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Biomedical subjects

L T Mackinnon

Publications and source records attributed to L T Mackinnon.

33 records · Page 2Linked to original sources
PubMed1996

The effect of endurance training on lipoprotein(a) [Lp(a)] levels in middle-aged males.

Serum lipoprotein(a) [Lp(a)] levels were measured before and after a 12-wk program of moderate-intensity endurance training. The training program consisted of walking and/or jogging, at least three sessions.wk-1 of at least 30 min duration, at an intensity producing 60-85% HRmax reserve. Twenty-eight previously sedentary middle-aged Caucasian males matched for age, body mass, and body mass index (BMI) were randomly allocated to either an exercise (N = 17, mean age +/- SEM = 51.57 +/- 1.25 yr) or a control (N = 11, mean age +/- SEM = 50.0 +/- 1.15 yr) group. Pre- and post-training median Lp(a) levels, measured by immunoturbidimetric analysis, were not significantly different in either the exercise (pre 13.0, post 15.0 mg.dl-1) or the control subjects (pre 14.0, post 12.0 mg.dl-1) (P > 0.05). Kendall Rank correlation analysis revealed no significant relationship between the level of Lp(a) and any other variable in either group before or after training. In the exercisers, a significant increase (P < 0.05) was recorded in the estimated mean VO2max (pre 33.39 +/- 1.70, post 37.7 +/- 1.75 ml.kg-1 min-1). These data indicate that the level of Lp(a) was not influenced by a 12-wk program of moderate-intensity endurance training, and are consistent with previous reports suggesting that Lp(a) level is not altered by lifestyle factors.

Body Composition↗
PubMed1995

Lipoprotein(a) [Lp(a)] levels in middle-aged male runners and sedentary controls.

Serum Lipoprotein(a) [Lp(a)] concentration was compared between middle-aged well-trained Caucasian male endurance runners (N = 57), (mean age +/- SEM 47.8 +/- 0.7 yr) and age-, body mass-, and body mass index (BMI)-matched male nonathletic control subjects (N = 62), (mean age +/- SEM 48.7 +/- 0.8). The mean weekly training distance of the runners was (60.7 +/- 2.8 km.wk-1) at the time of testing. Median Lp(a) levels were not significantly different (P > 0.05) between the runners (15.0 mg.dl-1) and the control subjects (12.5 mg.dl-1). As expected, compared with control subjects, in runners levels of other lipoproteins and apoproteins were significantly more favorable for cardiovascular health (all P < 0.01). There was no significant relationship between Lp(a) and any other measured variable (lipid, anthropometric, or dietary) in the runners group. In the control group, the significant positive correlation between Lp(a) and LDL-C was no longer significant after correction for the estimated contribution of Lp(a) cholesterol to LDL-C. These cross-sectional data suggest that a lifestyle of moderate to intense exercise training does not exert a significant impact on the Lp(a) level.

Adult↗
PubMed1995

Markers for monitoring overtraining and recovery.

Physiological and mood state parameters were monitored during a 6-month swimming season in an attempt to determine markers of overtraining and recovery. Fourteen elite male and female swimmers were tested early-, mid-, and late-season and shortly before and after major competition. Training details and subjective ratings of well-being were compiled by the athletes in daily logs. Three swimmers were classified as stale based upon performance deterioration and prolonged, high fatigue levels. Staleness scores were calculated for each athlete using performance change from early- to late-season and daily fatigue ratings for the season. Regression analysis revealed a battery of well-being ratings which predicted staleness scores, accounting for 76% of the variance. The late-season stress ratings and plasma catecholamine levels at rest predicted staleness scores, accounting for 85% of the variance. During tapering, well-being ratings predicted improvement in competitive performance, accounting for 72% of the variance of the improvement in race times from previous best times. It was concluded that self-reported ratings of well-being may provide an efficient means of monitoring both overtraining and recovery; plasma catecholamine levels at rest may provide an additional objective tool for diagnosis.

