Objectives: Research across a number of sports has identified a meaningful relationship between jump and sprint performance. The aim of this study was to investigate these relationships in first-class county cricketers. Design and Methods: Using a within-subjects repeated measures design, sixteen male cricketers (23.8 ± 3.7 years; body mass, 85.40 ± 9.37 kg; height, 185.34 ± 6.90 cm) performed countermovement jumps (CMJ), depth drop jumps (DDJ), and 20m sprints on three separate occasions. Results: Intraclass correlation coefficients (ICC) demonstrated a high within- (ICC ≥0.936; p≤0.001) and between- (ICC ≥0.807; p≤0.001) session reliability for all tests. Low smallest detectable differences (SDD), between-sessions, were observed for CMJ height (5.26%) and sprint times (2.72-5.80%). CMJ height demonstrated the strongest correlation with 20m sprint time (r = - 0.741, p = 0.006, power = 0.99), whereas DDJ reactive strength index demonstrated a moderate, although non-significant relationship with 20m sprint time (r = - 0.495, p>0.05, power = 0.70). Conclusion: The results demonstrate that athletes with a higher CMJ performance demonstrate quicker 20m sprint time. These findings also imply that the acceleration phase of a sprint may involve the slow stretch shortening cycle (SSC) to a greater extent than the fast SSC. Strength and conditioning coaches should, therefore, focus on enhancing these attributes through the development of maximal strength and enhancement of SSC ability through the use of appropriate plyometric tasks. Additionally, when identifying performance changes in CMJ height and 5, 10 and 20 m sprint times, changes of >5.26%, 5.80%, 2.98%, and 2.72%, respectively, signify a meaningful change.

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Objectives: The aim of this investigation was to assess the use of isometric strength testing as a determinant of sprint and change of direction performance in collegiate athletes. Design and Methods: Fourteen male collegiate athletes (mean ± SD; age = 21 ± 2.4 years; height =176 ± 9.0 cm; body mass = 72.8 ± 9.4 kg) participated in the study. Maximal strength was assessed via an isometric mid-thigh pull (IMTP). Isometric mid-thigh pull testing involved trials with peak force (IPF), maximum rate of force development (mRFD), impulse at 100 ms (IP 100) and 300 ms (IP 300) determined. Sprint and COD performance was measured using 5- and 20-m sprint performance, and a modified 505 test. Relationships between variables (IMTP, sprint and COD) were analysed using Pearson’s product – moment correlation. Results: Results suggest that IP 300 displayed the strongest relationships with 5- and 20-m sprint performance (r = −0.51 and −0.54, respectively). The results demonstrate maximum force production measures during IMTP correlate to sprint and COD ability in collegiate athletes. Conclusion: Isometric mid-thigh pull force-time measures are related to athletic performance (acceleration and sprinting), and thus are recommended for use in athlete monitoring and assessment.

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Objectives: To examine the relationships between performance during a backward overhead medicine ball (BOMB) throw and measures of countermovement jump (CMJ) performance among firefighter candidates. Design: Cross-sectional study. Methods: Forty-three firefighter candidates volunteered to participate in this study (age = 28.1 ± 7.1 yrs; height = 180.6 ± 6.0 cm; weight = 88.6 ± 12.3 kg). Bivariate Pearson correlations were used to examine the relationship between BOMB throw performance (m/kg) and measures of CMJ performance, including: peak CMJ height (cm/kg), peak CMJ force output (N/kg), peak CMJ velocity (cm/sec/kg), and peak CMJ power output (W/kg). Results: Statistically significant (p < 0.05) correlations were identified between: BOMB throw and peak CMJ height (r = 0.693, p < 0.001), peak CMJ force output (r = 0.349, p = 0.022), and peak CMJ velocity (r = 0.477, p < 0.001). Although significant relationships were identified between BOMB throw performance and several of CMJ performance measures, BOMB throw performance accounted for little of the total variance between these measures (R² = 7–48%). Furthermore, the relationship between BOMB throw and peak CMJ power output was not statistically significant (r = 0.292, p = 0.057). Conclusions: These results imply that the BOMB throw lacks criterion-reference validity to other standard field-based measures of power output. Thus, practitioners should exhibit caution when utilizing the BOMB throw to assess power out put among firefighter candidates. In addition, future research should examine the criterion-reference validity of other field-expedient assessments among firefighter candidates and active-duty firefighters.

