Partly Substituting Whey for Collagen Peptide Supplementation Improves Neither Indices of Muscle Damage Nor Recovery of Functional Capacity During Eccentric Exercise Training in Fit Males.

Previous studies showed that collagen peptide supplementation along with resistance exercise enhance muscular recovery and function. Yet, the efficacy of collagen peptide supplementation in addition to standard nutritional practices in athletes remains unclear. Therefore, the objective of the study was to compare the effects of combined collagen peptide (20 g) and whey protein (25 g) supplementation with a similar daily protein dose (45 g) of whey protein alone on indices of muscle damage and recovery of muscular performance during eccentric exercise training. Young fit males participated in a 3-week training period involving unilateral eccentric exercises for the knee extensors. According to a double-blind, randomized, parallel-group design, before and after training, they received either whey protein (n = 11) or whey protein + collagen peptides (n = 11). Forty-eight hours after the first training session, maximal voluntary isometric and dynamic contraction of the knee extensors were transiently impaired by ∼10% (Ptime < .001) in whey protein and whey protein + collagen peptides, while creatine kinase levels were doubled in both groups (Ptime < .01). Furthermore, the training intervention improved countermovement jump performance and maximal voluntary dynamic contraction by respectively 8% and 10% (Ptime < .01) and increased serum procollagen type 1N-terminal peptide concentration by 10% (Ptime < .01). However, no differences were found for any of the outcomes between whey and whey protein + collagen peptides. In conclusion, substituting a portion of whey protein for collagen peptide, within a similar total protein dose, improved neither indices of eccentric muscle damage nor functional outcomes during eccentric training.

Defining ketone supplementation: the evolving evidence for postexercise ketone supplementation to improve recovery and adaptation to exercise.

Over the last decade, there has been a growing interest in the use of ketone supplements to improve athletic performance. These ketone supplements transiently elevate the concentrations of the ketone bodies acetoacetate (AcAc) and d-ß-hydroxybutyrate (ßHB) in the circulation. Early studies showed that ketone bodies can improve energetic efficiency in striated muscle compared with glucose oxidation and induce a glycogen-sparing effect during exercise. As such, most research has focused on the potential of ketone supplementation to improve athletic performance via ingestion of ketones immediately before or during exercise. However, subsequent studies generally observed no performance improvement, and particularly not under conditions that are relevant for most athletes. However, more and more studies are reporting beneficial effects when ketones are ingested after exercise. As such, the real potential of ketone supplementation may rather be in their ability to enhance postexercise recovery and training adaptations. For instance, recent studies observed that postexercise ketone supplementation (PEKS) blunts the development of overtraining symptoms, and improves sleep, muscle anabolic signaling, circulating erythropoietin levels, and skeletal muscle angiogenesis. In this review, we provide an overview of the current state-of-the-art about the impact of PEKS on aspects of exercise recovery and training adaptation, which is not only relevant for athletes but also in multiple clinical conditions. In addition, we highlight the underlying mechanisms by which PEKS may improve exercise recovery and training adaptation. This includes epigenetic effects, signaling via receptors, modulation of neurotransmitters, energy metabolism, and oxidative and anti-inflammatory pathways.

Recreational Football Training Increases Leg-Extensor Velocity Production in 55- To 70-Year Old Adults: A Randomized Controlled Trial.

This study investigated the effects of 10 weeks of recreational football training on the leg-extensor force-velocity (F-V) profile in 55- to 70-year-old adults. Simultaneous effects on functional capacity, body composition and endurance exercise capacity were examined. Forty participants (age 63.5 ± 3.9 years; 36♂ 4♀) were randomized in a football training (FOOT, n = 20) and a control (CON, n = 20) group. FOOT performed 45-min to 1-h of football training sessions with small-sided games twice a week. Pre- and post-intervention assessments were performed. The results revealed a greater increase in maximal velocity (d = 0.62, pint = 0.043) in FOOT compared to CON. No interaction effects were found for maximal power and force (pint > 0.05). 10-m fast walk improved more (d = 1.39, pint < 0.001), 3-step stair ascent power (d = 0.73, pint = 0.053) and body fat percentage (d = 0.61, pint = 0.083) tended to improve more in FOOT than in CON. RPE and HR values at the highest speed level during a submaximal graded treadmill test decreased more in FOOT compared to CON (RPE: d = 0.96, pint = 0.005; HR: d = 1.07, pint = 0.004). Both the number of accelerations and decelerations as well as the distance spent in moderate- and high-speed zones increased markedly throughout the 10-week period (p < 0.05). Participants perceived the sessions as very enjoyable and feasible. In conclusion, recreational football training resulted in improved leg-extensor velocity production, which translated to a better performance on functional capacity tests that rely on a high execution velocity. Simultaneously, exercise tolerance was improved and body fat percentage tended to reduce. It appears that short-term recreational football training can induce broad-spectrum health benefits in 55- to 70-year-old adults with only 2 hours of training per week.

