Countermovement jumps (CMJ) are frequently used in strength and conditioning as a key performance indicator. Force platforms are often considered the standard for measuring ground reaction forces ...(GRF) and deriving subsequent performance metrics. Although force platforms are often the standard, they may not always fall within an allotted budget. Jump mats are another option for CMJ testing that are cheaper than the criterion force plates. Although cheaper, jump mats only measure flight time (FT) and jump height (JH), whereas the criterion measures GRF. Therefore, this study looks at the reliability and validity of the Just Jump System compared to the criterion reference ForceDecks force plates during a CMJ with a self-selected depth. This study examined the agreement between the metrics: jump mat FT to force plate FT, jump mat JH to force plate JH, jump mat JH derived by FT to force plate JH derived by impulse. Twelve participants (male n=7 and female n=5 with an average age of 24 years SD 3, average body mass of 83.7 kilograms SD 17.5, average height of 176.2 centimeters SD 11, and an average shoe thickness of 1.8 centimeters SD .5) completed a standardized warmup including a familiarization protocol. Following, the participant completed 5 sets of 5 repetitions of CMJ. Each repetition was followed by a 30 second rest period. Each set of 5 jumps was followed by two minutes of rest. Force plate data was analyzed in the proprietary ForceDecks software, and then exported to excel. Jump mat data was manually recorded on a data collection sheet which was then manually entered into excel. From excel, an interclass correlation coefficient (ICC) and the coefficient of variation (CV) for reliability were calculated. The ICC was reported as .96 and the CV was reported as 9.16%. These results indicated that the Just Jump mats have excellent reliability. For validity, means and standard deviations, a Pearson’s correlation, coefficient of determination, scatter plots, and a Bland-Altman 95% limits of agreement (LOA) were utilized. The means and standard deviations reported by the jump mat were flight time (ms) 541.37 (SD 49.64), jump height (cm) 36.74 (SD 6.79). The means and standard deviations reported by the force platforms were flight time (ms) 446.87 (SD 52.60), jump height derived by flight time (cm) 24.82 (SD 5.91), and jump height derived by impulse (cm) 24.69 (SD 5.83). The Pearson’s correlation indicated a very strong positive relationship with all metrics where force plate FT and jump mat FT (r = 0.991), force plate JH derived by FT and jump mat JH (r= 0.995), force plate JH derived by impulse and jump mat JH (r = 0.974). The Bland-Altman 95% limits of agreement (LOA) analysis between force plate FT and jump mat FT showed a mean bias ± LOA of 1.80 (LOA 14.77 ms). The Bland-Altman 95% LOA analysis between force plate JH derived by FT and jump mat JH showed a mean bias ± LOA of 2.02 (LOA 2.14 cm). The Bland-Altman 95% LOA analysis between force plate JH derived by impulse and jump mat JH showed a mean bias ± LOA of 2.07 (LOA 3.37 cm). The Just Jump mat overestimates FT, and thus, overestimates JH. Although reliable, the Just Jump mats are not valid in comparison to the criterion force plates.
An acute increase in maximum strength, power, or speed following a conditioning contraction known as a postactivation performance enhancement has been previously determined to be better performed ...when the initial exercise is of the same movement pattern. However, no research has been performed studying the effects of a hex-bar farmer’s walk on subsequent sprinting speeds. Therefore, this research examined the use of different loads of a hex-bar farmer’s walk completed at 20-m and their effect on subsequent 20-m sprinting performance. Through a randomized and counterbalanced design, resistance and running trained men and women (n = 12) performed five 20-m sprints (with 10-m splits) at baseline, 4, 8, 12, and 16-minutes after a bodyweight control (C), light farmer’s walk (LFW), and heavy farmer’s walk (HFW), utilizing 70% and 80% users hex-bar deadlift 1-RM respectively. Mean sprint velocities over 10-m and 20-m distances were similar at baseline. At 20-m, sprint velocity significantly increased during the LFW condition at 8 minutes (M = 6.03, SE = 0.14, p = 0.025), 12 minutes (M = 6.05, SE = 0.15, p = 0.016), and 16 minutes (M = 6.03, SE = 0.14, p = 0.011) when compared with C (M = 5.96, SE = 0.14, t(11) = -2.59, r = 0.98); (M = 5.97, SE = 0.15, t(11) = -2.85, r = 0.98); (M = 5.94, SE = 0.14, t(11) = -3.06, r = 0.98, p < 0.05). At 10-m, sprint velocity significantly increased during the LFW condition at 8 minutes (M = 5.10, SE = 0.12, p = 0.010), when compared with C (M = 5.01, SE = 0.12, t(11) = -3.08, p <0.05, r = 0.97). No change to sprinting velocity was witnessed across either of the C conditions or HFW conditions. These results help to substantiate the use of a load at near-maximal capacities during the warm-up preceding sprinting to acutely increase muscular force.
