Outcomes in total knee arthroplasty patients after inpatient rehabilitation: influence of age and gender

OBJECTIVES

To examine age and gender effects on outcomes after inpatient rehabilitation in primary total knee arthroplasty (TKA) and revision TKA patients.

DESIGN

This retrospective, comparative study was conducted in a 50-bed, university-affiliated rehabilitation hospital. Patients included primary TKA patients (n = 286) and revision TKA patients (n = 138) placed into one of three age brackets: <60 yrs, 60-70 yrs, or >70 yrs. Measurements included length of stay (LOS), FIM scores, hospital charges, and discharge disposition location.

RESULTS

FIM scores improved from admission to discharge in both primary and revision patients (P = 0.015). LOS was shorter in primary than revision patients (8.3 vs. 10.4 days, P = 0.001), and the LOS was longest in patients >70 yrs compared with those <60 or 60-70 yrs (10.6 vs. 8.7 and 8.8 days, respectively; P = 0.004). FIM efficiency was greater in primary than in revision TKA patients (3.68 vs. 2.77 points/day, P = 0.001), and greater for men than women in each age bracket regardless of TKA type (3.68 vs. 2.78 points/day, P = 0.001). Total hospital charges were lower for men than women for both TKA types ($9,656 +/- 823 vs. $11,544 +/- 1,359; P = 0.015), and were highest in patients >70 yrs of age (P = 0.015).

CONCLUSIONS

Primary and revision TKA patients make improvements in functional independence during inpatient rehabilitation. Although FIM gains were similar among age and gender groupings, FIM efficiency is lowest in women. Despite similar daily hospital costs among the groups, slower progress with functional gains (decreased FIM efficiency) increases the LOS and total hospital charges, especially in older women.

Inpatient rehabilitation outcomes in primary and revision total knee arthroplasty patients

Inpatient rehabilitation is an effective means of improving physical function and independence following total knee arthroplasty (TKA). Revision TKA (TKAR) is becoming increasingly more prevalent and it is unclear if revision TKAR patients attain similar improvements following inpatient rehabilitation compared to primary TKA (TKAP) patients. This investigation compared functional outcomes following interdisciplinary inpatient rehabilitation in 286 TKAP and 138 TKAR consecutive male and female patients. Functional Independence Measure (FIM) scores improved from admission to discharge for the TKAP (81.6 to 110.5) and TKAR (74.4 to 101.4) groups (p = 0.015). TKAP patients had shorter length of stay (LOS) compared to TKAR (9.2 and 11.3). FIM efficiency (FIM/LOS) was greater for the TKAP compared to TKAR (3.6 and 2.6). Total hospital charges were 11,399 dollars and 13,407 dollars for the TKAP and TKAR groups, respectively. TKAP patients were more likely to be discharged home compared to the TKAR patients (97.6 vs. 78.3%). Both TKAP and TKAR patients demonstrate gains in FIM scores during inpatient rehabilitation. However, the amount of FIM efficiency is lower, and LOS and hospital charges are greater when comparing TKAR and TKAP. In addition, discharge disposition may be influenced by the type of TKA, primary and revision.

LEVEL OF EVIDENCE

Prognostic study, level II-1 (retrospective study). See Guidelines for Authors for a complete description of levels of evidence.

Biomarkers and potential mechanisms of obesity-induced oxidant stress in humans

OBJECTIVE

Oxidative stress may be the unifying mechanism underlying the development of comorbidities in obesity. Evidence suggests that a clustering of sources of oxidative stress exists in obesity: hyperglycemia, hyperleptinemia, increased tissue lipid levels, inadequate antioxidant defenses, increased rates of free radical formation, enzymatic sources within the endothelium, and chronic inflammation.

METHOD

This review provides a summary of the available evidence on systemic oxidative stress in humans and specific metabolic pathways by which obesity may elevate systemic oxidant stress. The authors suggest possible methods of reducing oxidative stress such as antioxidant supplementation, caloric restriction and/or physical activity and surgical intervention to combat free radicals and reduce adipose tissue.

RESULTS

Obesity is associated with oxidative stress and can be reduced with weight loss (regardless of exercise or surgery induced weight loss), caloric restriction or antioxidant rich diets.

CONCLUSION

Oxidative stress levels are elevated in human obesity, and these levels are modifiable with various lifestyle modifications and surgical interventions.

