Augmented reality in spine surgery - past, present, and future.

BACKGROUND CONTEXT: Augmented reality (AR) is increasingly recognized as a valuable tool in spine surgery. Here we provides an overview of the key developments and technological milestones that have laid the foundation for AR applications in this field. We also assess the quality of existing studies on AR systems in spine surgery and explore potential future applications. PURPOSE: The purpose of this narrative review is to examine the role of AR in spine surgery. It aims to highlight the evolution of AR technology in this context, evaluate the existing body of research, and outline potential future directions for integrating AR into spine surgery. STUDY DESIGN: Narrative review. METHODS: We conducted a thorough literature search to identify studies and developments related to AR in spine surgery. Relevant articles, reports, and technological advancements were analyzed to establish the historical context and current state of AR in this field. RESULTS: The review identifies significant milestones in the development of AR technology for spine surgery. It discusses the growing body of research and highlights the strengths and weaknesses of existing investigations. Additionally, it presents insights into the potential for AR to enhance spine surgical education and speculates on future applications. CONCLUSIONS: Augmented reality has emerged as a promising adjunct in spine surgery, with notable advancements and research efforts. The integration of AR into the spine surgery operating room holds promise, as does its potential to revolutionize surgical education. Future applications of AR in spine surgery may include real-time navigation, enhanced visualization, and improved patient outcomes. Continued development and evaluation of AR technology are essential for its successful implementation in this specialized surgical field.

Using Lower Limb Wearable Sensors to Identify Gait Modalities: A Machine-Learning-Based Approach.

Real-world gait analysis can aid in clinical assessments and influence related interventions, free from the restrictions of a laboratory setting. Using individual accelerometers, we aimed to use a simple machine learning method to quantify the performance of the discrimination between three self-selected cyclical locomotion types using accelerometers placed at frequently referenced attachment locations. Thirty-five participants walked along a 10 m walkway at three different speeds. Triaxial accelerometers were attached to the sacrum, thighs and shanks. Slabs of magnitude, three-second-long accelerometer data were transformed into two-dimensional Fourier spectra. Principal component analysis was undertaken for data reduction and feature selection, followed by discriminant function analysis for classification. Accuracy was quantified by calculating scalar accounting for the distances between the three centroids and the scatter of each category's cloud. The algorithm could successfully discriminate between gait modalities with 91% accuracy at the sacrum, 90% at the shanks and 87% at the thighs. Modalities were discriminated with high accuracy in all three sensor locations, where the most accurate location was the sacrum. Future research will focus on optimising the data processing of information from sensor locations that are advantageous for practical reasons, e.g., shank for prosthetic and orthotic devices.

Global hotspots of traded phylogenetic and functional diversity.

Wildlife trade is a multibillion-dollar industry1 targeting a hyperdiversity of species2 and can contribute to major declines in abundance3. A key question is understanding the global hotspots of wildlife trade for phylogenetic (PD) and functional (FD) diversity, which underpin the conservation of evolutionary history4, ecological functions5 and ecosystem services benefiting humankind6. Using a global dataset of traded bird and mammal species, we identify that the highest levels of traded PD and FD are from tropical regions, where high numbers of evolutionary distinct and globally endangered species in trade occur. The standardized effect size (ses) of traded PD and FD also shows strong tropical epicentres, with additional hotspots of mammalian ses.PD in the eastern United States and ses.FD in Europe. Large-bodied, frugivorous and canopy-dwelling birds and large-bodied mammals are more likely to be traded whereas insectivorous birds and diurnally foraging mammals are less likely. Where trade drives localized extinctions3, our results suggest substantial losses of unique evolutionary lineages and functional traits, with possible cascading effects for communities and ecosystems5,7. Avoiding unsustainable exploitation and lost community integrity requires targeted conservation efforts, especially in hotspots of traded phylogenetic and functional diversity.

The ecological drivers and consequences of wildlife trade.

