Meta-analysis prediction intervals are under reported in sport and exercise medicine.

AIM: Prediction intervals are a useful measure of uncertainty for meta-analyses that capture the likely effect size of a new (similar) study based on the included studies. In comparison, confidence intervals reflect the uncertainty around the point estimate but provide an incomplete summary of the underlying heterogeneity in the meta-analysis. This study aimed to estimate (i) the proportion of meta-analysis studies that report a prediction interval in sports medicine; and (ii) the proportion of studies with a discrepancy between the reported confidence interval and a calculated prediction interval. METHODS: We screened, at random, 1500 meta-analysis studies published between 2012 and 2022 in highly ranked sports medicine and medical journals. Articles that used a random effect meta-analysis model were included in the study. We randomly selected one meta-analysis from each article to extract data from, which included the number of estimates, the pooled effect, and the confidence and prediction interval. RESULTS: Of the 1500 articles screened, 866 (514 from sports medicine) used a random effect model. The probability of a prediction interval being reported in sports medicine was 1.7% (95% CI = 0.9%, 3.3%). In medicine the probability was 3.9% (95% CI = 2.4%, 6.6%). A prediction interval was able to be calculated for 220 sports medicine studies. For 60% of these studies, there was a discrepancy in study findings between the reported confidence interval and the calculated prediction interval. Prediction intervals were 3.4 times wider than confidence intervals. CONCLUSION: Very few meta-analyses report prediction intervals and hence are prone to missing the impact of between-study heterogeneity on the overall conclusions. The widespread misinterpretation of random effect meta-analyses could mean that potentially harmful treatments, or those lacking a sufficient evidence base, are being used in practice. Authors, reviewers, and editors should be aware of the importance of prediction intervals.

Short-term heat acclimation preserves knee extensor torque but does not improve 20 km self-paced cycling performance in the heat.

PURPOSE: This study investigated the effect of 5 days of heat acclimation training on neuromuscular function, intestinal damage, and 20 km cycling (20TT) performance in the heat. METHODS: Eight recreationally trained males completed two 5-day training blocks (cycling 60 min day-1 at 50% peak power output) in a counter-balanced, cross-over design, with a 20TT completed before and after each block. Training was conducted in hot (HA: 34.9 ± 0.7 °C, 53 ± 4% relative humidity) or temperate (CON: 22.2 ± 2.6 °C, 65 ± 8% relative humidity) environment. All 20TTs were completed in the heat (35.1 ± 0.5 °C, 51 ± 4% relative humidity). Neuromuscular assessment of knee extensors (5 × 5 s maximum voluntary contraction; MVC) was completed before and after each 20TT and on the first and last days of each training block. RESULTS: MVC torque was statistically higher after 5 days of HA training compared to CON (mean difference = 14 N m [95% confidence interval; 6, 23]; p < 0.001; d = 0.77). However, 20TT performance after 5 days of HA training was not statistically different to CON, with a between-conditions mean difference in the completion time of 68 s [95% confidence interval; - 9, 145] (p = 0.076; d = 0.35). CONCLUSION: Short-term heat acclimation training may increase knee extensor strength without changes in central fatigue or intestinal damage. Nevertheless, it is insufficient to improve 20 km self-paced cycling performance in the heat compared to workload-matched training in a temperate environment. These data suggest that recreationally trained athletes gain no worthwhile performance advantage from short-term heat-training before competing in the heat.

Does lower extremity alignment during normal stance predict lower limb kinematics and kinetics during drop landings?

BACKGROUND: Static lower extremity alignment (LEA) during normal stance has been used clinically as a tool to determine the presence of known anterior cruciate ligament (ACL) risk factors during dynamic tasks. Previous work investigating the relationship between static LEA during normal stance and risk factors for ACL injury is limited by the use of imprecise methods or because it focuses on knee valgus only and no other potentially important variables. The aim of this investigation was to determine the relationships between static LEA and the corresponding LEA during drop landings. METHODS: Forty-one female athletes were recruited for the study (age: 19.8 ± 2.5 years, height: 1.73 ± 0.06 m, mass: 64.03 ± 6.66 kg). Lower limb kinematic data were collected using a 10 camera infrared motion capture system (500 Hz) with retro-reflective markers placed over key anatomical landmarks. This system was linked to two force platforms (1000 Hz) with subsequent three-dimensional kinematic and kinetic data developed using standard software (Visual3D). Following an appropriate warm-up, data collection involved participants standing with their arms partially abducted to record static LEA. This was following by a series of drop landings from a 0.4 m box onto the force platforms. Maximum LEA data during drop landings were then compared with static LEA. RESULTS: Analyses showed that in comparison to static stance, during landings the anterior tilt of the pelvis decreased while hip abduction and knee internal rotation increased. At best, static LEA variables were moderately correlated (r = -0.51 to 0.58) with peak values measured during drop landings. Additionally, regression analysis did not yield any significant predictors of any key peak hip or knee variables measured during drop landings (p = 0.15 to 0.89). CONCLUSION: When combined, the poor relationships observed between kinematics during static LEA and LEA during drop landings calls into question the practice of using static measures to predict LEA during even simple landing tasks. These findings suggest static assessments of LEA may have minimal value as an ACL injury screening tool.

Effect of concentric and eccentric hamstring training on sprint recovery, strength and muscle architecture in inexperienced athletes.

OBJECTIVES: To investigate whether five-weeks of concentric (CON) or eccentric (ECC) hamstring strength training have different effects on recovery from sprint running, eccentric strength and architecture of the biceps femoris long head (BFLH). DESIGN: Cohort study. METHODS: Thirty males (age, 22.8±4.1y; height, 180.1±6.4cm; weight, 85.2±14.6kg) were allocated into either a CON or ECC group, both performing nine sessions of resistance training. Prior to and immediately after the five-week intervention, each participant's BFLH fascicle length (FL), pennation angle (PA), muscle thickness (MT), peak isometric KF torque and Nordic eccentric strength were assessed. Post-intervention, participants performed two timed sprint sessions (10×80m) 48h apart. Blood samples and passive KF torques were collected before, immediately after, 24h and 48h after the first sprint session. RESULTS: After five-weeks of strength-training, fascicles lengthened in the ECC (p<0.001; d=2.0) and shortened in the CON group (p<0.001; d=0.92), while PA decreased for the ECC (p=0.001; d=0.52) and increased in the CON group (p<0.001; d=1.69). Nordic eccentric strength improved in both ECC (p<0.001; d=1.49) and CON (p<0.001; d=0.95) groups. No between-group differences were observed in peak isometric strength (p=0.480), passive KF torques (p=0.807), sprint performance decrements between sprint sessions (p=0.317) and creatine kinase (p=0.818). CONCLUSIONS: Despite inducing significant differences in BFLH muscle architecture, there were no significant between group differences in sprint performance decrements across two sprint sessions.