Training, detraining, and retraining effects on glycemic control and physical fitness in women with type 2 diabetes

Little is known about the detraining and retraining effects of exercise in patients with diabetes. The purpose of the present study was to investigate the effects of training, detraining, and retraining, using a combined strength and aerobic exercise program on glycemic control in women with type 2 diabetes. Thirteen postmenopausal women with type 2 diabetes (n = 13, age: 55.8 ± 5.1 years) followed a supervised aerobic and strength training program for 9 months, which was interrupted for 3 months (detraining) and resumed again for a period of 9 months (retraining). Anthropometric characteristics, glycemic control, and physical fitness were determined at baseline and after 9, 12, and 21 months. Training induced a small reduction in body mass index (BMI: -3.3%, 95% CI -5.1 to -1.5%), a moderate decrease in fasting plasma glucose (FPG: -12.0%, 95% CI -20.70 to -3.2%), glycosylated hemoglobin (HbA1c: -4.7%, 95% CI -12.1 to 2.7%), and a large decrease in postprandial glucose (PPG: - 12.1%, 95% CI -20.2 to -4.1%). In addition, there was an increase in power output (20.2%, 95% CI 6.9 to 33.6%) and total muscle strength (33.8%, 95% CI 21.4 to 46.1%). Detraining reversed PPG, HbA1c, and physical fitness. Resumption of training, however, led to a moderate decrease in BMI (-5.4%, 95% CI -8.1 to -2.7%), PPG (-9.5%, 95% CI -19.4 to 0.3%), and HbA1c (-6.8%, 95% CI -14.1 to 0.5%), and to large changes in FPG (-20.9%, 95% CI -31.9 to -9.9%), power output (33.1%, 95% CI 17.9 to 48.4%) and total muscle strength (48.2%, 95% CI 34.0 to 62.4%) compared to baseline. Thus, systematic training improves body composition, glycemic control and physical fitness in patients with type 2 diabetes. The cessation of exercise brings about negative alterations, while retraining restores all beneficial adaptations and improves them even more. Therefore, diabetic patients should follow a regular and an uninterrupted exercise program throughout life in order to control glucose metabolism and improve health.

The effects of pre-exercise glycemic index food on running capacity

This study examined the effects of pre-exercise food on different glycemic indexes (GI) on exercise metabolism and endurance running capacity. 9 subjects performed 3 exercise trials on different days 15 min after ingesting: lentils, (LGI), potatoes, (HGI), and placebo. Each subject ingested an equal amount of each food (1 g/kg body mass) and ran on a level treadmill for 5 min at 60%, 45 min at 70% and then at 80% of VO (2max) until exhaustion. Serum glucose concentrations were higher ( P<0.01) 15 min after the HGI trial compared to the LGI and placebo trials. In addition, serum glucose levels were higher ( P<0.05) during the LGI trial at the time of exhaustion compared to the HGI and placebo trials. Plasma insulin levels, 15 min after ingestion, were higher ( P<0.001) in the HGI trial as compared to the LGI and placebo trials. Exercise time was longer during the LGI trial ( P<0.05) compared to the placebo, but the time to exhaustion in the HGI condition did not differ from the placebo (LGI: 90.0 ± 7.9; HGI: 81.8 ± 5; placebo: 73.0 ± 6.4 min). These results suggest that lentils, the LGI food, ingested 15 min before prolonged exercise maintained euglycemia during exercise and enhanced endurance running capacity.

Alterations in maximal inspiratory mouth pressure during a 400-m maximum effort front-crawl swimming trial

AIM

The aim of this study was to examine the changes of maximal inspiratory mouth pressure (PImax) during a 400-m front crawl swimming trial.

METHODS

Eleven well-trained competitive swimmers (age: 17.6+/-0.8 years, mean+/-SE) performed a 400-m front-crawl trial with maximum effort (296.2+/-4.76 s). Then, on different days they swam a 300-m, 200-m and 100-m trials at a velocity corresponding to the 400-m trial. Measurements of PImax from residual volume at upright body position before and immediately after each trial were conducted using a portable mouth pressure meter.

