Laura Guidetti

Heart rate and match analysis in pre-pubescent soccer players

The aim of this study was to compare match analysis (using video recordings) and the physiological load (heart rate measured every 5s, blood lactate measured after the warm-up, first half and second half) of six 11-year-old soccer players during official games of eleven-a-side on a regular-sized pitch (100×65m) and of seven-a-side on a smaller pitch (60×40m). In both games, heart rate exceeded 170 beats·min-1 84% of the time, while blood lactate ranged from 1.4 to 8.1 mmol·l-1 . No significant differences were recorded for the physiological parameters. For both matches, walking comprised 38% of total time, running 55%, inactivity 3% and jumping 3%. Although there were no significant differences between halves or matches, running for less than 10s was 10% more frequent in the seven-a-side game. In the seven-a-side game, there were significantly more passes and significantly fewer tackles, suggesting that seven-a-side matches played on smaller pitches may be more suitable for pre-pubescent soccer players.

A simple method for individual anaerobic threshold as predictor of max lactate steady state.

BACKGROUND The individual anaerobic threshold (IAT) is defined (18) as the highest metabolic rate where blood lactate (La) concentrations are maintained at a steady-state during prolonged exercise. Stegmann et al.s (18) method to detect IAT, using La-performance relationship during incremental graded exercise, is based on the assumption that La is in relatively steady state by the end of each 3-min stage of work rate. However, at the end of a 3-min stage, an La steady state (Lass) is not reached (13). PURPOSE The present study was designed to investigate whether the IAT should be determined by attributing La value to the antecedent stage (IATa) or to the same stage of its measurement (IATm), then to verify whether this IAT would be a valid indicator of the max Lass during prolonged exercise. METHODS Forty-one athletes (21 male and 20 female), regularly involved in different physical training, performed three exercise tests on treadmill. The first one was a 3-min stage incremental test to detect the IATa and IATm. The other two tests were 30-min prolonged tests at the IATa and IATm workload. Lass were present in IATa intensity (about 4.0 mmol x L(-1)) both in male and female athletes, whereas at IATm intensity a Lass was not present and a premature break-off occurred in some cases. DISCUSSION This protocol can be useful for practical use because: 1) the method of choosing the anaerobic threshold is easy to apply; 2) it does not require to reach the maximal effort; and 3) although in some cases the IATa could probably underestimate the workload of max Lass, the IATa can be regarded as guideline to define the intensity of endurance training.

Psychophysiological Responses to Self-Paced Treadmill and Overground Exercise

UNLABELLED Speculation exists that a positive affective response experienced during exercise may play an important role in predicting exercise adherence. Previous studies using self-paced exercise protocols have been associated with health benefits and pleasant experiences. However, all of these studies were conducted in laboratories, and consequently, the external validity of the findings may be questionable. PURPOSE To determine whether environmental settings (treadmill vs overground) differentially influence physiological, perceptual, and affective responses to exercise at a self-selected pace. METHODS Thirty-four individuals (17 men and 17 women) between 18 and 30 yr volunteered to participate in this study. During the orientation session, individuals underwent an initial screening, anthropometric measurements, and familiarization with the experimental procedures. Next, subjects underwent a maximal treadmill test. In the two experimental trials, participants performed 20-min bouts of treadmill and overground walking at a self-selected pace, which were completed in a counterbalanced order. At least 48 h separated experimental trials. RESULTS Using repeated-measures ANOVA, overground walking speed was significantly faster than treadmill walking speed (P < 0.01) during the 20-min bout of self-paced exercise. However, exercise intensity (%VO2R and %HRR) and perceived exertion during the session of overground walking were significantly lower (P < 0.05) when compared with those during the treadmill session. In addition, affective valence was more positive during the session of overground walking than during the treadmill session (P < 0.01). CONCLUSIONS These data extend previous findings by showing that environmental setting influences physiological, perceptual, and affective responses during exercise at a self-selected pace. Self-paced exercise performed over ground resulted in lower perceptual and more positive affective responses.

EMG Patterns During Running: Intra- and Inter-individual Variability

Rectified surface electromyographic (EMG) patterns of five healthy, young, physically-fit subjects running at 4.2 m s(-1) on a treadmill were recorded with the objective of defining a normal profile of EMG activity for running gait. This knowledge is important in understanding how the central nervous system (CNS) controls simple running tasks under normal conditions. The EMG signals from seven muscles (erector spinae, rectus femoris, vastus medialis, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius) were recorded, together with footswitch signals. The intra- and inter-individual variability of each muscles EMG profile and peak times were analysed. Interindividual EMG peak time values were analysed to define the timing of the activity of the muscles studied relative to the stride cycle and its subphases. For each muscle, little variation was found within individuals in EMG profile and peak time across trials, but differences between subjects were significant (P < 0.01). EMG peak time analysis showed two distinct activation sequences of different muscles: the first at stance phase and the second at terminal swing. In conclusion, in spite of a significant variability among subjects in EMG profile and peak time values for each muscle, the EMG peak timing analysis showed a sequence of activation at stance phase, no EMG peak activity during the first double swing and another sequence of activation during terminal swing. These findings are evidence of a neuromuscular control strategy common to all subjects.

