Biomedical subjects

J P Wallace

Publications and source records attributed to J P Wallace.

At least 19 recordsLinked to original sources

PubMed2005

Reproducibility of postexercise ambulatory blood pressure in Stage I hypertension.

The accuracy and reproducibility of ambulatory blood pressure monitoring used in intervention and treatment studies is essential to assure the desired health outcomes. The reproducibility of ambulatory variables in pharmacological studies has been reported, however, the reproducibility of ambulatory blood pressure variables associated with exercise has not been reported. Thus, the purpose of this study was to investigate the reproducibility of the postexercise ambulatory blood pressure in Stage I hypertensive adults. It was hypothesized that the reproducibility of the ambulatory blood pressure variables would not be different following two corresponding exercise and control treatments. A total of 18 Stage I hypertensive adults (142.1+/-3.15/91.6+/-1.80 mmHg) performed four randomized, 24 h AmBP monitoring sessions: two following a 50 min treadmill walk (50% VO(2) peak) and two on control days. Variables measured were: (1) average systolic and diastolic pressures for 24 h, daytime (06:00-22:00 h) and night time (22:00-06:00 h) and (2) systolic and diastolic load for the same time periods. Both a nonsignificant paired t-test and an excellent intraclass correlation were used to define reproducibility of the variables between the 1st and 2nd exercise trials and between the 1st and 2nd control trials. Reproducibility was found for all the control variables except for nighttime diastolic load. Reproducibility was found for all the systolic and diastolic exercise variables. Ambulatory blood pressure measurements, including average systolic and diastolic blood pressures and systolic and diastolic loads for 24 h, daytime and night time periods are reproducible following exercise.

Adult↗

PubMed2005

Time of day for exercise on blood pressure reduction in dipping and nondipping hypertension.

UNLABELLED: Time of day (TOD) for exercise may influence blood pressure (BP) reduction in hypertension because of the diurnal variation of BP and the duration of BP reduction following a single bout of exercise. The purpose of this study was to observe the effects of TOD for exercise on ambulatory blood pressure reduction in dipping (n=5) and nondipping (n=9) hypertension (<10% drop in nighttime BP (BP(night))). HYPOTHESES: (1) evening exercise (PM(ex)) would exhibit a greater BP(night) reduction in Non-Dippers than Dippers, (2) morning exercise (AM(ex)) would exhibit similar daytime BP (BP(day)) reduction in Dippers and Non-Dippers, (3) AM(ex) would exhibit greater 24 h BP (BP(24 h)) reduction than PM(ex) in Dippers, and (4) AM(ex) and PM(ex) would exhibit similar BP(24 h) reduction in Non-Dippers. BP responses to AM(ex) (0600-0800 h; 30 min at 50% VO(2peak)) and PM(ex) (1700-1900 h) were compared to each control day in a randomized design. Systolic (S) and diastolic (D) BP were averaged for BP(24 h), BP(day), and BP(night). A two-way ANOVA (dipping X time of exercise) using BP reduction with repeated measures were performed at P<0.05. FINDINGS: (1) Non-Dippers respond to exercise despite of TOD for exercise, (2) PM(ex) exhibited a greater SBP(night) reduction in Non-Dippers than Dippers, (3) AM(ex) exhibited similar SBP(day) reductions in Dippers and Non-Dippers, and (4) AM(ex) and PM(ex) exhibited similar SBP(24 h) reduction in Dippers and Non-Dippers. Dippers and Non-Dippers respond differently to TOD for exercise. The duration of the BP reduction persists up to 24 h after exercise.

Blood Pressure Monitoring, Ambulatory↗

PubMed1999

The magnitude and duration of ambulatory blood pressure reduction following acute exercise.