Wildlife trade is a key driver of extinction risk, affecting at least 24% of terrestrial vertebrates. The persistent removal of species can have profound impacts on species extinction risk and selection within populations. We draw together the first review of characteristics known to drive species use - identifying species with larger body sizes, greater abundance, increased rarity or certain morphological traits valued by consumers as being particularly prevalent in trade. We then review the ecological implications of this trade-driven selection, revealing direct effects of trade on natural selection and populations for traded species, which includes selection against desirable traits. Additionally, there exists a positive feedback loop between rarity and trade and depleted populations tend to have easy human access points, which can result in species being harvested to extinction and has the potential to alter source-sink dynamics. Wider cascading ecosystem repercussions from trade-induced declines include altered seed dispersal networks, trophic cascades, long-term compositional changes in plant communities, altered forest carbon stocks, and the introduction of harmful invasive species. Because it occurs across multiple scales with diverse drivers, wildlife trade requires multi-faceted conservation actions to maintain biodiversity and ecological function, including regulatory and enforcement approaches, bottom-up and community-based interventions, captive breeding or wildlife farming, and conservation translocations and trophic rewilding. We highlight three emergent research themes at the intersection of trade and community ecology: (1) functional impacts of trade; (2) altered provisioning of ecosystem services; and (3) prevalence of trade-dispersed diseases. Outside of the primary objective that exploitation is sustainable for traded species, we must urgently incorporate consideration of the broader consequences for other species and ecosystem processes when quantifying sustainability.

Increased Surgeon-specific Experience and Volume is Correlated With Improved Clinical Outcomes in Lumbar Fusion Patients.

STUDY DESIGN: The present study design was that of a single center, retrospective cohort study to evaluate the influence of surgeon-specific factors on patient functional outcomes at 6 months following lumbar fusion. Retrospective review of a prospectively maintained database of patients who underwent neurosurgical lumbar instrumented arthrodesis identified the present study population. OBJECTIVE: This study seeks to evaluate surgeon-specific variable effects on patient-reported outcomes such as Oswestry Disability Index (ODI) and the effect of North American Spine Society (NASS) concordance on outcomes in the setting of variable surgeon characteristics. SUMMARY OF BACKGROUND DATA: Lumbar fusion is one of the fastest growing procedures performed in the United States. Although the impact of surgeon-specific factors on patient-reported outcomes has been contested, studies examining these effects are limited. METHODS: This is a single center, retrospective cohort study analyzing a prospectively maintained database of patients who underwent neurosurgical lumbar instrumented arthrodesis by 1 of 5 neurosurgery fellowship trained spine surgeons. The primary outcome was improvement of ODI at 6 months postoperative follow-up compared with preoperative ODI. RESULTS: A total of 307 patients were identified for analysis. Overall, 62% of the study population achieved minimum clinically important difference (MCID) in ODI score at 6 months. Years in practice and volume of lumbar fusions were statistically significant independent predictors of MCID ODI on multivariable logistic regression ( P =0.0340 and P =0.0343, respectively). Concordance with evidence-based criteria conferred a 3.16 (95% CI: 1.03, 9.65) times greater odds of achieving MCID. CONCLUSION: This study demonstrates that traditional surgeon-specific variables predicting surgical morbidity such as experience and procedural volume are also predictors of achieving MCID 6 months postoperatively from lumbar fusion. Independent of surgeon factors, however, adhering to evidence-based guidelines can lead to improved outcomes.

Exoscope improves visualization and extent of hippocampal resection in temporal lobectomy.

