Klotho and Clinical Outcomes in CKD

RATIONALE & OBJECTIVE

Klotho deficiency may affect clinical outcomes in chronic kidney disease (CKD) through fibroblast growth factor-23 (FGF23)-dependent and independent pathways. However, the association between circulating Klotho and clinical outcomes in CKD remains unresolved and was the focus of this study.

STUDY DESIGN

Prospective observational study.

SETTING & PARTICIPANTS

1088 participants of the Chronic Renal Insufficiency Cohort (CRIC) Study with estimated glomerular filtration rate (eGFR) 20-70 ml/min/1.73m2.

EXPOSURE

Plasma Klotho level at the year-1 study visit.

OUTCOMES

5-year risks of all-cause mortality, heart failure hospitalization, atherosclerotic cardiovascular events, and a composite kidney endpoint comprised of a sustained 50% decline in eGFR, dialysis, kidney transplantation, or eGFR <15 ml/min/1.73 m2.

ANALYTICAL APPROACH

We divided Klotho into six groups to account for its non-normal distribution. We used Cox proportional hazards regression and subdistribution hazards models to compare survival and clinical outcomes, respectively, between Klotho groups. We sequentially adjusted for demographics, kidney function, cardiovascular risk factors, sample age, and FGF23.

RESULTS

Mean eGFR was 42 ml/min/1.73m2, and median Klotho was 0.31 ng/ml (interquartile range 0.10-3.27 ng/ml). When compared to the lowest Klotho group, survival (hazard ratio [HR] 0.77, 95% confidence interval [CI] 0.32-1.89), heart failure hospitalization (HR 1.10, 95% CI 0.38-3.17), atherosclerotic cardiovascular events (HR 1.19, 95% CI 0.57-2.52), and CKD progression (HR 1.05, 95% CI 0.58-1.91) did not differ in the high Klotho group. In contrast, FGF23 was significantly associated with mortality and heart failure hospitalization independent of Klotho levels.

LIMITATIONS

Despite adjustments, we cannot exclude potential influence of residual confounding or sample storage on the results. A single measurement of plasma Klotho may not capture Klotho patterns over time.

CONCLUSIONS

In a large, diverse, well-characterized CKD cohort, Klotho was not associated with clinical outcomes, and Klotho deficiency did not confound the association of FGF23 with mortality or heart failure hospitalization.

Fibroblast Growth Factor (FGF) 23 and FGF Receptor 4 promote cardiac metabolic remodeling in chronic kidney disease

Chronic kidney disease (CKD) is a global health epidemic that significantly increases mortality due to cardiovascular disease. Left ventricular hypertrophy (LVH) is an important mechanism of cardiac injury in CKD. High serum levels of fibroblast growth factor (FGF) 23 in patients with CKD may contribute mechanistically to the pathogenesis of LVH by activating FGF receptor (FGFR) 4 signaling in cardiac myocytes. Mitochondrial dysfunction and cardiac metabolic remodeling are early features of cardiac injury that predate development of hypertrophy, but these mechanisms of disease have been insufficiently studied in models of CKD. Wild-type mice with CKD induced by adenine diet developed LVH that was preceded by morphological changes in mitochondrial structure and evidence of cardiac mitochondrial and metabolic dysfunction. In bioengineered cardio-bundles and neonatal rat ventricular myocytes grown in vitro, FGF23-mediated activation of FGFR4 caused a mitochondrial pathology, characterized by increased bioenergetic stress and increased glycolysis, that preceded the development of cellular hypertrophy. The cardiac metabolic changes and associated mitochondrial alterations in mice with CKD were prevented by global or cardiac-specific deletion of FGFR4. These findings indicate that metabolic remodeling and eventually mitochondrial dysfunction are early cardiac complications of CKD that precede structural remodeling of the heart. Mechanistically, FGF23-mediated activation of FGFR4 causes mitochondrial dysfunction, suggesting that early pharmacologic inhibition of FGFR4 might serve as novel therapeutic intervention to prevent development of LVH and heart failure in patients with CKD.

