Sprinting with bilateral transtibial running-specific prostheses versus biological limbs - are they comparable? Comments on Beck et al. (2022).

Since publication of this paper (Royal Society open science, 2022. 9(1): p. 211799), the authors have published a correction clarifying that the paper presents a case study that '… did not meet the definition for research with regard to human subjects'. The data are incorrectly referred to as experimental because the study has no experimental control. Furthermore, the paper has been presented previously but the version presented here selectively omits several analyses, posing a significant risk of bias. Of the prosthetic-related disadvantages identified by the authors, the most substantive was a 40% increase in time to 20 m (59.5 s.d. below the mean for NA sprinters). However the analysis was incomplete: acceleration modelling for NA sprinters continued up to 98% of maximum velocity, while Fastest BA was truncated at approximately 80%. We extrapolated the model, revealing the duration of maximum acceleration for Fastest BA is approximately 100% longer than NA sprinters. Important differences in Fastest BA contact lengths (0.10-0.15 m) were also identified. We posit that together, these large and important differences in sprint biomechanics and their likely physiological consequences suggest that running with and without prosthetics are so different that, although running times may be similar, the precautionary principle should apply and, in the interests of athletic competition integrity, runners with and without prosthetics should continue to compete separately.

A novel method to guide classification of para swimmers with limb deficiency.

The International Paralympic Committee has directed International Federations that govern Para sports to develop evidence-based classification systems. This study defined the impact of limb deficiency impairment on 100 m freestyle performance to guide an evidence-based classification system in Para Swimming, which will be implemented following the 2020 Tokyo Paralympic games. Impairment data and competitive race performances of 90 international swimmers with limb deficiency were collected. Ensemble partial least squares regression established the relationship between relative limb length measures and competitive 100 m freestyle performance. The model explained 80% of the variance in 100 m freestyle performance and found hand length and forearm length to be the most important predictors of performance. Based on the results of this model, Para swimmers were clustered into four-, five-, six-, and seven-class structures using nonparametric kernel density estimations. The validity of these classification structures, and effectiveness against the current classification system, were examined by establishing within-class variations in 100 m freestyle performance and differences between adjacent classes. The derived classification structures were found to be more effective than current classification based on these criteria. This study provides a novel method that can be used to improve the objectivity and transparency of decision-making in Para sport classification. Expert consensus from experienced coaches, Para swimmers, classifiers, and sport science and medicine personnel will benefit the translation of these findings into a revised classification system that is accepted by the Para swimming community.

The impact of strength level on adaptations to combined weightlifting, plyometric, and ballistic training.

The purpose of this investigation was to determine whether the magnitude of adaptation to integrated ballistic training is influenced by initial strength level. Such information is needed to inform resistance training guidelines for both higher- and lower-level athlete populations. To this end, two groups of distinctly different strength levels (stronger: one-repetition-maximum (1RM) squat = 2.01 ± 0.15 kg·BM-1 ; weaker: 1.20 ± 0.20 kg·BM-1 ) completed 10 weeks of resistance training incorporating weightlifting derivatives, plyometric actions, and ballistic exercises. Testing occurred at pre-, mid-, and post-training. Measures included variables derived from the incremental-load jump squat and the 1RM squat, alongside muscle activity (electromyography), and jump mechanics (force-time comparisons throughout the entire movement). The primary outcome variable was peak velocity derived from the unloaded jump squat. It was revealed that the stronger group displayed a greater (P = .05) change in peak velocity at mid-test (baseline: 2.65 ± 0.10 m/s, mid-test: 2.80 ± 0.17 m/s) but not post-test (2.85 ± 0.18 m/s) when compared to the weaker participants (baseline 2.43 ± 0.09, mid-test. 2.47 ± 0.11, post-test: 2.61 ± 0.10 m/s). Different changes occurred between groups in the force-velocity relationship (P = .001-.04) and jump mechanics (P ≤ .05), while only the stronger group displayed increases in muscle activation (P = .05). In conclusion, the magnitude of improvement in peak velocity was significantly influenced by pre-existing strength level in the early stage of training. Changes in the mechanisms underpinning performance were less distinct.

Assessing muscle strength for the purpose of classification in Paralympic sport: A review and recommendations.

