLUSIONS

These findings demonstrate that this short-term SIT intervention had limited effect on the serum metabolome at rest, but a subfraction of fatty acids are potentially sensitive to short-term exercise training.

Understanding the female athlete: molecular mechanisms underpinning menstrual phase differences in exercise metabolism

Research should equitably reflect responses in men and women. Including women in research, however, necessitates an understanding of the ovarian hormones and menstrual phase variations in both cellular and systems physiology. This review outlines recent advances in the multiplicity of ovarian hormone molecular signaling that elucidates the mechanisms for menstrual phase variability in exercise metabolism. The prominent endogenous estrogen, 17-β-estradiol (E2), molecular structure is bioactive in stabilizing plasma membranes and quenching free radicals and both E2 and progesterone (P4) promote the expression of antioxidant enzymes attenuating exercise-induced muscle damage in the late follicular (LF) and mid-luteal (ML) phases. E2 and P4 bind nuclear hormone receptors and membrane-bound receptors to regulate gene expression directly or indirectly, which importantly includes cross-regulated expression of their own receptors. Activation of membrane-bound receptors also regulates kinases causing rapid cellular responses. Careful analysis of these signaling pathways explains menstrual phase-specific differences. Namely, E2-promoted plasma glucose uptake during exercise, via GLUT4 expression and kinases, is nullified by E2-dominant suppression of gluconeogenic gene expression in LF and ML phases, ameliorated by carbohydrate ingestion. E2 signaling maximizes fat oxidation capacity in LF and ML phases, pending low-moderate exercise intensities, restricted nutrient availability, and high E2:P4 ratios. P4 increases protein catabolism during the luteal phase by indeterminate mechanisms. Satellite cell function supported by E2-targeted gene expression is countered by P4, explaining greater muscle strengthening from follicular phase-based training. In totality, this integrative review provides causative effects, supported by meta-analyses for quantitative actuality, highlighting research opportunities and evidence-based relevance for female athletes.

Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h-1 versus 90 g h-1 at different ratios

Purpose

This study aimed to investigate whether carbohydrate ingestion during 3 h long endurance exercise in highly trained cyclists at a rate of 120 g h⁻¹ in 0.8:1 ratio between fructose and glucose-based carbohydrates would result in higher exogenous and lower endogenous carbohydrate oxidation rates as compared to ingestion of 90 g h⁻¹ in 1:2 ratio, which is the currently recommended approach for exercise of this duration.

Methods

Eleven male participants (V̇O_2peak 62.6 ± 7 mL kg⁻¹ min⁻¹, gas exchange threshold (GET) 270 ± 17 W and Respiratory compensation point 328 ± 32 W) completed the study involving 4 experimental visits consisting of 3 h cycling commencing after an overnight fast at an intensity equivalent to 95% GET. During the trials they received carbohydrates at an average rate of 120 or 90 g h⁻¹ in 0.8:1 or 1:2 fructose-maltodextrin ratio, respectively. Carbohydrates were naturally high or low in ¹³C stable isotopes enabling subsequent calculations of exogenous and endogenous carbohydrate oxidation rates.

Results

Exogenous carbohydrate oxidation rates were higher in the 120 g h⁻¹ condition (120–180 min: 1.51 ± 0.22 g min⁻¹) as compared to the 90 g h⁻¹ condition (1.29 ± 0.16 g min⁻¹; p = 0.026). Endogenous carbohydrate oxidation rates did not differ between conditions (2.15 ± 0.30 and 2.20 ± 0.33 g min⁻¹ for 120 and 90 g h⁻¹ conditions, respectively; p = 0.786).

Conclusions

The results suggest that carbohydrate ingestion at 120 g h⁻¹ in 0.8:1 fructose-maltodextrin ratio as compared with 90 g h⁻¹ in 1:2 ratio offers higher exogenous carbohydrate oxidation rates but no additional sparing of endogenous carbohydrates. Further studies should investigate potential performance effects of such carbohydrate ingestion strategies.

Inducing low energy availability in trained endurance male athletes results in poorer explosive power

Purpose

Low energy availability in males needs more original research to understand its health and performance consequences. The aim of the study was to induce low energy availability in previously healthy male endurance athletes by reducing energy availability by 25% for 14 consecutive days and measure any potential changes in performance, health, mental state or energy markers.