A simplified, data-constrained approach to estimate the permafrost carbon-climate feedback

We present an approach to estimate the feedback from large-scale thawing of permafrost soils using a simplified, data-constrained model that combines three elements: soil carbon (C) maps and profiles to identify the distribution and type of C in permafrost soils; incubation experiments to quantify the rates of C lost after thaw; and models of soil thermal dynamics in response to climate warming. We call the approach the Permafrost Carbon Network Incubation-Panarctic Thermal scaling approach (PInc-PanTher). The approach assumes that C stocks do not decompose at all when frozen, but once thawed follow set decomposition trajectories as a function of soil temperature. The trajectories are determined according to a three-pool decomposition model fitted to incubation data using parameters specific to soil horizon types. We calculate litterfall C inputs required to maintain steady-state C balance for the current climate, and hold those inputs constant. Soil temperatures are taken from the soil thermal modules of ecosystem model simulations forced by a common set of future climate change anomalies under two warming scenarios over the period 2010 to 2100. Under a medium warming scenario (RCP4.5), the approach projects permafrost soil C losses of 12.2-33.4 Pg C; under a high warming scenario (RCP8.5), the approach projects C losses of 27.9-112.6 Pg C. Projected C losses are roughly linearly proportional to global temperature changes across the two scenarios. These results indicate a global sensitivity of frozen soil C to climate change (γ sensitivity) of -14 to -19 Pg C °C(-1) on a 100 year time scale. For CH4 emissions, our approach assumes a fixed saturated area and that increases in CH4 emissions are related to increased heterotrophic respiration in anoxic soil, yielding CH4 emission increases of 7% and 35% for the RCP4.5 and RCP8.5 scenarios, respectively, which add an additional greenhouse gas forcing of approximately 10-18%. The simplified approach presented here neglects many important processes that may amplify or mitigate C release from permafrost soils, but serves as a data-constrained estimate on the forced, large-scale permafrost C response to warming.

Impact of cardiopulmonary bypass and cardioplegic arrest on myocardial lymphatic function

Cardioplegic arrest (CPA) is associated with interstitial myocardial edema, which has been shown to impair myocardial function. The accumulation of interstitial myocardial edema may be enhanced by impaired myocardial lymph flow. The purpose of this study was to investigate the effects of CPA on myocardial lymphatic function. In nine anesthetized dogs, we cannulated a prenodal cardiac lymphatic and measured myocardial lymph flow rate (QL), myocardial lymph driving pressure (PL), and myocardial lymph hyaluronan (Hya) concentration. We determined left ventricular function using pressure-volume curves derived by sonomicrometry and micromanometry. The dogs were placed on cardiopulmonary bypass (CPB) (28 degrees C) and subjected to 60 min of hypothermic, crystalloid CPA. With the onset of asystole both QL and PL decreased significantly from 70.7 +/- 31.8 (SD) to 3.3 +/- 4.0 microliters/min and from 19.9 +/- 8.0 to 10.4 +/- 1.8 mmHg, respectively (P < 0.01). Following return of sinus rhythm after separation from CPB, QL and PL increased significantly to 135.4 +/- 28.0 microliters/min and 27.3 +/- 7.5 mmHg, respectively (P < 0.01). Post-CPA myocardial edema was demonstrated by gravimetric wet-to-dry weight determination of 3.67 +/- 0.20 (normal 2.90 +/- 0.20, P < 0.001) and was associated with significantly decreased left ventricular function. Myocardial Hya turnover rate was 1.3 +/- 1.0% per day under baseline conditions and increased significantly to 2.7 +/- 0.9% per day post-CPA (P < 0.01). We conclude that organized myocardial contraction is the major determinant of myocardial lymph flow. Myocardial lymph flow impairment during CPA may contribute to post-CPA myocardial edema and left ventricular dysfunction.

Glucose stimulates IGF-I gene expression in C6 glioma cells

Glucose stimulates expression of the insulin-like growth factor I (IGF-I) gene in cultured C6 glioma cells. This stimulation is specific, as the expression of other genes, including those encoding hypoxanthine guanine phosphoribosyl transferase (HPRT) and ubiquitin, is not similarly affected by glucose. IGF-I gene expression is also stimulated by lactate, suggesting that the stimulatory effect is mediated by a product of glycolysis. Additional results indicate that the abundance of IGF-I mRNA is considerably higher in stationary confluent cells than in log-phase growing cells. This regulation is also specific for IGF-I, as HPRT mRNA is regulated in the opposite direction.