Exogenous Ketosis Improves Sleep Efficiency and Counteracts the Decline in REM Sleep after Strenuous Exercise.

INTRODUCTION: Available evidence indicates that ketone bodies may improve sleep quality. Therefore, we determined whether ketone ester (KE) intake could counteract sleep disruptions induced by strenuous exercise. METHODS: Ten well-trained cyclists with good sleep quality participated in a randomized crossover design consisting of two experimental sessions each involving a morning endurance training and an evening high-intensity interval training ending 1 h before sleep, after which polysomnography was performed overnight. Postexercise and 30 min before sleeping time, subjects received either 25 g of KE (EX KE ) or a placebo drink (EX CON ). A third session without exercise but with placebo supplements (R CON ) was added to evaluate the effect of exercise per se on sleep. RESULTS: Blood d -ß-hydroxybutyrate concentrations transiently increased to ~3 mM postexercise and during the first part of the night in EX KE but not in EX CON or R CON . Exercise significantly reduced rapid eye movement sleep by 26% ( P = 0.001 vs R CON ) and increased wakefulness after sleep onset by 95% ( P = 0.004 vs R CON ). Interestingly, KE improved sleep efficiency by 3% ( P = 0.040 vs EX CON ) and counteracted the exercise-induced decrease in rapid eye movement sleep ( P = 0.011 vs EX CON ) and the increase in wakefulness after sleep onset ( P = 0.009 vs EX CON ). This was accompanied by a KE-induced increase in dopamine excretion ( P = 0.033 vs EX CON ), which plays a pivotal role in sleep regulation. In addition, exercise increased sleep spindle density by 36% ( P = 0.005 vs R CON ), suggesting an effect on neural plasticity processes during sleep. CONCLUSIONS: These data indicate that KE ingestion improves sleep efficiency and quality after high-intensity exercise. We provide preliminary evidence that this might result from KE-induced increases in dopamine signaling.

Exogenous ketosis increases circulating dopamine concentration and maintains mental alertness in ultra-endurance exercise.

Exogenous ketosis can improve psychocognitive functioning during exercise as well as stimulate postexercise muscular recovery. Therefore, we hypothesized that ketone ester (KE) supplementation can counteract the decline in psychocognitive functioning during ultra-endurance exercise and stimulate muscular recovery. Eighteen recreational runners participated in a full 100 km trail run (RUN, n = 8), or ran to premature exhaustion (80 km: n = 6; 60 km: n = 4). Before (25 g), during (25 g·h-1), and after (5 × 25 g in 24 h) RUN they received ketone ester (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE, n = 9) supplements or a noncaloric placebo (CON, n = 9). Blood samples and muscle biopsies were taken, and mental alertness was assessed by a psychocognitive test battery at different times before, during, and up to 36 h after RUN. Compared with CON (<0.3 mM), in KE blood d-ß-hydroxybutyrate concentration was consistently elevated to ∼2-3 mM during RUN. In CON, RUN increased visual reaction times from 353 ± 53 to 419 ± 54 ms, and movement execution times from 174 ± 47 to 245 ± 64 ms. But this effect was fully negated by KE (P < 0.05). Plasma dopamine concentrations doubled in KE during RUN but remained stable in CON, resulting in higher concentrations after RUN in KE (4.1 ± 1.7 nM) than in CON (2.4 ± 0.8 nM, P = 0.048). KE also inhibited muscular infiltration of macrophages and suppressed AMPK phosphorylation status until 36-h postexercise (P < 0.05 KE vs. CON). In conclusion, KE increases circulating dopamine concentration and improves mental alertness, as well as improves postexercise muscular inflammation in ultra-endurance exercise.NEW & NOTEWORTHY Oral ketone ester ingestion elevates circulating dopamine concentration during ultra-endurance exercise. This is associated with improved mental alertness. Furthermore, ketone ester intake inhibits postexercise skeletal muscle macrophage infiltration, and counteracts the increase in AMPK phosphorylation after exercise, which indicates improved muscular energy status.

