نشریه فیزیولوژی ورزش و فعالیت بدنی
سال هفدهم شماره 1 (بهار 1403)

Improvements in performance based on buffering capacity has been of great interest, where beneficial effects have been reported by using added respiratory dead space (ADRS) in endurance training. However, the use of ADRS in resistance training has not been investigated. The aim of this study was to investigate the effects of added respiratory dead space in weightlifting training on carbon dioxide, bicarbonate, and blood lactate.

Eighteen young healthy males (age, 28.72±14.14 years and body mass index 24.27±1.34 kg/m2) with at least 6 months experience of weightlifting training, were voluntarily selected and randomly divided into two groups of weightlifting+added respiratory dead space (WARDS, n = 9) and weightlifting training (n = 9). Both groups performed selected weightlifting training three sessions per week in the first to fourth weeks, four sessions per week in the fifth to sixth weeks and five sessions per week in the seventh to tenth weeks at an intensity corresponding to 80% of one-repetition maximum and rate of perceived exertion (RPE) 14 to 16. However, the WARDS group were breathing through a device that increased respiratory dead space volume to 1200-ml during the training. The anthropometric measurements and blood samples were taken before and after the first and last training session to determine carbon dioxide, HCO3- and lactate levels. For between-group comparisons repeated measures of ANOVA with between-group subjects was used.

No significant difference was observed between the two groups for body mass index (P=0.510), body weight (P=0.714) and body fat percentage (P=0.942). Changes in the CO2 (P=0.045) and lactate (P≥0.001) levels were significantly different in the mask group compared to non-mask group. No significant difference was observed between the two groups for HCO3- (P=0.947). As a result of comparing the responses of training variables, there was a significant increase in CO2 only after the last training session (P=0.019), while, lactate increased after the first and the last training session (P=0.001) and HCO3- after the first session (P=0.029) and the last training session (P=0.045) in the training group with mask.

Using an added respiratory dead space with a volume of 1200 ml during weightlifting training is a simple method to improve buffering capacity and increase lactate tolerance. Weightlifting training sessions are not considered more difficult with this strategy and can provide an alternative to well-known training protocols, and athletes can benefit from the adaptations in various directions such as hypertrophy, performance improvement.

Patients of heart failure with reduced left ventricular ejection fraction (HFrEF) have cardiac autonomic dysfunction that cause mortality. Poor HR and rate-pressure product (RPP) recovery immediately after a cardiopulmonary exercise test (CPET) is due in part to a reduction in vagal tone. There are limited studies evaluating the recovery of hemodynamic (HR, SBP and RPP) indices after moderate-term exercise and in response to a standard exercise protocol in patients with HF. The aim of current study was to determine whether 4 weeks of non-pharmacological interventions such as; virtual reality (VR), interval Nordic walking (INW) and Ambient music (AM) improves the cardiovascular hemodynamic recovery (1 and 3 minutes) in response to a standard CPET in patients with HF.

Forty-two stable HF patients with mean age: 60.36 ± 4.13 years and EF (30-55%); randomly assigned to four groups of VR training, INW, listen to Ambient music and control. VR, INW and AM groups performed the defined protocol for 4 weeks and 5 days each week. Measurements included HR, SBP, RPP and cardiorespiratory function (VO2peak, O2 pulse and time-to-exhaustion [TTE] were carried out using a 12-lead ECG system, immediately and the 1st and 3rd minute of recovery following an incremental CPET in the before and after 4 weeks of interventions. Multivariate analysis of variance was used to investigate the effect of interventions and CPET at different times.

CPET cause increase in cardiorespiratory hemodynamic parameters in baseline and after 4 weeks of non-pharmacological interventions. After 4 weeks of interventions, Heart rate recovery after 1 minute (HRR1) and Heart rate recovery after 3 minutes (HRR3), TTE and VO2peak were insignificantly higher in the INW and VR groups, when compared with the controls (P< 0.05). After 4 weeks of intervention, interestingly, the RPP values immediately after CPET showed an insignificant increase in the INW and VR groups, as compared to the control and music groups, which was in line with increase in TTE. 4 weeks of music had no significant effect on hemodynamic recovery and cardiorespiratory function of men with HF.

Improved recovery of HRR3 and SBP in response to CPET and a betterment in VO2peak and TTE after 4 weeks of INW and VR interventions may be a factor for increased vagal tone in patients with HFrEF. Both INW and VR training methods are suitable for improving cardiorespiratory hemodynamic recovery in patients with HF. However, faster recovery probably requires longer duration of exercises and may be a way to improve cardiorespiratory fitness and thus prevent cardiac events in the elderly with HF. future research should focus on other training methods, including HIIT exercises with nutritional interventions. Moreover, understanding the mechanisms responsible for the potential improvements warrant further study.