Sex and Age Effects on Outcomes of Total Hip Arthroplasty After Inpatient Rehabilitation

OBJECTIVE

To retrospectively examine the effects of sex and age on the inpatient rehabilitation outcomes of patients after total hip arthroplasty (THA).

DESIGN

Exploratory, retrospective study.

SETTING

A university-affiliated rehabilitation hospital.

PARTICIPANTS

Male and female THA patients (N=332) were stratified into age brackets (<65y, 65-84y, >or=85y). All patients completed interdisciplinary inpatient rehabilitation.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Length of stay (LOS), FIM instrument scores, FIM efficiency (FIM/LOS), hospital costs, and discharge disposition location were collected by chart review.

RESULTS

Regardless of age, women had lower FIM scores at admission and discharge than men (P<.05). FIM efficiency was 22% to 53% lower for women in primary THA and 16% to 85% lower in revision THA than men (P=.001). Women accrued higher total hospital charges than men (13,099 dollars vs 11,141 dollars; P<.05), and were discharged home less frequently than men (84.4% vs 90.9%; P<.05). Admission FIM scores were 10.6% and 8.9% lower and discharge FIM scores were 7.3% and 9.2% lower in patients 85 years or older than those less than 65 or 65 to 84 years (P<.01). FIM efficiency was 25% to 38% higher in patients less than 85 years than those 85 years and older (P=.015), and 37% higher in men than women (P=.001). Patients 85 years and older were discharged less frequently to home than patients less than 85 years (P<.05).

CONCLUSIONS

All patients made functional improvement after inpatient rehabilitation, but women and patients 85 years and older had longer LOS and lower FIM efficiency, incurred greater hospital charges, and were less likely to be discharged to home than men and younger counterparts.

Influence of Resistance Exercise on Lumbar Strength in Older, Overweight Adults

OBJECTIVE

To measure lumbar extensor strength in overweight (OVW) and nonoverweight (NOVW) elderly adults before and after resistance exercise training (RX).

DESIGN

Descriptive, comparative study.

SETTING

University-based wellness center and research facility.

PARTICIPANTS

Eighty-four adults (age range, 60-83 y) were placed into 1 of 2 groups based on body mass index (BMI): control (NOVW; mean BMI, 22.5 kg/m(2)) or OVW (mean BMI, 29.2 kg/m(2)). Subjects were then randomly assigned to either a resistance exercise (RX) or nonexercising group.

INTERVENTION

Six months of total body RX and isolated lumbar extension exercise.

MAIN OUTCOME MEASURES

Body composition, isometric lumbar extension strength, and 1-repetition maximum for each of the training exercises.

RESULTS

Upper-body strength increased by 18.3% and 17.2% for the NOVW-RX and OVW-RX groups, respectively. Lower-body strength increased by 12.7% and 19.5% for the NOVW-RX and OVW-RX groups, respectively. At baseline, the OVW participants had greater total lumbar extension strength (1067 Nm vs 714 Nm) compared with the NOVW participants (P<.05). When expressed per kilogram of fat-free mass, there were no differences in baseline total lumbar extension strength. After RX, lumbar extension strength increased by 58% and 34% for the NOVW-RX and OVW-RX groups, respectively (P<.05). No changes in lumbar extension, upper- or lower-body strength were noted for the nontraining groups.

CONCLUSIONS

OVW subjects were found to have greater absolute and similar relative, upper-body, lower-body, and lumbar extension strength at baseline when compared with their NOVW counterparts. Also, isolated lumbar extension exercise was effective in improving lumbar extensor strength in OVW and NOVW persons.

Obesity Exacerbates Oxidative Stress Levels after Acute Exercise

INTRODUCTION/PURPOSE

This study compared oxidative stress levels and antioxidant capacity in nonobese and obese participants after acute resistance (RX) and aerobic exercise (AX).

METHODS

Blood samples were collected from 28 nonobese (mean = 20.8% body fat) and obese (mean = 35.0% body fat) participants pre- and immediately post-RX and AX. Lipid hydroperoxides (PEROX), malondialdehyde (TBARS) and total antioxidant status (TAS) were measured. Oxygen consumption (VO2) and minute ventilation (VE) values were determined during each exercise session.

