Effect of caffeine ingestion after creatine supplementation on intermittent high-intensity sprint performance

The aim of this study was to investigate the effects of acute caffeine ingestion on intermittent high-intensity sprint performance after 5 days of creatine loading. After completing a control trial (no ergogenic aids, CON), twelve physically active men were administered in a double-blind, randomized crossover protocol to receive CRE + PLA (0.3 g kg⁻¹ day⁻¹ of creatine for 5 days then followed by 6 mg kg⁻¹ of placebo) and CRE + CAF (0.3 g kg⁻¹ day⁻¹ of creatine for 5 days and followed by 6 mg kg⁻¹ of caffeine), after which they performed a repeated sprint test. Each test consisted of six 10-s intermittent high-intensity sprints on a cycling ergometer, with 60-s rest intervals between sprints. Mean power, peak power, rating of perceived exertion (RPE), and heart rates were measured during the test. Blood samples for lactate, glucose, and catecholamine concentrations were drawn at specified intervals. The mean and peak power observed in the CRE + CAF were significantly higher than those found in the CON during Sprints 1 and 3; and the CRE + CAF showed significantly higher mean and peak power than that in the CRE + PLA during Sprints 1 and 2. The mean and peak power during Sprint 3 in the CRE + PLA was significantly greater than that in the CON. Heart rates, plasma lactate, and glucose increased significantly with CRE + CAF during most sprints. No significant differences were observed in the RPE among the three trials. The present study determined that caffeine ingestion after creatine supplements augmented intermittent high-intensity sprint performance.     

Enzyme activities in thoracic duct lymph and plasma of anaesthetized,conscious resting and exercising dogs

Summary The significance of changes in lymph flow for the extracellular distribution and transport of cellular enzymes and for the level of enzyme activities in plasma was investigated. Specimens of thoracic duct lymph were obtained from an extracorporal lymph shunt in anaesthetized, conscious resting and treadmill exercising dogs (6 km×h^–1 for 1 h) The activity of 10 enzymes and of protein content in lymph and plasma were studied, as well as lymph flow, lymphatic transport, and the lymph-plasma ratio of these compounds. Lactate, pH, and blood gases were monitored in venous blood. Lymph flow of 0.80 ml×min^–1 in anaesthetized dogs more than doubled (to 1.86 ml×min^–1) when the animals were conscious and resting. In anaesthetized dogs lymph enzyme activity was higher only for enzymes of predominately hepatic origin, such as choline esterase (CHE) and alanine aminoferase (ALAT), and was lower for aspartate aminotransferase (ASAT) and aldolase (ALD). In conscious dogs, due to activation of the skeletal muscle tissue pump, lymphatic transport of enzymes with rather high activity in skeletal muscle, and of protein, is significantly enhanced. Enzyme activities in plasma, however, did not differ between the groups. Lymph-plasma activity ratios higher than one were found for lactate dehydrogenase (LDH), malate dehydrogenase (MDH), ASAT, creatine kinase (CK), ALD, and phosphohexose isomerase (PHI). Exercise stimulated lymph flow up to 4.9 ml×min^–1, and increased the lymphatic activities of those enzymes with a lymph-plasma ratio higher than unity, these enzymes increasing in the plasma due to the highly increased lymphatic transport. It is concluded that exercise induced changes of enzyme activities in plasma do not necessarily require a pathological enzyme release, but can be explained fully for moderate exercise by the lymphatic influx of enzymes from the interstitial resting enzyme pool in muscle.Supported by the Deutsche Forschungsgemeinschaft     

Metabolic muscle damage and oxidative stress markers in an America’s Cup yachting crew