HintergrundZur Bestimmung der therapeutischen Impulsrichtung bei der Atlastherapie nach Arlen gilt die Anfertigung einer a.-p.-Röntgenaufnahme des zervikookzipitalen Übergangs traditionell als ...unverzichtbar. Überlegungen zum Strahlenschutz sowie technische und ökonomische Aspekte förderten die Suche nach einer klinischen Methode, die in der Lage ist, die radiologische Untersuchung zu ersetzen. Zur Diskussion stand der manualdiagnostische 3-Zeichen-Test nach CoenenMethodikDie Zuverlässigkeit des 3-Zeichen-Tests wurde an 438 neurologisch gesunden Patienten mit Funktionsstörung der oberen Halswirbelsäule (HWS) untersucht. Das Testergebnis jedes einzelnen Patienten wurde mit der Analyse seiner Atlas-a.-p.-Röntgenaufnahme verglichen. Jeder Patient erhielt die Atlastherapie nach Arlen gemäß dem 3-Zeichen-Test-Ergebnis; die Bestimmung der Sensitivität des Tests erfolgte aus dem Therapieergebnis nach einmaliger Behandlung.ErgebnisseEine Übereinstimmung des 3-Zeichen-Tests mit der Röntgenbildanalyse ergab sich bei 84,6 % der untersuchten Patienten, keine Übereinstimmung fand sich bei 8,5 % und unklar blieben 6,3 %. Eine Bestätigung des Tests durch das Therapieergebnis nach einmaliger Behandlung wurde bei 94,5 % der Patienten ermittelt, bei 5,3 % fand sich keine Bestätigung.SchlussfolgerungBei der Bestimmung der atlastherapeutischen Impulsrichtung erwies sich der 3-Zeichen-Test als mindestens gleichwertig mit der Röntgenbildanalyse. Der Test kann somit die rein therapeutisch indizierte Röntgenuntersuchung des zervikookzipitalen Übergangs ersetzen und leistet einen wichtigen Beitrag zur Minderung der Strahlenexposition. Er ist kein Ersatz für eine diagnostische Röntgenaufnahme zum Ausschluss pathologischer Prozesse an der HWS bei auffälliger Anamnese und suspekter Symptomatik.
Murine and cell culture models have identified Notch1 as a novel endothelial mechanosensor that may exert a protective role for vascular adjustments in response to changes in vascular wall shear ...stress. However, in vivo studies in humans are lacking. Accordingly, we sought to characterize the concentrations of Notch1 extracellular domain (ECD) prior to, during, and following 20-min of altered shear stress in the brachial artery of ten young and healthy adults (6M/4F). Alterations in shear were induced by placing a pneumatic cuff inflated to 220mmHg around the left wrist. Cuffs were also placed below the axilla of both arms and inflated to 40mmHg to trap the released Notch1 ECD. The right arm (no wrist cuff) was treated as a time control. Blood samples were collected from a superficial antecubital vein of both arms at baseline, 20-min of wrist cuff inflation, as well as 1-min and 15-min following wrist cuff release. The Notch1 ECD was quantified from plasma using a commercially available ELISA kit. Duplex ultrasound was used to confirm alterations in shear stress. In the experimental arm, concentrations of Notch1 ECD remained statistically similar to baseline values following 20-min of reduced antegrade shear stress, but were significantly elevated by ~50% (P=0.033) immediately following cuff release, coinciding with a ~100% increase in antegrade shear. Concentrations of Notch1 ECD remained unchanged in the control arm and were statistically similar to baseline values at 15 min recovery in both the control and experimental arm. These data indicate that Notch1 may be an important mechanistic regulator of vascular function, particularly in response to increased antegrade shear.