RESULTS

In both groups, PEROX and TBARS were elevated post-RX and AX, with the greater elevations occurring in the obese group in each case (P < 0.05). In the obese, TBARS increased by 42% and 41% post-RX and AX, respectively, compared with 7.1% and 26.9% in the nonobese group. PEROX increased by 100% and 70% post-RX and AX, respectively, in the obese, and by 85% and 62% in the nonobese. TAS was 17% higher (P < 0.05) post-RX in the nonobese compared with the obese, whereas TAS values were not different post-AX. Peak and average VE, and relative VO2). rates were higher in the obese post-AX compared with the nonobese (P < 0.05) Correlations existed between the exercise-induced change in PEROX and body fat, vitamin C and A intake, peak oxygen consumption, and exercise ventilation rates in the obese group (r = 0.784-0.776, P < 0.05). In both groups, the exercise-induced changes in PEROX were associated with vitamin C intake, exercise ventilation rates, VO2peak, and plasma triglycerides (r = 0.669-0.558, P < 0.05).

CONCLUSION

Lipid peroxidation is elevated in both RX and AX, and it is exacerbated in the obese. The mechanisms underlying this response in each exercise may be different but could involve plasma triglycerides, oxygen consumption, and antioxidant intake.

Homocysteine and lipoprotein levels following resistance training in older adults

This investigation examined the effect of 6 months of high- or low-intensity resistance exercise on serum homocysteine and lipoprotein (a) levels in adults aged 60-80 years. Forty-three men and women completed the study protocol. Subjects were randomly assigned to a control (n=10), low-intensity (LEX, n=18), or high-intensity (HEX, n=15) group. Subjects performed 6 months of resistance training at either 50% of their one-repetition maximum for 13 repetitions (LEX) or 80% of one-repetition maximum for eight repetitions (HEX) 3 times per week for 24 weeks. The load was increased by 5% when their rating of perceived exertion dropped below 18. One-repetition maximum; serum homocysteine; lipoprotein (a); total and high-density lipoprotein cholesterol; and dietary intake of vitamins B12, B6, and folic acid were measured pre- and poststudy. Upper and lower body strength significantly (p<0.05) increased for the LEX and HEX groups. Serum homocysteine decreased 5.30% and 5.34% for the LEX and HEX groups, respectively (p<0.05), but increased 6.1% for the control group. A significant increase in lipoprotein (a) levels was noted in the control and LEX groups from pre- to poststudy. No significant differences were noted either pre- or poststudy for total and high-density lipoprotein cholesterol or any dietary variables. These data indicate that significant reductions in serum levels of homocysteine in the elderly can be derived from resistance exercise training.

Strength training and hemodynamic responses to exercise

Sixty-two older adults (68.4+/-6 years) were randomized into a control group (n=16), low-intensity exercise group (n=22, LEX; 50% 1-repetition maximum; 13 repetitions per exercise), or a high-intensity exercise group (n=24, HEX; 80% 1-repetition maximum; eight repetitions per exercise) group. Subjects trained for 24 weeks, performing 1 set for each of 13 exercises. Subjects performed a graded exercise test (GXT) at baseline and after 24 weeks of strength training. Heart rate, systolic, and diastolic blood pressures were measured at rest, during the GXT and 1, 3, and 5-min post-GXT. Mean arterial pressure was also calculated. Post-training, time to peak systolic and diastolic blood pressures and heart rate was increased in the LEX and HEX groups by 22.9% and 44.5%, respectively (p<0.05). Diastolic blood pressure, heart rate, and mean arterial pressure during the GXT were significantly decreased (p<0.05) in the HEX group following training. Post-GXT heart rate was lower in the HEX and LEX groups compared to control (p<0.05) indicating a more rapid recovery. Resistance exercise prolongs the onset of peak cardiovascular responses, decreases the cardiovascular response to exertion, and improves recovery from maximal exertion.