Activities of enzymes involved in muscle damage [creatine kinase (CK) and aspartate aminotransferase (AST)] and levels of malondialdehyde (MDA) as a marker of oxidative stress were monitored in the plasma of 27 members of an America’s Cup yachting crew. The preventive benefits of allopurinol on muscle damage were also tested. In racing period A, the crew was divided into two groups according to their tasks on board. Blood samples from all 27 sailors were obtained before the start of a 5-day fleet race, after the last race, and after the ten match races. In period B, crew members were divided at random into two groups. One group (13 participants) received 300 mg/day of allopurinol 3 h before racing. The other ten members received placebo. Blood samples were collected just before and after the second round of the Louis Vuitton Cup. All participants showed increased CK and AST activities after the racing period A. The increase in CK activity was highest in sailors involved in strenuous physical work. At the end of period A, plasma MDA levels were higher in all participants as compared with non-participant athletes. In period B, a significant decrease in CK activity, but not in AST, appeared among participants receiving allopurinol. Plasma MDA decreased in sailors treated with allopurinol, but this reduction did not reach statistical significance. America’s Cup is a sailing sport with high physical demands, as shown by the increase in muscle-damage markers. Treatment with allopurinol appeared to decrease the levels of muscle damage markers.     

Effect of eccentric exercise on plasma enzyme activities previously elevated by eccentric exercise

The purpose of this study was to investigate whether plasma activities of creatine kinase (CK) and glutamic-oxaloacetic transaminase (GOT), elevated by eccentric exercise, would be affected by a second bout of eccentric exercise. A group of 26 male students [20.3 (SD 1.9) years] were placed in one of three groups. Group A (n = 8) performed one bout of 24 maximal eccentric actions (ECC) of the forearm flexors (ECC1), and groups B (n = 10) and C (n = 8) performed two bouts of ECC (ECC1, ECC2). The ECC2 was performed by the opposite arm 3 days (group B) or 5 days (group C) after ECC1. None of the subjects had performed this eccentric exercise prior to this study. Maximal isometric force (MIF), range of motion (ROM), upperarm circumference (CIR), muscle soreness level (SOR), and plasma CK and GOT activities were measured before and for 8 days (group B) or 10 days (groups A, C) postexercise. The MIF, ROM, CIR, and SOR changed significantly after exercise (P<0.01), and no significant differences in changes were found between ECC1 and ECC2, or among the groups. This suggested that ECC1 and ECC2 produced a similar stress to the forearm flexor muscles. Therefore, it was expected that CK and GOT activities would show similar increases after ECC1 and ECC2. However, increases in CK and GOT activities after ECC2 were significantly smaller (P<0.01) than after ECC1 in both groups B and C. The results of this study confirmed that CK and GOT responses were diminished when initial blood enzyme activities were elevated.     

The influence of muscle metabolic characteristics on physical performance

Summary This study describes the influence of muscle fiber type composition, enzyme activities and capillary supply on muscle strength, local muscle endurance or aerobic power and capacity. Muscle biopsies were obtained from m. vastus lateralis in thirteen physically active men. Histochemical staining procedures were applied to assess the percentage of fast twitch (FT) fibers, muscle fiber area, and capillary density. Also, the activity of citrate synthase (CS), creatine kinase (CK), hexokinase (HK), lactate dehydrogenase (LDH), and phosphofructokinase (PFK) were analysed using fluorometrical assays. Peak torque at ‘low’ and ‘high’ angular velocities was measured during leg extension. Similarly, muscle fatigue (e. g. peak torque decline) and recovery from a short-term exercise task were measured during maximal, voluntary consecutive leg extensions. Aerobic power ( ) and aerobic capacity (e.g. onset of blood lactate concentration; OBLA), as defined by a blood lactate concentration of 4 mol · l⁻¹ were measured during cycling. Peak torque at a high angular velocity was positively correlated with % FT area (p<0.001). Fatigue and recovery were correlated with LDH · CS⁻¹ (p<0.001). W_OBLA was best correlated with PFK and PFK · CS⁻¹ (p<0.001). Hence, muscle strength was partly determined by fiber type composition whereas local muscle endurance, recovery and aerobic capacity reflect mainly capillary supply and the activity of key enzymes involved in aerobic and anaerobic metabolism.     

