Validity of the 30-15 Intermittent Fitness Test in Subelite Female Athletes.

Bruce, LM and Moule, SJ. Validity of the 30-15 intermittent fitness test in subelite female athletes. J Strength Cond Res 31(11): 3077-3082, 2017-The purpose of this study was to assess the suitability of the 30-15 Intermittent Fitness Test (IFT) as a test in netball using female athletes. Twenty-six female subelite netballers (mean age = 19.7 ± 4.6 years, mean height = 176.0 ± 6.1 cm, mean body mass = 69.7 ± 9.3 kg) completed the yo-yo intermittent recovery test level 1 (yo-yo IRT1) and the 30-15 IFT. Participants performed both assessments 1 week apart before the intervention and both tests 1 week apart after the training intervention (for a total of 4 testing sessions). A 6-week training intervention occurred between the test occasions. Pearson's correlations revealed significant very strong relationships between the 30-15 IFT and yo-yo IRT on both test occasions (test occasion 1: r = 0.71, p = 0.003 [95% confidence interval {CI} 0.35-0.89], magnitude of effect, most likely; test occasion 2: r = 0.72, p = 0.001 [95% CI: 0.42-0.88], magnitude of effect, most likely). Repeated-measures analysis of variances examining the effect of position on performance changes revealed main effects for test occasion and a position × test occasion interaction for both the 30-15 IFT and the yo-yo IRT1 (30-15 IFT: test occasion [F(1,14) = 28.68, p = 0.001, ηp = 0.67], position × test occasion interaction [F(2,14) = 9.38, p = 0.003, ηp = 0.57]; yo-yo IRT1: test occasion [F(1,15) = 11.72, p = 0.004, ηp = 0.44], position × test occasion interaction [F(2,15) = 9.96, p = 0.002, ηp = 0.57]). Results show that the 30-15 IFT is a suitable test for female netballers as it was able to detect improvements in performance after a training intervention, in addition to having a very strong significant relationship with the yo-yo IRT1.

Impact of isolated germline JAK2V617I mutation on human hematopoiesis.

The association between somatic JAK2 mutation and myeloproliferative neoplasms (MPNs) is now well established. However, because JAK2 mutations are associated with heterogeneous clinical phenotypes and often occur as secondary genetic events, some aspects of JAK2 mutation biology remain to be understood. We recently described a germline JAK2V617I mutation in a family with hereditary thrombocytosis and herein characterize the hematopoietic and signaling impact of JAK2V617I. Through targeted sequencing of MPN-associated mutations, exome sequencing, and clonality analysis, we demonstrate that JAK2V617I is likely to be the sole driver mutation in JAK2V617I-positive individuals with thrombocytosis. Phenotypic hematopoietic stem cells (HSCs) were increased in the blood and bone marrow of JAK2V617I-positive individuals and were sustained at higher levels than controls after xenotransplantation. In signaling and transcriptional assays, JAK2V617I demonstrated more activity than wild-type JAK2 but substantially less than JAK2V617F. After cytokine stimulation, JAK2V617I resulted in markedly increased downstream signaling compared with wild-type JAK2 and comparable with JAK2V617F. These findings demonstrate that JAK2V617I induces sufficient cytokine hyperresponsiveness in the absence of other molecular events to induce a homogeneous MPN-like phenotype. We also provide evidence that the JAK2V617I mutation may expand the HSC pool, providing insights into both JAK2 mutation biology and MPN disease pathogenesis.