Exogenous ketosis elevates circulating erythropoietin and stimulates muscular angiogenesis during endurance training overload.

De novo capillarization is a primary muscular adaptation to endurance exercise training and is crucial to improving performance. Excess training load, however, impedes such beneficial adaptations, yet we recently demonstrated that such downregulation may be counteracted by ketone ester ingestion (KE) post-exercise. Therefore, we investigated whether KE could increase pro-angiogenic factors and thereby stimulate muscular angiogenesis during a 3-week endurance training-overload period involving 10 training sessions/week in healthy, male volunteers. Subjects received either 25 g of a ketone ester (KE, n = 9) or a control drink (CON, n = 9) immediately after each training session and before sleep. In KE, but not in CON, the training intervention increased the number of capillary contacts and the capillary-to-fibre perimeter exchange index by 44% and 42%, respectively. Furthermore, KE also substantially increased vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) expression both at the protein and at the mRNA level. Serum erythropoietin concentration was concomitantly increased by 26%. Conversely, in CON the training intervention increased only the protein content of eNOS. These data indicate that intermittent exogenous ketosis during endurance overload training stimulates muscular angiogenesis. This likely resulted from a direct stimulation of muscle angiogenesis, which may be at least partly due to stimulation of erythropoietin secretion and elevated VEGF activity, and/or an inhibition of the suppressive effect of overload training on the normal angiogenic response to training. This study provides novel evidence to support the potential of exogenous ketosis to benefit endurance training-induced muscular adaptation. KEY POINTS: Increased capillarization is a primary muscular adaptation to endurance exercise training. However, excess training load may impede such response. We previously observed that intermittent exogenous ketosis by post-exercise and pre-sleep ketone ester ingestion (KE) counteracted physiological dysregulations induced by endurance overload training. Therefore, we investigated whether KE could increase pro-angiogenic factors thereby stimulating muscular angiogenesis during a 3-week endurance training overload period. We show that the overload training period in the presence, but not in the absence, of KE markedly increased muscle capillarization (+40%). This increase was accompanied by higher circulating erythropoietin concentration and stimulation of the pro-angiogenic factors vascular endothelial growth factor and endothelial nitric oxide synthase in skeletal muscle. Collectively, our data indicate that intermittent exogenous ketosis may evolve as a potent nutritional strategy to facilitate recovery from strenuous endurance exercise, thereby stimulating beneficial muscular adaptations.

Exogenous ketosis suppresses diuresis and atrial natriuretic peptide during exercise.

We have previously demonstrated that exogenous ketosis reduces urine production during exercise. However, the underlying physiological mechanism of this antidiuretic effect remained unclear. Therefore, we investigated whether acute exogenous ketosis by oral ingestion of ketone ester (KE) during a simulated cycling race (RACE) affects the hormonal pathways implicated in fluid balance regulation during exercise. In a double-blind crossover design, 11 well-trained male cyclists participated in RACE consisting of a 3-h submaximal intermittent cycling (IMT180') bout followed by a 15-min time trial (TT15') in an environmental chamber set at 28°C and 60% relative humidity. Fluid intake was adjusted to maintain euhydration. Before and during RACE, the subjects received either a control drink (CON) or the ketone ester (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE), which elevated blood ß-hydroxybutyrate to ∼2-4 mM. Urine output during IMT180' was ∼20% lower in KE (1,172 ± 557 mL) than in CON (1,431 ± 548 mL, P < 0.05). Compared with CON, N-terminal proatrial natriuretic peptide (NT-pro ANP) concentration during RACE was ∼20% lower in KE (P < 0.05). KE also raised plasma noradrenaline concentrations during RACE. Performance in TT15' was similar between CON and KE. In conclusion, exogenous ketosis suppresses diuresis and downregulates NT-pro ANP secretion during exercise.NEW & NOTEWORTHY We previously demonstrated that exogenous ketosis reduces urine production during exercise, however, the underlying physiological mechanism remained unclear. Here, we, for the first time demonstrate that exogenous ketosis suppresses the exercise-induced release of atrial natriuretic peptide (ANP). However, given the limited effects of ANP on renal haemodynamics during exercise, the underlying physiological mechanism remains unknown. But downregulation of ANP might explain a new physiological mechanism by which exogenous ketosis lowers blood-free fatty acid levels.