Effects of a trail running competition on muscular performance and efficiency in well-trained young and master athletes

To determine the acute effects of a trail running competition and the age-dependent differences between young and master athletes, 23 subjects [10 young (30.5 ± 7 years), 13 master (45.9 ± 5.9 years)] participated in a 55-km trail running competition. The study was conceived as an intervention study compromising pre, post 1, 24, 48 and 72 h measurements. Measurements consisted of blood tests, ergometer cycling and maximal isometric voluntary contractions (MVC). Parameters monitored included MVC, twitch- and M-wave properties, EMG (RMS) of the vastus lateralis, two locomotion efficiency calculations and muscle damage markers in the blood (CK, LDH). Results indicate post-race increases in CK and LDH, decreases in MVC values (−32 vs. −40% in young and master, P < 0.01), decreases in EMG, increases in contraction time and concomitant decreases in peak twitch values, and a decrease in locomotion efficiency (−4.6 vs. −6.3% in young and master, P < 0.05). Masters showed similar fatigue and muscle damage than young but recuperation was slowed in masters. This study shows that trail runs are detrimental to muscle function, and gives indication that training may not halt muscle deterioration through aging, but can help maintain performance level.     

Light-intensity activities are important for estimating physical activity energy expenditure using uniaxial and triaxial accelerometers

This study evaluated the validity of the total energy expenditure (TEE) estimated using uniaxial (ACCuni) and triaxial (ACCtri) accelerometers in the elderly. Thirty-two healthy elderly (64–87 years) participated in this study. TEE was measured using the doubly labeled water (DLW) method (TEE_DLW). TEE_ACCuni (6.79 ± 1.08 MJ day⁻¹) was significantly lower than TEE_DLW (7.85 ± 1.54 MJ day⁻¹) and showed wider limits of agreement (−3.15 to 1.12 MJ day⁻¹) with a smaller correlation coefficient (r = 0.703). TEE_ACCtri (7.88 ± 1.27 MJ day⁻¹) did not differ from TEE_DLW and showed narrower limits of agreement (−1.64 to 1.72 MJ day⁻¹) with a larger correlation coefficient (r = 0.835, P < 0.001). The estimated intensities of light activities were significantly lower with ACCuni. Greater mediolateral acceleration was observed during 6-min walk tests. The results suggest that ACCtri is a better choice than ACCuni for assessing TEE in the elderly.     

Recovery after an Ironman triathlon: sustained inflammatory responses and muscular stress

Ultra-endurance exercise, such as an Ironman triathlon, induces muscle damage and a systemic inflammatory response. As the resolution of recovery in these parameters is poorly documented, we investigated indices of muscle damage and systemic inflammation in response to an Ironman triathlon and monitored these parameters 19 days into recovery. Blood was sampled from 42 well-trained male triathletes 2 days before, immediately after, and 1, 5 and 19 days after an Ironman triathlon. Blood samples were analyzed for hematological profile, and plasma values of myeloperoxidase (MPO), polymorphonuclear (PMN) elastase, cortisol, testosterone, creatine kinase (CK) activity, myoglobin, interleukin (IL)-6, IL-10 and high-sensitive C-reactive protein (hs-CRP). Immediately post-race there were significant (P < 0.001) increases in total leukocyte counts, MPO, PMN elastase, cortisol, CK activity, myoglobin, IL-6, IL-10 and hs-CRP, while testosterone significantly (P < 0.001) decreased compared to prerace. With the exception of cortisol, which decreased below prerace values (P < 0.001), these alterations persisted 1 day post-race (P < 0.001; P < 0.01 for IL-10). Five days post-race CK activity, myoglobin, IL-6 and hs-CRP had decreased, but were still significantly (P < 0.001) elevated. Nineteen days post-race most parameters had returned to prerace values, except for MPO and PMN elastase, which had both significantly (P < 0.001) decreased below prerace concentrations, and myoglobin and hs-CRP, which were slightly, but significantly higher than prerace. Furthermore, significant relationships between leukocyte dynamics, cortisol, markers of muscle damage, cytokines and hs-CRP after the Ironman triathlon were noted. This study indicates that the pronounced initial systemic inflammatory response induced by an Ironman triathlon declines rapidly. However, a low-grade systemic inflammation persisted until at least 5 days post-race, possibly reflecting incomplete muscle recovery.     