Endurance sports, including running, cycling, and swimming, remain popular among recreational athletes in the U.S. and across the world. Many of these athletes compete in local, regional, and ...national races throughout the year. Their performance in competitions is affected by many factors, including genetics, nutrition, and training. Often, recreational athletes receive conflicting recommendations regarding strategies to optimize performance. Direct-to-consumer genetic testing companies promise to give insights into supposed genetic markers of endurance ability; blogs and social media tout the latest diet strategies to lose weight and perform better; virtual coaches and performance-improvement websites sell training plans with sometimes contradictory training strategies. It remains unclear which of these strategies actually benefit endurance athletes. Therefore, this dissertation examined the effects of genetics, diet composition, and training characteristics on endurance performance in recreational athletes, who often spend a considerable percentage of their disposable income and their time on improving race outcomes.Single-nucleotide polymorphisms (SNPs), variations in a single base pair of a gene, have been proposed to affect physical performance. A SNP in the ACTN3 gene (XX genotype), results in deficiency of α-actinin-3, a structural muscle protein that appears important for explosive movements. Studies in rodents suggest that this deficiency could be beneficial for endurance performance. Yet, few studies in humans have directly assessed the effects of ACTN3 genotype on endurance performance. In our first study, we compared self-reported 1-mile and 5-km running personal records (PR) between participants expressing the three different ACTN3 genotypes. Among women, those with the ACTN3 XX genotype reported faster 1-mile PRs compared to those with the RR and RX genotype. We found no differences between genotypes for 1-mile PRs among men or 5-km PRs among either sex.A long-standing strategy to improve endurance performance is to increase carbohydrate (CHO) availability before and during competition to slow the fatigue process. An opposing approach introduced by researchers, coaches, and athletes, is to increase fat oxidation (FATox) capacities by employing a low-CHO or ketogenic diet (KD). This improved ability for FATox at typical race-intensities would open access to an essentially limitless supply of energy substrates stored in the body as fat. However, studies investigating the effects of KD and high-CHO diets (HC) on endurance performance have found conflicting results. In our second study, participants followed an HC and a KD for two weeks each in a random order. They performed a simulated 30-km cycling time trial (TT) at baseline and following each intervention. Participants’ average power output or endurance performance during the TT was substantially lower following the KD when compared with the HC.Endurance training is the main mechanism to improve general cardiorespiratory fitness and performance in races. Training characteristics include frequency, volume, intensity, and training intensity distribution (TID). TID can be determined by the time spent in the easy (Zone 1), moderate (Zone 2), and hard (Zone 3) training zones. Recently, a polarized TID (time in Z1 > Z3 > Z2) has gained popularity, after research suggested that many elite endurance athletes appear to follow this approach. However, the TID employed by recreational athletes and its association with performance is unknown. In our third study, we analyzed the training characteristics of recreational cyclists and triathletes. We investigated their association with endurance performance as measured by estimated relative critical power (CPrel). In our sample, very few recreational athletes followed a polarized TID. When controlling for age, we found that increased training volume and polarization were positively associated with CPrel.In conclusion, ACTN3 genotype does not appear to have a strong effect on endurance performance. Our results, along with findings from other studies investigating so-called endurance SNPs, suggest that individual genetic markers are not good indicators of endurance performance ability; thus, athletes and coaches should not rely upon direct-to-consumer genetic testing for talent identification and sport selection. Further, based on the results of our second study, the KD appears to decrease endurance performance. While additional research using longer nutrition interventions and different performance measures is needed, it appears that maximizing CHO availability remains the best strategy to improve endurance performance. Finally, we found that few recreational athletes follow a polarized TID despite its potentially beneficial effect on performance.