Exogenous ketosis increases blood and muscle oxygenation but not performance during exercise in hypoxia.

Available evidence indicates that elevated blood ketones are associated with improved hypoxic tolerance in rodents. From this perspective, we hypothesized that exogenous ketosis by oral intake of the ketone ester (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE) may induce beneficial physiological effects during prolonged exercise in acute hypoxia. As we recently demonstrated KE to deplete blood bicarbonate, which per se may alter the physiological response to hypoxia, we evaluated the effect of KE both in the presence and absence of bicarbonate intake (BIC). Fourteen highly trained male cyclists performed a simulated cycling race (RACE) consisting of 3-h intermittent cycling (IMT180') followed by a 15-min time-trial (TT15') and an all-out sprint at 175% of lactate threshold (SPRINT). During RACE, fraction of inspired oxygen ([Formula: see text]) was gradually decreased from 18.6% to 14.5%. Before and during RACE, participants received either 1) 75 g of ketone ester (KE), 2) 300 mg/kg body mass bicarbonate (BIC), 3) KE + BIC, or 4) a control drink in addition to 60 g of carbohydrates/h in a randomized, crossover design. KE counteracted the hypoxia-induced drop in blood ([Formula: see text]) and muscle oxygenation by ∼3%. In contrast, BIC decreased [Formula: see text] by ∼2% without impacting muscle oxygenation. Performance during TT15' and SPRINT were similar between all conditions. In conclusion, KE slightly elevated the degree of blood and muscle oxygenation during prolonged exercise in moderate hypoxia without impacting exercise performance. Our data warrant to further investigate the potential of exogenous ketosis to improve muscular and cerebral oxygenation status, and exercise tolerance in extreme hypoxia.

Two Weeks of Smoking Cessation Reverse Cigarette Smoke-Induced Skeletal Muscle Atrophy and Mitochondrial Dysfunction in Mice.

INTRODUCTION: Apart from its adverse effects on the respiratory system, cigarette smoking also induces skeletal muscle atrophy and dysfunction. Whether short-term smoking cessation can restore muscle mass and function is unknown. We, therefore, studied the impact of 1- and 2-week smoking cessation on skeletal muscles in a mouse model. METHODS: Male mice were divided into four groups: Air-exposed (14 weeks); cigarette smoke (CS)-exposed (14 weeks); CS-exposed (13 weeks) followed by 1-week cessation; CS-exposed (12 weeks) followed by 2 weeks cessation to examine exercise capacity, physical activity levels, body composition, muscle function, capillarization, mitochondrial function and protein expression in the soleus, plantaris, and diaphragm muscles. RESULTS: CS-induced loss of body and muscle mass was significantly improved within 1 week of cessation due to increased lean and fat mass. Mitochondrial respiration and protein levels of the respiratory complexes in the soleus were lower in CS-exposed mice, but similar to control values after 2 weeks of cessation. Exposing isolated soleus muscles to CS extracts reduced mitochondrial respiration that was reversed after removing the extract. While physical activity was reduced in all groups, exercise capacity, limb muscle force, fatigue resistance, fiber size and capillarization, and diaphragm cytoplasmic HIF-1α were unaltered by CS-exposure. However, CS-induced diaphragm atrophy and increased capillary density were not seen after 2 weeks of smoking cessation. CONCLUSION: In male mice, 2 weeks of smoking cessation reversed smoking-induced mitochondrial dysfunction, limb muscle mass loss, and diaphragm muscle atrophy, highlighting immediate benefits of cessation on skeletal muscles. IMPLICATIONS: Our study demonstrates that CS-induced skeletal muscle mitochondrial dysfunction and atrophy are significantly improved by 2 weeks of cessation in male mice. We show for the first time that smoking cessation as short as 1 to 2 weeks is associated with immediate beneficial effects on skeletal muscle structure and function with the diaphragm being particularly sensitive to CS-exposure and cessation. This could help motivate smokers to quit smoking as early as possible. The knowledge that smoking cessation has potential positive extrapulmonary effects is particularly relevant for patients referred to rehabilitation programs and those admitted to hospitals suffering from acute or chronic muscle deterioration yet struggling with smoking cessation.

