Validity and reliability of a novel optoelectronic device to measure movement velocity,force and power during the back squat exercise

This study analysed the validity and reliability of a new optoelectronic device (Velowin) for the measurement of vertical displacement and velocity as well as to estimate force and mechanical power. Eleven trained males with Mean (SD) age = 27.4 (4.8) years, completed an incremental squat exercise test with 5 different loads (<30–90% of their 1?repetition maximum) while displacement and vertical velocity of the barbell were simultaneously measured using an integrated 3D system (3D motion capture system + force platform) and Velowin. Substantial to almost perfect correlation (concordance correlation coefficient = 0.75–0.96), root mean square error as coefficient of variation ±90% confidence interval ≤10% and good to excellent intraclass correlation coefficient = 0.84–0.99 were determined for all the variables. Passing and Bablock regression methods revealed no differences for average velocity. However, significant but consistent bias were determined for average or peak force and power while systematic and not proportional bias was found for displacement. In conclusion, Velowin, in holds of some potential advantages over traditionally used accelerometer or linear transducers, represents a valid and reliable alternative to monitor vertical displacement and velocity as well as to estimate average force and mechanical power during the squat exercise.     

Validity and reliability of a novel iPhone app for the measurement of barbell velocity and 1RM on the bench-press exercise

The purpose of this study was to analyse the validity and reliability of a novel iPhone app (named: PowerLift) for the measurement of mean velocity on the bench-press exercise. Additionally, the accuracy of the estimation of the 1-Repetition maximum (1RM) using the load–velocity relationship was tested. To do this, 10 powerlifters (Mean (SD): age = 26.5 ± 6.5 years; bench press 1RM · kg^?1 = 1.34 ± 0.25) completed an incremental test on the bench-press exercise with 5 different loads (75–100% 1RM), while the mean velocity of the barbell was registered using a linear transducer (LT) and Powerlift. Results showed a very high correlation between the LT and the app (r = 0.94, SEE = 0.028 m · s^?1) for the measurement of mean velocity. Bland–Altman plots (R² = 0.011) and intraclass correlation coefficient (ICC = 0.965) revealed a very high agreement between both devices. A systematic bias by which the app registered slightly higher values than the LT (P < 0.05; mean difference (SD) between instruments = 0.008 ± 0.03 m · s^?1). Finally, actual and estimated 1RM using the app were highly correlated (r = 0.98, mean difference (SD) = 5.5 ± 9.6 kg, P < 0.05). The app was found to be highly valid and reliable in comparison with a LT. These findings could have valuable practical applications for strength and conditioning coaches who wish to measure barbell velocity in the bench-press exercise.     

Validity and reliability of a computer-vision-based smartphone app for measuring barbell trajectory during the snatch

ABSTRACT

The purpose of this study was to investigate the validity of a smartphone app to measure biomechanical barbell parameters during the snatch. Ten collegiate NCAA division I athletes performed two repetitions each at 40, 50, 60, 70, and 80% of their 1-repetition maximum snatch. Barbell motions were simultaneously recorded with a motion capture system and the smartphone app. The motion capture system recorded the 3-D position of a reflective marker attached to the end of the barbell while the smartphone app was used to record sagittal plane video and track the shape of the weight plate from which the barbell center was derived. Peak forward (PFD) and backward (PBD) displacements and peak vertical displacement (PVD) and velocity (PVV) were calculated from both sets of data. Significant, strong to very strong Pearson’s product-moment correlation coefficients between both systems were noted for all parameters (r = 0.729–0.902, all p < 0.001). Small significant biases between systems were observed for PVD (ES = 0.284, p < 0.001) and PFD (ES=0.340, p < 0.01), while trivial to small, non-significant biases were observed for PBD (ES = 0.143) and PVV (ES = –0.100). Collectively, the results suggest that the app can provide biomechanical data of barbell motions similar to a 3-D motion capture system.     