Cortisol, dehydroepiandrosterone sulphate and dehydroepiandrosterone sulphate/cortisol ratio responses to physical stress in males are influenced by pubertal development

To evaluate the influence of chronological age and pubertal development on the hypothalamus-pituitary-adrenal (HPA) axis response to stress, we studied the possible correlations between male pubertal characteristics and salivary cortisol (C), DHEAS and the DHEAS/ C ratio before (pre-stress) and after acute exercise-stress in young male volunteers (no. 87; 13.3±2.1 yr). In our overall study population, the mean pre-stress salivary C and DHEAS concentrations, significantly increased after exercise-related stress, whereas the DHEAS/C ratio significantly decreased. Pre-stress salivary C was positively correlated with chronological age, and after-stress salivary C concentration variations were negatively correlated with pubertal stage, mean testis volume and pre-stress salivary DHEAS. Furthermore, salivary DHEAS concentrations and the DHEAS/C ratio, before and after exercise stress, were positively correlated with chronological age, pubertal stage, pre-stress salivary testosterone (T), testis volume and body mass index (BMI). In contrast with late pubertal stages (P4, P5), young individuals at early stages of puberty (P1 to P3) showed higher C increase and lower DHEAS/C ratio after exercise-related stress. In conclusion, since C is also a mediator of stress-related negative effects on health and the DHEAS/C ratio has been hypothesized as an index for the degree to which an individual is buffered against the negative effects of stress, these data might suggest potentially increased stress-related risks at early stages of male puberty.

Acetylsalicylic acid inhibits the pituitary response to exercise-related stress in humans.

PURPOSE Prostaglandins (PGs) modulate the activity of the hypothalamus-pituitary axis, and pituitary hormones are largely involved in the physiological responses to exercise. The purpose of this study was to analyze the effects of acetylsalicylic acid (ASA), an inhibitor of PGs synthesis, in the pituitary responses to physical stress in humans. METHODS Adrenocorticotropin (ACTH), beta-endorphin, cortisol, growth hormone (GH), and prolactin (PRL) responses to exercise were evaluated after administration of either placebo or ASA. Blood samples for hormone evaluations before (-30, -15, and 0 pre) and after (0 post, +15, +30, +45, +60, and +90 min) a 30-min treadmill exercise (75% of .VO(2max)) were taken from 12 male athletes during two exercise trials. One tablet of ASA (800 mg), or placebo, was administered two times daily for 3 d before and on the morning of each exercise-test. RESULTS The results clearly show that, compared with placebo, ASA ingestion significantly blunted the increased serum ACTH, beta-endorphin, cortisol, and GH levels before exercise (anticipatory response) and was associated with reduced cortisol concentrations after exercise. Furthermore, although no differences in the GH response to exercise were shown, a significantly reduced total PRL response to stress condition was observed after ASA. CONCLUSION ASA influences ACTH, beta-endorphin, cortisol, GH, and PRL responses to exercise-related stress in humans (preexercise activation/exercise-linked response). Even though it is not possible to exclude direct action for ASA, our data indirectly confirm a role of PGs in these responses. We have to further evaluate the nature of the preexercise endocrine activation and, because of the large use of anti-inflammatory drugs in athletes, whether the interaction between ASA and hormones might positively or negatively influence health status, performance, and/or recovery.

The Type 5 Phosphodiesterase Inhibitor Tadalafil Influences Salivary Cortisol, Testosterone, and Dehydroepiandrosterone Sulphate Responses to Maximal Exercise in Healthy Men

CONTEXT Physical exercise-related stress activates hypothalamus-pituitary-adrenal (HPA) axis; nitric oxide is one of the mediators of the HPA axis response to stress, and phosphodiesterase type 5 inhibitors influences nitric oxide-linked biological activities. OBJECTIVE The objective of the study was to investigate whether a single oral long half-life phosphodiesterase type 5 inhibitor (tadalafil) administration influences the HPA axis response to exercise-related stress. DESIGN This was a double-blind, cross-over trial. PARTICIPANTS Participants included nine healthy male athletes. INTERVENTIONS All subjects performed a maximal exercise test in normoxia, after which they received a single oral administration of tadalafil or placebo. Then after a 2-wk washout period, they were crossed over and repeated the exercise test. Each subject was his own control. Salivary collections, for steroid evaluations [cortisol, dehydroepiandrosterone sulphate (DHEAS), testosterone] and respective ratio calculation (DHEAS to cortisol, testosterone to cortisol, testosterone to DHEAS), were performed before each exercise (Pre-Ex), immediately after (Post-Ex), and at 30 min during recovery. RESULTS As expected, mean salivary cortisol concentration increased immediately after exercise after both tadalafil and placebo (P = 0.014 and P =0.036 vs. Pre-Ex, respectively); however, the cortisol increase was significantly higher after tadalafil administration (P = 0.034 vs. placebo). Furthermore, an increased salivary testosterone after exercise was observed only after tadalafil administration (P = 0.029 vs. Pre-Ex). No effects of either exercise and/or tadalafil administration on salivary DHEAS concentrations were observed. DHEAS to cortisol and testosterone to cortisol ratios significantly decreased after exercise after tadalafil administration (P = 0.037, and P = 0.02 vs. placebo, respectively). CONCLUSION Tadalafil administration amplified the salivary cortisol and testosterone responses to a maximal exercise-related stress in healthy trained humans.