INTRODUCTION: Anterior temporal lobectomy (ATL) is a safe and well-validated procedure in the treatment of temporal lobe epilepsy (TLE), but is a challenging technique to master and still confers a risk of morbidity and mortality due to the complex anatomy of the mesial temporal lobe structures. Automated robotic 3D exoscopes have been developed to address limitations traditionally associated with microscopic visualization, allowing for ergonomic, high-definition 3D visualization with hands-free control of the robot. Given the potential advantages of using such a system for visualization of complex anatomy seen during mesial structure resection in ATL, this group sought to investigate impact on the percentage of hippocampal resection in both exoscope and microscope guided procedures. METHODS: We conducted a retrospective analysis of 20 consecutive patients undergoing standard ATL for treatment of medically refractory TLE at our institution. Using pre-operative and post-operative imaging, the coronal plane cuts in which either the head, body, or tail of the hippocampus appeared were counted. The number of cuts in which the hippocampus appeared were multiplied by slice thickness to estimate hippocampal length. RESULTS: Mean percentage of hippocampal resection was 61.1 (SD 13.1) and 76.5 (SD 6.5) for microscope and exoscope visualization, respectively (p = 0.0037). CONCLUSION: Use of exoscope for mesial resection during ATL has provided good visualization for those in the operating room and the potential for a safe increase in hippocampal resection in our series. Further investigation of its applications should be evaluated to see if it will improve outcomes.

Repetitions in Reserve Is a Reliable Tool for Prescribing Resistance Training Load.

ABSTRACT: Lovegrove, S, Hughes, L, Mansfield, S, Read, P, Price, P, and Patterson, SD. Repetitions in reserve is a reliable tool for prescribing resistance training load. J Strength Cond Res 36(10): 2696-2700, 2022-This study investigated the reliability of repetitions in reserve (RIR) as a method for prescribing resistance training load for the deadlift and bench press exercises. Fifteen novice trained men (age: 17.3 ± 0.9 years, height: 176.0 ± 8.8 cm, body mass: 71.3 ± 10.7 kg) were assessed for 1 repetition maximum (1RM) for deadlift (118.1 ± 27.3 kg) and bench press (58.2 ± 18.6 kg). Subsequently, they completed 3 identical sessions (one familiarization session and 2 testing sessions) comprising sets of 3, 5, and 8 repetitions. For each repetition scheme, the load was progressively increased in successive sets until subjects felt they reached 1-RIR at the end of the set. Test-retest reliability of load prescription between the 2 testing sessions was determined using intraclass correlation coefficient (ICC) and coefficient of variation (CV). A 2-way analysis of variance with repeated measures was used for each exercise to assess differences in the load corresponding to 1-RIR within each repetition scheme. All test-retest comparisons demonstrated a high level of reliability (deadlift: ICC = 0.95-0.99, CV = 2.7-5.7% and bench press: ICC = 0.97-0.99, CV = 3.8-6.2%). Although there were no differences between time points, there was a difference for load corresponding to 1-RIR across the 3 repetition schemes (deadlift: 88.2, 84.3, and 79.2% 1RM; bench press: 93.0, 87.3, and 79.6% 1RM for the 3-, 5-, and 8-repetition sets, respectively). These results suggest that RIR is a reliable tool for load prescription in a young novice population. Furthermore, the between-repetition scheme differences highlight that practitioners can effectively manipulate load and volume (repetitions in a set) throughout a training program to target specific resistance training adaptations.

Exploring the interaction of knee and ankle component use on mobility test performance in people with unilateral transfemoral amputation.