Adolescent↗
PubMed1994

Mucosal (secretory) immune system responses to exercise of varying intensity and during overtraining.

Athletes are susceptible to upper respiratory tract infection (URTI) during intense training and after major competition; high rates of URTI have also been associated with the overtraining syndrome (staleness). Secretory immunoglobulin A (IgA), the predominant immunoglobulin in mucosal secretion, is a major effector of resistance against pathogenic microorganisms causing URTI. Previous work has shown that salivary IgA levels decrease after a single bout of intense prolonged exercise. The purpose of these studies was to examine the IgA response to various exercise conditions. Whole, unstimulated saliva was obtained before and after exercise. IgA concentration (microgram.mg protein-1) was measured by ELISA and IgA secretion rate (microgram.min-1) calculated. Study 1: Recreational joggers ran on a treadmill for 40 min at 55% and 75% VO2peak and competitive distance runners ran for 90 min at the same intensites. In both groups, IgA secretion rate did not change significantly after exercise at either intensity. Study 2: Competitive runners ran on a treadmill for 90 min at 75% VO2peak on 3 consecutive days. IgA secretion rate decreased 20 to 50% after exercise (p < .001). Post-exercise IgA secretion rates were significantly lower (p < .05) on days 2 and 3 compared with day 1. Study 3: Elite swimmers were followed over a 6 month season, with IgA concentration measured at 5 times. Throughout the season, IgA concentration was significantly (p < .05) lower in stale compared with well-trained swimmers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Current challenges and future expectations in exercise immunology: back to the future.

The immune system response to exercise is multifaceted, depending on the nature of exercise. The motivation behind recent research on the immune response to exercise comes from four basic directions: (i) keeping competitive athletes healthy, based on the perception that athletes are susceptible to infectious illness during intense training and competition; (ii) community interest in health promotion, based on the beneficial effect of exercise in lessening the risk of other lifestyle-associated diseases such as heart disease; (iii) use of exercise as adjunct therapy to improve patient functional capacity in certain diseases such as acquired immune deficiency syndrome (AIDS) and cancer; and (iv) work in the field of psychoneuroimmunology showing significant interaction between the neuroendocrine and immune systems, and the role of lifestyle factors in modulating immune function. Future work in exercise immunology will focus on topics such as: identifying the role of neuroendocrine factors in regulating the immune response to exercise; understanding the effects and appropriate type of moderate exercise in patients with diseases which involve the immune system; and possible long-term role of regular exercise in preventing diseases such as cancer, or the decline in immune function which accompanies the aging process.

Aging↗
PubMed1993

Decreased salivary immunoglobulin A secretion rate after intense interval exercise in elite kayakers.

Endurance athletes have been shown to suffer a high incidence of upper respiratory tract infection (URTI; e.g. colds, sore throat) during intense training and after competition. Previous studies have shown that concentrations of secretory immunoglobulin A (IgA), the major effector of host defense against micro-organisms causing URTI, decrease after intense endurance exercise. Many athletes perform intense interval exercise as part of their normal training. The purpose of this study was to determine whether salivary IgA concentrations also decrease after intense interval exercise during the normal training regime in elite athletes. Timed saliva samples were obtained from eight elite male kayakers immediately before and after three on-water training sessions during a 3-week period. The concentrations of IgA, IgG and IgM were determined separately by enzyme-linked immunosorbent assay, and secretion rates calculated for each Ig. The IgA secretion rate (micrograms.min-1) decreased 27%-38% after all three training sessions (P = 0.007); the largest decrease (38%) was noted after the most intense session at the end of an especially intense week of training. The IgA concentration relative to total protein (micrograms.mg protein-1) was significantly lower (P < 0.05) on this training day compared with the other 2 days. Concentrations and secretion rates of IgG and IgM did not change after exercise, indicating a specific effect on IgA. These data would suggest that, in elite athletes, IgA concentration and secretion rate are reduced by intense interval exercise, and that exercise-induced changes in IgA output may be one mechanism contributing to URTI in elite athletes.