Methods

Energy availability was reduced in 12 trained, well-trained and elite endurance athletes by increasing energy expenditure and controlling energy intake. After intervention, health was assessed by blood draw, body composition was measured, energy markers by measuring resting energy expenditure, performance with three specific tests (measuring endurance, agility and explosive power) and two questionnaires were used for psychological assessment (the Three Factor Eating Questionnaire and Well-being questionnaire).

Results

Reduced energy availability (22.4 ± 6.3 kcal/kg FFM/day) caused significantly lower haemoglobin values (t(12) = 2.652, p = 0.022), there was a tendency for lower iron and IGF-1 (p = 0.066 and p = 0.077, respectively). Explosive power was reduced (t(12) = 4.570, p = 0.001), lactate metabolism was altered and athletes reported poorer well-being (t(12) = 2.385, p = 0.036). Cognitive restriction was correlated with energy availability (r = 0.528, p = 0.039).

Conclusion

This is the first research providing direct evidence that suboptimal energy availability negatively impacts explosive power before hormonal changes occur in male endurance athletes. It is also the first to show direct association of low energy availability and higher cognitive restriction. We also observed worse well-being and lower haemoglobin values. 25% of energy availability reduction as not enough to elicit changes in resting energy expenditure.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-021-04857-4.

Six high-intensity interval training sessions over 5 days increases maximal oxygen uptake, endurance capacity, and sub-maximal exercise fat oxidation as much as 6 high-intensity interval training sessions over 2 weeks

BACKGROUND

High-intensity interval training (HIIT) induces similar or even superior adaptations compared to continuous endurance training. Indeed, just 6 HIIT sessions over 2 weeks significantly improves maximal oxygen uptake (VO_2max), submaximal exercise fat oxidation, and endurance performance. Whether even faster adaptations can be achieved with HIIT is not known. Thus, we aimed to determine whether 2 sessions of HIIT per day, separated by 3 h, every other day for 5 days (double HIIT (HIIT-D), n = 15) could increase VO_2max, submaximal exercise fat oxidation, and endurance capacity as effectively as 6 sessions of HIIT over 2 weeks (single HIIT (HIIT-S), n = 13).

METHODS

Each training session consisted of 10 × 60 s of cycling at 100% of VO_2max interspersed with 75 s of low-intensity cycling at 60 watt (W). Pre- and post-training assessments included VO_2max, time to exhaustion at ∼80% of VO_2max, and 60-min cycling trials at ∼67% of VO_2max.

RESULTS

Similar increases (p < 0.05) in VO_2max (HIIT-D: 7.7% vs. HIIT-S: 6.0%, p > 0.05) and endurance capacity (HIIT-D: 80.1% vs. HIIT-S: 79.2%, p > 0.05) were observed. Submaximal exercise carbohydrate oxidation was reduced in the 2 groups after exercise training (HIIT-D: 9.2%, p = 0.014 vs. HIIT-S: 18.8%, p = 0.012) while submaximal exercise fat oxidation was significantly increased in HIIT-D (15.5%, p = 0.048) but not in HIIT-S (9.3%, p = 0.290).

CONCLUSION

Six HIIT sessions over 5 days was as effective in increasing VO_2max and endurance capacity and was more effective in improving submaximal exercise fat oxidation than 6 HIIT sessions over 2 weeks.

Effects of modern military backpack loads on walking speed and cardiometabolic responses of US Army Soldiers

INTRODUCTION

Military leaders must understand how modern military equipment loads affect trade-offs between movement speed and physiological strain to optimize pacing strategies.

PURPOSE

To evaluate the effects of load carried in a recently developed military backpack on the walking speed and cardiometabolic responses of dismounted warfighters.

METHODS

Fifteen soldiers (1 woman, 14 men; age, 22 ± 2 years; height, 173 ± 7 cm; body mass (BM), 73 ± 10 kg) completed incremental walking tests with four external load conditions (0, 22, 44, or 66% BM) using the US Army's newest backpack: the Modular Lightweight Load-Carrying Equipment 4000 (MOLLE 4000). Oxygen uptake (V̇O₂) and heart rate (HR) were evaluated relative to maximal values (V̇O_2max and HR_max respectively). Testing ceased when participants completed the highest tested speed (1.97 m s^-1), exceeded a respiratory exchange ratio (RER) of 1.00, or reached volitional exhaustion.