Adipose tissue lipolytic inhibition enhances the glucoregulatory properties of exercise in type 2 diabetes patients

Aims: Exercise combined with adipose tissue lipolytic inhibition augments intramuscular lipid and glycogen use in type 2 diabetes patients. The present study investigates the impact of adipose tissue lipolytic inhibition during exercise on subsequent postprandial glycemic control in type 2 diabetes patients.

Methods: Fourteen male type 2 diabetes patients (age 65?±?2 years, HbA_1c 6.7?±?0.1% (50?±?2?mmol/mol)) participated in a double-blind placebo-controlled randomized cross-over study in which subjects performed endurance-type exercise after being administered 250?mg of a nicotinic acid analogue (acipimox; ACP) or a placebo (PLA). A control experiment was included in which no exercise was performed (CON).

Results: Sixty minutes of endurance-type exercise (at 45% W_peak) did not significantly lower circulating plasma glucose and insulin excursions in PLA when compared with CON (P?=?.300). Acipimox administration strongly reduced circulating plasma FFA concentrations during exercise (P?i.e. postprandial) in ACP when compared with either CON (P?=?.041 and P?=?.002, respectively) or PLA (P?=?.009 and P?=?.001, respectively).

Conclusions: Collectively, exercise with adipose tissue lipolytic inhibition reduces postprandial blood glucose and insulin excursions and, as such, further improves glycemic control in male type 2 diabetes patients.     

急性低氧对优秀男子自行车运动员递增负荷运动时肌氧含量的影响

目的:探讨急性低氧环境下递增负荷运动时肌氧含量的变化。方法:通过无损伤近红外光谱学技术(NIRS)监测11名优秀男子自行车运动员常氧和急性低氧下进行递增负荷运动时肌氧含量和心肺系统功能的变化。结果:1)低氧运动时,无氧阈(VT)和最大摄氧量(VO2max)出现时对应的心率、指动脉血氧饱和度(SpO2)、气体代谢和功率均下降,显著低于常氧运动时的值;2)低氧环境下,从开始运动到75%最大功率,Δ[HbO2]降低、Δ[HHb]增高;由75%至100%最大功率时,Δ[HbO2]保持不变,而Δ[HHb]和Δ[THb]增加;在4个不同功率等级下低氧Δ[HbO2]均显著高于常氧值,Δ[HHb]在50%、75%和100%最大功率时均显著低于常氧对应值。结论:1)男子自行车运动员低氧下运动时低氧通气反应高于常氧水平,说明提高自行车运动员在高原训练时的低氧通气反应有利于提高其有氧能力,进而提高运动成绩。2)低氧运动时Δ[HbO2]高于常氧值,Δ[HHb]低于常氧值,提示肌氧含量是反映肌肉疲劳程度的敏感指标。     

Validity of the ActiGraph GT1M during walking and cycling

Abstract

The ActiGraph activity monitors have developed and newer versions of the ActiGraph accelerometers (GT1M, GT3X and GT3X +) are now available, including changes in hardware and software compared to the old version (AM7164). This is problematic as most of the validation and calibration work includes the AM7164. The aims of the study were to validate the ActiGraph GT1M during level and graded walking and to assess the potential underestimation of physical activity during cycling. Data were obtained from 20 participants during treadmill walking and ergometer cycling. Energy expenditure was measured via indirect calorimetry and used as the criterion method. Activity counts were highly correlated with energy expenditure during level walking (R² = 0.82) and graded walking at 5% and 8% (R² = 0.82 and R² = 0.67, respectively). There was no linear relationship between activity counts and energy expenditure during cycling. The average activity counts for all data points during cycling was 1,157 counts per minute (CPM) (SD = 974), and mean energy expenditure was 5.0 metabolic equivalents. The GT1M is a valid tool for assessing walking across a wide range of speeds and gradients. However, there is no relationship between activity counts and energy expenditure during cycling and physical activity is underestimated by ≈73% during cycling compared to walking.     

