Effects of bovine whey protein on exercise-induced gut permeability in healthy adults: a randomised controlled trial.

PURPOSE: Intestinal permeability is a critical component of gut barrier function. Barrier dysfunction can be triggered by certain stressors such as exercise, and if left unmanaged can lead to local and systemic disorders. The aim of this study was to investigate the effects of a specific whey protein fraction in alleviating exercise-induced gut permeability as assessed by recovery of lactulose/rhamnose (L/R) and lactulose/mannitol (L/M) urinary probes. METHODS: Eight males and eight females (aged 18-50) completed two arms of a double-blind, placebo-controlled, crossover study. For each arm participants performed two baseline intestinal permeability assessments, following which they consumed the treatment (2 g/day of milk powder containing 200 mg of whey protein) or placebo (2 g/day of milk powder) for 14 days, before performing a post-exercise permeability assessment. The exercise protocol involved a 20-min run at 80% of maximal oxygen uptake on a 1% incline. RESULTS: Mixed model analysis revealed an increase in L/R (23%; P < 0.001) and L/M (20%; P < 0.01) recovery following exercise. However, there was no treatment or treatment × exercise effect. CONCLUSION: The exercise protocol utilised in our study induces gut permeability. However, consuming whey protein, at the dose and timing prescribed, is not able to mitigate this effect.

Peak Power Output and Onset of Muscle Activation During High Pull Exercise.

ABSTRACT: Barnes, MJ, Petterson, A, and Cochrane, DJ. Peak power output and onset of muscle activation during high pull exercise. J Strength Cond Res 35(3): 675-679, 2021-The aim of this study was to determine the percentage of 1 repetition maximum (1RM) at which peak power output occurred during the high pull (HP) exercise. In addition, the onset time of the biceps femoris (BF) and gluteus maximus (GM), across a range of loads, was investigated. Twelve resistance-trained men performed 1RM testing for the HP followed by lifts at 10% increments from 30 to 80% 1RM. During each load of power, output was measured using a linear potentiometer, whereas surface electromyography was recorded from the BF and GM. Peak power output occurred at 70% (1881.9 ± 296.1 W); however, there was no significant difference between loads at 60-80% (all p > 0.05). Loads between 40 and 80% 1RM produced significantly higher power outputs than 30% while 80% generated greater power than 100% 1RM (all p < 0.05). There was no significant (p > 0.05) main effect of muscle or load in the onset of BF (156.5-212.1 ms) or GM (112.1-158.1 ms). Therefore, these results suggest that training at a load between 60 and 80% 1RM may be useful in increasing power in the HP. In addition, activation of 2 of the hip extensors occurs in a relatively synchronous order irrespective of load.

On exercise thermoregulation in females: interaction of endogenous and exogenous ovarian hormones.

KEY POINTS: One in two female athletes chronically take a combined, monophasic oral contraceptive pill (OCP). Previous thermoregulatory investigations proposed that an endogenous rhythm of the menstrual cycle still occurs with OCP usage. Forthcoming large international sporting events will expose female athletes to hot environments differing in their thermal profile, yet few data exist on how trained women will respond from both a thermoregulatory and performance stand-point. In the present study, we have demonstrated that a small endogenous rhythm of the menstrual cycle still affects Tcore and also that chronic OCP use attenuates the sweating response, whereas behavioural thermoregulation is maintained. Furthermore, humid heat affects both performance and thermoregulatory responses to a greater extent than OCP usage and the menstrual cycle does. ABSTRACT: We studied thermoregulatory responses of ten well-trained ( V̇O2max , 57 ± 7 mL min-1  kg-1 ) women taking a combined, monophasic oral contraceptive pill (OCP) (≥12 months) during exercise in dry and humid heat, across their active OCP cycle. They completed four trials, each of resting and cycling at fixed intensities (125 and 150 W), aiming to assess autonomic regulation, and then a self-paced intensity (30-min work trial) to assess behavioural regulation. Trials were conducted in quasi-follicular (qF) and quasi-luteal (qL) phases in dry (DRY) and humid (HUM) heat matched for wet bulb globe temperature (WBGT) (27°C). During rest and exercise at 125 W, rectal temperature was 0.15°C higher in qL than qF (P = 0.05) independent of environment (P = 0.17). The onset threshold and thermosensitivity of local sweat rate and forearm blood flow relative to mean body temperature was unaffected by the OCP cycle (both P > 0.30). Exercise performance did not differ between quasi-phases (qF: 268 ± 31 kJ, qL: 263 ± 26 kJ, P = 0.31) but was 5 ± 7% higher during DRY than during HUM (273 ± 29 kJ, 258 ± 28 kJ; P = 0.03). Compared to matched eumenorrhoeic athletes, chronic OCP use impaired the sweating onset threshold and thermosensitivity (both P < 0.01). In well-trained, OCP-using women exercising in the heat: (i) a performance-thermoregulatory trade-off occurred that required behavioural adjustment; (ii) humidity impaired performance as a result of reduced evaporative power despite matched WBGT; and (iii) the sudomotor but not behavioural thermoregulatory responses were impaired compared to matched eumenorrhoeic athletes.