RESULTS

Maximal inspiratory mouth pressure did not change significantly after the 100-m and 200-m trial compared to baseline (131.8+/-9.7 and 123.7+/-10.3 vs. 140.9+/-8.9 cmH(2)O, P>0.05). However, PImax was significantly lower after the 300-m (118.8+/-7 cmH(2)O, P=0.02) and 400-m trials (118.1+/-9.9 cmH(2)O, P=0.01).

CONCLUSIONS

These results indicate that during a maximum effort of 400-m front crawl, the reduction of inspiratory muscle strength occurs after 300-m. This should be considered for competitive swimming training by implementing swim race distance-specific respiratory muscle training.

Hormonal Responses after a Strength Endurance Resistance Exercise Protocol in Young and Elderly Males

This study examined testosterone, cortisol and growth hormone responses in elderly and young men after a strength endurance protocol. Eight elderly (age: 69 +/- 5 yrs) and nine young (age: 23 +/- 1 yrs) males with recreational experience in resistance training performed a strength endurance protocol, which included six exercises. At each exercise, the subjects performed 3 sets of 15 reps at 60 % of 1-RM with a 90 s rest interval between sets. The subjects also participated in a control session. Hormonal and blood lactate concentrations were measured before exercise, immediately after exercise and 15 min after the end of exercise. Blood lactate increased (p<0.05) with resistance exercise in both age groups with the highest increases observed in the young males. Testosterone and cortisol concentrations were higher (p<0.05) immediately and 15 min after exercise as compared to the respective control session values in both young and elderly subjects, whereas no differences were observed between groups (p>0.05). Growth hormone concentration increased (p<0.05) after resistance exercise compared to the control session in both age groups. This increase was higher (p<0.05) in the young as compared to the elderly group. The above results show that a moderate intensity - high repetition resistance exercise protocol for the improvement of strength endurance, seems to be a sufficient stimulus that increases testosterone, growth hormone and cortisol concentrations in elderly males. These hormonal responses may create an optimal metabolic environment, which improves muscular function after a strength endurance program although the elderly subjects present an attenuated growth hormone response compared to younger ones.

Attitudes towards exercise and physical activity behaviours in Greek schoolchildren after a year long health education intervention

OBJECTIVE

To examine the short term effects of a health education programme on Greek primary schoolchildren

METHODS

The school based intervention programme was applied to 29 children in the 6th grade of the 2nd Primary School of Agios Stefanos (approximately 12,000 inhabitants); 49 pupils from the 1st Primary School constituted the control group. To assess the effectiveness of the intervention, attitude and behavioural variables were measured before and after the intervention.

RESULTS

After adjustment for initial differences in the assessed variables, pupils who took part in the intervention had more positive attitudes towards physical activity than the control group and scored significantly more highly on their intention to participate in physical activity. Moreover, pupils in the intervention group reported more hours/week spent in organised physical activities than pupils in the control group (mean (SD) 3.54 (0.32) v 2.54 (0.26), p<0.020). Finally, a higher proportion of pupils in the intervention classes matched the recommendations of 60 minutes of moderate to vigorous physical activity daily (77.4% v 55.1%, p<0.043).

CONCLUSIONS

Within the limitations of the study, the data show that school health education programmes have the potential to slow the age related decline in physical activity and help pupils establish lifelong, healthy physical activity patterns. Promoting healthy habits and physical activity behaviours during childhood may prevent some of the leading causes of morbidity and mortality in the Greek population, and also decrease direct healthcare costs and improve quality of life.