OBJECTIVES: Classification in Paralympic Sport aims to minimize the impact of 10 eligible types of impairment on the outcome of competition. Methods for assessing the extent to which a given body structure or function has been impaired are required, but are challenging because it is not possible to directly measure an absence or loss. Rather, impairment must be inferred by measurement of extant body structures or functions. METHODS: This manuscript reviews the literature concerning the assessment of strength with the aim of identifying and describing the most appropriate method for inferring strength impairment in para-athletes. RESULTS: It is posited that the most appropriate voluntary strength assessment method for inferring strength loss in para-athletes will be multi-joint, isometric tests performed at joint angles that facilitate maximum force production. CONCLUSIONS: Evidence suggests such methods will permit development of tests that are specific to a variety of para-sports and which are reliable, ratio-scaled, and resistant to training. Future research should: develop sport-specific tests which are suitable for assessment of athletes with strength impairments of variable severity and distribution; and scientifically evaluate the extent to which such tests permit strength impairment to be validly inferred, including specific evaluation of the extent to which such measures respond to athletic training.

How much does lower body strength impact Paralympic running performance?

OBJECTIVES: Development of evidence-based methods of Paralympic classification requires research quantifying the relative strength of association between ratio-scaled measures of impairment and athletic performance. The purpose of this study was to quantify the extent to which muscle strength affects running performance in runners with and without brain impairment. DESIGN: Cross-sectional study. METHODS: Participants were 41 male runners: 13 with brain impairments (RBI) and 28 non-disabled (NDR). All participants completed a maximal 60-m sprint and a novel battery of three lower limb isometric strength tests. RESULTS: RBI showed significantly lower strength scores compared with NDR on the more affected side in leg flexion (176 vs. 243 N), leg extension (993 vs. 1661 N) and plantarflexion (824  vs. 1457 N). Significant differences were also seen on the less affected side in plantarflexion (1072 vs. 1508 N). RBI were significantly slower in the acceleration phase (0-15 m) (3.2 s ± 0.3 vs. 2.8 s ± 0.2) and top speed phase (30-60 m) (4.3 s ± 0.6 vs. 3.8 s ± 0.3). Correlation analysis showed stronger relationships between strength and running performance in RBI than NDR; however, the correlations were not significant. CONCLUSIONS: This study evaluated measures to assess strength for the purposes of classification and found that the measures were significantly different in RBI compared with NDR indicating the tests were able to capture strength impairment in this population. This study indicates that strength may be an important impairment type to assess in this population, as impairments of muscle strength may influence the outcome of running performance in athletes with more severe impairments.

Evaluation of methods for calculating maximum allowable standing height in amputees competing in Paralympic athletics.

The International Paralympic Committee has a maximum allowable standing height (MASH) rule that limits stature to a pre-trauma estimation. The MASH rule reduces the probability that bilateral lower limb amputees use disproportionately long prostheses in competition. Although there are several methods for estimating stature, the validity of these methods has not been compared. To identify the most appropriate method for the MASH rule, this study aimed to compare the criterion validity of estimations resulting from the current method, the Contini method, and four Canda methods (Canda-1, Canda-2, Canda-3, and Canda-4). Stature, ulna length, demispan, sitting height, thigh length, upper arm length, and forearm length measurements in 31 males and 30 females were used to calculate the respective estimation for each method. Results showed that Canda-1 (based on four anthropometric variables) produced the smallest error and best fitted the data in males and females. The current method was associated with the largest error of those tests because it increasingly overestimated height in people with smaller stature. The results suggest that the set of Canda equations provide a more valid MASH estimation in people with a range of upper limb and bilateral lower limb amputations compared with the current method.

Novel cell type-specific antiviral mechanism of interferon gamma action in macrophages.