Functional balance in humans can be characterized as maintaining the center of mass (COM) within the base of support (BOS). When the COM moves outside the BOS, a fall can occur if there is not an ...immediate reaction to modify the BOS. The ability to dynamically control the COM-BOS interaction declines with age, and this increases fall rates in older adults. Falls are multifactorial, and there are some common deficits connected to a change in motor control, as evidenced by greater variability in balance performance. Less variability in motor performance is indicative of a more functional and healthier neuromotor system.There is a gap in the literature with respect to the ability to objectively measure dynamic balance and how it relates to fall-risk. Clinical and perceptual assessments of balance are commonly employed; however, they rely on subjective judgements. Objective assessments have become more available in recent years through sensors in smartphone apps, including the AccWalker app that was developed in our laboratory. Yet, it has been unknown the extent to which these objective measures differ between groups based on age and fall status. This gap was important to address so that smartphone apps can be deployed to the clinical community in order to provide objective, evidence-based assessments of dynamic balance.Treating balance changes had been challenging, despite the designation of falls as a public health concern. Previously, less complete strategies have included strengthening exercises, T’ai Chi, physical therapy and the use of walking assistive devices. A newer strategy with success in the literature is the use of attentional focus cues, particularly external focus instruction. The addition of dynamic balance training with internal (IF) and external focus (EF) cues allows for the examination of the role of attentional focus on fall risk in older adults.This dissertation addressed these gaps in the literature via three specific aims. Manuscript 1 investigated whether older and younger adults were similar in the phone app task for timing of steps in response to the app cue, as well as peak flexion of the right hip. The older adults and younger adults were not different in any variable, but trends were noted with lower variability and greater excursion of thigh flexion for the younger adults and older adults who had not fallen. Manuscript 2 explored the results of the three groups of older adults who were trained with attentional focus cues or were part of the control group. The group that received IF training cues were unchanged for all seven variables of the AccWalker phone app over the twenty-week intervention. In addition, the headshake (HS) condition was unchanged for all seven AccWalker variables over the twenty-week intervention for all three groups. SD stride time, SD peak flexion, and COV peak flexion (variability) increased during training for both eyes open (EO) and eyes closed (EC) conditions, but dropped in the retention phase for EF condition only. Thigh ROM decreased for both control and EF in training but increased for EF only in retention. These results imply a delayed response with EF training, but no effect for IF training.Manuscript 3 investigated the correlation of the variables of standardized tests with the phone variables, and found the Timed Up and Go, Functional Gait Assessment, ABC Scale and Berg Balance Scale were correlated to Thigh ROM and Mean Peak Flexion with all conditions (EO, EC, HS), as well as with step timing variability for FGA and Berg in headshake and eyes closed condition. Grip strength only correlated with the training time frame of the study, but not with balance testing. Grip may be uncorrelated if changes of aging in the upper extremity have disparity to the changes of lower extremities.
This dissertation aimed to quantify the effects of randomized controlled trial (RCT) pediatric lifestyle interventions in treating childhood obesity. An additional aim of the dissertation was to ...examine the efficacy of the BRAVO!, the psychological need-support centered lifestyle intervention, on participants’ body composition and health-related fitness.A systematic review and meta-analysis were conducted to determine the efficacy of RCT pediatric lifestyle interventions in treating obesity among 11- to 17-year-old children. The primary outcome variables were body mass index (BMI), standardized BMI (BMIz), and waist circumference (WC). The results showed that pediatric lifestyle interventions were moderately effective in improving overweight and obese children’s BMI (-1.77 kg/m2, 95% CI -2.65, -.88, p < .001), BMIz (-.30, 95% CI -.44, -.17, p < .001), and WC (-3.72 cm, 95% CI -5.59, -1.85, p < .001). In addition, moderation analyses suggested that lifestyle interventions were the most effective when participants were 13 to 15 years old and at the higher end of the obesity spectrum.Furthermore, to test the efficacy of psychological need-support centered lifestyle intervention BRAVO!, an RCT was conducted with a sample of 40 pediatrician-referred participants (Mage = 13.20 ± 1.54) allocated to two parallel arms: 1) BRAVO! (n = 20) and b) “usual care” (n = 20). The 12-week BRAVO! consisted of 24 exercise sessions (twice/week, 60min/session) and family-based nutrition classes (once/week, 30min/session) and psychological need-support-centered behavior modification. The results showed that BRAVO! was efficacious in generating positive changes in participants’ BMI (F1, 31 = 23.83, p < .001, ηp2 = .45), WC (F1, 31 = 26.58, p < .001, ηp2 = .48), cardiovascular endurance (F1,31 = 8.18, p = .008, ηp2 = .23), upper body (F1, 31 = 28.33, p < .001, ηp2 = .50), and abdominal muscular strength/endurance (F1, 31 = 28.34, p < .001, ηp2 = .45). The changes in cardiovascular endurance vanished over time, but the changes in BMI, WC, upper body muscular and abdominal muscular strength/endurance remained for a longer term. Conclusions: BRAVO! lifestyle program was efficacious in improving at-risk Hispanic children’s body composition and health-related fitness, behavioral, and psychological outcomes in the short and longer term.