BACKGROUND: Ankle-foot and knee components are important determinants of mobility for individuals with transfemoral amputation. Individually, advanced ankle-foot and knee components have been shown to benefit mobility in this group of people. However, it is not clear what effect a variety of combinations of ankle-foot and knee components have on mobility test performance. OBJECTIVES: To assess whether outcomes from mobility tests in people with unilateral transfemoral amputation are influenced by varying combinations of ankle-foot and knee components. STUDY DESIGNS: Repeated measures. METHODS: Nine adults with unilateral transfemoral amputation completed the two-minute walk test, the timed up-and-go test, the L-test, and a custom locomotion course in four randomized prosthetic conditions. These conditions were each a combination of an ankle-foot component (rigid, nonarticulating [RIG] or hydraulically articulating [HYD]) and a knee component (non-microprocessor-controlled [NMPK] or microprocessor-controlled [MPK]). The test-retest reliability and concurrent validity of the custom locomotion course were also established. RESULTS: The best performance in all mobility tests was associated with the MPK + HYD combination, followed by the MPK + RIG, NMPK + HYD, and NMPK + RIG combinations. This effect was statistically significant for the two-minute walk test (P = 0.01, = 0.36) and on threshold for the L-test (P = 0.05, = 0.36), but not statistically significant for the locomotion course (P = 0.07, = 0.38) or the timed up-and-go test (P = 0.12, = 0.22). Locomotion course performance had good to excellent test-retest reliability and strong concurrent validity. CONCLUSION: Using a combination of a HYD ankle-foot and a MPK knee resulted in the highest performance in mobility tests. This was observed in contrast to combinations of prosthetic components that included a rigid ankle-foot component and/or a NMPK knee component.

The Impact of Incorporating Evidence-Based Guidelines for Lumbar Fusion Surgery in Neurosurgical Resident Education.

BACKGROUND: Instrumented fusion procedures are essential in the treatment of degenerative lumbar spine disease to alleviate pain and improve neurological function, but they are being performed with increasing incidence and variability. We implemented a training module for neurosurgery residents that is based on evidence-based criteria for lumbar fusion surgery and measured its effectiveness in residents' decision making regarding whether patients should or should not undergo instrumented fusion. METHODS: The study design was a pretest versus posttest experiment conducted from September 2019 until July 2020 to measure improvement after formalized instruction on evidence-based guidelines. Neurosurgery residents of all training levels at our institution participated. A test was administered at the beginning of each academic year. The highest possible score was 18 points in each pretest and posttest. RESULTS: There was a general trend of test score improvement across all levels of training with a greater degree of change for participants with lower compared with higher pretest scores, indicating a possible ceiling effect. Paired t test demonstrated an overall mean score increase of 2 points (P < 0.0001), equivalent to an 11.11% increase (P < 0.0001). Stratified by training group, mean absolute change in test score was 2 (P = 0.0217), 1.67 (P = 0.0108), and 2.25 (P = 0.0173) points for junior, midlevel, and senior training groups, respectively. CONCLUSIONS: Incorporating a targeted evidence-based learning module for lumbar spine fusion surgery can improve neurosurgery residents' clinical decision making toward a more uniform practice supported by published data.

The Use of Integra Dermal Regeneration Templates and Cortical Bone Fenestrations over Exposed Tibia.

We present the case of an 86-year-old woman who suffered full-thickness soft tissue loss secondary to degloving injury to the lower left limb, resulting in an exposed tibia. This patient underwent drilling to create artificial fenestrations in the cortical bone followed by placement of Integra dermal regeneration template. The technique of drilling fenestrations to expose underlying vasculature of cortical bone has not previously been described in its relationship with Integra dermal regeneration templates in large degloving injuries of the lower limb. This technique enabled us to perform earlier skin grafting and ultimately resulted in complete and timely wound closure. We present this case as a comparable alternative treatment in cases of reconstructive surgery secondary to severe burns or trauma to reduce the time required for successful wound closure over exposed bone in full-thickness tissue loss injuries of the lower limb.

Intradural extramedullary capillary hemangioma of the cauda equina: case report of a rare spinal tumor.