Body position does not affect the hemodynamic response to venous air embolism in dogs

Current therapy for massive venous air embolism (VAE) includes the use of the left lateral recumbent (LLR) position. This recommendation is based on animal studies, conducted 50 yr ago, which looked primarily at survival. Little is known, however, about the concomitant hemodynamic response after VAE in various body positions. The purpose of this study was to investigate the hemodynamic and cardiovascular changes in various body positions after VAE. Twenty-two mechanically ventilated supine mongrel dogs received a venous air infusion of 2.5 mL/kg at a rate of 5 mL/s. One minute after the infusion, 100% oxygen ventilation was commenced and the body position of the dogs was changed to either the LLR (n = 6), the LLR with the head 10 degrees down (LLR-10 degrees; n = 6) or the right lateral recumbent (RLR; n = 5) position. Five dogs were maintained in the supine position (SUP; n = 5). One dog died in every group except in the SUP group, where all the dogs recovered. There were no significant differences among the various body positions in terms of heart rate, mean arterial pressure, pulmonary artery pressure, central venous pressure, left ventricular end-diastolic pressure, or cardiac output. The acute hemodynamic changes occurring during the first 5-15 min after VAE recovered to 80% of control within 60 min. Our data suggest that body repositioning does not influence the cardiovascular response to VAE. Specifically, our data do not support the recommendation of repositioning into the LLR position for the treatment of VAE.

Protein restriction specifically decreases the abundance of serum albumin and transthyretin nuclear transcripts in rat liver

The expression of the genes for serum albumin and several other plasma proteins is decreased in animals consuming inadequate amounts of dietary protein. To define the specificity of this phenomenon, we examined the effect of dietary protein restriction on the abundance of the mRNA for nine genes in rat liver. The results of this and previous studies indicate that genes in liver can be divided into two classes based on their response to protein restriction. Group I genes (albumin, transthyretin, carbamyl phosphate synthetase-I, class I alcohol dehydrogenase, insulin-like growth factor-I) exhibit decreased expression in response to protein restriction. In contrast, the expression of group II genes (hypoxanthine-guanine phosphoribosyl transferase, ubiquitin, H-ferritin, insulin-like growth factor binding proteins-1, -2 and -4) is either unchanged or increased in response to protein restriction. To investigate the molecular mechanism(s) leading to the decreased level of albumin and transthyretin mRNA in protein-restricted animals, the effect of protein restriction on the abundance of albumin and transthyretin nuclear transcripts was examined. The results demonstrated that protein restriction specifically decreased the abundance of albumin and transthyretin nuclear transcripts, indicating that the reduction in mRNA levels is caused at least partly by a decrease in gene transcription.

Hyaluronan in cerebrospinal fluid after head injury

Hyaluronan (HYA) is a large molecular weight polysaccharide which functions in various roles throughout the body. Little is known regarding HYA in human cerebrospinal fluid (CSF). We measured CSF and serum HYA concentrations in eleven patients with varying degrees of head injury. In these patients, CSF HYA ranged from 46 to 772 micrograms/l and serum HYA from 16 to 573 micrograms/l. We did not find any relationship between HYA values in CSF or serum and underlying disease or Glasgow Coma Scale (GCS). The role of CSF HYA in the injured human brain has yet to be elucidated.

Effect of amino acid limitation on the expression of 19 genes in rat hepatoma cells