The purpose of this study was to observe the magnitude and duration of the ambulatory blood pressure (BP) reduction following exercise and to identify the peak intervals of BP reduction throughout the 24-h diurnal period. Subjects were 25 normo- (N = 116.7/ 78.2+/-10.0/7.2 mm Hg) and 21 hypertensive (H = 140.8/96.9+/-13.9/9.6 mm Hg) adults. Twenty-four hour ambulatory blood pressures (SBP = systolic and DBP = diastolic) were recorded following exercise (E = 50 min @ 50% VO2 max) and during a non-exercise control day (C). The 24-h pressures were compared between the E and C days for (1) duration and magnitude of the BP reduction following exercise, and for (2) the time of day for the diurnal patterns to exhibit reductions in BP. No BP differences were found for N between E and C days. Significant reductions in BP were found for 24-h average SBP (decrease 6.8 mm Hg) and DBP (decrease 4.1 mm Hg), daytime (06.00-22.00 hrs) SBP (decrease 6.9 mm Hg) and DBP (decrease 3.3 mm Hg), and sleep (22.00-06.00) SBP (decrease 5.1 mm Hg) and DBP (decrease 4.4 mm Hg) for H subjects only. H also demonstrated an 11 h reduction in SBP (chi = decrease 8.3+/-2.2 mm Hg) and 4h reduction in DBP (chi = decrease 6.0+/-1.7 mm Hg) following exercise. For the diurnal variation, the peak interval of reduction in SBP (chi = 17.0+/-2.6 mm Hg) was for 11 h; from 11.00-21.00 hrs. For DBP, a significant reduction (chi = decrease 5.7+/-0.7 mm Hg) was found for 5 h; from 11.00-15.00 h. Thus, exercise reduces both systolic and diastolic BP for a significant length of time postexercise as well as reduces pressures during the time of day that typically exhibits higher diurnal pressures.

Adult↗

PubMed1999

Ageing of the cardiovascular system during 33 years of aerobic exercise.

BACKGROUND: increasing age affects aerobic capacity, with an average loss of 10% or more per decade. AIM: to determine the effect of ageing on the circulatory system in middle-aged men during 33 years of physical training. METHODS: 15 men initially aged 45 years took part in an exercise training programme for 25-33 years. Nine serial measurements were made at rest and during maximal effort. Aerobic training consisted of swimming, jogging, walking and cycling 3-4 times per week. Sessions were for 61-70 min at 77-84% of heart rate reserve. RESULTS: there was no change in resting heart rate, blood pressure, percentage fat or body composition. Minimal cardiovascular losses at maximal work included 5.8-6.8% in maximal oxygen uptake per decade, 25 beats in maximum heart rate and 26 beats in heart rate reserve. CONCLUSION: exercise training has a favourable effect on ageing of the cardiovascular system in older men, resulting in minimal loss of oxygen uptake, no rise in resting blood pressure and no change in body composition.

Adult↗

PubMed1998

Major mineral concentrations in human milk do not change after maximal exercise testing.

Fourteen healthy, lactating women (aged 25-38 y and between 2 and 8 mo postpartum) participated in both a maximal graded exercise test and a 30-min rest period to determine the influence of exercise on the concentration of selected milk minerals and electrolytes. Treatment order was randomized and treatments were conducted on different days. Milk was expressed before treatment and at 10, 30, and 60 min postexercise or after the rest period. Milk was wet-ashed by using nitric and sulfuric acids. Aliquots were analyzed for total phosphorus concentration by colorimetric assay and for calcium, magnesium, sodium, and potassium by inductively coupled plasma atomic emission spectrophotometry. Baseline mineral concentrations were not significantly different (P>0.05). Repeated expression of milk at 10, 30, and 60 min did not show significantly altered mineral concentrations (P>0.05). Interwoman variation was responsible for most of the variation in mineral concentrations. A portion of this may be explained by the variation in stage of lactation, which is known to affect mineral composition. Stage of lactation was inversely correlated with concentration of calcium, total phosphorus, magnesium, and sodium (P<0.05). In conclusion, maximal exercise did not alter concentrations of phosphorus, calcium, magnesium, potassium, or sodium in milk. Thus, with respect to mineral concentrations in milk, there is no contraindication for exercise during lactation.

Adult↗

PubMed1998

Derivation of prediction equations for RV in overweight men and women.

PURPOSE: The purpose of this research was to derive and compare regression equations for predicting residual volume (RV) in overweight and normal weight adults. METHODS: RV was determined on land, in 311 men and women, following an overnight fast, using the nitrogen-dilution technique. Subjects were then weighed underwater at RV; 5-10 underwater weights were recorded; and the heaviest 3 measurements were averaged as the underwater weight. Percent body fat was calculated using the Siri equation. Group analyses were performed on overweight men (N = 59, body fat > 25%) and women (N = 126, body fat > 30%) compared with normal weight men (N = 68, body fat < or = 25%) and women (N = 58, body fat < or = 30%). A stepwise regression was performed for each group using the Systat Statistical Package (Evanston, IL). RESULTS: When RV was regressed on sex, age (yr), body weight (kg), and height (cm), sex was not found to be a significant predictor variable for RV. Subsequent regressions revealed that prediction equations for the overweight (RV = 0.0277 AGE + 0.0048 WT + 0.0138 HT - 2.3967, F = 44.0, P < 0.0000, SEE = 0.403) were different from those generated for normal weight men and women (RV = 0.0275 AGE + 0.0189 HT - 2.6139, F = 58.6, P < 0.0000, SEE = 0.405). Similar equations were obtained when a cross validation was performed on a separate sample of normal weight (N = 31) and overweight (N = 46) men and women. CONCLUSION: These data suggest that prediction equations for RV are separate and distinct for the overweight and normal weight populations.