Critical Velocity and Lactate Threshold in Young Swimmers

The purpose of the present study was to compare the critical swimming velocity (CV) in children, with the lactate threshold (LT) and the velocity corresponding to a blood lactate concentration of 4 mmol x l(-1) (V4). Twenty swimmers (ten females and ten males, mean +/- SD age: 12.9 +/- 1.1 years, body weight: 51.2 +/- 10.0 kg, height: 157.1 +/- 9.7 cm) performed four repetitions of 200 m swimming with increasing intensity (80, 85, 90 and 100% of their 200 m maximum velocity), interspersed with 15 minutes of passive rest. Blood lactate concentration was determined after each repetition. From the speed-lactate curve, the velocity corresponding to LT and V4 was calculated. In order to calculate CV, all swimmers were timed exerting maximum effort, on distances of 50, 100, 200 and 400 m. CV was expressed as the slope of the linear relationship of time versus distance and was calculated from combinations of four (CV4) three or two timed distances. Velocity on LT (1.079 +/- 0.114 m x s(-1)) and V4 (1.106 +/- 0.112 m x s(-1)) was comparable to CV4 (1.085 +/- 0.121 m x s(-1)). CV calculated from a combination including distances of 50, 100 or 200 m were higher compared to LT (p < 0.05). V4 was higher compared to CV of 100-200-400, CV of 200-400, CV of 100-400 (p < 0.05). The CV calculated from distances of 50 and 100 m was significantly higher than all other velocities (p < 0.05). These results confirm that the critical velocity seems to be a valid, practical and time-saving, non-invasive alternative method which can be applied in the swimming pool by a coach for the evaluation of the endurance capacity of young swimmers. For practical reasons, combinations of less than four distances can be used (i.e. 50-400 m, or 50-100-400 m).

Resistance training in older women: effect on vertical jump and functional performance

AIM

Few studies have determined the effects of a heavy resistance training on vertical jump performance in older adults. The purpose of the present study was to evaluate the effects of a 12 week heavy resistance training in vertical jump and functional performance in healthy, inactive, older women.

METHODS

Seventeen sedentary older women (aged 53-69 years) were assigned either to a control (C, n=8), or to a heavy resistance training (RT, n=9). The RT group trained knee extensors and flexors at 80% of 1-repetition maximum (1-RM), 3 days per week for 12 weeks. Both groups were evaluated in 1-RM lower body strength, squat jump (SJ) and countermovement jump (CMJ) height, and chair rising time, before and after the training period.

RESULTS

After the training period, RT significantly improved (P<0.001) the 1-RM lower body strength, SJ, CMJ height, and chair rising by 68.9%, 24.5%, 21.7%, and 13%, respectively. Significant correlations were observed among the percent (%) change in 1-RM lower body strength and SJ (r=0.849, P<0.001), CMJ height (r=0.797, P<0.001), and chair rising time (r=-0.917, P<0.001).

CONCLUSIONS

Muscle power improved after a short-term heavy resistance training, as measured by vertical jump and chair rising performance, in inactive older adults. The gains in muscle strength may contribute to the gains in chair rising time, SJ and CMJ height.

Serum leptin responses after acute resistance exercise protocols

This study examined the acute effects of maximum strength (MS), muscular hypertrophy (MH), and strength endurance (SE) resistance exercise protocols on serum leptin. Ten young lean men (age = 23 +/- 4 yr; body weight = 79.6 +/- 5.2 kg; body fat = 10.2 +/- 3.9%) participated in MS [4 sets x 5 repetitions (reps) at 88% of 1 repetition maximum (1 RM) with 3 min of rest between sets], MH (4 sets x 10 reps at 75% of 1 RM with 2 min of rest between sets), SE (4 sets x 15 reps at 60% of 1 RM with 1 min of rest between sets), and control (C) sessions. Blood samples were collected before and immediately after exercise and after 30 min of recovery. Serum leptin at 30 min of recovery exhibited similar reductions from baseline after the MS (-20 +/- 5%), MH (-20 +/- 4%), and SE (-15 +/- 6%) protocols that were comparable to fasting-induced reduction in the C session (-12 +/- 3%) (P < 0.05). Furthermore, no differences were found in serum leptin among the MS, MH, SE, and C sessions immediately after exercise and at 30 min of recovery (P > 0.05). Cortisol was higher (P < 0.05) after the MH and SE protocols than after the MS and C sessions. Glucose and growth hormone were higher (P < 0.05) after exercise in the MS, MH, and SE protocols than after the C session. In conclusion, typical resistance exercise protocols designed for development of MS, MH, and SE did not result in serum leptin changes when sampled immediately or 30 min postexercise.