RESULTS

Peak speed significantly decreased (p < 0.03) with successively heavier loads (0% BM, 1.95 ± 0.06 m s^-1; 22% BM, 1.87 ± 0.10 m s^-1; 44% BM, 1.69 ± 0.13 m s^-1; 66% BM, 1.48 ± 0.13 m s^-1). Peak V̇O₂ was significantly lower (p < 0.01) with 0% BM (47 ± 5% V̇O_2max) than each load (22% BM, 58 ± 8% V̇O_2max; 44% BM, 63 ± 10% V̇O_2max; 66% BM, 61 ± 11% V̇O_2max). Peak HR was significantly lower (p < 0.01) with 0% BM (71 ± 5% HR_max) versus each load (22% BM, 83 ± 6% HR_max; 44% BM, 87 ± 6% HR_max; 66% BM, 88 ± 6% HR_max).

CONCLUSION

Overburdened warfighters suffer severe impairments in walking speed even when carrying recently developed military load carriage equipment. Our results suggest that the relative work intensity of heavy load carriage may be better described when expressed relative to HR_max versus V̇O_2max.

The day-to-day reliability of peak fat oxidation and FATMAX

PURPOSE

Prior studies exploring the reliability of peak fat oxidation (PFO) and the intensity that elicits PFO (FATMAX) are often limited by small samples. This study characterised the reliability of PFO and FATMAX in a large cohort of healthy men and women.

METHODS

Ninety-nine adults [49 women; age: 35 (11) years; [Formula: see text]O2peak: 42.2 (10.3) mL·kg BM-1·min-1; mean (SD)] completed two identical exercise tests (7-28 days apart) to determine PFO (g·min-1) and FATMAX (%[Formula: see text]O2peak) by indirect calorimetry. Systematic bias and the absolute and relative reliability of PFO and FATMAX were explored in the whole sample and sub-categories of: cardiorespiratory fitness, biological sex, objectively measured physical activity levels, fat mass index (derived by dual-energy X-ray absorptiometry) and menstrual cycle status.

RESULTS

No systematic bias in PFO or FATMAX was found between exercise tests in the entire sample (- 0.01 g·min-1 and 0%[Formula: see text]O2peak, respectively; p > 0.05). Absolute reliability was poor [within-subject coefficient of variation: 21% and 26%; typical errors: ± 0.06 g·min-1 and × / ÷ 1.26%[Formula: see text]O2peak; 95% limits of agreement: ± 0.17 g·min-1 and × / ÷ 1.90%[Formula: see text]O2peak, respectively), despite high (r = 0.75) and moderate (r = 0.45) relative reliability for PFO and FATMAX, respectively. These findings were consistent across all sub-groups.

CONCLUSION

Repeated assessments are required to more accurately determine PFO and FATMAX.

Effect of a four-week ketogenic diet on exercise metabolism in CrossFit-trained athletes

BACKGROUND

The ketogenic diet is becoming a popular nutritional model among athletes. However, the relationship between its use and metabolism during exercise seems to have not been fully investigated.

METHODS

The aim of the study was to assess the effects of a four-week ketogenic diet (KD) on fat and carbohydrate (CHO) utilization during an incremental cycling test (ICT) in CrossFit-trained female (n = 11) and male (n = 11) athletes. During the ICT (while consuming the customary diet and after the KD), oxygen uptake and carbon dioxide exhalation were registered, and CHO and fat utilization as well as energy expenditure were calculated.

RESULTS

In males, the KD led to an increase in fat utilization (g·min- 1·kgFFM- 1 and % oxidation). It was particularly noticeable at exercise intensities up to 80% of VO2max. An increase in the area under the curve (AUC) was seen in males but not in females at up to ≤65% VO2max of fat utilization.

CONCLUSIONS

Male CrossFit-trained athletes seem to be more prone to shifts in macronutrient utilization (in favor of fat utilization) during submaximal intensity exercise under a ketogenic diet than are female athletes.

TRIAL REGISTRATION

Clinical Trials Gov, NCT03665948 . Registered 11 September 2018 (retrospectively registered).