Effects of weightlifting exercise,traditional resistance and plyometric training on countermovement jump performance: a meta-analysis

Jump performance is considered an important factor in many sports. Thus, strategies such as weightlifting (WL) exercises, traditional resistance training (TRT) and plyometric training (PT) are effective at improving jump performance. However, it is not entirely clear which of these strategies can enable greater improvements on jump height. Thus, the purpose of the meta-analysis was to compare the improvements on countermovement jump (CMJ) performance between training methods which focus on WL exercises, TRT, and PT. Seven studies were included, of which one study performed both comparison. Therefore, four studies comparing WL exercises vs. TRT (total n = 78) and four studies comparing WL exercises vs. PT (total n = 76). The results showed greater improvements on CMJ performance for WL exercises compared to TRT (ES_diff: 0.72 ± 0.23; _95%CI: 0.26, 1.19; P = 0.002; Δ % = 7.5 and 2.1, respectively). The comparison between WL exercises vs. PT revealed no significant difference between protocols (ES_diff: 0.15 ± 0.23; _95%CI: ?0.30, 0.60; P = 0.518; Δ % = 8.8 and 8.1, respectively). In conclusion, WL exercises are superior to promote positive changes on CMJ performance compared to TRT; however, WL exercises and PT are equally effective at improving CMJ performance.     

The 3-minute all-out cycling test is sensitive to changes in cadence using the Lode Excalibur Sport ergometer

This study investigated the effect cadence has on the estimation of critical power (CP) and the finite work capacity (W?) during the 3-minute all-out cycling test. Ten participants completed 8 tests: 1) an incremental test to calculate gas exchange threshold (GET), maximal aerobic power (MAP) and peak oxygen uptake (V?O_2peak), 2–4) three time-to-exhaustion tests at 80, 100 and 105% MAP to calculate CP and W?, 5–7) four 3-minute all-out tests to calculate end power (EP) and work done above EP (WEP) using cadences ranging from preferred ?5 to preferred +10 rev·min^?1 to set the fixed resistance. Significant differences were seen between CP and EP-preferred (267.5 ± 22.6 W vs. 296.6 ± 26.1 W, P < 0.001), CP and EP?5 (267.5 ± 22.6 W vs. 303.6 ± 24.0 W, P < 0.001) and between CP and EP+5 (267.5 ± 22.6 W vs. 290.0 ± 28.0 W, P = 0.002). No significant differences were seen between CP and EP+10 (267.5 ± 22.6 W vs. 278.1 ± 30.9 W, P = 0.331). Significant differences were seen between W? and WEP at all tested fixed resistances. EP is reduced when cycling at higher than preferred cadences, providing better estimates of CP.     

Differences in the magnitude and reliability of velocity variables collected during 3 variants of the bench press exercise

ABSTRACT

This study aimed to compare the reliability and magnitude of velocity variables between 3 variants of the bench press (BP) exercise in participants with and without BP training experience. Thirty males, 15 with and 15 without BP experience, randomly performed 3 variants of the BP on separate sessions: (I) concentric-only, (II) fast-eccentric and (III) controlled-eccentric. The mean velocity (MV) and maximum velocity (V_max) of the concentric phase were collected against 3 loads (≈30%1RM, 50%1RM, and 75%1RM) with a linear velocity transducer. Reliability was high regardless of the variable, BP variant, and load (coefficient of variation [CV] ≤ 4.47%, intraclass correlation coefficient [ICC] ≥ 0.87). The comparison of the CVs suggested a higher reliability for the fast-eccentric BP (8 out of 12 comparisons), followed by the concentric-only BP (5 out of 12 comparisons), and finally the controlled-eccentric BP (never provided a higher reliability). No differences in reliability were observed between experienced (CV ≤ 4.71%; ICC ≥ 0.79) and non-experienced (CV ≤ 6.29%; ICC ≥ 0.76) participants. The fast-eccentric BP provided the highest MV (p < 0.05) and no differences were observed for V_max. These results support the assessment of movement velocity during the fast-eccentric BP even in participants without experience.     