Adipose Tissue↗

PubMed1997

A comparison of 24-h average blood pressures and blood pressure load following exercise.

Although the use of 24-h ambulatory blood pressure monitoring has been recommended in the study of blood pressure and exercise, consistent results have not been found for average 24-h systolic or diastolic blood pressures. Systolic load and diastolic load (the percentage of pressures >140/90 mm Hg during daytime hours and >120/80 mm Hg during sleep) have recently been identified as an important variable, but has had limited use with exercise. The purpose of this study was to compare the average systolic and diastolic pressures to systolic and diastolic loads from 24-h data recorded after a 50-min treadmill walk at 50% VO2max to data from a nonexercise control day. Subjects were 36 normotensive (116.9 +/- 10.7/77.0 +/- 8.9 mm Hg) and 25 hypertensive (141.0 +/- 13.7/96.6 +/- 9.0 mm Hg) adults. No significant differences were found for systolic and diastolic pressures or loads between the control and exercise days for normotensives. Even though no significant changes were found for any of the average systolic and diastolic pressures between the control and exercise days for the hypertensives, significant reductions were found in systolic load for 24-h (-25.7%), day (6 AM to 10 PM, -23.1%), work (6 AM to 5 PM, -22.9%), and leisure (5 PM to 10 PM, -26.7%) periods; and in diastolic load for the work (-22.5%) period. Thus, the measurement of systolic and diastolic load may be more sensitive than average systolic and diastolic blood pressures for the detection of 24-h ambulatory blood pressure changes with exercise in borderline hypertension.

Adult↗

PubMed1997

Effect of exercise on milk immunoglobulin A.

The major immunoglobulin (Ig) in human secretions is IgA. The immune properties of breast milk are well documented; however, the immunological influence of maximal exercise has not been established. The objective of this study was to investigate the role that exercise has on breast milk IgA and IgA subclasses. Breast milk was collected from 17 lactating women (4.6 +/- 2.3 months postpartum) before and after randomized exercise and control periods. The exercise treatment was a maximal graded treadmill test (VO2max = 30.3 +/- 5.7 mL x min-1 x kg-1). Milk was collected at rest, the breasts were emptied, and samples obtained 10, 30, and 60 min following either exercise or 30-min control rest periods. IgA concentrations were established by enzyme-linked immunosorbent assay. The results indicated that samples taken 10 and 30 min after the exercise period had significantly lower (P < or = 0.05) milk IgA concentrations (21.0 +/- 1.8 and 21.8 +/- 1.4 microg x mL-1, respectively) than the corresponding control resting samples (52.8 +/- 3.5 and 79.3 +/- 7.7 microg x mL-1). The exercise samples were similar to the control samples at 60 min (134.0 +/- 24.6 and 116.0 +/- 15.4 microg x mL-1, respectively), indicating that by 1 h, milk IgA production had recovered. The IgA1 data showed a similar significant decrease (P < or = 0.05) at 10 min postexercise, which also returned to control concentrations by the 30- and 60-min collection intervals. There was no significant change in the milk IgA2 concentrations at any of the time points studied. Milk IgA concentrations increased significantly in both exercise and resting control groups after the breasts were emptied, suggesting that breast emptying stimulated milk IgA synthesis. The results provide evidence that exercise alters milk IgA and IgA1 concentrations for 10-30 min after exhaustive exercise, but recovers by 1 h, and provide additional support for exercise effects on the mucosal immune system.

Adult↗

PubMed1996

Reliability and comparison of RPE during variable and constant exercise protocols performed by older women.