Die Erfassung von Konduktorinnen der progressiven Muskeldystrophie Typ Duchenne mittels Diskriminanzanalyse verschiedener Serumenzymaktivitäten

Zusammenfassung Bei einem Kollektiv von 32 Müttern und 11 Schwestern von Patienten mit Muskeldystrophie vom Typ Duchenne wurden die Aktivitäten der ALD, CPK, GOT, GPT, LDH und MDH im Serum bestimmt. Die Kontrollgruppe bestand aus 51 muskelgesunden weiblichen Personen gleicher Altersgruppierung.Für eine Diskriminanzanalyse der Enzymaktivitäten erwiesen sich die Werte der CPK, GOT und MDH als ungeeignet. Mit den drei restlichen Enzymen wurde folgende Trennformel erhalten: 108 — 4,9 GPT — 0,2 LDH — 19,6 ALD.Werden die individuellen Meßwerte eines Falles in diese Formel eingesetzt, so spricht ein Ergebnis mit negativem Vorzeichen für eine Konduktorin, während bei Gesunden positive Resultate auftreten.Bei den hier durchgeführten Untersuchungen hatten von den Patientenmüttern alle sicheren und wahrscheinlichen Konduktorinnen sowie 16 von 24 möglichen Konduktorinnen pathologische Werte. Ein gleiches Ergebnis zeigten 8 von 11 untersuchten Schwestern.

---

Summary The serum activities of ALD, CPK, GOT, GPT, LDH and MDH were determined in a group of 32 mothers and 11 sisters of patients with muscular dystrophy of the Duchenne type. The control group consisted of 51 healthy females of the same age distribution.The values of CPK, GOT and MDH proved to be unsuitable for carrying out a discriminative analysis of the enzyme activities.The three remaining enzymes yielded the following discriminative formula: 108 — 4,9 GPT — 0,2 LDH — 19,6 ALD.If the individual activity values of a given case are substituted in this formula, negative results will suggest that the patient is a carrier whereas healthy individuals will reveal positive results.In these studies, pathological values were found in all definite and probable carriers as well as in 16 out of 24 possible carriers. The same result was obtained in 8 out of 11 sisters under study.

     

Enzyme activities in tissues and elimination half-lives of homologous muscle and liver enzymes in the racing pigeon (Columba Livia domestica)

Tissue enzyme profiles of heart, liver, pectoral muscle, quadriceps muscle, duodenum, kidney and brain from racing pigeons were established. The enzymes were alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), glutamate dehydrogenase (GLDH), lactate dehydrogenase (LDH), gamma glutamyltransferase (y-GT), alkaline phosphatase (AP), and creatine kinase (CK). Elimination half-lives (tyss) of certain enzymes were also determined. The mean values (+/- SD) were: ASAT, 7.66 +/- 1.55 (liver) and 6.51 +/- 0.83 (muscle); ALAT, 15.69 + 1.70 (liver) and 11.99 +/- 1.32 (muscle); LDH, 0.71 + 0.10 (liver) and 0.48 +/- 0.07 (muscle); GLDH, 0.68 +/- 0.17 (liver), CK 3.07 +/- 0.59 hours (muscle). GLDH is the most liver-specific enzyme in the pigeon, but increased activities in the plasma are likely only in the acute stage of severe liver cell damage, since this enzyme is localised within the mitochondria and has a short half life. LDH and ASAT seem to be the most sensitive indicators of liver cell damage, though contributions come from muscle damage. Muscle cell damage can be differentiated from liver cell damage by measuring plasma CK activity, since CK is both a specific and a sensitive indicator of muscle cell damage. In a clinical setting the combined use of LDH, ASAT and CK permits differentiation between liver and muscle cell damage in racing pigeons.     