Bicarbonate Unlocks the Ergogenic Action of Ketone Monoester Intake in Endurance Exercise.

PURPOSE: We recently reported that oral ketone ester (KE) intake before and during the initial 30 min of a 3 h 15 min simulated cycling race (RACE) transiently decreased blood pH and bicarbonate without affecting maximal performance in the final quarter of the event. We hypothesized that acid-base disturbances due to KE overrules the ergogenic potential of exogenous ketosis in endurance exercise. METHODS: Nine well-trained male cyclists participated in a similar RACE consisting of 3 h submaximal intermittent cycling (IMT180') followed by a 15-min time trial (TT15') preceding an all-out sprint at 175% of lactate threshold (SPRINT). In a randomized crossover design, participants received (i) 65 g KE, (ii) 300 mg·kg-1 body weight NaHCO3 (BIC), (iii) KE + BIC, or (iv) a control drink (CON), together with consistent 60 g·h-1 carbohydrate intake. RESULTS: KE ingestion transiently elevated blood D-ß-hydroxybutyrate to ~2-3 mM during the initial 2 h of RACE (P < 0.001 vs CON). In KE, blood pH concomitantly dropped from 7.43 to 7.36 whereas bicarbonate decreased from 25.5 to 20.5 mM (both P < 0.001 vs CON). Additional BIC resulted in 0.5 to 0.8 mM higher blood D-ß-hydroxybutyrate during the first half of IMT180' (P < 0.05 vs KE) and increased blood bicarbonate to 31.1 ± 1.8 mM and blood pH to 7.51 ± 0.03 by the end of IMT180' (P < 0.001 vs KE). Mean power output during TT15' was similar between KE, BIC, and CON at ~255 W but was 5% higher in KE + BIC (P = 0.02 vs CON). Time to exhaustion in the sprint was similar between all conditions at ~60 s (P = 0.88). Gastrointestinal symptoms were similar between groups. DISCUSSION: The coingestion of oral bicarbonate and KE enhances high-intensity performance at the end of an endurance exercise event without causing gastrointestinal distress.

Exogenous Ketosis Impairs 30-min Time-Trial Performance Independent of Bicarbonate Supplementation.

PURPOSE: We recently demonstrated that coingestion of NaHCO3 to counteract ketoacidosis resulting from oral ketone ester (KE) intake improves mean power output during a 15-min time trial (TT) at the end of a 3-h cycling race by ~5%. This ergogenic effect occurred at a time when blood ketone levels were low, as ketosis was only induced during the initial ~2 h of the race. Therefore, in the current study, we investigated whether performance also increases if blood ketone levels are increased in the absence of ketoacidosis during high-intensity exercise. METHODS: In a double-blind crossover design, 14 well-trained male cyclists completed a 30-min TT (TT30') followed by an all-out sprint at 175% of lactate threshold (SPRINT). Subjects were randomized to receive (i) 50 g KE, (ii) 180 mg·kg-1 body weight NaHCO3 (BIC), (iii) KE + BIC, or (iv) a control drink (CON). RESULTS: KE ingestion increased blood d-ß-hydroxybutyrate to ~3-4 mM during the TT30' and SPRINT (P < 0.001 vs CON). In KE, blood pH and bicarbonate concomitantly dropped, causing 0.05 units lower pH and 2.6 mM lower bicarbonate in KE compared with CON during the TT30' and SPRINT (P < 0.001 vs CON). BIC coingestion resulted in 0.9 mM higher blood d-ß-hydroxybutyrate (P < 0.001 vs KE) and completely counteracted ketoacidosis during exercise (P > 0.05 vs CON). Mean power output during TT30' was similar between CON and BIC at 281 W, but was 1.5% lower in the KE conditions (main effect of KE: P = 0.03). Time to exhaustion in the SPRINT was ~64 s in CON and KE and increased by ~8% in the BIC conditions (main effect of BIC: P < 0.01). DISCUSSION: Neutralization of acid-base disturbance by BIC coingestion is insufficient to counteract the slightly negative effect of KE intake during high-intensity exercise.