Adaptation of upper airway muscles to chronic endurance exercise

We tested the hypothesis that chronic endurance exercise is associated with the recruitment of four major upper airway muscles (genioglossus, digastric, sternohyoid, and omohyoid) and results in an increased oxidative capacity and a fast-toward-slow shift in myosin heavy chain (MHC) isoforms of these muscles. Female Sprague-Dawley rats (n = 8; 60 days old) performed treadmill exercises for 12 weeks (4 days/week; 90 minutes/day). Age-matched sedentary female rats (n = 10) served as control animals. Training was associated with an increase (p < 0.05) in the activities of both citrate synthase and superoxide dismutase in the digastric and sternohyoid muscles, as well as in the costal diaphragm. Compared with the control animals, Type I MHC content increased (p < 0.05) and Type IIb MHC content decreased (p < 0.05) in the digastric, sternohyoid, and diaphragm muscles of exercised animals. Training did not alter (p > 0.05) MHC phenotype, oxidative capacity, or antioxidant enzyme activity in the omohyoid or genioglossus muscle. These data indicate that endurance exercise training is associated with a fast-to-slow shift in MHC phenotype together with an increase in both oxidative and antioxidant capacity in selected upper airway muscles. It seems possible that this exercise-mediated adaptation is related to the recruitment of these muscles as stabilizers of the upper airway.

Resistance exercise training attenuates exercise-induced lipid peroxidation in the elderly

This study examined the effects of 6 months of resistance exercise (RX) on basal and post-aerobic exercise lipid peroxidation (LIPOX). Men and women [n = 62, mean (SD) age 68.4 (6) years] were divided randomly into either a control (n = 16, CON), low-intensity training [LEX n = 24; 50% one-repetition maximum (1RM), 13 repetitions/exercise], or high-intensity training (HEX n = 22, 80% 1RM, 8 repetitions/exercise) group. Pre- and post-training, subjects performed a graded aerobic exercise test (GXT). Blood samples were collected prior to and 10 min following each GXT. Subjects trained 3 times per week for 6 months using 12 RX machines. LIPOX was determined by measuring levels of thiobarbituric reactive acid substances (TBARS) and lipid hydroperoxides (PEROX). RX had no effect on resting LIPOX. Post-training, post-GXT TBARS were lower in the LEX and HEX groups by 14% and 18%, respectively, compared to CON (P < 0.05). Post-GXT PEROX levels were lower (P < 0.05) in LEX and HEX compared to CON [CON 3.51 (0.56) nmol/ml, LEX 2.89 (0.80) nmol/ml, HEX 2.99 (0.63) nmol/ml]. Serum total and non-protein (glutathione) thiols were higher in the LEX and HEX groups following training compared to CON (P < 0.05). These data suggest that RX can (1) reduce serum LIPOX, (2) provide protection against oxidizing agents in vitro, and (3) provide a "cross-protection" against the oxidative stress generated by aerobic exercise, perhaps mediated by improvements in the thiol portion of the antioxidant defense.

Mechanism for obesity-induced increase in myocardial lipid peroxidation

OBJECTIVE

To determine the mechanisms underlying the obesity-induced increase in myocardial lipid peroxidation in the fa/fa rat. We hypothesized that elevated heart work (ie rate-pressure product), an increased rate of superoxide (O2*-)) production, total myocardial lipid content, and/or insufficient antioxidant defenses are potential contributors to myocardial lipid peroxidation in obesity.

DESIGN

Comparative, experimental study of myocardial tissue in 16-week-old lean control (Fa/?, normal diet), obese high-fat fed (Fa/?, 45% dietary fat), and obese fatty (fa/fa, normal diet) Zucker rats.

MEASUREMENTS

Myocardial work (heart rate x systolic blood pressure), myocardial lipid content, oxidative and antioxidant enzyme activities (citrate synthase (CS), catalase (CAT), glutathione peroxidase (GPX), superoxide dismutase (SOD)), the rate of papillary muscle superoxide radical production in vitro, thiol content, basal and post-oxidative challenge myocardial lipid peroxidation levels using thiobarbituric reactive acid substances (TBARS) and lipid hydroperoxides (PEROX) as indices of lipid peroxidation.

RESULTS

Compared to lean controls, the high-fat fed and fatty animals had similar elevations (P<0.05) in myocardial TBARS and PEROX (23%, 25% and 29% 45%, respectively; P<0.05), and elevated susceptibilities to oxidative stress in vitro following exposure to oxidizing agents (P<0.05). Resting heart work was slightly higher (P<0.05) in both the high-fat fed and fatty animals compared to controls. Myocardial lipid content, SOD activities and non-protein thiol (glutathione) levels were elevated (P<0.05) in high-fat fed and fatty animals compared to controls. The rate of superoxide formation by isolated papillary muscles in vitro did not differ among groups (P<0.05). Regression analysis revealed that the myocardial lipid content contributed most to myocardial lipid peroxidation (R2=0.76, P<0.05).