INTRODUCTION: Intradural extramedullary capillary hemangiomas of the cauda equina are exceedingly rare, with only 20 previous cases reported. In the adult population, these tumors are rare and can arise in the central and peripheral nervous systems from the dura or spinal nerve roots. Intradural capillary hemangiomas of the cauda equina can yield symptoms such as lower extremity weakness, pain, and bladder and bowel dysfunction. The clinical symptomology and surgical management of this rare spinal lesion are reviewed in this case report. CASE PRESENTATION: A 50-year-old male presented with progressive bilateral lower extremity weakness for 2 years, with recent bladder and bowel dysfunction. On physical exam, strength was symmetrically impaired in both lower extremities. Pre-operative magnetic resonance imaging (MRI) of the lumbar spine demonstrated a gadolinium-enhanced intradural lesion at the L4 level. Laminectomy was performed and the lesion was resected. Histopathological analysis determined that the tumor demonstrated features consistent with a capillary hemangioma. DISCUSSION: Clinically, patients with capillary hemangiomas of the cauda equina present with space-occupying compressive deficits, including progressive low back and lower extremity pain, motor deficits, paresthesias, sensory loss, and bowel and bladder dysfunction. Acute presentation can transpire following a hemorrhagic episode, although this is more associated with cavernous rather than capillary hemangiomas. Our patient demonstrated non-acute, progressive weakness, and late-onset bladder and bowel dysfunction. This report demonstrates that this rare lesion should be included in the differential diagnosis of cauda equina lesions.

Use of the color Doppler twinkle artifact for teaching ultrasound guided peripheral vascular access.

BACKGROUND: The optimal method for teaching ultrasound guided peripheral IV (USGPIV) insertion is unknown. Poor needle tip visualization has been cited for USGPIV failure. Twinkle artifact (TA), visualized with color Doppler, is used in other clinical settings. Our objective was to investigate whether teaching students USGPIV placement utilizing TA would enhance needle tip visualization and improve first pass success. METHODS: This was a prospective, randomized study of premedical and preclinical medical students without prior USGPIV experience. Students were given a standardized didactic session on USGPIV placement before being randomized and separated to learn and practice USGPIV with or without TA (control). The students were given 5 min to perform USGPIV on phantom models. The primary outcome was the rate of first pass success. Secondary outcomes included total time to cannulation, rate of posterior venous wall puncture, and total number of attempts. RESULTS: Rates of first pass success were similar in both the TA (82%) and control groups (57%), p = 0.095. There was a difference in the mean time to cannulation. The TA group achieved success at 50.76 s (SD 26.93) while the control group achieved success at 85.30 s (SD 65.47), p = 0.048. CONCLUSION: In this study of utilizing TA to aid in USGPIV placement, students were able to achieve successful cannulation in a shorter amount of time. There was no significant difference in first pass success. Future studies should utilize a larger sample size and evaluate the utility of TA when placing USGPIV on patients.

A comparison of homemade vascular access ultrasound phantom models for peripheral intravenous catheter insertion.

BACKGROUND: Ultrasound (U/S) guided peripheral IV catheter (PIV) placement is often needed after unsuccessful traditional IV attempts. Commercial U/S PIV training phantoms are expensive and difficult to alter. Non-commercial phantoms have been described; however, there has been no comparison of these models. The primary objectives of this study were to compare the echogenic and haptic properties of various non-commercial phantoms. Secondary objectives were to characterize the cost and ease of making the phantoms. METHODS: This prospective observational study trialed six unique phantom models: Amini Ballistics; Morrow Ballistics; University of California San Diego (UCSD) gelatin; Rippey Chicken; Nolting Spam; and Johnson Tofu. Total cost and creation time were noted. Emergency Ultrasound Fellowship trained physicians performed U/S guided PIV placement on each model to evaluate their resemblance to human tissue haptic and echogenicity properties, utility for training, and comparability to commercial phantoms (Likert scale 1-5; higher performance = 5). RESULTS: The Rippey model scored highest for each primary objective with an aggregate score of 4.8/5. UCSD ranked second and Nolting last for all primary objectives, with aggregate scores 3.7/5 and 1.3/5 respectively. Cost of production ranged from $4.39 (Johnson) to $29.76 (UCSD). Creation times ranged from 10 min (Johnson) to 120 min (UCSD). CONCLUSION: In our study the Rippey model performed best and offered a mid-level cost and creation time. Non-commercial U/S phantoms may represent cost-effective and useful PIV practice tools. Future studies should investigate the utility of these phantoms in teaching U/S guided PIV to novices and compare non-commercial to commercial phantoms.