Cardiotoxin-induced skeletal muscle injury elicits profound changes in anabolic and stress signaling, and muscle fiber type composition.

To improve muscle healing upon injury, it is of importance to understand the interplay of key signaling pathways during muscle regeneration. To study this, mice were injected with cardiotoxin (CTX) or PBS in the Tibialis Anterior muscle and were sacrificed 2, 5 and 12 days upon injection. The time points represent different phases of the regeneration process, i.e. destruction, repair and remodeling, respectively. Two days upon CTX-injection, p-mTORC1 signaling and stress markers such as BiP and p-ERK1/2 were upregulated. Phospho-ERK1/2 and p-mTORC1 peaked at d5, while BiP expression decreased towards PBS levels. Phospho-FOXO decreased 2 and 5 days following CTX-injection, indicative of an increase in catabolic signaling. Furthermore, CTX-injection induced a shift in the fiber type composition, characterized by an initial loss in type IIa fibers at d2 and at d5. At d5, new type IIb fibers appeared, whereas type IIa fibers were recovered at d12. To conclude, CTX-injection severely affected key modulators of muscle metabolism and histology. These data provide useful information for the development of strategies that aim to improve muscle molecular signaling and thereby recovery.

Exogenous ketosis impacts neither performance nor muscle glycogen breakdown in prolonged endurance exercise.

Available evidence indicates that ketone bodies inhibit glycolysis in contracting muscles. Therefore, we investigated whether acute exogenous ketosis by oral ketone ester (KE) intake early in a simulated cycling race can induce transient glycogen sparing by glycolytic inhibition, thereby increasing glycogen availability in the final phase of the event. In a randomized crossover design, 12 highly trained male cyclists completed a simulated cycling race (RACE), which consisted of 3-h intermittent cycling (IMT180'), a 15-min time trial (TT15'), and a maximal sprint (SPRINT). During RACE, subjects received 60 g carbohydrates/h combined with three boluses (25, 20, and 20 g) (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE) or a control drink (CON) at 60 and 20 min before and at 30 min during RACE. KE intake transiently increased blood d-ß-hydroxybutyrate to ~3 mM (range: 2.6-5.2 mM) during the first half of RACE (P < 0.001 vs. CON). Blood pH concomitantly decreased from approximately 7.42 to 7.36 (range: 7.29-7.40), whereas bicarbonate dropped from 26.0 to 21.6 mM (range: 20.1-23.7; both P < 0.001 vs. CON). Net muscle glycogen breakdown during IMT180' [KE: -78 ± 30 (SD); CON: -60 ± 22 mmol/kg wet wt; P = 0.08] and TT15' (KE: -9 ± 18; CON: -18 ± 18 mmol/kg wet wt; P = 0.35) was similar between KE and CON. Accordingly, mean power output during TT15' (KE: 273 ± 38; CON: 272 ± 37 W; P = 0.83) and time-to-exhaustion in the SPRINT (KE: 59 ± 16; CON: 58 ± 17 s; P = 0.66) were similar between conditions. In conclusion, KE intake during a simulated cycling race does not cause glycogen sparing, nor does it affect all-out performance in the final stage of a simulated race.NEW & NOTEWORTHY Exogenous ketosis produced by oral ketone ester ingestion during the early phase of prolonged endurance exercise and against the background of adequate carbohydrate intake neither causes muscle glycogen sparing nor improves performance in the final stage of the event. However, such exogenous ketosis may decrease buffering capacity in the approach of the final episode of the event. Furthermore, ketone ester intake during exercise may reduce appetite immediately after exercise.

Ketone ester supplementation blunts overreaching symptoms during endurance training overload.