Women and exercise in aging

Aging is associated with physiological declines, notably a decrease in bone mineral density (BMD) and lean body mass, with a concurrent increase in body fat and central adiposity. Interest in women and aging is of particular interest partly as a result of gender specific responses to aging, particularly as a result of menopause. It is possible that the onset of menopause may augment the physiological decline associated with aging and inactivity. More so, a higher incidence of metabolic syndrome (an accumulation of cardiovascular disease risk factors including obesity, low-density lipoprotein cholesterol, high blood pressure, and high fasting glucose) has been shown in middle-aged women during the postmenopausal period. This is due in part to the drastic changes in body composition, as previously discussed, but also a change in physical activity (PA) levels. Sarcopenia is an age related decrease in the cross-sectional area of skeletal muscle fibers that consequently leads to a decline in physical function, gait speed, balance, coordination, decreased BMD, and quality of life. PA plays an essential role in combating physiological decline associated with aging. Maintenance of adequate levels of PA can result in increased longevity and a reduced risk for metabolic disease along with other chronic diseases. The aim of this paper is to review relevant literature, examine current PA guidelines, and provide recommendations specific to women based on current research.     

运动训练中的若干运动生理学常用指标研究

本文结合运动实践,通过文献资料法,对运动训练中的心率、最大摄氧量、无氧阈、乳酸等运动生理学常用指标进行了系统研究,以希对运动训练、全民健身运动中的运动生理学指标的选择有所帮助,对提高科学化训练水平有一定实践意义。     

Validity and reliability of a low-cost digital dynamometer for measuring isometric strength of lower limb

Lower limb isometric strength is a key parameter to monitor the training process or recognise muscle weakness and injury risk. However, valid and reliable methods to evaluate it often require high-cost tools. The aim of this study was to analyse the concurrent validity and reliability of a low-cost digital dynamometer for measuring isometric strength in lower limb. Eleven physically active and healthy participants performed maximal isometric strength for: flexion and extension of ankle, flexion and extension of knee, flexion, extension, adduction, abduction, internal and external rotation of hip. Data obtained by the digital dynamometer were compared with the isokinetic dynamometer to examine its concurrent validity. Data obtained by the digital dynamometer from 2 different evaluators and 2 different sessions were compared to examine its inter-rater and intra-rater reliability. Intra-class correlation (ICC) for validity was excellent in every movement (ICC > 0.9). Intra and inter-tester reliability was excellent for all the movements assessed (ICC > 0.75). The low-cost digital dynamometer demonstrated strong concurrent validity and excellent intra and inter-tester reliability for assessing isometric strength in the main lower limb movements.     

Ventilation and blood lactate increase exponentially during incremental exercise.

This study examined whether the ventilatory (V) compensation for metabolic acidosis with increasing O2 uptake (VO2) and CO2 output (VCO2) might be more in accord with the theoretical expectation of a progressive acceleration of proton production from carbohydrate oxidation rather than a sudden onset of blood lactate (BLa) accumulation. The interrelationships between V, VO2, VCO2 and BLa concentration, [BLa], were investigated in 10 endurance-trained male cyclists during incremental (120 +/- 15 W min-1) exercise tests to exhaustion. Regression analyses on the V, VCO2 and [BLa] vs VO2 data revealed that all were better fitted by continuous Y = A.exp.[B.VO2] + C rate laws than by threshold linear rate equations (P < 0.0001). Plots of V vs VCO2 and [BLa] were also non-linear. Ventilation increased as an exponential V = 27 +/- 4.exp.[0.37 +/- 0.03.VCO2] function of VCO2 and as a hyperbolic function of [BLa]. In opposition to the 'anaerobic (lactate) threshold' hypothesis, we suggest these data are more readily explained by a continuous development of acidosis, rather than a sudden onset of BLa accumulation, during progressive exercise.     