Acute Neuromuscular and Endocrine Responses to Two Different Compound Exercises: Squat vs. Deadlift.

Barnes, MJ, Miller, A, Reeve, D, and Stewart, RJ. Acute neuromuscular and endocrine responses to two different compound exercises: squat vs. deadlift. J Strength Cond Res 33(9): 2381-2387, 2019-Anecdotally, it is believed that the deadlift exercise brings about greater levels of central fatigue than other exercises; however, no empirical evidence exists to support this view. In addition, little is known about the acute endocrine response to heavy deadlift exercise and how this may differ from other similar compound exercises. Therefore, the aim of this study was to identify and compare the acute, neuromuscular and endocrine responses to squat and deadlift exercises. Ten resistance-trained males completed 8 sets of 2 repetitions at 95% of 1 repetition maximum. Maximum voluntary isometric contraction (MVIC) force of the quadriceps, along with measures of central (voluntary activation [VA] and surface electromyography) and peripheral (electrically evoked control stimulus) fatigue were made before and 5 and 30 minutes after exercise. In addition, salivary testosterone and cortisol were measured at these same time points. MVIC was reduced after the completion of both exercises (p = 0.007); however, no difference between exercises was evident. Similarly, although VA changed over time (p = 0.0001), no difference was observed between exercises. As a measure of peripheral fatigue, force from the control stimulus changed over time (p = 0.003) with a greater decrease evident after the squat (p = 0.034). Electromyography was reduced over time (p = 0.048) but no difference was seen between exercises. No change was seen in testosterone and cortisol. Although a greater absolute load and larger volume load were completed for the deadlift, no difference in central fatigue was evident between the 2 compound exercises. The greater peripheral fatigue observed after squat exercise may be due to the greater work completed by the quadriceps with this exercise. These results suggest that separate periodization, tapering, and programming considerations may be unnecessary when using the squat and deadlift to develop muscular strength.

Multiday Pomegranate Extract Supplementation Decreases Oxygen Uptake During Submaximal Cycling Exercise, but Cosupplementation With N-acetylcysteine Negates the Effect.

Pomegranate extract (POMx) has been suggested as an ergogenic aid due to its rich concentration of polyphenols, which are proposed to enhance nitric oxide bioavailability, thereby improving the efficiency of oxygen usage and, consequently, endurance exercise performance. Although acute POMx supplementation improves aerobic exercise performance in untrained individuals, trained athletes appear to require chronic supplementation for a similar effect. Furthermore, the combination of POMx with a thiol antioxidant may prove more effective than POMx alone, due to the protective effects of thiols on nitric oxide. Thus, this study hypothesized that multiday POMx supplementation would decrease the oxygen uptake (VO2) required by trained cyclists to perform submaximal exercise and increase performance during a time trial, and that thiol (N-acetylcysteine [NAC]) cosupplementation would enhance these effects. Eight cyclists completed four 8-day supplementation periods: POMx only, NAC only, POMx + NAC (BOTH), and placebo. Following supplementation, they performed submaximal cycling and a 5-min time trial, with VO2 and muscle oxygen saturation (SmO2) being recorded. A three-way (POMx × NAC × Intensity) repeated-measures analysis of variance with a Fisher's least significant difference post hoc assessment was performed for dependent variables (p ≤ .05). VO2 during submaximal exercise was reduced with POMx versus placebo (-2.6 ml·min-1·kg-1, p = .009) and BOTH (-2.5 ml·min-1·kg-1, p < .05) and increased with NAC (+1.9 ml·min-1·kg-1, p < .03), despite no main effect of treatment on SmO2 or performance. It appears that POMx's high polyphenol content reduced the VO2 required during submaximal exercise. However, NAC cosupplementation annulled this effect; thus, NAC may interact with nitric oxide to reduce its bioavailability.