Estimating Repetitions in Reserve in Four Commonly Used Resistance Exercises.

ABSTRACT: Hughes, LJ, Peiffer, JJ, and Scott, B. Estimating repetitions in reserve in four commonly used resistance exercises. J Strength Cond Res XX(X): 000-000, 2020-This study aimed to determine the accuracy and reliability of estimating repetitions in reserve (RIR) across the squat, bench press, overhead press, and prone row exercises, using both free-weight and Smith machine modalities. Twenty-one trained men attended the laboratory on 14 occasions. They were assessed for 1 repetition maximum (1RM) for the squat, bench press, prone row, and overhead press exercises and subsequently completed 6 RIR testing sessions using 65, 75, and 85% 1RM. In these trials, subjects indicated when they reached 2 RIR (i.e., perceive they could only perform 2 more repetitions), before continuing the set to failure. The same process was then replicated using the alternative equipment modality. To determine accuracy of 2-RIR estimates, 1-sample t-tests assessed differences between 2 and the actual number of repetitions completed after subjects indicated they had reached 2 RIR. Intraclass correlation coefficients were used to determine the reliability of test-retest RIR estimated. There were no clear differences in the accuracy or reliability of estimating RIR between free-weight and Smith machine exercises. Load, however, proved an important factor with the highest accuracy associated with RIR estimations performed when using 85%, followed by 75 and 65% 1RM, respectively. When using loads of 75 and 65% 1RM, it was increasingly likely that individuals would underestimate RIR by >1 repetition, which would practically lead to an undesired reduction in training volume. These results highlight that although estimates of 2 RIR may be accurate and reliable in heavy load resistance training (≥85% 1RM), practitioners should be wary of using this measure with lighter loads.

Estimating Repetitions in Reserve for Resistance Exercise: An Analysis of Factors Which Impact on Prediction Accuracy.

Mansfield, Sean, K, Peiffer, Jeremiah, J, Hughes, Liam, J, and Scott Brendan, R. Estimating repetitions in reserve for resistance exercise: an analysis of factors which impact on prediction accuracy. J Strength Cond Res XX(X): 000-000, 2020-The purpose of this study was to examine the influence of knowing the load being lifted on the accuracy of repetitions-in-reserve (RIR) estimates, during both moderate- (60% 1 repetition maximum [RM]) and heavy-load (80% 1RM) exercise. Twenty trained men (age: 25.9 ± 4.5 years, height: 181 ± 7 cm, body mass: 86.5 ± 13.7 kg) were assessed for 1RM in bench press (98.4 ± 16.4 kg) and prone row (72.0 ± 11.7 kg), before being randomized into control (i.e., informed of the load; n = 10) or blinded (noninformed; n = 10) conditions. Subjects then completed 2 protocols in a randomized order: 3 sets at 80% 1RM and 3 sets at 60% 1RM. During each set of these protocols, subjects were asked to estimate their RIR before continuing the set to failure. Differences in estimated and actual RIR between sets and conditions were determined via 3-way repeated measures analysis of variance for the 60 and 80% 1RM protocols independently. No differences in RIR accuracy were observed between blinded vs nonblinded conditions. Repetitions-in-reserve estimates were lower than actual RIR for the first set of both exercises in 60 and 80% protocols (p ≤ 0.007, effect size [ES]: 1.30-2.89 [moderate-large]) and for set 2 of the 80% bench press protocol (p = 0.046, ES: 0.39 [small]). Knowing the load during resistance exercise or the %1RM of the load lifted did not influence the estimates of RIR. The ability to accurately determine RIR in the 60 and 80% 1RM protocols improved from sets 1-3, indicating that estimation of RIR is enhanced when an individual is estimating RIR at a closer point to actual failure.