CONCLUSIONS

Myocardial oxidative injury is closely associated with myocardial lipid content, but is not closely correlated with heart work, insufficient antioxidant defenses or a greater rate of superoxide production.

Alterations in bilateral force judgment following strenuous eccentric exercise

This study investigated the effects of strenuous eccentric exercise on bilateral force-matching ability. After unilaterally performing 50 maximal eccentric elbow actions, participants were evaluated for bilateral force-matching ability. Participants were asked to match a reference force held by the control (CNT) arm with their exercised (EXD) arm. The experimental condition was then reversed. Constant error (bias) of the EXD arm was increased through 5 days postexercise, when it underestimated the CNT force in all trials. In contrast, an overestimation of the EXD force by the CNT arm resulted in an increased constant and variable error (variability around the bias) through 5 days postexercise, when the EXD arm served as the force reference. Strenuous eccentric exercise severely compromises bilateral force-matching ability, regardless of whether the EXD attempted to match the reference force or served as the force reference, indicating central or peripheral alterations to force judgment.

Vitamin E deficiency fails to affect myocardial performance during in vivo ischemia-reperfusion

Vitamin E content of cardiac tissue has been proposed to play a major role in the damage caused by myocardial ischemia-reperfusion (I-R). Previous studies using in vitro models have examined vitamin E deficiency and I-R-induced myocardial damage with equivocal results. The purpose of this study was to use an in vivo model of myocardial I-R to determine the effects of vitamin E deficiency on myocardial I-R-induced damage. Female Sprague-Dawley rats (4-mo old) were assigned to either: 1) control diet (CON), or 2) vitamin E deficient diet (VE-DEF). The CON diet was prepared to meet AIN-93M standards, which contains 75 IU vitamin E/kg diet. The VE-DEF diet was the AIN-93M diet prepared with tocopherol stripped corn oil and no vitamin E. Following a 14-week feeding period, significant differences (p < 0.05) existed in mean myocardial VE levels between groups (mean values +/- SEM: CON = 48.2 +/- 3.5; VE-DEF = 12.4 +/- 1.4 micrograms VE/g wet weight). Animals from both experimental groups were subjected to an in vivo I-R protocol consisting of 25 minutes of left coronary artery occlusion followed by 10 minutes of reperfusion. No group differences (p > 0.05) existed in cardiac performance (peak arterial pressure or ventricular work) or the incidence of ventricular arrhythmias during the I-R protocol. VE-DEF animals had significantly higher (p < 0.05) levels of myocardial lipid peroxidation and lower (p < 0.05) protein thiols following I-R compared to the CON animals. These data suggest that although vitamin E deficiency increases oxidative damage resulting from myocardial I-R, it does not affect cardiac performance during the insult.

Effect of combined supplementation with vitamin E and alpha-lipoic acid on myocardial performance during in vivo ischaemia-reperfusion

Reactive oxygen species (ROS) contribute significantly to myocardial ischaemia-reperfusion (I-R) injury. Recently the combination of the antioxidants vitamin E (VE) and alpha-lipoic acid (alpha-LA) has been reported to improve cardiac performance and reduce myocardial lipid peroxidation during in vitro I-R. The purpose of these experiments was to investigate the effects of VE and alpha-LA supplementation on cardiac performance, incidence of dysrhythmias and biochemical alterations during an in vivo myocardial I-R insult. Female Sprague-Dawley rats (4-months old) were assigned to one of the two dietary treatments: (1) control diet (CON) or (2) VE and alpha-LA supplementation (ANTIOXID). The CON diet was prepared to meet AIN-93M standards, which contains 75 IU VE kg-1 diet. The ANTIOXID diet contained 10 000 IU VE kg(-1) diet and 1.65 g alpha-LA kg(-1) diet. After the 14-week feeding period, significant differences (P<0.05) existed in mean myocardial VE levels between dietary groups. Animals in each experimental group were subjected to an in vivo I-R protocol which included 25 min of left anterior coronary artery occlusion followed by 10 min of reperfusion. No group differences (P>0.05) existed in cardiac performance (e.g. peak arterial pressure or ventricular work) or the incidence of ventricular dysrhythmias during the I-R protocol. Following I-R, two markers of lipid peroxidation were lower (P<0.05) in the ANTIOXID animals compared with CON. These data indicate that dietary supplementation of the antioxidants, VE and alpha-LA do not influence cardiac performance or the incidence of dysrhythmias but do decrease lipid peroxidation during in vivo I-R in young adult rats.