Short-Term Training Cessation as a Method of Tapering to Improve Maximal Strength.

Pritchard, HJ, Barnes, MJ, Stewart, RJC, Keogh, JWL, and McGuigan, MR. Short-term training cessation as a method of tapering to improve maximal strength. J Strength Cond Res 32(2): 458-465, 2018-The aim of this study was to determine the effects of 2 different durations of training cessation on upper- and lower-body maximal strength performance and to investigate the mechanisms underlying performance changes following short-term training cessation. Eight resistance trained males (23.8 ± 5.4 years, 79.6 ± 10.2 kg, 1.80 ± 0.06 m, relative deadlift 1 repetition maximum of 1.90 ± 0.30 times bodyweight [BW]) each completed two 4-week strength training periods followed by either 3.5 days (3.68 ± 0.12 days) or 5.5 days (5.71 ± 0.13 days) of training cessation. Testing occurred pretraining (T1), on the final day of training (T2), and after each respective period of training cessation (T3). Participants were tested for salivary testosterone and cortisol, plasma creatine kinase, psychological profiles, and performance tests (countermovement jump [CMJ], isometric midthigh pull, and isometric bench press [IBP]) on a force plate. Participants' BW increased significantly over time (p = 0.022). The CMJ height and IBP peak force showed significant increases over time (p = 0.013, 0.048, and 0.004, respectively). Post hoc testing showed a significant increase between T1 and T3 for both CMJ height and IBP peak force (p = 0.022 and 0.008 with effect sizes of 0.30 and 0.21, respectively). No other significant differences were seen for any other measures. These results suggest that a short period of strength training cessation can have positive effects on maximal strength expression, perhaps because of decreases in neuromuscular fatigue.

Cerebrovascular, cardiovascular and strength responses to acute ammonia inhalation.

PURPOSE: Ammonia is used as a stimulant in strength based sports to increase arousal and offset fatigue however little is known about its physiological and performance effects. The purpose of this study was twofold (1) establish the physiological response to acute ammonia inhalation (2) determine whether the timing of the physiological response corresponds with a performance enhancement, if any. METHODS: Fifteen healthy males completed two trials. Trial one investigated the beat-to-beat middle cerebral artery blood flow velocity (MCAv), heart rate (HR) and mean arterial pressure (MAP) response to ammonia inhalation. During trial two, participants performed a maximal single mid-thigh pull (MTP) at various time points following ammonia inhalation in a randomised order: MTPs were conducted immediately, 15, 30 and 60 s following ammonia inhalation. A MTP with no ammonia inhalation served as the control. During this trial maximal MTP force, rate of force development (RFD) and electromyography (EMG) activity were recorded. RESULTS: MCAvmean increased and peaked on average by 6 cm s(-1) (P < 0.001), 9.4 ± 5.5 s following ammonia inhalation. Similarly, HR was increased by 6 ± 11 beats per minute 15 s following ammonia inhalation (P < 0.001). MAP remained unchanged following inhalation (P = 0.51). The use and timing of ammonia inhalation had no effect on maximal force, RFD or EMG (all P > 0.2) compared to control. CONCLUSIONS: MCAv was elevated despite no increase in MAP occurring; this is indicative of a cerebrovascular vasodilation. Despite the marked cerebrovascular and cardiovascular response to ammonia inhalation no ergogenic effect was observed during the MTP, irrespective of the timing of administration.

Tapering Practices of New Zealand's Elite Raw Powerlifters.