Nutritional intake and body composition changes in a UCI World Tour cycling team during the Tour of Spain

Abstract

The aim of this study was to quantify the food intake of an International Cyclist Union (UCI) World Tour professional cyclist team and to analyse changes in body composition during the Tour of Spain. Nine male professional road cyclists (31.3?±?3.0 years) volunteered to participate in the study. Nutritional data were collected each day throughout the 3-week Tour by two trained investigators who weighed the food ingested by the cyclists. Mean nutritional intake of the cyclists was as follows: carbohydrate, 12.5?±?1.8?g/kg/day of body weight (BW) (65.0?±?5.9%); fat, 1.5?±?0.5 g/kg/day BW (17.9?±?5.6%); and protein, 3.3?±?0.3?g/kg/day BW (17.1?±?1.6%). Intake of all micronutrients, except for folate, vitamin D and potassium (which were 78.7%, 46% and 84% of Recommended Dietary Allowances (RDA), respectively), exceeded the RDA. Height, weight, skinfolds, circumferences and diameters were taken following the guidelines outlined by the International Society for the Advancement of Kinanthropometry. Body density, body fat percentage, muscle mass, total muscle mass and fat mass of the arms and thighs were calculated. Percentage body fat, fat mass and upper arm fat mass significantly decreased (p < .05) after the Tour independent of the equation method used in the calculations. Total muscle mass remained unchanged. Generally, this sample of cyclists consumed more protein and less fat than the recommended amount and had low weight, BMI and fat mass. It is suggested that sports nutritionists design personalised diets in order to maintain a correct proportion of nutrients as well as controlling possible anthropometrical changes that could affect performance.     

Effects of a phase change cooling garment during exercise in the heat

The purpose of our study was to examine the physiological, perceptual, and performance effects of wearing a phase change cooling garment (CG) during an interval exercise routine in the heat. Sixteen male participants (age 23?±?3 years, ht 1.76?±?0.11?m; wt 78.5?±?11.2?kg; body fat 15.2?±?5.8%) completed two trials (one with phase change inserts, CG, and one control without inserts) consisting of two submaximal exercise portions separated by 5-minute seated rest, and a final maximal effort performance bout. Each submaximal bout involved 30?seconds or 1?minute of muscular endurance and agility exercises and 5?minutes of treadmill jogging and step-ups. The performance bout included 30?seconds or 1?minute of muscular endurance and agility exercises, with participants completing as many repetitions as possible, followed by a 15-minute recovery (active and passive). Rectal temperature (T_re) and heart rate were not different between trials, however change in T_re from baseline was improved during 10 and 15 minutes of recovery with the CG (P?<?.05). Mean skin temperature was lower using the CG vs control throughout the trial (P?<?.05). Thermal sensation was lower when using the CG compared to control (P?<?.001). There were no differences in any outcomes of the performance exercises (P?>?.05). These findings indicate that the continuous use of a CG during an interval style workout in the heat provides improvements in thermal sensation, however, only minimal thermophysiological benefits, and no performance augmentation.     

Six high-intensity interval training sessions over 5 days increases maximal oxygen uptake,endurance capacity,and sub-maximal exercise fat oxidation as much as 6 high-intensity interval training sessions over 2 weeks