The effects of strength training, cardiovascular training and their combination on flexibility of inactive older adults

The purpose of this study was to investigate the effects of aerobic training, strength training and their combination on joint range of motion of inactive older individuals. Thirty-two inactive older men (65 - 78 yr) were assigned to one of four groups (n = 8 per group): control (C), strength training (ST), cardiovascular training (CT), and combination of strength and aerobic training (SA). Subjects in the S, A, and SA trained three times a week for 16 weeks. ST included 10 resistance exercises for the major muscle groups at an intensity of 55 - 80% of 1-RM and CT included walking/jogging at 50 - 80 % of maximal heart rate. Body weight and height, physical activity level and maximal oxygen uptake (.VO(2)max) were measured before the training period. Isokinetic (60 and 180 deg x sec(-1)) and concentric strength (1-RM in bench and leg press) were assessed prior to and at the end of the training period. Hip flexion, extension, abduction, and adduction, shoulder extension, flexion, and adduction, knee flexion, elbow flexion and sit-and-reach score were determined before and at 8 and 16 weeks of training. There were no differences between groups in .VO(2)max, body weight, and height (p < 0.05). ST and SA but not CT and C increased isokinetic and concentric strength at the end of the training period (p < 0.05). ST and SA increased significantly (p < 0.05) sit-and-reach performance, elbow flexion, knee flexion, shoulder flexion and extension and hip flexion and extension both at mid- and post-training. CT increased (p < 0.05) only hip flexion and extension at post training. Results indicate that resistance training may be able to increase range of motion of a number of joints of inactive older individuals possibly due to an improvement in muscle strength.

Pre-exercise glucose ingestion at different time periods and blood glucose concentration during exercise

The purpose of this study was to investigate the effects of glucose ingestion (GI) at different time periods prior to exercise on blood glucose (BG) levels during prolonged treadmill running. Eight subjects (X+/-SD), age 20+/-0.5yr, bodymass 70.7+/-4.1 kg, height 177+/-4 cm, VO2max 52.8+/-7.8 ml x kg(-1) x min(-1) who underwent different experimental conditions ingested a glucose solution (1 g/kg at 350 ml) 30 min (gl-30), 60 min (gl-60), 90 min (gl-90), and a placebo one 60 min (pl-60) prior to exercise in a counterbalanced design. Afterwards they ran at 65% of VO2max for 1 hour and then at 75 % of VO2max till exhaustion. Fingertip blood samples (10 microl) were drawn every 15 min before and during exercise for the determination of BG levels. Oxygen uptake (VO2), heart rate (HR), and blood lactate (La) were also measured every 15 min during exercise. Peak BG values were reached within 30 min after GI but were different (p < 0.01) at the onset of exercise (gl-30: 147+/-22, gl-60: 118+/-25, gl-90: 109+/-22, pl-60: 79+/-5mg/dl). The two-way ANOVA repeated measures and the Tukey post-hoc test revealed a higher BG concentration (p < 0.05) for the gl-30 and the pl-60 as compared to the gl-60 and gl-90 during running (e.g. 15min run: 82+/-11, 68+/-5, 64+/-3, 78+/-7, and 60min run: 98+/-12, 85+/-12, 83+/-11, 94+/-11 mg/dl for gl-30, gl-60, gl-90, and pl-60, respectively). However, this did not significantly affect the duration of treadmill running. The La levels were higher (p < 0.05) after GI as compared to placebo throughout exercise (values at exhaustion: 4.6+/-0.2, 5.0+/-1.5, 4.8+/- 1.7 mmol/l for gl-30, gl-60, gl-90, and 3.5+/-0.8 mmol/l for placebo). The gl-30 and the placebo fluctuated closer to normoglycaemic levels. The glucose ingestion (60 to 90 min) prior to exercise lowered the blood glucose levels without affecting the duration of running performance at 75% VO2max. Thus, in order to maintain normoglycaemic levels, pre-exercise glucose supplementation should be given 30 min before the onset of exercise.