Adult↗
PubMed1992

The acute effect of 30 min of moderate exercise on high density lipoprotein cholesterol in untrained middle-aged men.

Fifteen middle-aged, untrained (defined as no regular exercise) men (mean age 49.9 years, range 42-67) cycled on a cycle ergometer at 50 rpm for 30 min at an intensity producing 60% predicted maximum heart rate [(fc,max), where fc,max = 220 - age]. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglyceride (Tg) concentrations were measured from fasting fingertip capillary blood samples collected at rest, after 15 and 30 min of exercise, and at 15 min post-exercise. The mean HDL-C level increased significantly from the resting level of 0.85 mmol.l-1 to 0.97 mmol.l-1 (P < 0.05) after 15 min of exercise, increased further to 1.08 mmol.l-1 (P < 0.01) after 30 min of exercise and remained elevated at 1.07 mmol.l-1 (P < 0.01) at 15 min post-exercise. These increases represented changes above the mean resting level of 14.1%, 27.1% and 25.9% respectively. The HDL-C/LDL-C ratio increased significantly from a resting ratio of 0.20 to 0.26 after 30 min of exercise (P < 0.01) and to 0.24 at 15 min post-exercise (P < 0.05). The mean Tg level increased significantly from a resting level of 0.88 mmol.l-1 to 1.05 mmol.l-1 after 15 min, and to 1.06 mmol.l-1 after 30 min of exercise (P < 0.05 at each time). The TC/HDL-C ratio decreased significantly (P = 0.05) after 30 min of exercise and at 15 min post-exercise by 18.8% and 14%, respectively. No significant changes were observed in the levels of TC or LDL-C over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

The validation of backward extrapolation of submaximal oxygen consumption from the oxygen recovery curve.

The purpose of this study was to determine the validity and practicality of exponential vs linear backward extrapolation of the O2 recovery curve for prediction of exercise oxygen consumption (VO2). Eight men and women, age 20.1, 0.9 years, body mass 66.0, 2.5 kg (mean, SEM), completed seven bouts of cycle ergometer exercise at submaximal power outputs ranging from 50 to 175 W. Respiratory gases were collected from each subject during exercise and recovery. The monoexponential extrapolation of five recovery samples (r2 = 0.85) and linear extrapolation of one recovery sample taken during the first 20-s of recovery (r2 = 0.83) accounted for similar amounts of variance in predicting exercise VO2. The linear regression equation was the most practical predictor, as only one recovery gas sample was necessary and it did not require the complicated mathematical techniques used in exponential regression.

Adult↗
PubMed1990

Blood lactate responses in older swimmers during active and passive recovery following maximal sprint swimming.

The purpose of this study was to determine the effect of age on three blood lactate parameters following maximal sprint swimming. The parameters examined were maximal blood lactate concentration, time to reach maximal blood lactate concentration, and half recovery time to baseline lactate concentration. These parameters were examined in 16 male competitive masters swimmers (n = 4 for each age group: 25-35, 36-45, 46-55, and 56 plus years) during both passive and active recovery following a maximal 100 m freestyle sprint. Passive recovery consisted of 60 min sitting in a comfortable chair and active recovery consisted of a 20-min swim at a self-selected pace. Capillary blood samples were obtained every 2 min up to 10 min of recovery then at regular intervals to the end of the recovery period. Curves of blood lactate concentration against time were drawn and the three parameters determined for each condition for each subject. There were no significant differences between age groups in any of the lactate parameters examined. A significant difference (P less than 0.05) was noted in each of the parameters between active and passive recovery over all age groups. As expected, active recovery produced lower maximal blood lactate concentrations, lower time to maximal blood lactate values, and lower half recovery times. These data suggest that intensive swimming training may prevent or delay the decline with age in the physiological factors affecting blood lactate values following a maximal sprint swim. Older sprint swimmers appeared to be capable of producing and removing lactic acid at the same rate as younger swimmers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Physical exercise increases natural cellular-mediated tumor cytotoxicity in elderly women.