Pritchard, HJ, Tod, DA, Barnes, MJ, Keogh, JW, and McGuigan, MR. Tapering practices of New Zealand's elite raw powerlifters. J Strength Cond Res 30(7): 1796-1804, 2016-The major aim of this study was to determine tapering strategies of elite powerlifters. Eleven New Zealand powerlifters (28.4 ± 7.0 years, best Wilks score of 431.9 ± 43.9 points) classified as elite were interviewed, using semistructured interviews, about their tapering strategies. Interviews were transcribed verbatim and content analyzed. Total training volume peaked 5.2 ± 1.7 weeks from competition while average training intensity (of 1 repetition maximum) peaked 1.9 ± 0.8 weeks from competition. During tapering, volume was reduced by 58.9 ± 8.4% while intensity was maintained (or slightly reduced) and the final weight training session was performed 3.7 ± 1.6 days out from competition. Participants generally stated that tapering was performed to achieve full recovery; that accessory work was removed around 2 weeks out from competition; and deadlifting takes longer to recover from than other lifts. Typically participants stated that trial and error, and changes based on "feel" were the sources of tapering strategies; equipment used and movements performed during tapering are the same as in competition; nutrition was manipulated during the taper (for weight cutting or performance aims); and poor tapering occurred when too long (1 week or more) was taken off training. These results suggest that athletes may benefit from continuing to strength train before important events with reduced volume and maintained intensity. Only exercises that directly assist sports performance should remain in the strength program during tapering, to assist with reductions in fatigue while maintaining/improving strength expression and performance.

Vibration exercise as a warm-up modality for deadlift power output.

Vibration exercise (VbX) has gained popularity as a warm-up modality to enhance performance in golf, baseball, and sprint cycling, but little is known about the efficacy of using VbX as a warm-up before resistance exercise, such as deadlifting. The aim of this study was to compare the effects of a deadlift (DL)-specific warm-up, VbX warm-up, and Control on DL power output (PO). The DL warm-up (DL-WU) included 10, 8, and 5 repetitions performed at 30, 40, and 50% 1-repetition maximum (1RM), respectively, where the number of repetitions was matched by body-weight squats performed with vibration and without vibration (Control). The warm-up conditions were randomized and performed at least 2 days apart. Peak power (PP), mean power, rate of force development (RFD), and electromyography (EMG) were measured during the concentric phase of 2 consecutive DLs (75% 1RM) at 30 seconds and 2:30 minutes after the warm-up conditions. There was no significant (p > 0.05) main effect or interaction effect between the DL-WU, VbX warm-up, and Control for PP, mean power, RFD, and EMG. Vibration exercise warm-up did not exhibit an ergogenic effect to potentiate muscle activity more than the specific DL-WU and Control. Therefore, DL PO is affected to a similar extent, irrespective of the type of stimuli, when the warm-up is not focused on raising muscle temperature.

Muscle Activation and Onset Times of Hip Extensors during Various Loads of a Closed Kinetic Chain Exercise.

The aim of this study was to determine the muscle activity and onset time of hip extensors during a closed kinetic chain exercise (deadlift) at sub-maximal loads of 30%, 40%, 50%, and 75% of one repetition maximum (1RM). Twelve healthy males with at least three years of resistance training experience volunteered for the study. Biceps femoris (BF) and gluteus maximus (GM) muscle activity, onset time, peak and mean power were measured during the concentric phase of the deadlift. There was no main effect (p > 0.05) or no interaction effect for the onset time in BF and GM and for each load BF and GM had similar muscle activity. Increasing the external load during deadlift had no adverse effect on the relative onset time and it did not promote BF onset to occur before GM onset, thus both muscles were simultaneously activated, which should not compromise a delay in GM.

Nicotine exacerbates exertional heat strain in trained men: a randomized, placebo-controlled, double-blind study.

