Alison C. Jozsi

Aged human muscle demonstrates an altered gene expression profile consistent with an impaired response to exercise

The gene expression profile of skeletal muscle from healthy older (62-75 years old) compared with younger (20-34 years old) men demonstrated elevated expression of genes typical of a stress or damage response, and decreased expression of a gene encoding a DNA repair/cell cycle checkpoint protein. Although the expression of these genes was relatively unaffected by a single bout of resistance exercise in older men, acute exercise altered gene expression in younger men such that post-exercise gene expression in younger men was similar to baseline gene expression in older men. The lack of response of muscle from older subjects to resistance exercise was also apparent in the expression of the inflammatory response gene IL-1beta, which did not differ between the age groups at baseline, but increased within 24 h of the exercise bout only in younger subjects. Other genes with potentially important roles in the adaptation of muscle to exercise, specifically in the processes of angiogenesis and cell proliferation, showed a similar response to exercise in older compared with younger subjects. Only one gene encoding the multifunctional, early growth response transcription factor EGR-1, showed an opposite pattern of expression in response to exercise, acutely decreasing in younger and increasing in older subjects. These results may provide a molecular basis for the inherent variability in the response of muscle from older as compared with younger individuals to resistance training.

Dietary protein adequacy and lower body versus whole body resistive training in older humans

This study assessed the effects of long‐term consumption of the United States Recommended Dietary Allowance (RDA) for protein by older people who were sedentary or performed resistive training (RT) on body composition, skeletal muscle size and protein metabolism, and if the number of muscle groups trained influenced the muscle hypertrophy response to RT. Twelve men and 17 women (age range 54–78 years) completed this 14 week controlled diet and exercise study. Throughout the study, each subject completely consumed daily euenergetic menus that provided the RDA of 0.8 g protein kg−1 day−1. From study weeks 3–14 (weeks RT1‐RT12), 10 subjects (four men, six women) performed whole body RT (WBRT), nine subjects (four men, five women) performed lower body RT (LBRT) and 10 subjects (four men, six women) remained sedentary (SED). Both the LBRT and WBRT groups performed knee extension and flexion exercises, and the WBRT group also performed chest press and arm pull exercises (three sets per exercise at 80 % of one repetition maximum, 3 days per week for 12 weeks). From week 2 (baseline) to week RT12, muscle strength increased in muscle groups trained in the LBRT and WBRT groups, and was not changed in the SED group. From baseline to week RT12, whole body muscle mass and protein‐mineral mass were not changed, fat‐free mass (P= 0.004) and total body water (P= 0.013) were decreased, and percentage body fat was increased (P= 0.011) in these weight‐stable older people, independent of group assignment. The RT‐induced increases in mid‐thigh muscle area (from computed tomography scans) were comparable in the LBRT and WBRT groups (2.13 ± 1.26 cm2 and 2.17 ± 1.24 cm2, respectively), and were different from those in the SED group, which lost muscle area (‐1.74 ± 0.57 cm2; group‐by‐time P < 0.05). From baseline to week RT12, 24 h urinary total nitrogen excretion decreased (P < 0.001), nitrogen balance shifted from near equilibrium to positive, whole body leucine oxidation (from the infusion of L‐[13C]leucine) decreased (P < 0.05) and net (postabsorptive vs. postprandial) leucine balance (P < 0.05) increased from near equilibrium to positive, with no differences in responses over time among the three groups. In conclusion, the number of muscle groups trained did not influence whole body protein metabolism or RT‐induced muscle hypertrophy in older people. Most of these data are consistent with a successful adaptation to the RDA for protein. However, research should continue to question whether the decreases in fat‐free mass and total body water observed in all subjects, and the decrease in mid‐thigh muscle area in the SED group, are physiological accommodations, and whether the RDA for protein might be marginally inadequate for older people to maintain skeletal muscle.