Within-subject training models, whereby researchers apply an exercise condition to one limb, and a separate exercise condition to the opposing limb, have become routine amongst the exercise ...literature. However, no study has directly tested whether exercising one limb with a high-load condition will influence strength adaptations within the opposing limb, even when the opposite limb is training. Furthermore, muscle post-activation performance enhancement (PAPE) is representing local level changes, however, more research is warranted to understand if this can be differentially impacted with different types (e.g. low load vs. high load) of resistance training. The purpose of this study was to determine if unilateral high-load training influences strength adaptations within the contralateral limb. A secondary purpose was to discern whether PAPE could be increased with resistance training. 116 participants were randomized to one of three intervention groups, and completed 18 training sessions involving isotonic elbow flexion exercise. Group 1 trained their dominant arm only, with a one-repetition maximum (1RM) test (maximum five attempts), followed by four sets of traditional exercise at an 8–12 RM. Group 2 completed the same training as Group 1 in their dominant arm, whilst the non-dominant arm completed four sets of low-load exercise (30–40 RM). Group 3 trained their non-dominant arm only, performing the same low-load exercise as Group 2. Participants were compared for changes in muscle thickness, isotonic elbow flexion 1RM, and postactivation performance enhancement (PAPE). Groups 1 (Δ 1.5 kg) and 2 (Δ1.1 kg) presented the greatest changes in non-dominant strength, as compared to Group 3 (Δ 0.3 kg). Only the arms being directly trained saw changes in muscle thickness, when compared to the untrained limbs. There were no differences amongst groups for changes in PAPE. Unilateral high-load training appears to influence strength changes in the contralateral arm, despite the contralateral arm training with a low-load exercise. Results of this study have broader implications for future research, and suggest that within-subject training models cannot be used when the primary outcome is strength changes.
Accelerometers are frequently used to measure physical activity (PA) in children, which is important for overall health and development. Lack of uniformity in data processing methods, such as the ...metric used to summarize accelerometer data, limits comparability between studies. The objective was to determine the convergent validity of five accelerometer metrics for characterizing the intensity and temporal patterns of first and second graders’ (n=88) recess PA. At a 5-s epoch level, Pearson’s correlations between various metrics ranged from 0.69 to 0.98. When each epoch was classified into one of four activity levels based on quartiles, agreement between metrics as indicated by weighted kappa ranged from 0.81 to 0.96. When collapsed to time spent in each activity level, metrics were most often statistically equivalent for estimating time spent in quartile 3 or 4. Children were ranked from least to most active, and agreement between metrics was strong with Spearman’s correlation coefficients of over r=0.86. Temporal patterns were characterized using five fragmentation indices calculated using each of the five metrics. Pearson’s correlations between metrics ranged from r=0.53 to 0.99, with the strongest associations for number of high activity bouts. Most fragmentation indices were not statistically equivalent between metrics. While metrics captured similar trends in activity intensity and temporal patterns, caution is warranted when making comparisons of point estimates derived from different metrics. However, all metrics were able to similarly capture higher intensity activity (i.e., quartile 3 or 4), the most common outcome of interest in intervention studies.
Normal aging is often associated with the decline in postural stability and balance in older adults. Consequently, many older adults may face difficulties when using virtual reality (VR) systems, ...where users often experience imbalance effects. Age-related deficits in balance and the imbalance effects caused by VR systems presents a challenging limitation for older adults and general VR usability. However, methods to reduce these effects have not been thoroughly explored. We recruited 20 older adults (>50 years) and 20 young adults (18-24 years) in the present study to investigate and compare the effects of several audio-based feedbacks on postural stability and balance while in an immersive virtual environment (VE). In this study, we used four audio-based feedback conditions: spatial feedback, static feedback, rhythmic feedback, Center of Pressure (CoP)-based feedback, and a no-feedback in VR condition. Participants performed a non-VR standing balance task and a standing reach-to-grasp task. Then, using a head-mounted display (HMD), each participant performed a virtual replication of both the standing balance and standing reach-to-grasp task in VR. We used a force plate to calculate the participant's mean CoP velocity for each audio-based feedback condition during each balance study task. The within-subject results indicated that when spatial feedback was available, older adults exhibited significantly decreased CoP velocity and therefore increased postural stability for both the standing balance task and standing reach-to-grasp task. However, we did not find significant differences in CoP velocity for the static, rhythmic, and CoP-based feedback conditions, nor did we find significant differences in CoP velocities within the young adult participants. In this study, results suggest that spatial feedback techniques can be used in immersive VR environments to improve postural stability and balance in older adult users.