Effect of creatine supplementation on metabolism and performance in humans during intermittent sprint cycling

This double blind study investigated the effect of oral creatine supplementation (CrS) on 4 × 20 s of maximal sprinting on an air-braked cycle ergometer. Each sprint was separated by 20 s of recovery. A group of 16 triathletes [mean age 26.6 (SD 5.1) years. mean body mass 77.0 (SD 5.8) kg, mean body fat 12.9 (SD 4.6)%, maximal oxygen uptake 4.86 (SD 0.7) l · min⁻¹] performed an initial 4 × 20 s trial after a muscle biopsy sample had been taken at rest. The subjects were then matched on their total intramuscular creatine content (TCr) before being randomly assigned to groups to take by mouth either a creatine supplement (CRE) or a placebo (CON) before a second 4 × 20 s trial. A muscle biopsy sample was also taken immediately before this second trial. The CrS of 100 g comprised 4 × 5 g for 5 days. The initial mean TCr were 112.5 (SD 8.7) and 112.5 (SD 10.7) mmol · kg⁻¹ dry mass for CRE and CON, respectively. After creatine loading and placebo ingestion respectively, CRE [128.7 (SD 11.8) mmol · kg⁻¹ dry mass] had a greater (P=0.01) TCr than CON [112.0 (SD 10.0) mmol · kg⁻¹ dry mass]. While the increase in free creatine for CRE was statistically significant (P=0.034), this was not so for the changes in phosphocreatine content [trial 1: 75.7 (SD 6.9), trial 2: 84.7 (SD 11.0) mmol · kg⁻¹ dry mass, P=0.091]. There were no significant differences between CRE and CON for citrate synthase activity (P=0.163). There was a tendency towards improved performance in terms of 1 s peak power (in watts P=0.07; in watts per kilogram P=0.05), 5 s peak power (in watts P=0.08) and fatigue index (P=0.08) after CrS for sprint 1 of the second trial. However, there was no improvement for mean power (in watts P=0.15; in watts per kilogram P=0.1) in sprint 1 or for any performance values in subsequent sprints. Our results suggest that, while CrS elevates the intramuscular stores of free creatine, this does not have an ergogenic effect on 4 × 20 s all-out cycle sprints with intervening 20-s rest periods. Accepted: 2 October 2000     

Combined carbohydrate-protein supplementation improves competitive endurance exercise performance in the heat

Laboratory-based studies have demonstrated that adding protein (PRO) to a carbohydrate (CHO) supplement can improve thermoregulatory capacity, exercise performance and recovery. However, no study has investigated these effects in a competitive sporting context. This study assessed the effects of combined CHO–PRO supplementation on physiological responses and exercise performance during 8 days of strenuous competition in a hot environment. Twenty-eight cyclists participating in the TransAlp mountain bike race were randomly assigned to fitness-matched placebo (PLA 76 g L⁻¹ CHO) or CHO–PRO (18 g L⁻¹ PRO, 72 g L⁻¹ CHO) groups. Participants were given enough supplements to allow ad libitum consumption. Physiological and anthropometric variables were recorded pre- and post-exercise. Body mass decreased significantly from race stage 1 to 8 in the PLA group (−0.75 ± 0.22 kg, P = 0.01) but did not change in the CHO–PRO group (0.42 ± 0.42 kg, P = 0.35). Creatine kinase concentration and muscle soreness were substantially elevated during the race, but were not different between groups (P = 0.82, P = 0.44, respectively). Urine osmolality was significantly higher in the CHO–PRO versus the PLA group (P = 0.04) and the rise in tympanic temperature from pre- to post-exercise was significantly less in CHO–PRO versus PLA (P = 0.01). The CHO–PRO group also completed the 8 stages significantly quicker than the PLA group (2,277 ± 127 vs. 2,592 ± 68 min, respectively, P = 0.02). CHO–PRO supplementation therefore appears to prevent body mass loss, enhance thermoregulatory capacity and improve competitive exercise performance despite no effect on muscle damage.     