KEY POINTS: Overload training is required for sustained performance gain in athletes (functional overreaching). However, excess overload may result in a catabolic state which causes performance decrements for weeks (non-functional overreaching) up to months (overtraining). Blood ketone bodies can attenuate training- or fasting-induced catabolic events. Therefore, we investigated whether increasing blood ketone levels by oral ketone ester (KE) intake can protect against endurance training-induced overreaching. We show for the first time that KE intake following exercise markedly blunts the development of physiological symptoms indicating overreaching, and at the same time significantly enhances endurance exercise performance. We provide preliminary data to indicate that growth differentiation factor 15 (GDF15) may be a relevant hormonal marker to diagnose the development of overtraining. Collectively, our data indicate that ketone ester intake is a potent nutritional strategy to prevent the development of non-functional overreaching and to stimulate endurance exercise performance. ABSTRACT: It is well known that elevated blood ketones attenuate net muscle protein breakdown, as well as negate catabolic events, during energy deficit. Therefore, we hypothesized that oral ketones can blunt endurance training-induced overreaching. Fit male subjects participated in two daily training sessions (3 weeks, 6 days/week) while receiving either a ketone ester (KE, n = 9) or a control drink (CON, n = 9) following each session. Sustainable training load in week 3 as well as power output in the final 30 min of a 2-h standardized endurance session were 15% higher in KE than in CON (both P < 0.05). KE inhibited the training-induced increase in nocturnal adrenaline (P < 0.01) and noradrenaline (P < 0.01) excretion, as well as blunted the decrease in resting (CON: -6 ± 2 bpm; KE: +2 ± 3 bpm, P < 0.05), submaximal (CON: -15 ± 3 bpm; KE: -7 ± 2 bpm, P < 0.05) and maximal (CON: -17 ± 2 bpm; KE: -10 ± 2 bpm, P < 0.01) heart rate. Energy balance during the training period spontaneously turned negative in CON (-2135 kJ/day), but not in KE (+198 kJ/day). The training consistently increased growth differentiation factor 15 (GDF15), but ∼2-fold more in CON than in KE (P < 0.05). In addition, delta GDF15 correlated with the training-induced drop in maximal heart rate (r = 0.60, P < 0.001) and decrease in osteocalcin (r = 0.61, P < 0.01). Other measurements such as blood ACTH, cortisol, IL-6, leptin, ghrelin and lymphocyte count, and muscle glycogen content did not differentiate KE from CON. In conclusion, KE during strenuous endurance training attenuates the development of overreaching. We also identify GDF15 as a possible marker of overtraining.

A noninterfering system to measure in-cage spontaneous physical activity in mice.

Due to lack of low-cost and convenient measurement procedures, uncontrolled changes in spontaneous physical activity (SPA) level often are insufficiently considered as a confounding factor in rodent studies. Nonetheless, alterations in SPA can significantly impact on a wide range of physiological measurements. Therefore, we developed an accurate, low-cost video tracking procedure to allow routine assessment of SPA in the home cage of experimental animals (i.e., mice) and in the absence of any distress that might cause alterations in SPA. SPA parameters acquired (movement distance, movement time, and movement speed) with the novel tracking system were identical to those simultaneously obtained with a high-end and well-validated movement-tracking device (mean error = 0.15 ± 0.07%, r = 0.99, P < 0.001). To further validate the setup, we also demonstrated caffeine-induced stimulation of SPA (195% more activity compared with vehicle, P < 0.01), we adequately reproduced typical SPA fluctuations inherent to day/night cycles (146 and 702% more active during nocturnal compared with diurnal cycle for Balb/c and C57BL/6J mice, respectively, P < 0.001), and we confirmed previously documented SPA differences between animal strains (24% less activity in C57BL/6J mice compared with Balb/c mice, P < 0.05). Taken together, we provide data to prove that this novel low-cost methodology can be conveniently used in any mouse experiment where uncontrolled changes in SPA due to experimental interventions might confound data interpretation. By analogy, the system can be used to document a beneficial impact of therapeutic interventions on SPA in any disease mouse model. NEW & NOTEWORTHY We developed a low-cost procedure to routinely measure SPA in mice. The procedure maintains normal SPA because the animals continue to stay in their home cage in the absence of any external manipulation by the investigators and under habitual dark/light ambient conditions. This novel methodology can be conveniently used in any mouse experiment to quantify experimentally induced alterations in SPA or to assess natural variations in SPA that might confound data interpretation.