Acute amino acids supplementation enhances pituitary responsiveness in athletes.

PURPOSE The purpose of this study was to determine the effect of a mixture of amino acids on pituitary responsiveness to a stimulation test (GnRH + CRH) in athletes. METHODS In a double blinded counterbalanced experimental protocol, 10 moderately trained male athletes performed the pituitary stimulation test 60 min after a single oral administration of a placebo (P1-AS) or an amino acid mixture solution (AS) (L-arginine hydrochloride 100 mg x kg(-1) + L-ornithine hydrochloride 80 mg x kg(-1) + L-branched chain amino acids 140 mg x kg(-1): 50% L-leucine, 25% L-isoleucine, 25% L-valine) on two different occasions. Plasma ACTH, LH, FSH, GH, and cortisol were evaluated before (-60, -30, 0 min) and after (+15, +30, +45, +60, +90 min) the stimulation test. RESULTS The ACTH, LH and FSH response to CRH + GnRH was significantly higher in AS group both as absolute values and area under curve (AUC) values than in P1-AS group. Pre-test and post-test cortisol AUC levels were significantly higher in P1-AS group although a higher percent increase in post-test cortisol was found in AS group. The total GH-AUC was higher in AS group and, as expected, the absolute GH concentrations at different time points were not influenced by CRH + GnRH administration. CONCLUSION The amino acid mixture used enhanced the ACTH, LH, and FSH response to CRH + GnRH.

Intra- and Interday Reliability of Spine Rasterstereography

To determine intra- and interday reliability of spine rasterstereographic system Formetric 4D with and without reflective markers. Twenty-six healthy volunteers (M group) had two markers placed in correspondence of vertebra prominens and intergluteal cleft, and 24 volunteers (NM group) were assessed without markers. All participants were analyzed two times in the same day and one time on a separate day. Trunk length, kyphotic angle, lordotic angle, pelvic inclination, kyphotic and lordotic apex, right and left lateral deviation, flèche cervicale and lombaire, trunk imbalance, pelvic tilt, inflection point, rotation correction, right and left surface rotation, pelvic torsion, and trunk torsion were measured. Intraclass correlation coefficient (ICC) and Cronbach Alpha (Cα) were calculated. In M group, for intra-, interday, and overall evaluations, the higher reliability coefficients were 0.971, 0.963, and 0.958 (ICC) and 0.987, 0.983, and 0.985 (Cα) for trunk length, kyphotic angle, and lordotic apex, respectively; while in NM group, they were 0.978, 0.982, and 0.972 and 0.989, 0.991, and 0.991 for trunk length. In M group, the lower values were 0.598, 0.515, and 0.534 (ICC) and 0.742, 0.682, and 0.784 (Cα) for trunk and pelvic torsion and in NM group 0.561, 0.537, and 0.461 and 0.731, 0.695, and 0.729 for left lateral deviation. The reliability of most parameters was excellent.

Effects of Aging on Visual Attentional Focusing

Background: Visual attentional performance is affected by aging, but there are methodological barriers to the understanding of this phenomenon that are due, above all, to the concomitant deterioration of sensory or central factors such as visual acuity and information processing speed. Objective: The aim of the present study was to verify the effects of aging on visual attentional focusing by analyzing the space- and object-based components as well as the exogenous and endogenous dimensions of the attentional allocation. Methods: Focusing of visual attention was investigated in 14 youngsters, 14 younger adults and 14 older adults (age ranges 12–15, 24–38 and 60–75 years, respectively). In two discrimination reaction time (RT) experiments, attention was cued by means of spatial cues of different size followed by compound stimuli at a shorter (150 ms) and a longer (500 ms) stimulus-onset asynchrony (SOA). The compound stimuli contained a predefined target letter at a local or global level. Results: Older adults showed generally slower RTs and higher rates of delayed responses than younger individuals and reduced discrimination speed of local objects at 150-ms SOA, particularly when attention was invalidly cued to focus at a larger spatial scale. Conclusions: This pattern of results suggests that aging causes a dysfunction of the space-based and the object-based components of the attentional ‘zooming in’. Such information may be of practical relevance for developing attentional training programs for older adults.