To determine whether using nicotine exacerbates exertional heat strain through an increased metabolic heat production (Hprod) or decreased skin blood flow (SkBF), 10 nicotine-naïve trained males [37 ± 12 yr; peak oxygen consumption (V̇o2peak): 66 ± 10 mL·min-1·kg-1] completed four trials at 20°C and 30°C following overnight transdermal nicotine (7 mg·24 h-1) and placebo use in a crossover, double-blind design. They cycled for 60 min (55% V̇o2peak) followed by a time trial (∼75% V̇o2peak) during which measures of gastrointestinal (Tgi) and mean weighted skin ([Formula: see text]sk) temperatures, SkBF, Hprod, and mean arterial pressure (MAP) were made. The difference in ΔTgi between nicotine and placebo trials was greater during 30°C (0.4 ± 0.5°C) than 20°C (0.1 ± 0.7°C), with [Formula: see text]sk higher during nicotine than placebo trials (0.5 ± 0.5°C, P = 0.02). SkBF became progressively lower during nicotine than placebo trials (P = 0.01) and progressively higher during 30°C than 20°C trials (P < 0.01); MAP increased from baseline (P < 0.01) and remained elevated in all trials. The difference in Hprod between 30°C and 20°C trials was lower during nicotine than placebo (P = 0.01) and became progressively higher during 30°C than 20°C trials with exercise duration (P = 0.03). Mean power output during the time trial was lower during 30°C than 20°C trials (24 ± 25 W, P = 0.02), and although no effect of nicotine was observed (P > 0.59), two participants (20%) were unable to complete their 30°C nicotine trials as one reached the ethical limit for Tgi (40.0°C), whereas the other withdrew due to "nausea and chills" (Tgi = 39.7°C). These results demonstrate that nicotine use increases thermal strain and risk of exertional heat exhaustion by reducing SkBF.NEW & NOTEWORTHY In naïve participants, acute nicotine use exerts a hyperthermic effect that increases the risk of heat exhaustion during exertional heat strain, which is driven by a blunted skin blood flow response. This has implications for 1) populations that face exertional heat strain and demonstrate high nicotine use (e.g., athletes and military, 25%-50%) and 2) study design whereby screening and exclusion for nicotine use or standardization of prior use (e.g., overnight abstinence) is encouraged.

Nutrition-Based Strategies to Reduce Exercise-Induced Muscle Damage and Soreness.

Exercise induced-muscle damage (EIMD) occurs after strenuous and/or novel exercise that involves repeated eccentric contractions [...].

A comparison of the effects of sheep's milk and cow's milk on recovery from eccentric exercise.

Introduction: When consumed after eccentric exercise, cow's milk has been shown to improve recovery and alleviate symptoms of exercise induced muscle damage. Although currently less commercially available than cow's milk, sheep's milk may offer similar or greater benefits for recovery as it is higher in protein and energy; however, the effect of sheep's milk in any exercise context has not been explored. This study compared the effects of a sheep's milk beverage and a cow's milk beverage on recovery from strenuous eccentric exercise. Additionally, the effects of each beverage on satiety and gastrointestinal comfort were assessed. Methods: Ten healthy males completed baseline measures of perceived muscle soreness and maximal voluntary concentric, eccentric, and isometric quadriceps force of one leg before completing 200 maximal eccentric knee extensions on an isokinetic dynamometer. Measures were repeated 0.5, 24, 48 and 72 h post-eccentric exercise. After 0.5 h measures, participants consumed either 450 ml of chocolate flavored sheep's milk or chocolate flavored cow's milk. Following a washout period, participants completed a second trial on the contralateral leg and consumed the other beverage. Additionally, a satiety and gastrointestinal comfort questionnaire was completed before and after each beverage was consumed. Results: Eccentric exercise brought about a significant decrease in muscle function over time (all P < 0.012). No difference between treatments (all P > 0.097) was found. Measures of muscle soreness increased over time (all P < 0.002), however no difference was observed between treatments (all P > 0.072). Only sheep's milk altered perceived satiety, however, only the response to "How full do you feel" differed between treatments (P = 0.04). Discussion: The results of this study suggest that consuming sheep's milk may provide similar benefits as cow's milk when recovering from exercise-induced muscle damage. While these findings provide initial support for the use of sheep's milk in a muscle recovery context, further research is warranted to confirm these findings. Given its superior nutritional profile, greater impact on satiety and lower environment impact, sheep's milk may be a more efficient post-exercise recovery beverage, compared to cow's milk.

The effects of vibration therapy on muscle force loss following eccentrically induced muscle damage.