The purposes of this study were to assess if women 60 to 75 years of age perceived a series of exercise intensities differently from selected intensities in that series and to determine if a particular intensity was perceived more reliably. Twenty-four women (65 +/- 3.8 yr) completed a walking VO2max treadmill test. Subjects were either assigned to a variable, randomly ordered exercise protocol (GP1) or to one of three constant exercise protocols (Gps2-4). Each subject performed relative exercise intensities of 30, 50, and 70% of peak VO2 for three 5 min work bouts over 3 test days. Differences in RPE (p < 0.05) were found between each intensity and between the same intensities from both protocols. Women in GP1 rated exercise higher than women who exercised at a constant exercise intensity (p < 0.05). Intraclass correlation coefficients indicated that the exercise intensity of 50% of maximum was more reliable regardless of the protocol (Gp1: R = 0.97, Gp3: r = 0.94). When the RPE-HR correlation coefficients were transformed into a log scale, neither protocol had a stronger association (p > 0.05) between RPE-HR. It was concluded that older women should be given a range of exercise intensities that include the 50% relative exercise intensity as a perceptual marker in order to reach a reliable rate of exertion.

Aged↗

PubMed1995

Cardiovascular changes with age and exercise. A 28-year longitudinal study.

Various studies report a 0-22% per decade decline in circulatory function (VO2max) with advancing age. Twelve exercising men (E) were followed for 28 years, mean age 43 and 71 years, initial to final measurement, while 12 dropouts (C) detrained for 21 years, with a mean age from first to last measurement of 48 and 69 years, respectively. VO2 max in E changed from 45.9 to 39.4 ml.min-1.kg-1, 5% per decade, whereas C declined from 36.0 to 21.4 ml.min-1.kg-1, 19% per decade. Resting blood pressure was unchanged in E, 119/75 mmHg, whereas C rose from 128/85 to 149/90 mmHg. The data suggest that regular aerobic exercise forestalls the usual loss of circulatory function with increasing age.

Adult↗

PubMed1995

Twelve month adherence of adults who joined a fitness program with a spouse vs without a spouse.

OBJECTIVE: The purpose was to determine adherence of apparently healthy adults who joined an exercise program with a spouse (Married Pairs) vs. without a spouse (Married Singles). It was hypothesized that Married Pairs would have significantly higher adherence than Married Singles; and that self motivation would be associated with adherence. EXPERIMENTAL DESIGN: Twelve month adherence of Married Pairs and Married Singles were compared to self motivation in a retrospective design. SETTING: Subjects in this study did not volunteer for a scientific investigation, instead they were spontaneous participants in a university fitness program. PARTICIPANTS: Married Pairs were 16 couples and Married Singles were 16 married men and 14 married women. INTERVENTIONS: This study observed the 12 month spontaneous participation in a fitness program. The only intervention was the self motivation questionnaire. MEASURES: Adherence was defined as monthly attendance, compliance to the exercise prescription, dropout, and reason(s) for dropout. Self motivation was also measured. RESULTS: For Married Pairs, monthly attendance was significantly higher (54.2% +/- 10.3 vs 40.3% +/- 14.3) and dropout (6.3% vs 43.0%) was significantly lower than for Married Singles. Compliance to the exercise prescription was good for all of the groups except for the Married Single Men. Fifty percent of the dropouts left because of family responsibilities/lack of spousal support; 25% dropped-out to continue exercising on their own. Self motivation did not differ between Married Pairs and Married Singles. Monthly attendance of spouses in the Married Pairs demonstrated a significant correlation. CONCLUSIONS: Married Pairs had significantly higher attendance and lower dropout than Married Singles which appeared to be primarily influenced by spousal support rather than by self motivation.

Adult↗

PubMed1994

Dietary fat, sugar, and fiber predict body fat content.

