Jay H. Williams

Caffeine, maximal power output and fatigue.

The purpose of this investigation was to determine the effects of caffeine ingestion on maximal power output and fatigue during short term, high intensity exercise. Nine adult males performed 15 s maximal exercise bouts 60 min after ingestion of caffeine (7 mg.kg-1) or placebo. Exercise bouts were carried out on a modified cycle ergometer which allowed power output to be computed for each one-half pedal stroke via microcomputer. Peak power output under caffeine conditions was not significantly different from that obtained following placebo ingestion. Similarly, time to peak power, total work, power fatigue index and power fatigue rate did not differ significantly between caffeine and placebo conditions. These results suggest that caffeine ingestion does not increase ones maximal ability to generate power. Further, caffeine does not alter the rate or magnitude of fatigue during high intensity, dynamic exercise.

Effects of varied fatigue protocols on sarcoplasmic reticulum calcium uptake and release rates

The purpose of this investigation was to examine changes in sarcoplasmic reticulum (SR) function in muscles subjected to different patterns of muscle activity. Frog sartorius muscles were stimulated with tetanic trains (100 ms, 100 Hz) delivered at rates of 2.0, 0.5, and 0.2 trains/s. In one set of experiments, stimulation was continued until force had declined to ∼17% of initial (constant fatigue), whereas in the other set, stimulation was continued for 1 min (constant duration). In the constant-fatigue experiments, Ca2+ uptake (1 mM MgATP) and release rates (25 μM AgNO3, 5 mM 4-chloro- m-cresol) were depressed by similar extents following each protocol. This occurred despite 1, 4, and 17 min of stimulation, respectively, used to induce fatigue. In the constant-duration experiments, larger reductions in SR function occurred following the highest frequency stimulation protocol. These data suggest that when muscles are fatigued to similar extents, depressions in SR function are independent of the activity protocol. On the other hand, when a constant duration of activity is imposed, changes in SR function are closely linked to the extent of force reduction.The purpose of this investigation was to examine changes in sarcoplasmic reticulum (SR) function in muscles subjected to different patterns of muscle activity. Frog sartorius muscles were stimulated with tetanic trains (100 ms, 100 Hz) delivered at rates of 2.0, 0.5, and 0.2 trains/s. In one set of experiments, stimulation was continued until force had declined to approximately 17% of initial (constant fatigue), whereas in the other set, stimulation was continued for 1 min (constant duration). In the constant-fatigue experiments, Ca2+ uptake (1 mM MgATP) and release rates (25 microM AgNO3, 5 mM 4-chloro-m-cresol) were depressed by similar extents following each protocol. This occurred despite 1, 4, and 17 min of stimulation, respectively, used to induce fatigue. In the constant-duration experiments, larger reductions in SR function occurred following the highest frequency stimulation protocol. These data suggest that when muscles are fatigued to similar extents, depressions in SR function are independent of the activity protocol. On the other hand, when a constant duration of activity is imposed, changes in SR function are closely linked to the extent of force reduction.

Effects of lactate on force production by mouse EDL muscle : implications for the development of fatigue

Numerous studies suggest that the accumulation of lactate during exercise contributes to the fatigue process. This notion is based on close negative correlations between force and intracellular muscle lactate concentrations during fatigue and recovery. In this investigation, we attempted to determine if lactate directly affects muscle force output. This was accomplished by incubating mouse extensor digitorum longus muscles in extracellular concentrations of 10, 20, 30 and 50 mM L-(+)-lactate at 21 and 37 degrees C and monitoring force output. At 21 degrees C, 30 and 50 mM, extracellular lactate significantly reduced tetanic force (Po 250 ms, 100 Hz) to 95 and 93% of initial, respectively. In addition, the rate of force development (+dP/dt) was reduced to 93 and 89% of initial. At 37 degrees C, the effects of extracellular lactate were augmented as Po was reduced to 73 and 62% of initial and +dP/dt was reduced to 55 and 44% of initial at 30 and 50 mM, respectively. We next sought to determine if the reduction in Po was due to altered sarcoplasmic reticulum (SR) function using a muscle homogenate fraction. The rate of AgNO3-induced SR Ca2+ release was depressed by 31% in the presence of 25 mM lactate. These results suggest that elevated lactate depresses force production by whole muscle and may play some role in the fatigue process. In addition, it appears that lactate depresses force production, in part, by inhibiting Ca2+ release from the SR.

Effect of oral sodium loading on high-intensity arm ergometry in college wrestlers.