Physiological and behavioral processes of almost all organisms depend on the time of day. In mammals, light enters these processes in the suprachiasmatic nucleus of the hypothalamus, which forms the body's central clock, and synchronizes the body's functions with the 24-hour cycle of light and darkness. he does. In addition to perceptual and cognitive aspects of performance, circadian rhythms affect many aspects related to physiological performance such as muscle strength and flexibility. There is also a strong relationship between physical performance and (circadian) changes in body temperature, with optimal physical performance coinciding with peak body temperature in the early evening. The circadian clock, which is responsible for the circadian rhythm, exists in almost every cell, and its disruption leads to many diseases such as type 2 diabetes and metabolic syndrome. The findings show that skeletal muscle homeostasis may be disrupted not only due to lack of exercise and low dietary protein intake, but also due to disruption of circadian rhythm conditions such as continuous night work, shift work, lack of sleep, and jet lag.

In this review study, articles related to the subject were selected and studied from published texts and authoritative sites using keywords muscle molecular clock, exercise performance, circadian rhythm, and phenotype.

The time of sports activities is very important in performance. Despite the timing of the activity, individual preference for doing the activity in the morning or in the evening can be a very important factor on performance. According to the reviewed studies, most of the sports performance such as strength, speed, endurance, accuracy, recovery ability, harmony, etc., were better in the evening and early night in the athletes of different team and individual disciplines. This superiority in the evening can be attributed to body temperature, hormone release, circadian rhythm, rest and recovery, etc. In some cases, such as swimming, strength and endurance are better in the morning.

Based on the information collected in this review study, biological and physiological rhythms have an effect on people's physical performance. Despite individual differences and personal preferences in determining training hours, taking into account a specific training time each day and training at the beginning of the day can improve people's performance. Higher body temperature in the evening, increasing the level of secretion of hormones such as cortisol and testosterone, etc. can be one of the factors affecting the better performance of athletes in the evening. But depending on the type of activity, skill level, gender of the athletes and individual differences, the time to perform the activity for better performance can vary. In addition to the mentioned cases, individual preference to perform activities during the day or night is an important factor in improving performance.

Based on the information collected in this review study, biological and physiological rhythms have effect on people's physical performance. Despite individual differences and personal preferences in determining training hours, by considering a specific training time each day and training at the beginning of the day, people's performance can be improved.

Beta-alanine supplement, which is a precursor of carnosine, may improve performance by providing a buffering effect. The purpose of this study was to investigate the effect of beta-alanine supplementation and regular Taekwondo training on anaerobic, aerobic, and endurance activity substrate metabolism in female Taekwondo athletes.

Twenty-four female professional taekwondo practitioners (age, 18.0±2.5 years), from Tehran province volunteered to participate in this research. Based on the body composition and training history, the subjects were divided into two groups (n=12) of supplement and placebo. The pre-tests consisted of the an aerobic specific test (Progressive Specific Taekwondo Test, PSTT) including repeated strikes of Bandal-Tchagui to exhaustion time during a maximum duration of 15 minutes and a taekwondo anaerobic test (Frequency Speed of Kick Te, FSKT) including 5 sets of 10-second high-speed Bandal-Tchagui kicks with maximum strength. Furthermore, the substrate metabolism of the endurance activity was measured by a gas analyzer, and the VCO2, VO2, VO2peak, HR, and HRpeak were measured. During and immediately after the test, the level of perception of fatigue was evaluated. Moreover, blood lactate levels were measured using a lactometer after the anaerobic and aerobic tests. After 28 days of receiving the supplement or placebo (5g/day) at the designated day times, the pre-test measurements were repeated. Repeated measures of ANOVA with between-group factor and Bonferroni post-hoc tests were used to compare the data.

There was no significant difference between the two supplement and placebo groups for anaerobic capacity, aerobic capacity, and substrate metabolism (p<0.05). Although, both groups (supplement and placebo) showed significant improvements in the time to exhaustion and the number of steps to exhaustion in the post-test compared to the pre-test, these improvements were significantly higher in the supplement group compared to the placebo (p<0.05).

During the research period, beta-alanine supplementation had only an effect on some performance indicators and probably more pronounced effects on the performance of elite athletes would be seen in the long term. However, this little gain can be important in professional athletes, and more studies are needed in this field for a concrete conclusion.