Short-term exercise training improves diaphragm antioxidant capacity and endurance

These experiments tested the hypothesis that short-term endurance exercise training would rapidly improve (within 5 days) the diaphragm oxidative/antioxidant capacity and protect the diaphragm against contraction-induced oxidative stress. To test this postulate, male Sprague-Dawley rats (6 weeks old) ran on a motorized treadmill for 5 consecutive days (40-60 min x day(-1)) at approximately 65% maximal oxygen uptake. Costal diaphragm strips were excised from both sedentary control (CON, n=14) and trained (TR, n=13) animals 24 h after the last exercise session, for measurement of in vitro contraction properties and selected biochemical parameters of oxidative/antioxidant capacity. Training did not alter diaphragm force-frequency characteristics over a full range of submaximal and maximal stimulation frequencies (P > 0.05). In contrast, training improved diaphragm resistance to fatigue as contraction forces were better-maintained by the diaphragms of the TR animals during a submaximal 60-min fatigue protocol (P < 0.05). Following the fatigue protocol, diaphragm strips from the TR animals contained 30% lower concentrations of lipid hydroperoxides compared to CON (P < 0.05). Biochemical analysis revealed that exercise training increased diaphragm oxidative and antioxidant capacity (citrate synthase activity +18%, catalase activity +24%, total superoxide dismutase activity +20%, glutathione concentration +10%) (P < 0.05). These data indicate that short-term exercise training can rapidly elevate oxidative capacity as well as enzymatic and non-enzymatic antioxidant defenses in the diaphragm. Furthermore, this up-regulation in antioxidant defenses would be accompanied by a reduction in contraction-induced lipid peroxidation and an increased fatigue resistance.

Exercise training protects against contraction-induced lipid peroxidation in the diaphragm

Endurance exercise training promotes a small but significant increase in antioxidant enzyme activity in the costal diaphragm (DIA) of rodents. It is unclear if these training-induced improvements in muscle antioxidant capacity are large enough to reduce oxidative stress during prolonged contractile activity. To test the hypothesis that training-related increases in DIA antioxidant capacity reduces contraction-induced lipid peroxidation, we exercise trained adult female Sprague-Dawley (n = 7) rats on a motor-driven treadmill for 12 weeks at approximately 75% maximal O2 consumption (90 min/day). Control animals (n = 8) remained sedentary during the same 12-week period. After training, DIA strips from animals in both experimental groups were excised and subjected to an in vitro fatigue contractile protocol in which the muscle was stimulated for 60 min at a frequency of 30 Hz, every 2 s, with a train duration of 330 m. Compared to the controls, endurance training resulted in an increase (P < 0.05) in diaphragmatic non-protein thiols and in the activity of the antioxidant enzyme superoxide dismutase. Following the contractile protocol, lipid peroxidation was significantly lower (P < 0.05) in the trained DIA compared to the controls. These data support the hypothesis that endurance exercise training-induced increases in DIA antioxidant capacity protect the muscle against contractile-related oxidative stress.

Obesity is associated with increased myocardial oxidative stress

OBJECTIVE

To determine: 1) whether obesity predisposes the myocardium to oxidative stress as evidenced by higher tissue levels of myocardial lipid peroxidation, and 2) what cellular mechanisms are responsible for this predisposition.

DESIGN

Comparative, descriptive study of the myocardial tissue of lean and obese Fatty Zucker animals.

ANIMALS

12 month old lean (-/fa; n = 6; mean body weight = 590 g) and obese (fa/fa; na = 7; mean body weight= 882 g) male Fatty Zucker rats.

MEASUREMENTS

Basal lipid peroxidation (assessed using thiobarbituric reactive acid substances (TBARS) and cumene hydroperoxide equivalents), oxidative and antioxidant enzyme activities (citrate synthase (CS), superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT), thiol content, heat shock protein expression (HSP72/73) and TBARS concentrations following an iron-mediated challenge in vitro.