Coordination of mitochondrial biogenesis by PGC-1α in human skeletal muscle: A re-evaluation

The transcriptional co-activator peroxisome proliferator-activated receptor gamma co-activator-1 alpha (PGC-1α) is proposed to coordinate skeletal muscle mitochondrial biogenesis through the integrated induction of nuclear- and mitochondrial-encoded gene transcription. This paradigm is based largely on experiments demonstrating PGC-1α's ability to co-activate various nuclear transcription factors that increase the expression of mitochondrial genes, as well as PGC-1α's direct interaction with mitochondrial transcription factor A within mitochondria to increase the transcription of mitochondrial DNA. While this paradigm is supported by evidence from cellular and transgenic animal models, as well as acute exercise studies involving animals, the up-regulation of nuclear- and mitochondrial-encoded genes in response to exercise does not appear to occur in a coordinated fashion in human skeletal muscle. This review re-evaluates our current understanding of this phenomenon by highlighting evidence from recent studies examining the exercise-induced expression of nuclear- and mitochondrial-encoded genes targeted by PGC-1α. We also highlight several possible theories that may explain the apparent inability of PGC-1α to coordinately up-regulate the expression of genes required for mitochondrial biogenesis in human skeletal muscle, and provide directions for future work exploring mitochondrial biogenic gene expression following exercise.

The interaction between nutrition and exercise for promoting health and performance

The theme of The Nutrition Society Spring Conference 2017 was on the interaction between nutrition and exercise for promoting healthy ageing, maintaining cognitive function and improving the metabolic health of the population. The importance of this theme is highlighted by the public health issues surrounding obesity, diabetes and the age-related loss of skeletal muscle mass (sarcopenia). The opening symposium provided a historical perspective of both invasive and non-invasive methodologies for measuring exercise energetics and energy balance. Data derived from these techniques underpin current understanding regarding the metabolic response to nutrition and exercise. Further symposia examined the importance of skeletal muscle for healthy ageing in older men and postmenopausal women. From a nutritional perspective, the potential for animal- v. plant-based protein sources to offset the age-related decline in muscle mass was discussed. The day concluded by discussing the link(s) between nutrition, exercise and brain function. Day 2 commenced with examples of applied equine research illustrating the link between nutrition/exercise and insulin resistance to those of a human model. The final symposium examined the combined role of nutrition and exercise in reducing risk of type 2 diabetes and dyslipidaemia. The overall conclusion from the meeting was that the interaction between diet and physical activity confers greater benefits to human health and performance than either component alone.

Blood lactate accumulation decreases during the slow component of oxygen uptake without a decrease in muscular efficiency

Pulmonary oxygen uptake ([Formula: see text]) slowly increases during exercise above the anaerobic threshold, and this increase is called the slow component of [Formula: see text]. The mechanism of the increase in [Formula: see text] is assumed to be due to increasing energy cost associated with increasingly inefficient muscle contraction. We hypothesized that the increase in [Formula: see text] would be accompanied by a constant or increasing rate of accumulation of blood lactate, indicating sustained anaerobic metabolism while [Formula: see text] increased. Ten male subjects performed cycle ergometry for 3, 6, and 9 min at a power output representing 60% of the difference between lactate threshold and maximal [Formula: see text] while [Formula: see text] and blood lactate accumulation were measured. Blood lactate accumulation decreased over time, providing the energy equivalent of (mean ± SD) 1586 ± 265, 855 ± 287, and 431 ± 392 ml of [Formula: see text] during 0-3, 3-6, and 6-9 min of exercise, respectively. As duration progressed, [Formula: see text] supplied 86.3 ± 2.0, 93.6 ± 1.9, and 96.8 ± 2.9% of total energy from 0 to 3, 3 to 6, and 6 to 9 min, respectively, while anaerobic contribution decreased. There was no change in total energy cost after 3 min, except that required by ventilatory muscles for the progressive increase in ventilation. The slow component of [Formula: see text] is accompanied by decreasing anaerobic energy contribution beyond 3 min during heavy exercise.