PURPOSE The aim of this study was to examine the effect of 0.3 g x kg(-1) of NaHCO3, 0.21 g x kg(-1) of NaCl, and a low-calorie placebo control (PC) on high-intensity arm ergometry in eight college wrestlers (aged 20.6 +/- 0.8 yr, body mass 70.4 +/- 2.1 kg). METHODS Subjects performed eight 15-s intervals of maximal effort arm ergometry separated by 20 s of recovery cranking. Treatments were administered in a randomized, double-blind manner in two equal doses at 90 and 60 min before testing. Venous blood samples were withdrawn at baseline, preexercise, and postexercise intervals. RESULTS Preexercise pH (7.33 +/- 0.01, 7.31 +/- 0.01, and 7.40 +/- 0.01) and base excess (2.41 +/- 0.35, 0.93 +/- 0.39, and 8.45 +/- 0.51) after PC and NaCl ingestion, respectively, were similar, whereas ingestion of NaHCO3 resulted in significantly higher values (P < or = 0.05). Postexercise pH (7.02 +/- 0.01, 7.02 +/- 0.03, and 7.09 +/- 0.03) and base excess (-13.29 +/- 0.96, -14.49 +/- 1.01, and -8.83 +/- 1.38) were significantly lower after both PC and NaCl ingestion compared with NaHCO3 ingestion. Postexercise plasma [lactate] was also greater in both PC and NaHCO3 trials (21.42 +/- 1.52, 20.07 +/- 1.39, and 22.65 +/- 1.77 mmol x L(-1)). However, peak power (370.7 +/- 26.0, 346.3 +/- 13.6, and 354.3 +/- 18.9 W) and total work accomplished in eight intervals (30.2 +/- 1.5, 29.6 +/- 1.1, and 29.9 +/- 1.1 kJ), and percent fatigue (31.0 +/- 2.7, 29.0 +/- 3.2, and 29.2 +/- 4.0%) were similar. CONCLUSIONS These data contradict previous reports of ergogenic benefits NaHCO3 and NaCl administration before exercise and further suggest that performance in this type of activity may not be enhanced by exogenously induced metabolic alkalosis or sodium ingestion.

Changes in skeletal muscle sarcoplasmic reticulum function and force production following myocardial infarction in rats

In patients following myocardial infarction (MI), exercise tolerance and muscular strength are often markedly reduced. The purpose of this investigation was to determine if calcium (Ca2+) uptake and release by skeletal muscle sarcoplasmic reticulum (SR) are altered following MI and if such changes are associated with diminished muscular performance. SR vesicles were isolated from rat gastrocnemius muscle at 6 and 12 weeks following MI (via left coronary artery ligation) or sham surgery. At both post‐surgery intervals, the rates of Ca2+ uptake (measured using fura‐2) were 35% greater in the MI group. In addition, the rates of Ca2+ release were increased in the MI group by 10 and 30% at 6 and 12 weeks, respectively. At 12 weeks post‐surgery, animals of the MI group showed significant reduction in in situ twitch and tetanic forces and significant elevations in the rates of tension increase and decrease. These data indicate that SR Ca2+ exchange is altered following MI. In addition, changes in SR function are associated with changes in force production by the whole muscle.

Changes in skeletal muscle myosin heavy chain isoform content during congestive heart failure.

Abstract. Recent investigations have suggested that changes in contractile protein expression contribute to reductions in skeletal muscle function during congestive heart failure (CHF). Myosin heavy chain (MHC), a major contractile protein, has been shown to undergo alterations in protein isoform expression during CHF. The purpose of this investigation was twofold: (1) to determine whether muscles of the same functional group undergo similar changes in MHC expression, and (2) determine whether the magnitude of alterations in MHC is related to the severity of CHF. Using the rat coronary ligation model, mild and severe forms of CHF were produced and muscles of the plantar flexor group were analyzed. Whole-muscle MHC isoform proportions were not altered in the soleus and white gastrocnemius muscle, however significant increases in the percentage of fast MHC isoforms (7–9% increases in MHC IIx and IIb expression) were found in the red gastrocnemius muscle. In addition, there were significant proportional increases (8%) in MHC type IIb at the expense of MHC type IIx in the plantaris muscle. Many of the changes in the proportions of MHC isoforms were significantly correlated with indices of CHF severity. This indicates that changes in skeletal muscle MHC isoform expression are related to the severity of CHF and suggests that some peripheral skeletal muscles are more susceptible to shifts in MHC expression due to CHF. These changes in MHC isoform expression may contribute to alterations in the physiological performance of skeletal muscle and exercise capacity during CHF.