RESULTS

Compared to lean, lipid peroxidation was greater (P < 0.05) in the left ventricle (LV) from obese rats as indicated by higher levels of lipid hydroperoxides (mean = 11.48 vs 13.7 cumene hydroperoxide equivalents (CHPE)/mg lipid) and TBARS (mean = 11.1 vs 13.9 nMol/mg lipid.). The activity of the manganese isoform of superoxide dismutase in the LV was higher (P < 0.05) in obese animals, compared to controls (mean = 135 vs 117 U/mg protein). In contrast, LV catalase and glutathione peroxidase activities did not differ (P > 0.05) between groups. Also, LV levels of HSP 72 (inducible) and 73 (constitutive) did not differ (P > 0.05)( between lean and obese animals. Following an iron-stimulated oxidative challenge in vitro, TBARS concentration was significantly greater (P < 0.05) in LV of obese rats compared to the lean (mean = 12.7 vs 16.7 nMol/mg lipid).

CONCLUSIONS

These results support the notion that obesity predisposes the myocardium to oxidative stress. However, the postulate that obesity is associated with elevated myocardial antioxidant enzyme activities and HSPs was only partially supported by these findings.

Exercise training improves myocardial tolerance to in vivo ischemia-reperfusion in the rat

Experimental studies examining the effects of regular exercise on cardiac responses to ischemia and reperfusion (I/R) are limited. Therefore, these experiments examined the effects of endurance exercise training on myocardial biochemical and physiological responses during in vivo I/R. Female Sprague-Dawley rats (4 mo old) were randomly assigned to either a sedentary control group or to an exercise training group. After a 10-wk endurance exercise training program, animals were anesthetized and mechanically ventilated, and the chest was opened by thoracotomy. Coronary occlusion was achieved by a ligature around the left coronary artery; occlusion was maintained for 20 min, followed by a 10-min period of reperfusion. Compared with untrained, exercise-trained animals maintained higher (P < 0.05) peak systolic blood pressure throughout I/R. Training resulted in a significant (P < 0.05) increase in ventricular nonprotein thiols, heat shock protein (HSP) 72, and the activities of superoxide dismutase (SOD), phosphofructokinase (PFK), and lactate dehydrogenase. Furthermore, compared with untrained controls, left ventricles from trained animals exhibited lower levels (P < 0. 05) of lipid peroxidation after I/R. These data demonstrate that endurance exercise training improves myocardial contractile performance and reduces lipid peroxidation during I/R in the rat in vivo. It appears likely that the improvement in the myocardial responses to I/R was related to training-induced increases in nonprotein thiols, HSP72, and the activities of SOD and PFK in the myocardium.

The effect of training status on the serum creatine kinase response, soreness and muscle function following resistance exercise

Untrained individuals develop muscle soreness and increased serum creatine kinase (CK) activity in the blood after strenuous, unaccustomed exercise. An unpublished observation in our laboratory revealed that trained weightlifters also experience considerable soreness after unaccustomed exercise, but may not show a dramatic CK response. This study examined the CK and soreness responses to strenuous exercise in weightlifters (TR, n = 10) and untrained subjects (UTR, n = 10). Trained subjects had a minimum of three years weightlifting experience, and regularly performed squats and leg presses. Untrained subjects had not participated in any regular resistance exercise for the past three years. Following two acclimation sessions, subjects reported to the lab on seven consecutive days and on the tenth day after knee extensor exercise. Weight training sessions occurred on day 1 for the knee extensors (KE) and day 2 for the knee flexors (KF). The weight training consisted of these exercises (sets): squat (5), leg press (3), leg extension and lunge (3) for the KE, double leg curls (6), single leg curls (3), stiff-legged deadlifts (4, TR group only) for the KF at 12 RM for all exercises. To document the stress due to exercise, the loss in strength (isometric peak torque, IPT) was assessed on a Biodex isokinetic dynamometer. Maximal voluntary IPT of the KE at 90 degrees and the KF at 80 degrees decreased 17-30% with no significant differences between groups. Muscle soreness during simulated squat leg curl movement was assessed by a 100 mm visual analog scale (VAS). Average peak KE soreness was 76 mm for TR and 58 mm for UTR, KF soreness was 60 mm for TR and 47 mm for UTR post-exercise. Serum CK levels were significantly different between groups with a peak of 1349 IU for TR and 3272 IU for the UTR (p < 0.01). Although the TR group experienced greater soreness than the UTR, peak serum CK activity was significantly lower, suggesting that trained individuals can develop severe soreness without the same degree of increase in serum CK activity observed in untrained individuals.