Failure to obtain a unique threshold on the blood lactate concentration curve during exercise

The purpose of this study was to compare various methods and criteria used to identify the anaerobic threshold (AT), and to correlate the AT obtained with each other and with running performance. Furthermore, a number of additional points throughout the entire range of lactate concentrations [La-] were obtained and correlated with performance. A group of 19 runners [mean age 33.7 (SD 9.6) years, height 173 (SD 6.3) cm, body mass 68.3 (SD 5.4) kg, maximal O2 Uptake (VO2max) 55.2 (SD 5.9) ml x kg(-1) x min(-1)] performed a maximal multistage treadmill test (1 km x h[-1] every 3.5 min) with blood sampling at the end of each stage while running. All AT points selected (visual [La-], 4 mmol x l(-1) [La-], 1 mmol x l(-1) above baseline, log-log breakpoint, and 45 degrees tangent to the exponential regression) were highly correlated one with another and with performance (r > 0.90) even when there were many differences among the AT (P < 0.05). The additional points (ranging from 3 to 8 mmol x l(-1) [La-], 1 to 6 mmol x l(-1) [La-] above the baseline, and 30 to 70 degrees tangent to the exponential curve of [La-]) were also highly correlated with performance (r > 0.90). These results failed to demonstrate a distinct AT because many points of the curve provided similar information. Intercorrelations and correlations between AT and performance were, however, reduced when AT were expressed as the percentage of maximal treadmill speed obtained at AT or percentage of VO2max. This would indicate that different attributes of aerobic performance (i.e. maximal aerobic power, running economy and endurance) are measured when manipulating units. Thus, coaches should be aware of these results when they prescribe an intensity for training and concentrate more on the physiological consequences of a chosen [La-] rather than on a "threshold".

Comparison of mathematically determined blood lactate and heart rate "threshold" points and relationship with performance

The purpose of this study was to investigate the relationship between threshold points for heart rate (Thfc) and blood lactate (Thla) as determined by two objective mathematical models. The models used were the mono-segmental exponential (EXP) model of Hughson et al. and the log-log (LOG) model of Beaver et al. Inter-correlations of these threshold points and correlations with performance were also studied. Seventeen elite runners (mean, SD = 27.5, 6.5 years; 1.73, 0.05 m; 63.8, 7.3 kg; and maximum oxygen consumption of 67.8, 3.7 ml.kg-1.min-1) performed two maximal multistage running field tests on a 183.9-m indoor track with inclined turns. The initial speed of 9 km.h-1 (2.5 m.s-1) was increased by 0.5 km.h-1 (0.14 m.s-1) every lap for the fc test and by 1 km.h-1 (0.28 m.s-1) every 4 min for the la test. After fitting the la or the fc data to the two mathematical models, the threshold speed was assessed in the LOG model from the intersection of the two linear segments (LOG-la; LOG-fc) and in the EXP model from a tangent point (TI-la; TI-fc). Thla and Thfc speeds computed with the two models were significantly different (P less than 0.001) and poorly correlated (LOG-la vs LOG-fc: r = 0.36, TI-la vs TI-fc: r = 0.13). In general, Thfc were less well correlated with performance than Thla. With two different objective mathematical models, this study has shown significant differences and poor correlations between Thla and Thfc.(ABSTRACT TRUNCATED AT 250 WORDS)