Francisco Tavares

Assessing a smartphone application to measure counter-movement jumps in recreational athletes

The use of counter-movement jumps as a measure of neuromuscular performance in athletes has become common in the sport setting. Accurate methods of measuring jump parameters are often expensive, difficult to transport and require expert knowledge. A new smartphone application (My Jump) claims to be a valid and reliable tool for assessing jump height but is yet to be evaluated by independent researchers. Sixty-one recreational athletes (30 male/31 female, mean ± SD; age: 20 ± 4 years) each performed three counter-movement jumps (totalling 183 jumps) on a force plate following a standardised warm-up. All jumps were recorded using an iPhone 6 s and analysed for jump height (m) and flight time (s) using the My Jump application. Jumps were compared between a force plate and My Jump for validity with inter-scorer reliability also assessed. Results show that My Jump is valid (mean bias = 0.9 cm, r = 0.96) and reliable (typical error of estimate = 1.4 cm) for assessing jump performance in recreational athletes using an iPhone 6 s with a 240 Hz high-speed camera. My Jump is a cost-effective and easy-to-use alternative for measuring vertical jump performance without the need for specialist equipment or expertise.

The validity and reliability of the GymAware linear position transducer for measuring counter-movement jump performance in female athletes

ABSTRACT The current study aimed to assess the validity and test–retest reliability of a linear position transducer when compared to a force plate through a counter-movement jump in female participants. Twenty-seven female recreational athletes (19 ± 2 years) performed three counter-movement jumps simultaneously using the linear position transducer and force plate for validity. In addition, 11 elite female athletes (23 ± 6 years) performed 3 counter-movement jumps with the linear position transducer on three separate days for test–retest reliability. Pearson correlations for jump height between the devices were at a high level (r = .90), with the linear position transducer overestimating jump height by 7.0 ± 2.8 cm. The reliability measured by the linear position transducer resulted in a mean intraclass correlation of .70 for jump height, .90 for peak velocity, and .91 for mean velocity. The linear position transducer was reliable for measuring counter-movement jumps in elite female athletes; however, caution should be taken for one-off jump measures as it may over-estimate jump height.

What wrist should you wear your actigraphy device on? Analysis of dominant vs. non-dominant wrist actigraphy for measuring sleep in healthy adults

OBJECTIVE Differences in sleep results due to the placement of actigraphy devices (non-dominant vs. dominant wrist) are yet to be determined. METHODS 65 nights of data from 13 adult participants was collected while participants wore two actigraphy devices, one on each wrist. Sleep indices including total sleep time (TST), total time in bed (TTB), sleep efficiency (SE%), sleep latency (SL), wake after sleep onset (WASO), sleep onset time (SOT) and wake time (WT) were assessed between the two devices. RESULTS There were no significant differences between devices for any of the measured sleep variables (p>0.05). SE%, SL and WASO resulted in high correlations between devices (0.89, 0.89 and 0.76, respectively), with all other sleep variables resulting in very high correlations (>0.90) between devices. CONCLUSIONS Based on our results, it does not seem critical which wrist the actigraphy device is worn on for measuring key sleep variables.

A Novel Method to Reduce the Impact of Countermovement Jump Monitoring In Professional Rugby Athletes

The countermovement jump (CMJ) is widely used to monitor jump performance, with greater interest being demonstrated in the propulsive phase. When landing from a CMJ, high forces are produced; this can increase the risk of injury. The present study aimed to test the validity and reliability of a countermovement jump to a box (CMBJ) where the forces associated with the landing are reduced. Eighteen professional rugby athletes (age=22 ± 2 years; body mass=104.2 ± 13.0 kg; height=187.4 ± 7.1 cm) performed 3 CMJ’s and 3 CMBJ’s on 3 different occasions. Net impulse (N.s), peak and mean absolute and relative force (N; N/kg) were obtained from a force plate system. The kinetic validity of the CMBJ was assessed by calculating the intraclass correlation coefficient, Pearson product-moment correlation, Cohen’s effect sizes and statistical hypothesis testing (paired t-test) in comparison to the CMJ. Intraday and interday reliability was assessed for each variable for both jumping conditions by calculating typical error, within subject coefficient of variation and intraclass correlation coefficient. Nonsignificant, trivial differences between the CMJ and CMBJ were observed for all jump variables. Low within-subject variability was observed between the CMJ and CMBJ for all variables. Interday and intraday variability showed good reliability and an almost perfect interday agreement score. In conclusion, net impulse, peak and mean force and relative peak and mean force obtained from a CMBJ are valid and reliable to monitor jump performance. This data demonstrates that the CMBJ is a viable alternative to monitor jump performance in athletes.

Adding omega-3 fatty acids to a protein-based supplement during pre-season training results in reduced muscle soreness and the better maintenance of explosive power in professional Rugby Union players

Abstract Evidence suggests that omega-3 fatty acid supplementation could reduce muscle soreness and maintain muscle function following eccentric exercise-induced muscle damage. The aim of this applied field study was to investigate the effectiveness of consuming a protein-based supplement containing 1546 mg of omega-3 polyunsaturated fatty acid (PUFA) (551 mg eicosapentaenoic acid (EPA) and 551 mg docosahexaenoic acid (DHA)) twice daily (FO) compared to a protein-based placebo (P) on muscle soreness, countermovement jump (CMJ) performance and psychological well-being in 20 professional Rugby Union players during 5 weeks of pre-season training. Players completed a 5-point-Likert soreness scale with 5 indicating “no soreness” and a questionnaire assessing fatigue, sleep, stress and mood each morning of training, plus they performed CMJ tests once or twice per week. Data were analysed using magnitude-based inferential statistics and are presented as percent beneficial/trivial/harmful. On day 35, there was a likely (% beneficial/trivial/harmful: 94/5/1) moderate (0.75, standardized mean difference (SMD)) beneficial effect of FO vs. P on the change in lower body muscle soreness compared with day 0 (FO: −3.8 ± 21.7%; P: −19.4 ± 11.2%). There was a likely (92/7/0) moderate (SMD: 0.60) beneficial effect of FO vs. P on CMJ performance (change from baseline to day 35, FO: +4.6 ± 5.9%; P: −3.4 ± 8.6%). From day 20, a moderate beneficial effect of FO on fatigue was observed. In terms of practical relevance, the moderate beneficial effect of adding fish oil to a protein-based supplement on muscle soreness translated into the better maintenance of explosive power in elite Rugby Union players during pre-season training.