A meta-analysis of in vivo vertebrate cardiac performance: implications for cardiovascular support in the evolution of endothermy

Endothermy in birds and mammals is associated with high body temperatures, and high rates of metabolism that are aerobically supported by elevated rates of cardiovascular O2 transport. The purpose of this meta-analysis was to examine cardiovascular data from ectothermic and endothermic vertebrates, at rest and during exercise, with the goal of identifying key variables that may have contributed to the role of the cardiovascular system in supporting high rates of O2 transport associated with endothermy. Vascular conductance, cardiac power and stroke work were summarized and calculated from a variety of studies at rest and during exercise for five classes of vertebrates where data were available. Conductance and cardiac power were linearly related to cardiac output from rest to exercise and also interspecifically. Exercise cardiac power and stroke work were greater in the endothermic species, owing to increased flow resulting from increased heart rate and increased pressure. Increased relative ventricle mass (RVM) was related to increased stroke volume in both groups. However, the increased RVM of endotherms was related to the increased pressure, as stroke work per gram of ventricle during exercise was equivalent between the groups. Cardiac power was linearly related to aerobic metabolic power, with 158 mW aerobic power output achieved per mW of cardiac power input. This analysis indicates that the greatly increased heart rate and cardiac stroke work leading to increased blood flow rate and blood pressure was necessary to support the metabolic requirements of endothermy.

Physiological and molecular responses to an acute bout of reduced-exertion high-intensity interval training (REHIT)

PURPOSE

We have previously shown that 6 weeks of reduced-exertion high-intensity interval training (REHIT) improves VO2max in sedentary men and women and insulin sensitivity in men. Here, we present two studies examining the acute physiological and molecular responses to REHIT.

METHODS

In Study 1, five men and six women (age: 26 ± 7 year, BMI: 23 ± 3 kg m(-2), VO2max: 51 ± 11 ml kg(-1) min(-1)) performed a single 10-min REHIT cycling session (60 W and two 20-s 'all-out' sprints), with vastus lateralis biopsies taken before and 0, 30, and 180 min post-exercise for analysis of glycogen content, phosphorylation of AMPK, p38 MAPK and ACC, and gene expression of PGC1α and GLUT4. In Study 2, eight men (21 ± 2 year; 25 ± 4 kg·m(-2); 39 ± 10 ml kg(-1) min(-1)) performed three trials (REHIT, 30-min cycling at 50 % of VO2max, and a resting control condition) in a randomised cross-over design. Expired air, venous blood samples, and subjective measures of appetite and fatigue were collected before and 0, 15, 30, and 90 min post-exercise.

RESULTS

Acutely, REHIT was associated with a decrease in muscle glycogen, increased ACC phosphorylation, and activation of PGC1α. When compared to aerobic exercise, changes in VO2, RER, plasma volume, and plasma lactate and ghrelin were significantly more pronounced with REHIT, whereas plasma glucose, NEFAs, PYY, and measures of appetite were unaffected.

CONCLUSIONS

Collectively, these data demonstrate that REHIT is associated with a pronounced disturbance of physiological homeostasis and associated activation of signalling pathways, which together may help explain previously observed adaptations once considered exclusive to aerobic exercise.

The effect of carbohydrate and marine peptide hydrolysate co-ingestion on endurance exercise metabolism and performance

BACKGROUND

The purpose of this study was to examine the efficacy of introducing a fish protein hydrolysate (PEP) concurrently with carbohydrate (CHO) and whey protein (PRO) on endurance exercise metabolism and performance.

METHODS

In a randomised, double blind crossover design, 12 male volunteers completed an initial familiarisation followed by three experimental trials. The trials consisted of a 90 min cycle task corresponding to 50% of predetermined maximum power output, followed by a 5 km time trial (TT). At 15 min intervals during the 90 min cycle task, participants consumed 180 ml of CHO (67 g(.)hr(-1) of maltodextrin), CHO-PRO (53.1 g(.)hr of CHO, 13.6 g(.)hr(-1) of whey protein) or CHO-PRO-PEP (53.1 g(.)hr(-1) of CHO, 11 g(.)hr(-1) of whey protein and 2.4 g(.)hr(-1)of hydrolyzed marine peptides).

RESULTS AND CONCLUSIONS

During the 90 min cycle task, the respiratory exchange ratio (RER) in the CHO-PRO condition was significantly higher than CHO (p < 0.001) and CHO-PRO-PEP (p < 0.001). Additionally, mean heart rate for the CHO condition was significantly lower than that for CHO-PRO (p = 0.021). Time-to-complete the 5 km TT was not significantly different between conditions (m ± SD: 456 ± 16, 456 ± 18 and 455 ± 21 sec for CHO, CHO-PRO and CHO-PRO-PEP respectively, p = 0.98). Although the addition of hydrolyzed marine peptides appeared to influence metabolism during endurance exercise in the current study, it did not provide an ergogenic benefit as assessed by 5 km TT performance.