Quantifying the mechanical work of resting quadriceps muscle tone

Our laboratory has shown that resting muscle, commonly thought to be mechanically inert, is actually mechanically active. We report a study of the mechanics of resting quadriceps muscle in adult surgical patients that determines how much metabolic activity can be attributed to quadriceps resting-muscle mechanical work. This was calculated by studying the motion of relaxed supine subjects’ instrumented legs dropped onto a pillow before and after anesthesia with muscle paralysis. By subtracting the acceleration of the dropping leg of the conscious subject before the quadriceps is paralysed from that found after paralysis, resting muscle tensile force and power of the quadriceps muscles can be calculated. Mechanomyography was also recorded, using an accelerometer. Paralysis produced an increase in acceleration in all cases (pre-paralysis 6.99 ± 1.51 m s⁻²; post-paralysis 7.65 ± 1.51 m s⁻²; P = 0.00007) and a decrease in mechanomyographic mean absolute amplitude (pre-paralysis 10.6 ± 3.7 mm s⁻²; post-paralysis 4.5 ± 2.6 mm s⁻²; P = 0.00003). Calculated force exerted by resting quadriceps was 22.6 ± 16.8 N; power 0.34 ± 0.17 W, corresponding to a daily caloric expenditure of 7.0 ± 3.6 kcal day⁻¹. This corresponds to approximately 205 kcal day⁻¹ for all skeletal muscle. Knowledge of the phenomenon of resting muscle mechanical activity may be of clinically importance in the study and treatment of obesity and of disorders of muscle tone.     

The effect of 4 weeks β-alanine supplementation and isokinetic training on carnosine concentrations in type I and II human skeletal muscle fibres

Seven male students were supplemented with β-alanine (β-ALG) for 4 weeks (6.4 g day⁻¹) and seven with a matching placebo (PLG). Subjects undertook 4 weeks of isokinetic training with the right leg (T) whilst the left leg was untrained (UT), serving as a control. Each training session consisted of 10 × 10 maximal 90° extension and flexion contractions at 180°/s using a Kin-Com isokinetic dynamometer, with 1 min rest between bouts. Muscle biopsies were taken from the vastus lateralis immediately before and at the end of the supplementation period. Following freeze drying muscle fibres were dissected and characterised by their MHC profile, as type I, IIa, IIx, or as hybrids of these. Carnosine was measured by HPLC. There was a significant increase in carnosine in both T and UT legs of the β-ALG (9.63 ± 3.92 mmol kg⁻¹ dry muscle and 6.55 ± 2.36 mmol kg⁻¹ dry muscle respectively). There was a significant increase in the carnosine content of all fibre phentotypes, with no significant difference between types. There were no significant differences in the changes in muscle or in fibres between the T and UT legs. In contrast there was no significant change in the carnosine content in either the T or UT legs with placebo. The results indicate that 4 weeks training has no effect on the muscle carnosine content. Whilst an increase was seen with β-alanine supplementation, this was not further influenced by training. These findings suggest that β-alanine availability is the main factor regulating muscle carnosine synthesis.     