Load-velocity relationship 1RM predictions: A comparison of Smith machine and free-weight exercise.

This study aimed to determine differences in the validity and reliability of 1RM predictions made using load-velocity relationships in Smith machine and free-weight exercise. Twenty well-trained males attended six sessions, comprising the Smith machine and free-weight squat, bench press, prone row and overhead press. Load-velocity relationship-based 1RM predictions were performed using minimal velocity threshold (1RMMVT), load at zero velocity (1RMLD0) and force-velocity (1RMFV) methods, with 5- or 7-loads. Measured 1RM did not differ from 1RMMVT or 1RMLD0 for any of the Smith machine exercises, while it was higher than 1RMFV for all exercises except the prone row. For the free-weight variations all 1RM predictions differed from measured 1RM for the squat and overhead press, while measured and predicted 1RM did not differ in the bench press and prone row. No differences were observed between 7-and 5-load predictions. 1RMMVT was the most reliable and valid of the methods. Smith machine exercises resulted in more reliable predictions than free weight exercises. 1RMMVT provides valid and reliable predictions for the Smith machine, squat, bench press, prone row and overhead press and free-weight bench press and prone row. Practitioners must be aware of the poor validity of free-weight squat and overhead press predictions.

Meeting the Challenge of Analgesia in a Pregnant Woman With Burn Injury Using Subanesthetic Ketamine: A Case Report and Literature Review.

Pain management guidelines for burn injury in pregnant women are scarce. Maternal and fetal morbidity and mortality in pregnant burn patients have been shown to be higher than that of the general population, especially in severe burns. Early intervention and interdisciplinary treatment are critical to optimize maternal and fetal outcomes. Proper pain management is central to wound treatment, as poor control of pain can contribute to delayed healing, re-epithelialization, as well as persistent neuropathic pain. We present this case of a 34-year-old female patient who suffered an 18% total body surface area burn during the third trimester of pregnancy to demonstrate that ketamine can be considered as an adjunct for procedural and background analgesia during the third trimester, as part of a multimodal strategy in a short-term, monitored setting after a thorough and complete analysis of risks and benefits and careful patient selection.

Using a Load-Velocity Relationship to Predict One repetition maximum in Free-Weight Exercise: A Comparison of the Different Methods.

Hughes, LJ, Banyard, HG, Dempsey, AR, and Scott, BR. Using a load-velocity relationship to predict one repetition maximum in free-weight exercise: a comparison of the different methods. J Strength Cond Res 33(9): 2409-2419, 2019-The purpose of this study was to investigate the reliability and validity of predicting 1 repetition maximum (1RM) in trained individuals using a load-velocity relationship. Twenty strength-trained men (age: 24.3 ± 2.9 years, height: 180.1 ± 5.9 cm, and body mass: 84.2 ± 10.5 kg) were recruited and visited the laboratory on 3 occasions. The load-velocity relationship was developed using the mean concentric velocity of repetitions performed at loads between 20 and 90% 1RM. Predicted 1RM was calculated using 3 different methods discussed in existing research: minimal velocity threshold 1RM (1RMMVT), load at zero velocity 1RM (1RMLD0), and force-velocity 1RM methods (1RMFV). The reliability of 1RM predictions was examined using intraclass correlation coefficient (ICC) and coefficient of variation (CV). 1RMMVT demonstrated the highest reliability (ICC = 0.92-0.96, CV = 3.6-5.0%), followed by 1RMLD0 (ICC = 0.78-0.82, CV = 8.2-8.6%) and 1RMFV (ICC = -0.28 to 0.00, CV = N/A). Both 1RMMVT and 1RMLD0 were very strongly correlated with measured 1RM (r = 0.91-0.95). The only method which was not significantly different to measured 1RM was the 1RMLD0 method. However, when analyzed on an individual basis (using Bland-Altman plots), all methods exhibited a high degree of variability. Overall, the results suggest that the 1RMMVT and 1RMLD0 predicted 1RM values could be used to monitor strength progress in trained individuals without the need for maximal testing. However, given the significant differences between 1RMMVT and measured 1RM, and the high variability associated with individual predictions performed using each method, they cannot be used interchangeably; therefore, it is recommended that predicted 1RM is not used to prescribe training loads as has been previously suggested.