We showed previously that the abundance of serum albumin mRNA is decreased in H4-II-E rat hepatoma cells limited for a single essential amino acid (phenylalanine, methionine, leucine, or tryptophan). To define the specificity of this phenomenon, we examined the effect of amino acid limitation on the abundance of mRNAs for 19 genes in the H4-II-E cells. These genes included six genes whose expression is either completely liver-specific or highly enriched in the liver compared with other tissues [albumin, transthyretin (TTR), transferrin, carbamyl phosphate synthetase-I, urate oxidase, class I alcohol dehydrogenase], as well as a number of ubiquitously expressed "housekeeping" genes. The results indicated that the 19 genes could be divided into three classes based on their response to amino acid limitation. Class I genes (the six liver-specific genes and alpha-tubulin) exhibit decreased expression in response to amino acid limitation. The expression of class II genes [beta 2-microglobulin, hypoxanthine-guanine phosphoribosyl transferase (HPRT), H-ferritin, ubiquitin (UbB), insulin-like growth factor binding protein-4, HNF-1 alpha] is not significantly affected by amino acid limitation. Class III genes [gadd153, beta-actin, ubiquitin (UbC), phosphoglycerate kinase-1, C/EBP alpha, C/EBP beta] exhibit increased expression in response to amino acid limitation. Thus, specific inductive as well as repressive effects on gene expression are quite common in amino acid-limited cells. The observation that all six genes whose expression is liver-specific exhibited decreased expression in amino acid-limited cells suggests a common mode of regulation of these genes by amino acid availability. The strong induction by amino acid limitation of the C/EBP inhibitor gadd153 is of interest in this regard, as increased levels of gadd153 could interfere with C/EBP, which is required for high expression of most liver-specific genes. To investigate further the molecular mechanism for the decrease in albumin mRNA abundance, albumin nuclear transcript levels were quantified in control and tryptophan-limited cells. Tryptophan limitation caused a decrease in albumin nuclear transcript abundance, and this decrease preceded the decrease in albumin mRNA, suggesting that the decrease in albumin mRNA was caused at least partly by a decrease in albumin gene transcription. Additional experiments with actinomycin D indicated that albumin mRNA was also destabilized in the tryptophan-limited cells. Thus, the overall results indicate that the decrease in albumin mRNA in the tryptophan-limited cells is caused by a specific decrease in albumin nuclear transcript abundance and destabilization of albumin mRNA.

The effect of fasting on insulin-like growth factor-I nuclear transcript abundance in rat liver

The abundance of insulin-like growth factor I (IGF-I) messenger RNA (mRNA) is decreased in the liver of fasting, protein-restricted, and energy-restricted rats. The extent to which this decrease in steady state mRNA abundance may be attributed to a decrease in IGF-I gene transcription remains unresolved. In the present study, we used an RNase protection assay to quantify IGF-I nuclear transcript (pre-mRNA) and mRNA abundance in whole cellular RNA isolated from liver of fasted and nonfasted male rats (4-6 weeks of age). The results of the RNase protection assay of IGF-I nuclear transcripts were strongly correlated with the results of nuclear transcription elongation (run-on) assays (r > 0.90; P < 0.001). In addition, the RNase protection assay allows for a greater capability for sensitively monitoring gene transcription in a large number of samples. In four different experiments, a consistent decrease in the quantity of IGF-I nuclear transcripts was observed in liver of animals fasted for 72 h, whereas IGF-I pre-mRNA abundance in animals fed ad libitum was highly variable (average intraassay coefficient of variation = 74% vs. 34% for nonfasted and fasted groups). When data from the four experiments were pooled, fasting reduced IGF-I pre-mRNA and mRNA levels by 78% and 70% (P < 0.001), respectively. Fasting also caused a significant decrease in mRNA and nuclear transcript abundance for another nutritionally sensitive gene, the gene encoding transthyretin (TTR). To determine whether the decrease in IGF-I and TTR nuclear transcripts was gene specific, levels of nuclear transcripts for serum albumin, H-ferritin, and ribosomal RNA were also quantified. The results indicated that serum albumin, H-ferritin, and ribosomal RNA nuclear transcripts were not decreased by fasting, demonstrating that the negative effect of fasting was specific for IGF-I and TTR. In summary, these results indicate that IGF-I and TTR nuclear transcripts are specifically decreased by fasting. The decrease in IGF-I mRNA is matched by a similar decrease in IGF-I nuclear transcripts, suggesting that fasting controls IGF-I gene expression primarily at the transcriptional level.

Aesthetic inlays: composite or ceramic?

As the aesthetic aspect of dental care becomes increasingly important to patients, the dental practitioner should be aware of the applications and limitations of the various tooth-coloured restorative systems available for the restoration of posterior teeth. Among currently available systems are direct placement resin composites, which may find application in small to medium preparations, and composite or ceramic inlays, which may have wider applications. Similar principles of inlay cavity preparation and restoration placement may be applied to both composite or ceramic systems, with both having the advantage over directly placed composite materials of improved control over anatomic form. Ceramic inlays may provide a high level of wear resistance, but are less simple to construct or repair than composite inlays. While initial clinical trials of composite and ceramic inlays show promise, long-term trials are now required to more fully assess the longevity of these restorations in clinical use.