The purpose of this study was to investigate the effects of acute vibration therapy (VT) on performance recovery after a bout of strenuous eccentric exercise. Eight healthy males completed 300 maximal eccentric contractions of the quadriceps of one leg on an isokinetic dynamometer. Immediately after exercise and 12 and 24 h post-exercise, the subjects underwent either VT or a control treatment of no VT. Five sets of 1 min VT was performed at 26 Hz, with 6 mm peak-to-peak displacement, on a commercially available vibration machine. At least 2 weeks after the initial trial, the subjects completed the second trial using the contralateral leg and other treatment. Peak and average peak isometric tension and isokinetic concentric and eccentric torque were measured prior to exercise and 24 and 48 h post-exercise. Treatment with VT resulted in significantly (all P < 0.05) greater decrements in peak (-38%) and average peak eccentric (-39%) torque 24 h after eccentric exercise as compared to a control treatment (-24 and -29%, respectively). These results suggest that the use of 26 Hz VT in the first 24 h after damaging exercise may be detrimental to the magnitude of force loss and/or recovery over this period.

The effects of acute alcohol consumption on recovery from a simulated rugby match.

In this study, we investigated the effects of acute post-exercise alcohol consumption on measures of physical performance, creatine kinase, and immunoendocrine function in the 48 h following a rugby game simulation. Ten male senior rugby union players completed a rugby game simulation after which they consumed either 1 g of alcohol per kilogram of body mass or a non-alcoholic control beverage. Agility, 15 m sprint, countermovement jump, and srummaging performance were assessed pre-simulation and 24 and 48 h post-simulation. White blood cell count, testosterone, cortisol, and creatine kinase were measured before the simulation and 30 min, 12, 24, 36, and 48 h after the simulation. One week after the first trial, participants completed the second simulation after which the other beverage was consumed. The acute consumption of alcohol after a rugby game simulation negatively affected countermovement jump performance in the days following the simulation (P = 0.028). No differences between treatments were observed for the other criterion measures made in this study. In conclusion, after 80 min of a simulated rugby game, the consumption of 1 g of alcohol per kg body mass negatively impacts lower body vertical power output. However, performance of tasks requiring repeated maximal muscular effort is not affected.

Nutritional Compounds to Improve Post-Exercise Recovery.

The metabolic and mechanical stresses associated with muscle-fatiguing exercise result in perturbations to bodily tissues that lead to exercise-induced muscle damage (EIMD), a state of fatigue involving oxidative stress and inflammation that is accompanied by muscle weakness, pain and a reduced ability to perform subsequent training sessions or competitions. This review collates evidence from previous research on a wide range of nutritional compounds that have the potential to speed up post-exercise recovery. We show that of the numerous compounds investigated thus far, only two-tart cherry and omega-3 fatty acids-are supported by substantial research evidence. Further studies are required to clarify the potential effects of other compounds presented here, many of which have been used since ancient times to treat conditions associated with inflammation and disease.

Astragalosides Supplementation Enhances Intrinsic Muscle Repair Capacity Following Eccentric Exercise-Induced Injury.

Astragalosides have been shown to enhance endurance exercise capacity in vivo and promote muscular hypertrophy in vitro. However, it remains unknown whether astragalosides supplementation can alter inflammatory response and enhance muscle recovery after damage in humans. We therefore aimed to evaluate the effect of astragalosides supplementation on muscle's intrinsic capacity to regenerate and repair itself after exercise-induced damage. Using a randomized double-blind placebo-controlled cross-over design, eleven male participants underwent 7 days of astragalosides supplementation (in total containing 4 mg of astragalosides per day) or a placebo control, following an eccentric exercise protocol. Serum blood samples and variables related to muscle function were collected prior to and immediately following the muscle damage protocol and also at 2 h, and 1, 2, 3, 5, and 7 days of the recovery period, to assess the pro-inflammatory cytokine response, the secretion of muscle regenerative factors, and muscular strength. Astragalosides supplementation reduced biomarkers of skeletal muscle damage (serum CK, LDH, and Mb), when compared to the placebo, at 1, 2, and 3 days following the muscle damage protocol. Astragalosides supplementation suppressed the secretion of IL-6 and TNF-α, whilst increasing the release of IGF-1 during the initial stages of muscle recovery. Furthermore, following astragaloside supplementation, muscular strength returned to baseline 2 days earlier than the placebo. Astragalosides supplementation shortens the duration of inflammation, enhances the regeneration process and restores muscle strength following eccentric exercise-induced injury.

An experimental model of contusion injury in humans.

