Effects of exercise induced muscle damage on cardiovascular responses to isometric muscle contractions and post-exercise circulatory occlusion.

PURPOSE: The aim of the present study was to investigate whether exercise-induced muscle damage (EIMD) influences cardiovascular responses to isometric exercise and post-exercise circulatory occlusion (PECO). We hypothesized that EIMD would increase muscle afferent sensitivity and, accordingly, increase blood pressure responses to exercise and PECO. METHODS: Eleven male and nine female participants performed unilateral isometric knee extension at 30% of maximal voluntary contraction (MVC) for 3-min. A thigh cuff was rapidly inflated to 250 mmHg for two min PECO, followed by 3 min recovery. Heart rate and blood pressure were monitored beat-by-beat, with stroke volume and cardiac output estimated from the Modelflow algorithm. Measurements were taken before and 48 h after completing eccentric knee-extension contractions to induce muscle damage (EIMD). RESULTS: EIMD caused 21% decrease in MVC (baseline: 634.6 ± 229.3 N, 48 h: 504.0 ± 160 N), and a 17-fold increase in perceived soreness using a visual-analogue scale (0-100 mm; VASSQ) (both p < 0.001). CV responses to exercise and PECO were not different between pre and post EIMD. However, mean arterial pressure (MAP) was higher during the recovery phase after EIMD (p < 0.05). Significant associations were found between increases in MAP during exercise and VASSQ, Rate of Perceived Exertion (RPE) and Pain after EIMD only (all p < 0.05). CONCLUSION: The MAP correlations with muscle soreness, RPE and Pain during contractions of damaged muscles suggests that higher afferent activity was associated with higher MAP responses to exercise.

Validation and utilisation of a digital version of the survey instrument for natural history, Aetiology and Prevalence of Patellofemoral pain studies (eSNAPPS).

OBJECTIVE: This study validated the newly adapted electronic SNAPPS (eSNAPPS) against the original paper SNAPPS. Subsequently, the study estimated the prevalence of PFP in running participants and spectators attending three mass-participant running events in the United Kingdom by using the eSNAPPS tool. DESIGN: This study had two parts. Firstly, a validation of the original paper version of the SNAPPS tool. Secondly, if validation was achieved, eSNAPPS was used in a prevalence study. PARTICIPANTS: A convenience sample of running participants and spectators aged 18-40 years attending the mass participation running events. MAIN OUTCOME MEASURE: The 12-month prevalence of PFP. RESULTS: eSNAPPS was valid in identifying those with PFP (ICC 0.99 for Overall agreement, p < 0.0001). In the prevalence study, a total of 1080 running participants and spectators completed the eSNAPPS. The overall prevalence of PFP was 17.4% (95%CI: 15.2%, 19.8%); 20.5% of males (16.5, 24.9) and 15.7% of females (13.1, 18.7) had PFP. Prevalence was 17.4% (15.2, 19.8) in spectators and 16.7% in running participants (14.5, 19.0). CONCLUSION: The overall PFP prevalence in this study was slightly smaller than those previously reported in the literature. Findings also show that there were similar prevalence estimates in spectators and running participants.

Effect of mouthguard design on retention and potential issues arising with usability in sport.

BACKGROUND/AIMS: Mouthguard retention could potentially increase an athlete's motivation to wear the device, due to potential improvements in physical comfort. The aim of this study was to examine the retentive properties of selected customised mouthguard designs, during normal conditions (dry) and within the presence of artificial saliva (wet). Additionally, the correlation between thickness and retention was investigated. MATERIAL AND METHODS: Six different custom mouthguard designs (MG1-MG6) reported in previous studies, were pressure-formed with 2 and 4 mm blanks accordingly. Thickness was measured 10 times at seven anatomical points and the mean (±SD) was recorded. A novel rig was fabricated to connect the mouthguards to a Hounsfield H10KS Tensometer, which was used to fully displace each device from the model at a constant rate of 50 mm/min. The test was repeated under both dry and wet conditions. RESULTS: Retention forces recorded at the anterior region demonstrated higher measurements under wet conditions than dry (P < 0.001). The total retention of the mouthguards was influenced by alterations in their design. Trend analysis indicated that 64% of MG retention could be explained by their thickness under dry conditions and 55% when wet. CONCLUSIONS: Design and thickness of mouthguards are key factors in retention. Mouthguard fabrication techniques should be considered in order to minimize dislodgment of the devices as well as potentially increasing the wearability of mouthguards during sport.

Postprandial triacylglycerol in adolescent boys: a case for moderate exercise.

PURPOSE: To compare the effects of 60-min bouts of intermittent moderate and vigorous exercise on postprandial plasma triacylglycerol (TAG) metabolism in eight healthy adolescent boys (mean +/- SD age: 13 +/- 0.3 yr). METHODS: Participants completed three conditions in a counterbalanced order. On day 1, they either rested for 110 min (CON), completed 6 x 10-min blocks of intermittent treadmill exercise at 53% peak V O2 (MOD), or 6 x 10-min blocks at 75% peak V O2 (VIG). On day 2 after a 12-h fast, a capillary blood sample was taken for [TAG] and [glucose] (mmol.L) and then a high-fat milkshake was consumed (1.50 g.kg fat, 1.22 g.kg CHO, and 0.22 g.kg protein; 80 kJ.kg). Further blood samples were taken every hour for a 6-h postprandial rest period for [TAG] and [glucose]. RESULTS: Estimated energy expenditure was 45% higher in VIG than in MOD (95% confidence interval [CI] 23-72%). Fasting [TAG] and [glucose] did not differ between the conditions. Average [TAG] for the postprandial period was lower by 24% in MOD (95% CI -47% to 9%, P = 0.06) and by 21% in VIG (95% CI -42% to 8%, P = 0.08) than CON, with no meaningful difference (4%; 95% CI -27% to 48%, P = 0.50) between MOD and VIG. The total area under the [TAG] versus time curve (mmol.L 6 h) was lower by 24% in MOD (95% CI -42% to 0%, P = 0.05) and by 20% in VIG (95% CI -37% to 0%, P = 0.07) than CON. MOD and VIG were not different from each other (4%; 95% CI -18% to 32%, P = 0.54). CONCLUSION: Both 60 min of moderate and vigorous intermittent exercises reduced postprandial [TAG]. However, the extra energy expended in the vigorous condition did not produce a dose-related reduction compared with the moderate-intensity condition.