AcuteBabesia bovis infections: Plasma creatine kinase,lactate dehydrogenase and creatinine levels and associated muscle damage

Two groups of five two-year-old Hereford steers were infected with two virulent strains ofB. bovis. The plasma concentrations of creatine kinase (CK), lactate dehydrogenase (LDH), and creatinine rose early in infection and showed highly significant increases terminally. Extensive skeletal muscle degeneration was observed terminally as was degeneration of myocardium, although this was much less extensive. Terminal clinical signs included posterior muscle wasting, weakness, and recumbency. It was concluded that the extensive changes to muscle and to CK and LDH were caused by anoxia due primarily to shock and stasis of the circulation induced by the parasites.     

Plasma biochemistry in pregnant Spanish purebred broodmares

The aim of this study was to determine if physiological changes occur in plasma total proteins (TPP) and albumin (ALB) concentrations and the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), creatine kinase (CK), alkaline phosphatase (ALP) and gamma glutamyl transferase (GGT) in Spanish Purebred mares during pregnancy. Blood samples were collected by jugular puncture and anticoagulated in tubes with lithium heparin. In plasma obtained after centrifugation the concentrations of TPP and ALB and activities of AST, ALT, LDH, CK, ALP and GGT were determined by spectrophotometry. Pregnancy caused an increase in TPP and decrease in AST, CK and GGT (p?<?0.05) without modifications in ALB, ALT, LDH and ALP concentrations. Pregnancy has a significant influence on TPP, CK, GGT and AST dynamics in the mare, resulting in the development of reference ranges for this physiological condition. The decrease in values for plasma CK, AST, LDH and GGT enzymes activities during pregnancy should be considered a physiological condition related to pregnancy in the mare. It is important to know the direction and magnitude of these biochemical changes in pregnant mares, contributing to a better understanding of biochemical processes that occur in pregnant mares and providing practical help for the diagnosis of diseases that may present with similar biochemical findings.     

No acute effects of short-term creatine supplementation on muscle properties and sprint performance

In a double-blind, placebo, controlled study, we investigated the acute effects of short-term oral creatine supplementation (20 g · day⁻¹ for 6 days) on muscle activation, fatigue and recovery of the m. quadriceps femoris during electrical stimulation, and on maximal performance during sprint cycling. The quadriceps muscles of 23 well-trained rowers were stimulated at different frequencies (10, 20, 50, 100, 150 and 200 Hz). Furthermore, 40 repetitive, electrically stimulated (duration 220 ms, stimulation frequency 150 Hz) concentric contractions were imposed at a constant angular velocity of 180° · s⁻¹ over a range of 50° (from 90 to 140° knee angle), each extension/flexion cycle lasting 1200 ms. To determine recovery, torque was measured at 20, 50, 80, 120, 180 and 300 s after the last contraction. In addition, two maximal 30-s sprints were performed on a cycle ergometer with 4 min rest in between. Following short-term creatine supplementation, body mass [mean (SEM)] increased (P < 0.05) from 85.7 (2.7) kg to 87.3 (2.9) kg. Creatine supplementation had no effect on maximal voluntary isometric torque and muscle activation, or on fatigue and recovery of dynamic exercise. There was also no significant effect on peak power, time to peak power and work to peak power, or total work during both sprints on the cycle ergometer. It was concluded that short-term oral creatine supplementation resulted in increased body mass, but did not enhance muscle performance or maximal output during sprint cycling. Accepted: 16 March 2000     

Plasma concentration of creatine kinase and lactate dehydrogenase in houbara bustards ( Chlamydotis undulata macqueenii ) immediately following capture

Blood samples were obtained from clinically normal aviary housed houbara bustards (Chlamydotis undulata macqueenii) sampled promptly (<10 min) after capture in order to establish reference values for creatine kinase (CK) and lactate dehydrogenase (LDH). Plasma CK and LDH values (mean±SEM U/l (range)) were 335.9±24.2 U/l (134–684 U/l) and 493.3±24.1 U/l (273–793 U/l), respectively in this group. These values were compared with levels in clinically normal birds sampled at different time intervals following capture and translocation. Plasma CK and LDH concentrations were markedly elevated in bustards following routine capture, handling and translocation at 0.5–1, 6, 24, 48 and 72 h, but had returned to normal ranges after 14 days. Maximum CK and LDH levels occurred in samples collected 24 h after capture and they were 15 and 3.5-fold higher than the reference levels, respectively. These results show that a significant amount of muscle damage may occur during routine capture, handling and translocation procedures of bustards. They also indicate that consideration should be given to previous episodes of handling or translocation when interpreting plasma CK and LDH values in bustards.     