INTRODUCTION: Contusion injuries are common in sport, but our knowledge of the responses to injury primarily come from animal studies and research using eccentric exercise. Therefore, the aim of this study was to develop a model of contusion injury in human participants and, additionally, investigate and compare physiological responses to four impact loads. METHODS: Thirty-two males were exposed to a single impact of either 4.2, 5.2, 6.2 or 7.2kg, dropped from 67 cm, on to the vastus lateralis of one leg. Maximum voluntary and electrically induced quadriceps force, and pressure pain threshold were measured, and blood sampling carried out, prior to and 30min, 24, 48 and 72h post-impact. Magnetic resonance imaging was carried out 24h post-impact to quantify oedema. RESULTS: Despite impact force with 7.2kg (1681.4 ± 235.6 N) not being different to 6.2kg (1690.7 ± 117.6 N), 7.2kg resulted in greater volume of oedema, voluntary force loss, pain and elevations in creatine kinase than the other loads. Although electrically induced force changed over time, post-hoc analysis failed to identify any changes. Interleukin-6 and prostaglandin-E2 did not change over time for any of the loads. Significant correlations were found between oedema volume, pressure pain threshold and maximum voluntary contraction force. CONCLUSIONS: This is the first experimental study to investigate traumatic loading of skeletal muscle and the subsequent physiological responses associated with contusion injuries in humans. The absence of immediate elevations in creatine kinase and changes in electrically induced force suggest impact, with forces similar to those experienced in contact sport, does not cause significant, direct damage to skeletal muscle. However, the relationship between oedema volume, changes in pressure pain threshold and maximum voluntary contraction force suggests central inhibition plays a role in contusion-related muscle dysfunction.

A low dose of alcohol does not impact skeletal muscle performance after exercise-induced muscle damage.

Moderate, acute alcohol consumption after eccentric exercise has been shown to magnify the muscular weakness that is typically associated with exercise-induced muscle damage (EIMD). As it is not known whether this effect is dose-dependent, the aim of this study was to investigate the effect of a low dose of alcohol on EIMD-related losses in muscular performance. Ten healthy males performed 300 maximal eccentric contractions of the quadriceps muscles of one leg on an isokinetic dynamometer. They then consumed either a beverage containing 0.5 g of alcohol per kg bodyweight (as vodka and orange juice) or an isocaloric, isovolumetric non-alcoholic beverage. At least 2 weeks later, they performed an equivalent bout of eccentric exercise on the contralateral leg after which they consumed the other beverage. Measurement of peak and average peak isokinetic (concentric and eccentric) and isometric torque produced by the quadriceps was made before and 36 and 60 h post-exercise. Significant decreases in all measures of muscular performance were observed over time under both conditions (all P < 0.05); however, no difference between treatments was evident at any of the measured time points (all P > 0.05). Therefore, consumption of a low dose of alcohol after damaging exercise appears to have no effect on the loss of force associated with strenuous eccentric exercise.

Post-exercise alcohol ingestion exacerbates eccentric-exercise induced losses in performance.

The effect of acute alcohol intake on muscular performance in both the exercising and non-exercising legs in the days following strenuous eccentric exercise was investigated to ascertain whether an interaction between post-exercise alcohol use and muscle damage causes an increase in damage-related weakness. Ten healthy males performed 300 maximal eccentric contractions of the quadriceps muscles of one leg on an isokinetic dynamometer. They then consumed either a beverage containing 1 g of ethanol per kg bodyweight ethanol (as vodka and orange juice; ALC) or a non-alcoholic beverage (OJ). At least 2 weeks later they performed an equivalent bout of eccentric exercise on the contralateral leg after which they consumed the other beverage. Measurement of peak and average peak isokinetic (concentric and eccentric) and isometric torque produced by the quadriceps of both exercising and non-exercising legs was made before and 36 and 60 h post-exercise. Greatest decreases in exercising leg performance were observed at 36 h with losses of 28.7, 31.9 and 25.9% occurring for OJ average peak isometric, concentric, and eccentric torques, respectively. However, average peak torque loss was significantly greater in ALC with the same performance measures decreasing by 40.9, 42.8 and 44.8% (all p < 0.05). Performance of the non-exercising leg did not change significantly under either treatment. Therefore, consumption of moderate amounts of alcohol after damaging exercise magnifies the loss of force associated with strenuous eccentric exercise. This weakness appears to be due to an interaction between muscle damage and alcohol rather than the systemic effects of acute alcohol consumption.