Using Load-Velocity Relationships to Quantify Training-Induced Fatigue.

Hughes, LJ, Banyard, HG, Dempsey, AR, Peiffer, JJ, and Scott, BR. Using load-velocity relationships to quantify training-induced fatigue. J Strength Cond Res 33(3): 762-773, 2019-The purpose of this study was to investigate using load-velocity relationships to quantify fluctuations in maximal strength (1 repetition maximum [1RM]), which occur as a result of training-induced fatigue. The 19 well-trained men (age: 24.3 ± 2.9 years, height: 180.1 ± 5.9 cm, body mass: 84.2 ± 10.5 kg, and squat 1RM: 151.1 ± 25.7 kg) who were recruited for this study attended 5 sessions. After baseline strength testing, individual load-velocity relationships were established using mean concentric velocity during visits 2, 4, and 5, with visit 3 consisting of a bout of fatiguing exercise (5 sets of squats performed to muscular failure with 70% 1RM). Predicted 1RM values were calculated using the minimal velocity threshold (1RMMVT), load at zero velocity (1RMLD0), and force-velocity (1RMFV) methods. Measured 1RM, maximal voluntary contractions, and perceived muscle soreness were used to examine the effects of fatigue in relation to the predicted 1RM scores. The 1RMMVT and 1RMLD0 demonstrated very strong and strong correlations with measured 1RM during each of the sessions (r = 0.90-0.96 and r = 0.77-0.84, respectively), while no strong significant correlations were observed for the 1RMFV. Further analysis using Bland-Altman plots demonstrated substantial interindividual variation associated with each method. These results suggest that load-velocity-based 1RM predictions are not accurate enough to be used for daily training load prescription, as has been previously suggested. Nevertheless, these predictions are practical to implement during an individual's warm-up and may be useful to indicate general fluctuations in performance potential, particularly if used in conjunction with other common monitoring methods.

Hyperpolarized gas diffusion MRI of biphasic lung inflation in short- and long-term emphysema models.

During lung inflation, airspace dimensions are affected nonlinearly by both alveolar expansion and recruitment, potentially confounding the identification of emphysematous lung by hyperpolarized helium-3 diffusion magnetic resonance imaging (HP MRI). This study aimed to characterize lung inflation over a broad range of inflation volume and pressure values in two different models of emphysema, as well as in normal lungs. Elastase-treated rats (n = 7) and healthy controls (n = 7) were imaged with HP MRI. Gradual inflation was achieved by incremental changes to both inflation volume and airway pressure. The apparent diffusion coefficient (ADC) was measured at each level of inflation and fitted to the corresponding airway pressures as the second-order response equation, with minimizing residue (χ2 < 0.001). A biphasic ADC response was detected, with an initial ADC increase followed by a decrease at airway pressures >18 cmH2O. Discrimination between treated and control rats was optimal when airway pressure was intermediate (between 10 and 11 cmH2O). Similar findings were confirmed in mice following long-term exposure to cigarette smoke, where optimal discrimination between treated and healthy mice occurred at a similar airway pressure as in the rats. We subsequently explored the evolution of ADC measured at the intermediate inflation level in mice after prolonged smoke exposure and found a significant increase (P < 0.01) in ADC over time. Our results demonstrate that measuring ADC at intermediate inflation enhances the distinction between healthy and diseased lungs, thereby establishing a model that may improve the diagnostic accuracy of future HP gas diffusion studies.