The effects of a novel “fluid loading” strategy on cardiovascular and haematological responses to orthostatic stress

Water drinking reduces the occurrence of syncope in healthy volunteers but the effects of hyperhydration are unknown. This study assessed the effects of combined creatine (Cr) and glycerol (Gly) induced hyperhydration on the cardiovascular and haematological responses to postural change. Subjects in all trials lay supine for 30 min before being tilted head-up to 70° for a further 30 min or until the limit of their tolerance. Following 2 baseline trials, 19 subjects were matched for body mass and assigned to ingest either 20 g Cr and 2 g Gly kg⁻¹ body mass (BM) plus 2 l of water or 2 l of water alone (Pl) each day for 6 days and once more 5 h prior to the experimental trial. Subjects ingested 500 ml of water prior to all trials to ensure euhydration. During baseline trials, 3 subjects in the Cr/Gly group and 2 in the Pl group experienced presyncope during head-up tilt. Following Cr/Gly supplementation, BM increased by (mean ± S.D.) 0.9 ± 0.3 and total body water (TBW) increased by 0.7 ± 0.2 l with no change in the Pl group. Cr/Gly supplementation resulted in a significant increase in systolic (11 mmHg) and diastolic (7 mmHg) blood pressure during head-up tilt with no change following Pl supplementation. Cr/Gly. Following Cr/Gly supplementation the number of subjects who became presyncopal was reduced from 3 to 1, with no change in the Pl group. These data suggest that hyperhydration mediated by Cr and Gly can enhance orthostatic tolerance in healthy individuals.     

Exercise-induced muscle damage on the contractile properties of the lumbar paraspinal muscles: a laser displacement mechanomyographic approach

Purpose

This study investigated whether laser displacement mechanomyography (MMG) could detect acute injury of low back muscles following strenuous eccentric exercise.

Methods

Sixteen healthy adults (10 females, 6 males, mean ± standard deviation, age 21 ± 2.90 years, BMI 21.63 ± 1.99 kg/m²), without low back pain or low back resistance training, were recruited. Strength [maximum voluntary isometric contraction force (MVC)], pain intensity [visual analogue scale (VAS)], biological markers of muscle injury (serum myoglobin and creatine kinase levels), and MMG-derived muscle contractile properties were measured at seven different time points. Pre-exercise ‘control’ measures were taken prior to a strenuous eccentric exercise task, followed by an immediate post-exercise measurement and further four consecutive daily measurements. A final post-exercise measurement was completed on day 12 post-exercise.

Results

Compared to pre-exercise control, MVC was lower immediately post-exercise (day 1) and on days 2–3. VAS scores were higher post-exercise (day 1) and from days 2–5. Myoglobin was significantly higher on day 4, whilst creatine kinase was significantly higher on days 4–5. MMG-derived maximum muscle displacement (D_max) was significantly diminished post-exercise (day 1) at all vertebral segments (L1-MT), while contraction velocity (V_c) was significantly slower at all segments except sacral multifidus. V_c recovered rapidly (by day 2), while mid-lumbar D_max resolved on day 12. D_max had moderate correlations with MVC (R = 0.61) and VAS (R = − 0.50), and low correlations with myoglobin (R = − 0.36).

Conclusion

MMG appears capable of detecting changes in muscle contractile properties associated with an acute bout of low back pain.