The influence of acute treadmill exercise on natural killer (NK) cell tumor cytotoxicity in vitro was studied in elderly women after participation in a program of physical exercise training (PET) (n = 7) or after participation in a paralleling nonexercise control (NEC) condition (n = 7). The two study groups were equated (p greater than 0.05) according to age, percent total body fat, functional status as measured by multi-inventory ranking, and exercise capacity. After the experimental period, the PET subjects had a greater basal level of NK activity than the NEC subjects (PET 38.2 percent specific lysis, %SL, vs. NEC 28.8 %SL; p less than 0.05). Both groups experienced an increase in NK activity after acute treadmill exercise (PET 38.2-57.4 %SL, p less than 0.01; NEC 28.8-37.8 %SL, p less than 0.05), but the increase in the PET subjects was significantly (p less than 0.05) greater than that observed in the NEC subjects. We conclude that natural cellular-mediated tumor cytotoxicity is increased in response to acute exercise and long-term PET in elderly women.

Activities of Daily Living↗
PubMed1987

The effect of exercise on secretory and natural immunity.

Secretory immunity. 1. Intense endurance exercise suppresses salivary immunoglobulins. The exercise-induced decrease is specific for the secretory antibodies IgA and IgM. 2. The suppression of secretory Ig is transitory, lasting at least one hour, and returning to pre-exercise levels by 24 hours after a single bout of severe exercise. These results suggest that anecdotal statements by athletes and their coaches of an increased susceptibility to upper respiratory infection after severe exercise could be related to changes in secretory immunity. Natural immunity. 1. Natural killer activity of PBL is suppressed one hour after intense endurance exercise. This effect is transitory, since activity returns to pre-exercise levels by 24 hours after a single bout of exercise. 2. The decrease in NK lytic activity is due to a decrease in the percentage of NK cells (Leu-11a+ cells). When NK cell activity is expressed on a per cell basis, it appears that activity is enhanced after exercise.

Adult↗
PubMed1987

Exogenous growth hormone treatment alters body composition and increases natural killer cell activity in women with impaired endogenous growth hormone secretion.

In order to assess the potential relationship between human growth hormone (GH) and body composition (BC) and natural immunity (NI), we measured the effects of exogenous GH on fat weight (FW), fat-free weight (FFW), and the cytotoxic activity of natural killer (NK) cells in women with impaired GH secretion. Mean peak serum concentrations of GH in response to L-dopa/arginine stimulation were 6.2 +/- 1.1 (SEM) ng/mL in 6 untreated subjects (US) and 5.4 +/- 1.5 ng/mL in 6 GH-treated subjects (TS). Moreover, the pretreatment circulating levels of IGF-I were low in both groups (US 684 +/- 121 mU/mL and TS 583 +/- 83 mU/mL), and they correlated with pretest levels of NK cell activity (r = .59, P less than .05) when both groups were combined. The TS were given 700 micrograms of human GH IM for an average of 14 days while the US were studied in parallel without GH treatment. As measured by hydrodensitometry or skinfold anthropometry, FW decreased (26.1 +/- 6.8 kg to 23.8 +/- 6.3 kg, P less than .05) and FFW increased (44.9 +/- 3.3 kg to 46.2 +/- 3.8 kg, P less than .05) in the TS. In the US, there were no significant (P less than .05) changes in either FW or FFW. Using a standard 51Cr release assay to measure the specific lytic (SL) activity of NK cells, mean SL activity increased from 24.4 +/- 7.0% to 44.1 +/- 8.9% (P less than .05) in the TS, whereas levels in the US were not altered significantly (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