Interferon (IFN)-gamma and macrophages (Mphi) play key roles in acute, persistent, and latent murine cytomegalovirus (MCMV) infection. IFN-gamma mechanisms were compared in embryonic fibroblasts (MEFs) and bone marrow Mphi (BMMphi). IFN-gamma inhibited MCMV replication in a signal transducer and activator of transcription (STAT)-1alpha-dependent manner much more effectively in BMMphi (approximately 100-fold) than MEF (5-10-fold). Although initial STAT-1alpha activation by IFN-gamma was equivalent in MEF and BMMphi, microarray analysis demonstrated that IFN-gamma regulates different sets of genes in BMMphi compared with MEFs. IFN-gamma inhibition of MCMV growth was independent of known mechanisms involving IFN-alpha/beta, tumor necrosis factor alpha, inducible nitric oxide synthase, protein kinase RNA activated (PKR), RNaseL, and Mx1, and did not involve IFN-gamma-induced soluble mediators. To characterize this novel mechanism, we identified the viral targets of IFN-gamma action, which differed in MEF and BMMphi. In BMMphi, IFN-gamma reduced immediate early 1 (IE1) mRNA during the first 3 h of infection, and significantly reduced IE1 protein expression for 96 h. Effects of IFN-gamma on IE1 protein expression were independent of RNaseL and PKR. In contrast, IFN-gamma had no significant effects on IE1 protein or mRNA expression in MEFs, but did decrease late gene mRNA expression. These studies in primary cells define a novel mechanism of IFN-gamma action restricted to Mphi, a cell type key for MCMV pathogenesis and latency.

Murine cytomegalovirus inhibits interferon gamma-induced antigen presentation to CD4 T cells by macrophages via regulation of expression of major histocompatibility complex class II-associated genes.

CD4 T cells and interferon gamma (IFN-gamma) are required for clearance of murine cytomegalovirus (MCMV) infection from the salivary gland in a process taking weeks to months. To explain the inefficiency of salivary gland clearance we hypothesized that MCMV interferes with IFN-gamma induced antigen presentation to CD4 T cells. MCMV infection inhibited IFN-gamma-induced presentation of major histocompatibility complex (MHC) class II associated peptide antigen by differentiated bone marrow macrophages (BMMphis) to a T cell hybridoma via impairment of MHC class II cell surface expression. This effect was independent of IFN-alpha/beta induction by MCMV infection, and required direct infection of the BMMphis with live virus. Inhibition of MHC class II cell surface expression was associated with a six- to eightfold reduction in IFN-gamma induced IAb mRNA levels, and comparable decreases in IFN-gamma induced expression of invariant chain (Ii), H-2Ma, and H-2Mb mRNAs. Steady state levels of several constitutive host mRNAs, including beta-actin, cyclophilin, and CD45 were not significantly decreased by MCMV infection, ruling out a general effect of MCMV infection on mRNA levels. MCMV effects were specific to certain MHC genes since IFN-gamma-induced transporter associated with antigen presentation (TAP)2 mRNA levels were minimally altered in infected cells. Analysis of early upstream events in the IFN-gamma signaling pathway revealed that MCMV did not affect activation and nuclear translocation of STAT1alpha, and had minor effects on the early induction of IRF-1 mRNA and protein. We conclude that MCMV infection interferes with IFN-gamma-mediated induction of specific MHC genes and the Ii at a stage subsequent to STAT1alpha activation and nuclear translocation. This impairs antigen presentation to CD4 T cells, and may contribute to the capacity of MCMV to spread and persist within the infected host.

Femoral venous pulsations during open-chest cardiac massage.

We describe the cases of two children with easily palpated femoral pulses during open-chest cardiac massage after aortic occlusion. These pulsations must have arisen from the femoral veins, implying that during CPR in children the usual anatomic landmarks for femoral venous access may be unreliable, and femoral pulsations do not necessarily reflect arterial flow. Femoral pulses may signify to-and-fro inferior vena caval flow that compromises venous return, adversely affecting cardiac output and the effectiveness of medication administration to the lower extremity.

Complete analysis of tRNA-modified nucleosides by high-performance liquid chromatography: the 29 modified nucleosides of Salmonella typhimurium and Escherichia coli tRNA.

A high-performance liquid chromatography (HPLC) method has been developed to quantify the major and modified nucleoside composition of total, unfractionated transfer RNA. The method is rapid and sensitive and offers a high degree of chromatographic resolution suitable for quantifying both stable and unstable modified nucleosides. It is nondestructive and allows the recovery of nucleosides for further characterization. We apply the method in the analysis of the 29 modified nucleosides in tRNA from Salmonella typhimurium (and Escherichia coli) and show it to be useful in examining changes in the modified nucleoside content of tRNA. Such changes may be important in regulation.