OBJECTIVE: This study was conducted to determine the relationships among the specific components of dietary fat and carbohydrate and body fatness in lean and obese adults. DESIGN: Body composition determination was performed on each subject by hydrostatic weighing at residual volume. Subsequently, the individual components of dietary fat and carbohydrate were examined relative to body fatness using a 3-day food diary and a food frequency questionnaire. SUBJECTS: Subjects were 23 lean (11.1 +/- 2.9% body fat) men, 23 obese (29.2 +/- 3.8% body fat) men, 17 lean (16.7 +/- 3.3% body fat) women, and 15 obese (42.7 +/- 3.9% body fat) women who volunteered for free diet and body composition analyses. Inclusion criteria were 15% body fat for lean men, 25% for obese men, 20% for lean women, and 35% for obese women. STATISTICAL ANALYSIS PERFORMED: Group comparisons for dietary variables were made with a multivariate analysis of variance. RESULTS: No differences were found between lean and obese subjects for energy intake or total sugar intake, but obese subjects derived a greater portion of their energy from fat (33.1 +/- 2.6% and 36.3 +/- 2.3% for obese men and women, respectively, vs 29.1 +/- 1.3% and 29.6 +/- 2.0%, lean men and women, respectively). Percent of fat intake for saturated, monounsaturated, and polyunsaturated fats was not different among groups. Obese subjects derived a greater percentage of their sugar intake from added sugars than lean subjects (38.0 +/- 3.5% vs 25.2 +/- 2.0%, respectively, for men; 47.9 +/- 8.0% vs 31.4 +/- 3.4%, respectively, for women). Dietary fiber was lower for obese men (20.9 +/- 1.8 g) and women (15.7 +/- 1.1 g) than for lean men (27.0 +/- 1.8 g) and women (22.7 +/- 2.1 g). APPLICATIONS/CONCLUSIONS: Obesity is maintained primarily by a diet that is high in fat and added sugar and relatively low in fiber. Alterations in diet composition rather than energy intake may be a weight control strategy for overweight adults.

Adipose Tissue↗

PubMed1994

Influence of metabolic control on the ventilatory threshold in adults with non insulin-dependent diabetes mellitus.

Metabolic control, as assessed by glycosylated hemoglobin (HbA1c), has been reported to have a relationship to various submaximal exercise responses. However, due to the narrow range of HbA1c and the limited exercise data from previous studies on individuals with diabetes, little support for the above statement exists in the literature. The current study assessed the relationship between HbA1c and submaximal, or ventilatory threshold (VT), and maximal exercise (VO2 peak) responses in subjects with non-insulin-dependent diabetes mellitus (NIDDM). Sixteen subjects (age = 56.5 +/- 14.4 yrs; Wt = 82.6 +/- 17.2 kg; B.M.I. = 29.5 +/- 2.7 kg.m-2) performed a ramp (20 watts.min-1) leg cycle ergometer test (GXT). Their HbA1c was 11.8 +/- 2.8% (range 6.5 to 16.6%). Breath by breath respiratory analysis was performed using a Med Graphics 2001 cart. Ventilatory threshold (VT) was determined using the V-slope method. The VT was 1,151 +/- 487 ml.min-1 or 70.2 +/- 10% VO2peak; VO2peak was 1,645 +/- 740 ml.min-1. There were no significant relationships found between HbA1c and the VO2 at the VT (r = 0.04), the % of VO2peak at the VT (r = 0.23), and the VO2peak (r = 0.17). In conclusion, metabolic control, as assessed by HbA1c, did not influence selected submaximal and maximal exercise responses in NIDDM. Therefore, exercise prescription for individuals with NIDDM may not need to consider the individual's HbA1c concentration as a modifier of their exercise response.

Adult↗

PubMed1993

Successful weight loss in a self-taught, self-administered program.

There is little evidence concerning the effectiveness of self-help materials for weight control. The purpose of this research was to evaluate a self-help weight-loss program. Obese (body fat > or = 25.0%, range = 25.0-48.6%, mean +/- SEM = 36.5 +/- 1.3%) men (n = 14) and women (n = 21) were given a workbook detailing a behavior modification approach to weight loss that emphasizes self-monitoring of diet and exercise behaviors, and then sent home for 6 months to learn how to lose weight on their own. A group of 9 controls (CONT) who did not get a workbook were used for comparison. ANOVA showed that the experimental group (EXP) lost 8.1 +/- 0.9 (mean +/- SEM) kg body weight, 6.4 +/- 0.8 kg fat, and 3.9 +/- 0.6% body fat; all significant over time (p < 0.001) and different from the CONT (p < 0.0001) who showed no change in these variables. The EXP also reduced their fat intake (% of joules) from 36.1 +/- 1.0% to 27.9 +/- 1.3% (p < 0.0001), increased their carbohydrate intake from 45.7 +/- 1.2% to 50.0 +/- 1.7% (p < 0.007) and their protein intake from 16.3 +/- 0.05% to 20.7 +/- 0.7% (0 < 0.03), all of which were significantly different (p < 0.03) than the CONT who did not change. Dietary fiber increased in the EXP from 19.8 +/- 1.4 to 27.3 +/- 2.2 g/d (p < 0.001) even with a significant reduction in energy intake (11.3 +/- 0.6 vs. 8.9 +/- 0.5 Mj/d; p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Effect of exercise on cardiovascular ageing.