The effect of physical activity and living in enriched environment on some cognitive mechanisms in Alzheimer's disease (AD) is not yet well understood. Therefore, this study aimed to investigate the effect of aerobic training along with enriched environment on spatial memory and brain-derived neurotrophic factor in the Hippocampal tissue of elderly female Wistar rats with Alzheimer's disease.

In this experimental study, 30 elderly female Wistar rats with twenty-one-month-old and average weight of 260±20 grams were used and divided into 6 groups: control-healthy, Alzheimer's, sham group, Alzheimer's + aerobic exercise (treadmill), Alzheimer's + enriched environment, Alzheimer's + enriched environment + aerobic exercise (treadmill). Rats in the training groups performed two 15-min sessions with 5-minute passive rest at a speed of 10 m/min in the first and second weeks. In the third week, they performed three sessions at a speed of 15 m/min with a 5-min break, and in the fourth week, four sessions per day at a speed of 15 m/min with a 5-min break. In the enriched environment group, the animals were kept in a plexiglass material larger than the standard cage (60×50×70 cm3). In these cages, devices such as ladders, hollow pipes, wooden blocks and plastic toys were placed. In Alzheimer's groups, rats were anesthetized by intraperitoneal injection of ketamine (80 mg/kg) and xylazine (20 mg/kg). Then, Alzheimer's Aβ was induced by intracerebroventricular injections (10μg/rat). Spatial memory was measured by Morris water maze, barin derived neurotrophic factor (BDNF) and Trk-B by western blot. In a pilot study in order to evaluate the spatial memory of rats, one week after beta-amyloid injection, all rats were divided into Alzheimer's and control groups. Rats were trained in the maze for four days and the mean percentage permanence in the platform area was recorded. The results of the independent t-test showed that there is a significant difference between the control group and Alzheimer's group (P=0.0152). Therefore,  One-way analysis of variance with Tukey's post-hoc test (P<0.05) were used to analyze the data.

BDNF increased in all groups significantly (P<0.001), and comparisons between groups were significant except for control vs sham (P=0.27) and Alzheimer's vs Aerobic Alzheimer's (P=0.20) groups. Trk-B increased in all groups and between-group comparisons were significant except for control vs sham (P=0.22), aerobic Alzheimer's vs Alzheimer's enriched environment (P=0.32). However, for spatial memory  only between-group comparisons for Alzheimer's vs control (P=0.02), and Alzheimer's vs Alzheimer's + enriched environment + aerobic training (P<0.001) groups were significant.

Based on the findings, it can be concluded that aerobic exercise and living in enriched environment can be effective on the spatial memory of elderly Alzheimer's rats through the increase of neurotrophic factors.

Multiple sclerosis (MS) is a chronic inflammatory, autoimmune, and multi-factorial disease that substantially reduces patients’ quality of life. Since physical activity may offer anti-inflammatory and axonal protection benefits to these patients, this study aimed to explore the impact of swimming training on the proteins critical for the myelination of hippocampal tissue in cuprizone-induced rat’s model of MS.

In the current investigation, 20 male Wistar rats with an average age of 12 weeks and the weight of 230 g were purchased and divided randomly into four groups: healthy control, MS control, healthy training, and MS training. The MS disease model was induced by administering food containing 0.5% cuprizone for 12 weeks. Upon confirming MS induction through the rotarod test, rats underwent a six-week swimming protocol. In the first week, they performed 10 min swimming without applying loads, and thereafter the duration of swimming was added by 5 min every week. In order to maintain the adaptations the duration of the swimming for the fifth and sixth weeks was constant and was kept at 30 min. At the end of the training protocol, memory and balance were assessed via shuttle box and rotarod tests. Subsequently, the hippocampal tissue was extracted, and analyzed for determining the proteolipid protein (PLP) and Myelin basic protein (MBP) protein levels by using western blot and the amount of Nerve growth factor (NGF) protein was measured by using the ELISA method. The data were analyzed using one-way ANOVA and post-hoc comparisons were made by using Tukey's test at a significance level of p<0.05.

The findings of the shuttle box and rotarod tests revealed that the MS group had impaired memory function and balance maintenance, but these improved significantly after swimming training (p<0.001). No significant difference was observed in the results of the shuttle box and rotarod tests between healthy training and healthy control groups (p>0.05). The results of the present study showed that NGF, PLP and MBP proteins in the patient control group were significantly lower compared to the healthy control group (p<0.05). Furthermore, data analyses showed that the amounts of these proteins increased significantly in the MS training group compared to the MS control group (p<0.05). The results showed that there was a significant difference for NGF and PLP proteins between healthy training group and healthy control group (p<0.05), whereas, no significant differences in MBP protein levels were found between the healthy training and healthy control groups (p>0.05).