Energy expenditure of swimmers during high volume training

The purpose of this study was to examine the total energy expenditure (TEE) of swimmers during high volume training (17.5 +/- 1.0 km.d-1) using the doubly labeled water method. Five female swimmers (age, 19 +/- 1 yr; height, 178.3 +/- 2.2 cm; weight 65.4 +/- 1.6 kg) were administered a dose of 2H2(18)O and monitored for 5 days. Training consisted of two sessions per day, lasting a total of 5-6 h. Energy intake (EI) was calculated from dietary records. Resting energy expenditure (REE) was measured on a non-training day and averaged 7.7 +/- 0.5 MJ.d-1 (1840 +/- 130 kcal.d-1). There were no changes in body weight (day 1, 65.4 +/- 1.6; day 5, 65.2 +/ 1.5 kg) over the measurement period. TEE of the swimmers during the training period averaged 23.4 +/- 2.1 MJ.d-1 (5593 +/- 495 kcal.d-1). EI averaged 13.1 +/- 1.0 MJ.d-1 (3136 +/- 227 kcal.d-1), implying a negative energy balance of 43 +/- 2%. TEE expressed as a multiple of REE was 3.0 +/- 0.2. The results of this investigation describe the total energy demands of high volume swimming training, which may be used to address the dietary concerns of the competitive swimming athlete.

Regulation of blood volume during training in post-menopausal women

UNLABELLED In younger people the increase in aerobic capacity following training is related, in part, to blood volume (BV) expansion and the consequent improvements in maximal cardiac output. This training-induced hypervolemia is associated with a decrease in cardiopulmonary baroreflex (CPBR) control of peripheral vascular tone. PURPOSE To test the hypothesis that improvement in peak oxygen consumption (VO2peak) during training in older women is associated with specific central adaptations, such as BV expansion and a reduction in CPBR control of vascular tone. METHODS Seventeen healthy older women were randomized into training (N = 9, 71 +/- 2 yr) and control (N = 8, 73 +/- 3 yr) groups. The training group exercised three to four times per wk for 30 min at 60% peak heart rate for 12 wk and then 40-50 min at 75% peak heart rate for 12 wk. The control group participated in yoga exercises over the same time period. We measured resting BV (Evans blue dye), VO2peak, and the forearm vascular resistance response to unloading low pressure mechanoreceptors during low levels of lower body negative pressure (through -20 mm Hg) before and after aerobic training. The slope of the increase in forearm vascular resistance (response) per unit decrease in central venous pressure (stimulus) was used to assess CPBR responsiveness. RESULTS Aerobic training increased VO2peak 14.2% from 24.2 mL x kg(-1) x min(-1) to 27.7 mL x kg(-1) x min(-1) (P < 0.05), a smaller improvement than typically seen in younger subjects. Blood volume (59.9 +/- 1.9 and 60.9 +/- 1.9 mL x kg[-1]) and CPBR function (-3.98 +/- 0.92 and -3.46 +/- 0.94 units x mm(-1) Hg) were similar before and after training. CONCLUSIONS These data indicate that the inability to induce adaptations in CPBR function may limit BV expansion during training in older women. In addition, the absence of these specific adaptations may contribute to the relatively poor improvements in VO2peak in older women during short (10-12 wk) periods of training.

Effect of swimming suit design on the energy demands of swimming.

Eight competitive male swimmers completed a standardized 365.8 m (400 yd) freestyle swimming trial at a fixed pace (approximately 90% of maximal effort) while wearing a torso swim suit (TOR) or a standard racing suit (STD). Oxygen uptake (VO2), blood lactate, heart rate (HR), and distance per stroke (DPS) measurements were obtained. In addition, a video-computer system was used to collect velocity data during a prone underwater glide following a maximal leg push-off from the side of the pool while wearing the TOR and STD suits. These data were used to calculate the total distance covered during the glides. VO2 (3.76 +/- 0.16 vs 3.92 +/- 0.18 l.min-1) and lactate (8.08 +/- 0.53 vs, 9.66 +/- 0.66 mM) were significantly (P < 0.05) lower during the TOR trial than the STD trial. HR was not different (P > 0.05) between the TOR (170.1 +/- 5.1 b.min-1) and STD (173.5 +/- 5.7 b.min-1) trials. DPS was significantly greater during the TOR (2.70 +/- 0.066 m.stroke-1) versus STD (2.58 +/- 0.054 m.stroke-1) trial. A significantly greater total distance was covered during the prone glide while wearing the TOR (2.05 +/- 0.067 m) compared to the STD (2.00 +/- 0.080 m) suit. These findings demonstrate that a specially designed torso suit reduces the energy demand of swimming compared to a standard racing suit which may be due to a reduction in body drag.