Functional overload attenuates plantaris atrophy in tumor-bearing rats

BackgroundLate stage cancer malignancies may result in severe skeletal muscle wasting, fatigue and reduced quality of life. Resistance training may attenuate these derangements in cancer patients, but how this hypertrophic response relates to normal muscle adaptations in healthy subjects is unknown. Here, we determined the effect of resistance training on muscle mass and myosin heavy chain (MHC) isoform composition in plantaris muscles from tumor-bearing (TB) rats.MethodsAge- and gender-matched Buffalo rats were used for all studies (n = 6/group). Suspensions of Morris Hepatoma MH7777 cells or normal saline were injected subcutaneously into the dorsum. Six weeks after cell implantation, muscles from TB rats were harvested, weighed and processed for ATP-independent proteasome activity assays. Once tumor-induced atrophy had been established, subgroups of TB rats underwent unilateral, functional overload (FO). Healthy, sham-operated rats served as controls. After six weeks, the extent of plantaris hypertrophy was calculated and MHC isoform compositions were determined by gel electrophoresis.ResultsSix weeks of tumor growth reduced body mass and the relative masses of gastrocnemius, plantaris, tibialis anterior, extensor digitorum longus, and diaphragm muscles (p ≤ 0.05). Percent reductions in body mass had a strong, negative correlation to final tumor size (r = -0.78). ATP-independent proteasome activity was increased in plantaris muscles from TB rats (p ≤ 0.05). In healthy rats, functional overload (FO) increased plantaris mass ~44% compared to the contralateral control muscle, and increased the relative percentage of MHC type I and decreased the relative percentage of MHC type IIb compared to the sham-operated controls (p ≤ 0.05). Importantly, plantaris mass was increased ~24% in TB-FO rats and adaptations to MHC isoform composition were consistent with normal, resistance-trained muscles.ConclusionDespite significant skeletal muscle derangements due to cancer, muscle retains the capacity to respond normally to hypertrophic stimuli. Specifically, when challenged with functional overload, plantaris muscles from TB rats displayed greater relative mass, increased percentages of MHC type I and decreased percentages of MHC type IIb. Therefore, resistance training paradigms should provide relative morphological and functional benefits to cancer patients suffering from muscle wasting.

Glucose 6‐phosphate alters rat skeletal muscle contractile apparatus and sarcoplasmic reticulum function

We investigated the effects of glucose 6‐phosphate (G6P) on skeletal muscle contractile apparatus and sarcoplasmic reticulum (SR) function. Using rat extensor digitorum longus fibres, the presence of 5 mM G6P decreased the Ca2+ sensitivity of both force production and actomyosin ATPase (AM‐ATPase) activity. Conversely, maximal Ca(2+)−activated force was unaffected while maximal AM‐ATPase activity was increased by 37%. In SR vesicles isolated from rat gastrocnemius, G6P markedly altered Ca2+ handling. It increased Ca(2+)‐stimulated Ca(2+)‐ATPase activity but depressed the net rate of Ca2+ uptake. This latter effect appears to be due to G6P‐stimulated Ca2+ release. When G6P was added to Ca(2+)‐loaded vesicles, a small, transient release of Ca2+ was elicited. In addition, G6P lowered the threshold for Ca(2+)‐induced Ca2+ release but depressed the net rates of both AgNO3‐ and caffeine‐induced releases. It is possible that the accumulation of G6P during muscular activity may adversely affect muscle force production and contribute to the fatigue process via its action on the contractile apparatus and SR.

A Meta-Analysis of Soccer Injuries on Artificial Turf and Natural Grass.

The goal of this investigation was to determine if playing or training on third-generation artificial turf (AT) surfaces increases the incidence rate of injuries compared to natural grass (NG) surfaces. This was accomplished by a meta-analysis performed on previously published research. Eight studies met the criteria of competitive soccer players, participation on both surfaces, and presentation of both exposure time and injury occurrence. Exposure time and injury incidence values were used to generate injury rate ratios (IRRs, AT/NG) for all injuries as well as specific injuries. Subgroup analyses were also performed by condition (match or training), gender, and age (youth or adult). The overall IRR was 0.86 (P < 0.05) suggesting a lower injury risk on AT than NG. However, there was considerable heterogeneity between studies. Analyses of individual injuries and subgroups found that in many cases IRR values were significantly less than 1.0. In no case was the IRR significantly greater than 1.0. Based on this, it appears that the risk of sustaining an injury on AT under some conditions might be lowered compared to NG. However, until more is known about how issues such as altered playing styles affect injury incidence, it is difficult to make firm conclusions regarding the influence of AT on player safety.

Use of social media to communicate sport science research.

Scientists and coaches acknowledge that an information gap exists between research and practice. Communication barriers hinder applying research findings in a timely manner. This investigation examined the usefulness of social media to communicate sport science research. A Facebook fan page and a website dedicated to translating soccer-related research (Science of Soccer Online, SSO) were established. The Facebook fan page accounted for the largest number referrals to the SSO website. Those accessing SSO via Facebook spent nearly 5 min on the site and viewed 1–2 articles per visit. A survey about the usefulness of the Facebook indicated that most respondents noticed and utilized links posted on the Facebook fan page. Survey participants also indicated that they used the fan page to access the SSO website. The results suggest a Facebook fan page that provides links to practical scientific information is a potentially useful means of communicating sport science to practitioners.