Induction of insulin-like growth factor binding protein-1 gene expression in liver of protein-restricted rats and in rat hepatoma cells limited for a single amino acid

Restriction of the dietary protein intake of young growing animals results in a rapid cessation of growth. In order to gain further insight into the molecular mechanisms for metabolic adaptation to protein restriction, the expression of the insulin-like growth factor binding protein-1 (IGFBP-1) gene was examined in 4-week-old male rats fed isocaloric diets containing 20%, 8%, or 4% protein over a 10-day period. Expression of the IGFBP-1 gene was strongly induced in the protein-restricted animals. Animals on the 8% protein diet exhibited a 14-fold increase, and animals on the 4% protein diet exhibited a 33-fold increase in hepatic IGFBP-1 messenger RNA (mRNA) abundance relative to the abundance of IGFBP-1 mRNA in animals on the 20% protein diet. Expression of the IGFBP-1 gene was also strongly increased by severe energy restriction: IGFBP-1 mRNA abundance was increased 15-fold in animals maintained for 10 days on a diet with energy restricted to 50% of the ad libitum intake rate. In animals fasted for 24 h there was a 6-fold increase in IGFBP-1 mRNA abundance, a lower induction than was observed in either of the two chronic nutritional restriction models. To determine whether limitation for substrate (i.e. amino acids) might have a direct effect on IGFBP-1 gene expression, we examined the effect on IGFBP-1 gene expression of limitation of H4-II-E rat hepatoma cells for a single essential amino acid (phenylalanine, methionine, leucine, or tryptophan) for a period of 24 h. The abundance of IGFBP-1 mRNA was increased by approximately 4- to 5-fold in cultures limited for any of these four amino acids as compared with its abundance in cells incubated in medium containing all essential amino acids. To study further the molecular mechanism for induction of IGFBP-1 gene expression by nutritional restriction, probes specific for intron 3 or intron 1 of the rat IGFBP-1 gene were used to quantify levels of the IGFBP-1 primary nuclear transcript in protein-restricted rats and amino acid-limited cultured cells. The level of the IGFBP-1 primary transcript was increased by 8-fold in animals on the 8% protein diet and 14-fold in animals on the 4% protein diet, suggesting that the induction of IGFBP-1 mRNA was caused largely by an increase in transcription.(ABSTRACT TRUNCATED AT 400 WORDS)

Home- vs. clinic-based biofeedback treatment for pediatric migraine: results of treatment through one-year follow-up

While temperature biofeedback and related bio-behavioral procedures have become common in the treatment of adult migraineurs, the application of these techniques to the pediatric population has lagged far behind. The current investigation was undertaken to examine various methods for delivering biofeedback with this population. Nine children participated in this single-subject, clinical replication series in which clinic-based therapist-administered, home-based child-administered, and home-based parent-administered treatment formats were evaluated. Headache activity was assessed through the use of a daily headache log. Overall, results supported the utility of temperature biofeedback in the treatment of pediatric migraine. Further, it was suggested that home-based treatments may represent an equally efficacious and more cost-effective alternative to traditional clinic-based treatments. Finally, treatment effects were found to be stable, with results maintaining through a one-year follow-up period.

A comparison of four treadmill protocols for determination of maximum oxygen uptake in 10- to 12-year-old boys

Little information is available regarding the relative effectiveness of various treadmill exercise protocols in eliciting maximal oxygen consumption (VO2 max) values in children. In this study of 10- to 12-year-old boys, running protocols produced significantly higher VO2 max levels compared with walking, but there were no important differences in continuous, intermittent, and handrail-supported running schedules. The intermittent run protocols, however, prolonged the test duration. Studies examining VO2 max in children should utilize standard criteria for demonstrating peak oxygen intake. In this study criteria of VO2 plateau, peak heart rate over 198 and respiratory quotient exceeding 1.0 were satisfied most commonly with running protocols.

Body Fat Assessment: A Comparison of Visual Estimation and Skinfold Techniques

In brief: The purpose of this study was to compare skinfold measurement and visual estimation as methods of measuring percent body fat by testing them against densitometry. Seventy-one male volunteers underwent skinfold measurements and underwater weighing and were photographed from the front, side, and rear. The skinfold measurements and underwater weighing were used to determine percent fat by accepted mathematical methods. Two experts then visually estimated the subjects' percent fat by comparing the photographs with five sets of reference photographs The results suggest that some individuals can visually estimate percent fat about as accurately as it can be calculated from skinfold measurements.