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Objectives: The purpose of the study was to identify the level of accuracy in velocity measurement from a newly developed inertia sensor. Design and Methods: Five subjects performed two dumbbell exercises for total of four sets of ten repetitions with a light intensity. Velocity data were taken and considered for analysis from two devices; the inertia sensor, wirelessly connected via Bluetooth™ to a smartphone, and a motion capture system. Both data were taken at the sampling frequency of 200 Hz. Identical data sets of peak and average velocity were analyzed with Pearson product-moment zero-order correlation using total 200 data points (5 subjects, 4 sets, and 10 repetitions) on both exercises with p value of 0.05. Data were also analyzed using the same statistical procedure for left and right side to ensure the device-device data consistency. Results: Results showed high correlations in both exercises between the two velocity measurement methods (0.80 - 0.92), indicating the accuracy of the data from the inertia sensor is supportive. Left and right side correlations were also high from the inertia sensor (0.90 - 0.93) indicating that the data were similar with relatively identical movements between the two limbs. Conclusions: With the accuracy of the velocity measurement, this would potentially replace currently used, wired devices to accommodate user-friendly, accessible to more exercises to measure velocity.

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Objectives: This study investigated the performance enhancing effects of bicarbonate ingestion on soccer specific perfor mance. Design: A randomized and double-blinded study. Methods: Division III collegiate male soccer players (N = 7) participated in the study. Participants ingested either an alkaline treatment (.3 g/kg NaHCO3) or placebo (cornflower) 60 min prior to exercise on two separate testing sessions spaced 7 days apart. Distance to fatigue in the Yo-Yo Intermittent Recovery Test Level 2 was used to assess performance. Capillary blood was sampled pre-ingestion (PE), 60 min post ingestion (PI), exhaustion (EX), following 15 min of recovery (RC) and analyzed for lactate ([La^–]) and pH. Results: No significant ( p > .05) differences between conditions existed for performance. A significant ( p < .05) main effect was found for [La^–]: values at EX were significantly greater than PE, PI, and RC; however, no interaction ( p > .05) existed between time and condition. pH values at PE and PI were significantly greater than EX and RC in both conditions; however, pH was significantly ( p < .05) greater at PI than PE in treatment but not placebo. Conclusion: Bicarbonate ingestion increased extracellular buffering capacity but does not appear to enhance shuttle run per formance in Division III soccer players. mance.

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Objectives: This study investigated chronic changes in cell free DNA (cf-DNA) throughout a collegiate soccer season. The relationship between cf-DNA, C-reactive protein (CRP), creatine kinase (CK), testosterone (T), cortisol (C), testoster one-cortisol ratio (T:C), body mass and body composition were also examined. Design: Longitudinal study design with repeated measures and group comparisons. Methods: Twenty three NCAA Division I male soccer players were divided into two groups. Starters were placed in Group 1 (G1) and non-starters were placed in Group 2 (G2). cf-DNA, CRP, CK, T, C, T:C, body mass and body composition were taken three times, corresponding to pre-season, approximately mid-season and immediately after the concluding the season. Results: In G1, cf-DNA, CRP, CK, cf-DNA %∆, CRP %∆ and, CK %∆ were all statistically higher at T2 and T3 than T1. In G2, CRP %∆ was statistically higher at T2 than T1. In G2, cf-DNA %∆, CRP %∆ and CK %∆ were higher at T2 and T3 than T1. Conclusions: This suggests that cf-DNA may be a useful marker that can reflect accumulated soccer training and competi tive stressors.

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