Thermal responses to swimming in three water temperatures: influence of a wet suit.

The primary objective of this investigation was to determine the thermal and metabolic effects of wearing a rubberized wet suit (WS) while swimming for 30 min in 20.1, 22.7, and 25.6 degrees C water. Metabolic and body temperature measurements were recorded in each water temperature with subjects wearing either a WS or a competitive swimming suit (SS). Immediately after each swim the subjects cycled for 15 min on a stationary cycle ergometer. Energy expenditure (VO2), heart rate, post-swim blood lactate, work completed on the cycle ergometer, and rating of perceived exertion (RPE) were similar in all trials. Mean (+/- SE) core temperature (Tc) during swimming in the SS trials increased 0.56 (+/- 0.33), 0.48 (+/- 0.20), and 1.22 (+/- 0.24) degrees C, whereas in the WS trial Tc rose 0.62 (+/- 0.22), 1.02 (+/- 0.15), and 0.89 (+/- 0.13) degrees C in the 20.1, 22.7, and 25.6 degrees C treatments, respectively. Following swimming many of the subjects experienced a decrease in Tc, but it was significantly elevated above preimmersion by the end of cycling in all trials except the SS 20.1 degrees C trial. Mean trunk temperatures (Ttr) during swimming in the WS trials were 4.32 +/- 0.16 (20.1 degrees C), 3.90 +/- 0.25 (22.7 degrees C), and 3.21 +/- 0.20 (25.6 degrees C) degrees C warmer than in the SS. Ttr rose after the subjects exited the water, but remained significantly below baseline throughout cycling in all trials.(ABSTRACT TRUNCATED AT 250 WORDS)

THE INFLUENCE OF STARCH STRUCTURE ON GLYCOGEN RESYNTHESIS AND SUBSEQUENT CYCLING PERFORMANCE 7

The present study was designed to evaluate the influence of starch structure on muscle glycogen resynthesis and cycling performance. Eight male cyclists (22 +/- 1 yr) completed an exercise protocol (DP) to decrease vastus lateralis glycogen concentration. This exercise consisted of 60 min cycling at 75% VO2max, followed by six 1-min sprints at approximately 125% VO2max with 1 min rest intervals. In the 12 hr after the exercise each subject consumed approximately 3000 kcal (65:20:15% carbohydrate, fat and protein). All of the carbohydrate (CHO) consumed was derived from one of four solutions; 1) glucose, 2) maltodextrin (glucose polymer), 3) waxy starch (100% amylopectin), or 4) resistant starch (100% amylose). Muscle biopsies were taken from the vastus lateralis muscle after DP and 24 hr later to determine glycogen concentrations. A 30 min cycling time trial (TT) was performed following the 24 hr post-DP muscle biopsy to examine the influence of the feeding regimen on total work output. The post-DP glycogen concentrations were similar among the four trials, ranging from 220.3 +/- 29.2 to 264 +/- 48.3 mmol.kg-1 dry weight (d.w.) muscle. Twenty-four hours after DP, muscle glycogen concentration had increased less (p < 0.05) in the resistant starch trial (+90.8 +/- 12.8 mmol.kg-1 d.w.) than in the glucose (+197.7 +/- 31.6 mmol.kg-1 d.w.), maltodextrin (+136.7 +/- 24.5 mmol.kg-1 d.w.) and waxy starch (+171.8 +/- 37.1 mmol.kg-1 d.w.) trials. There were no differences in total work output during the TT, or blood lactate concentration immediately following the TT in any of the CHO trials. In summary, glycogen resynthesis was attenuated following ingestion of starch with a high amylose content, relative to amylopectin or glucose; however, short duration time trial performance was unaffected.