Left ventricular size and function in body builders using anabolic steroids

Although controversial, there is evidence to support a direct effect of improved skeletal muscle strength and mass by anabolic steroids in weight-training athletes. The influence of these drugs on the myocardial hypertrophy demonstrated by these individuals is unknown. Echocardiographic measurements of left ventricular dimensions and function were evaluated in 15 steroid-using body builders and compared to body builders not taking these drugs as well as an inactive control group. Significant increase in left ventricular posterior wall (LVPW) and ventricular septal (VS) thickness as well as an elevated VS/LVPW ratio were noted in both weight-lifting groups compared to controls. There were no differences, however, between the weight lifters with and without anabolic steroid use in any of the measurements. These data indicate no potentiating effects of these drugs on the myocardial hypertrophy observed with weight training.

Amelioration of hemodialysis-induced fall in PaO2 with exercise

The hypoxemia of acetate hemodialysis may result from a decrease in alveolar ventilation (VA) related to a reduction in pulmonary carbon dioxide excretion (VCO2). To test this theory, ventilation was increased by exercise during dialysis on 6 patients and the effect on arterial oxygen tension (PaO2) measured. With hemodialysis the PaO2 fell from 102 to 92 mm Hg and with exercise rose to 102 mm Hg. These changes in PaO2 paralleled changes in VA and VCO2 induced by acetate dialysis and then exercise. The correlation coefficient between VA and VCO2 was 0.997. This close correlation suggests that CO2 load may be the main controlling factor for ventilation under these conditions. We conclude that the fall in PaO2 that occurs with acetate hemodialysis is due to decreased ventilation secondary to decreased VCO2 and that exercise can ameliorate the fall in PaO2 by increasing ventilation.

Psycho-physiological analysis of an aerobic dance programme for women

The purpose of this study was to determine: (1) the energy cost and (2) the psycho-physiological effects of an aerobic dance programme in young women. Twenty-one college-age women participated 40 minutes a day, three days a week, for a 10-week training period. Each work session included a five-minute warm-up period, a 30-minute stimulus period (including walk-runs) and a five-minute cool-down period. During the last four weeks of the training period, the following parameters were monitored in six of the subjects during two consecutive sessions: perceived exertion (RPE) utilising the Borg 6-20 scale, Mean = 13.19; heart rate (HR) monitored at regular intervals during the training session, Mean = 166.37; and estimated caloric expenditure based on measured oxygen consumption (V̇O₂) utilising a Kofranyi-Michaelis respirometer, Mean = 289.32. Multivariate analysis of variance (MANOVA) computed between pre and post tests for the six dependent variables revealed a significant approximate F-ratio of 5.72 (p <.05). Univariate t-test analysis of mean changes revealed significant pre-post test differences for V̇O₂ max expressed in ml/kg min^-1, maximal pulmonary ventilation, maximal working capacity on the bicycle ergometer, submaximal HR and submaximal RPE. Body weight was not significantly altered. It was concluded that the aerobic dance training programme employed was of sufficient intensity to elicit significant physiological and psycho-physiological alterations in college-age women.

Effect of salivary pellicle on enamel subsurface demineralization in vitro

Diffusion fluxes of two anionic species through hydroxyapatite membranes were found to be reduced up to 50% by the presence of adsorbed salivary pellicles developed on the membrane surfaces. By contrast, water fluxes were only marginally affected, indicating that salivary pellicles display ionic permselectivity. This property is used to explain a remarkable protection of the enamel observed when salivary pellicles were developed on extracted teeth before exposure to acid lactate buffers.

Effect of three levels of work intensity on performance of a fine motor skill

The purpose of this study was to investigate the effect of three levels of work intensity on the performance of a fine motor skill during steady-state exercies. Subjects were administered a progressive bicycle ergometer test to exhaustion in order to determine maximum heart rate (HRmax). Following practice sessions on the pursuit rotor, subjects performed 3 different rides on a bicycle ergometer at 60, 75, and 90% of HRmax. The order to test administration was varied randomly in an attempt to control for sequential effects. Analysis of variance with repeated measures was used to determine differences in pursuit rotor performance by days and by levels of work intensity. No confounding of learning was noted. A significant F ratio (p less than .001) between work intensities showed that fine motor performance during steady-state exercise is affected by levels of work intensity.