Ageing of the cardiovascular system presents several costly public health problems, loss of quality of life, dependency, and other various health hazards. Large declines of 0-24% per decade in cardiovascular function have been cited in the literature but no long-term longitudinal studies have been reported. Serially measured cardiovascular function was performed on 12 normal men, aged 44-79 years, at 0, 10, 15, 20 and 25 years. Over the same time period, daily exercise training data were reported monthly including mode, frequency, intensity, and duration. Although seven men developed some form of pathological disease, the total group's cardiovascular function remained 60% greater than the average of ten investigations. The overall decline in cardiovascular function (Vo2 max) was 13%, or 5% per decade, 45.4 ml.min-1.kg-1 to 39.5 ml.min-1.kg-1. In summary, cardiovascular function was one-half, or 0.24 ml.min-1.kg-1.year-1 of the 0.45 ml.min-1.kg-1.year-1 reported to be the average decline for ageing cited in the literature.

Aged↗

PubMed1993

Predicting max HR and the HR-VO2 relationship for exercise prescription in obesity.

This research derived regression equations for predicting maximal heart rate (MHR) and examined the relationship between relative oxygen consumption (VO2) and heart rate (HR) in obese (N = 86, body fat > 30%, hydrostatic weighing) compared with normal-weight (N = 51, body fat < or = 30%) adults. Simultaneous measurements of HR and VO2 were recorded at rest and every minute during a maximal graded exercise test. When MHR was regressed on age, two distinct equations for the obese and normalweights were generated. The relationship between %MHR and %max VO2 was similar between groups (r = 0.83, obese; r = 0.87 normalweights). Likewise, when %max VO2 was regressed on %max heart rate range similar equations were derived fro the obese (r = 0.81) and normalweights (r = 0.84). Correlation between Karvonen's predicted HR at a submaximal VO2 and the true HR at that VO2 was 0.88, regardless of adiposity. These data indicate that when predicting MHR in normalweights the equation 220-Age can be used, but for obese individuals the equation 200-0.5 x Age is more accurate; each having 12 as a standard error of estimate. Once MHR is determined, either the straight percentage technique or Karvonen's method would be appropriate for prescribing exercise intensity for both populations.

Adipose Tissue↗

PubMed1992

The influence of the fullness of milk in the breasts on the concentration of lactic acid in postexercise breast milk.

The purpose of this study was to observe the influence of the fullness of breast milk in the breasts prior to exercise on the concentration of lactic acid in breast milk following exercise. Twenty-three lactating women were randomly assigned to Group E (n = 11), which nursed and/or collected as much of the breast milk as possible prior to maximal exercise, and Group F (n = 12), which did not nurse or collect milk at least two hours prior to maximal exercise. Milk was collected at rest preexercise and 10, 30, 60 and 90 minutes postexercise and was analyzed for concentrations of lactic acid. ANOVA demonstrated 1) a significant increase in lactic acid in the milk at all postexercise collections for both groups and 2) a significant group vs postexercise time interaction for lactic acid concentration in milk. These differences represented differences in 1) time to peak lactic acid concentrations in milk (Group F = 10 min; Group E = 30 min) and 2) time for postexercise decreases in lactic acid concentrations in milk. Thus, the state of fullness of milk in the breasts is a factor which affects the concentration of lactic acid in breast milk following maximal exercise.

Adult↗

PubMed1992

Infant acceptance of postexercise breast milk.

The purpose of this study was to observe the infant acceptance of postexercise breast milk. Twenty-six lactating postpartum women exercised to maximum (maximum oxygen consumption = 35.1 +/- 9.2 [SD] mL min-1 kg-1) on a treadmill. Breast milk was collected via self-expression at rest before exercise and at 10 and 30 minutes postexercise and analyzed for lactic acid by enzymatic methods. Following exercise, infants were presented with their mothers' pre-exercise and postexercise milk in a double-blind design. The mother rated the infant's acceptance of the milk samples. There was a significant difference in acceptance of pre-exercise and postexercise milk as analyzed by analysis of variance. Maximal exercise resulted in a significant increase in lactic acid concentration in breast milk that may be high enough to affect the taste of the milk. The decreased acceptance of postexercise milk was associated with increased lactic acid concentration. Suggestions to circumvent the decreased acceptance are offered.

Adult↗