Based on the current research findings, it can be concluded that swimming exercise has notable anti-inflammatory and neuroprotective effects through favourable molecular adaptations, and it can probably be considered as a safe, non-pharmacological and complication-free method to improve the symptoms in MS patients.

Children with spastic cerebral palsy have many problems in terms of movement and balance. The crooked structure of children with spastic cerebral palsy disturbs their balance function. Due to the constant muscle tension in these people, a permanent spasm is seen in their flexor muscles. Together with other features of the disease, this leads to limited mobility for those affected. Recently, training in water and on land have become very popular in both sports and rehabilitation, especially for people with limited mobility. The aim of this study was to investigate the effects of a functional training protocol combining water and land exercises on the balance and proprioception of the lower limbs of children with cerebral palsy and diplegia.

Thirty children with diplegia cerebral palsy were selected through available sampling and randomly divided into two equal groups of experimental (age, 9.33±1.63 years; height, 1.32±0.06 m; weight, 33.88±3.63 kg) and control group (age, 9.46±1.30 years; height, 1.30±0.05 m; weight, 32.04±3.52 kg). Subjects in the experimental group performed a training protocol on the ground including strength exercises, balance exercises and functional exercises and training protocol in water for 8 weeks and 4 sessions per week.  Before and after the training period static balance was evaluated by using the functional reaching test, the dynamic balance by using the time up and go test (TUG), and joint proprioceptive by measuring the angle of dorsiflexion. To statistically analyze the data, two-way repeated measures of ANOVA was used at a significant level of p≤0.05.

After 8 weeks of land and water combined training, there were significant improvements in the functional balance test (p<0.05) and ankle joint proprioception (p=0.001), as well as a significant reduction in time of TUG test(p=0.001). No significant within-group differences were observed in any of the variables in the control group (p˃ 0.05).

The results of the present study showed that performing combined strength, aquatic, functional and balance exercises improve balance, joint proprioception, movement and walking performance in children. In addition, combined water and land exercises can improve the balance and proprioception of children with cerebral palsy and diplegia, and as a result the movement problems and falls of these children could be reduced, which is important for improving the health and lifestyle of these children. Therefore, prescribing this exercise training modality is recommended to trainers and therapists.

Cardiovascular diseases are the most important cause of death among women. Hormonal changes around and after menopause can affect inflammatory factors such as interleukins and tumor necrosis factor alpha (TNF-α) as well as vascular function. The aim of this research was to determine the effect of a session of aerobic exercise with moderate intensity on interleukins 6 and 8, TNF-α, as well as vascular function (flow mediated dilation) in premenopausal and postmenopausal women.

In this semi-experimental study, 30 inactive women without any cardiovascular disease participated in the study voluntarily, which were allocated into two equal groups (n=15) of premenopausal women (age, 47.7±1.3 years) and postmenopausal women (age, 56.8±1.5 years). Participants in both groups performed a session of moderate intensity aerobic exercise included 30 min of running on a treadmill at 60-70% of heart rate reserve. Participants' blood samples were collected 30 min before and 30 min after the exercise and were analyzed to measure inflammatory factors (interleukin 6, interleukin 8 and TNF-α). Vascular function was evaluated by measuring flow mediated dilation at 15 min before and 15 min after aerobic exercise. Data were analyzed by using SPSS software and covariance test (P>0.05).

In response to a session of moderate intensity aerobic exercise, no significant difference was seen in interleukin 6 and 8 between two groups of premenopausal and postmenopausal women (P=0.432, P=0.097), but TNF-α decreased significantly in premenopausal whereas it it did not change in postmenopausal women (P=0.003). In addition, vascular dilation after a session of moderate intensity aerobic exercise was significantly (P=0.001) different between premenopausal and postmenopausal women , where, flow mediated dilation increased in premenopausal compared to postmenopausal women.

Based on the increased FMD and decreased TNF-α in premenopausal women, in general our findings show that following acute exercise factors associated with endothelial responsiveness are improved in premenopausal women while responses are decreased in postmenopausal womenHowever, lack of differences in interleukins 6 and 8 between premenopausal and postmenopausal women might indicate increased inflammation in premenopausal women, which is a reason for the onset or increases in disorders of endothelial function during menopause.