BackgroundHigh-intensity interval training (HIIT) induces similar or even superior adaptations compared to continuous endurance training. Indeed, just 6 HIIT sessions over 2 weeks significantly improves maximal oxygen uptake (VO_2max), submaximal exercise fat oxidation, and endurance performance. Whether even faster adaptations can be achieved with HIIT is not known. Thus, we aimed to determine whether 2 sessions of HIIT per day, separated by 3 h, every other day for 5 days (double HIIT (HIIT-D), n = 15) could increase VO_2max, submaximal exercise fat oxidation, and endurance capacity as effectively as 6 sessions of HIIT over 2 weeks (single HIIT (HIIT-S), n = 13).MethodsEach training session consisted of 10 × 60 s of cycling at 100% of VO_2max interspersed with 75 s of low-intensity cycling at 60 watt (W). Pre- and post-training assessments included VO_2max, time to exhaustion at ∼80% of VO_2max, and 60-min cycling trials at ∼67% of VO_2max.ResultsSimilar increases (p < 0.05) in VO_2max (HIIT-D: 7.7% vs. HIIT-S: 6.0%, p > 0.05) and endurance capacity (HIIT-D: 80.1% vs. HIIT-S: 79.2%, p > 0.05) were observed. Submaximal exercise carbohydrate oxidation was reduced in the 2 groups after exercise training (HIIT-D: 9.2%, p = 0.014 vs. HIIT-S: 18.8%, p = 0.012) while submaximal exercise fat oxidation was significantly increased in HIIT-D (15.5%, p = 0.048) but not in HIIT-S (9.3%, p = 0.290).ConclusionSix HIIT sessions over 5 days was as effective in increasing VO_2max and endurance capacity and was more effective in improving submaximal exercise fat oxidation than 6 HIIT sessions over 2 weeks.     

Quantifying the effects of acute hypoxic exposure on exercise performance and capacity: A systematic review and meta-regression

Objective: To quantify the effects of acute hypoxic exposure on exercise capacity and performance, which includes continuous and intermittent forms of exercise. Design: A systematic review was conducted with a three-level mixed effects meta-regression. The ratio of means method was used to evaluate main effects and moderators providing practical interpretations with percentage change. Data sources: A systemic search was performed using three databases (Google scholar, PubMed and SPORTDiscus). Eligibility criteria for selecting studies: Inclusion was restricted to investigations that assessed exercise performance (time trials (TTs), sprint and intermittent exercise tests) and capacity (time to exhaustion test, TTE) with acute hypoxic (<24?h) exposure and a normoxic comparator. Results: Eighty-two outcomes from 53 studies (N?=?798) were included in this review. The results show an overall reduction in exercise performance/capacity ?17.8?±?3.9% (95% CI ?22.8% to ?11.0%), which was significantly moderated by ?6.5?±?0.9% per 1000 m altitude elevation (95% CI ?8.2% to ?4.8%) and oxygen saturation (?2.0?±?0.4%; 95% CI ?2.9% to ?1.2%). TT (?16.2?±?4.3%; 95% CI ?22.9% to ?9%) and TTE (?44.5?±?6.9%; 95% CI ?51.3% to ?36.7%) elicited a negative effect, whilst indicating a quadratic relationship between hypoxic magnitude and both TTE and TT performance. Furthermore, exercise less than 2 min exhibited no ergolytic effect from acute hypoxia.

Summary/Conclusion: This review highlights the ergolytic effect of acute hypoxic exposure, which is curvilinear for TTE and TT performance with increasing hypoxic levels, but short duration intermittent and sprint exercise seem to be unaffected.     

Validity of the Actical activity monitor for assessing steps and energy expenditure during walking

This study examined the validity of the Actical accelerometer step count and energy expenditure (EE) functions in healthy young adults. Forty-three participants participated in study 1. Actical step counts were compared to actual steps taken during a 200 m walk around an indoor track at self-selected pace and during treadmill walking at different speeds (0.894, 1.56 and 2.01 m · s^–1) for 5 min. The Actical was also compared to three pedometers. For study 2, 15 participants from study 1 walked on a treadmill at their predetermined self-selected pace for 15 min. Actical EE was compared to EE measured by indirect calorimetry. One-way analysis of variance and t-tests were used to examine differences. There were no statistical difference between Actical steps and actual steps in self-selected pace walking and during treadmill walking at moderate and fast speeds. During treadmill walking at slow speed, the Actical step counts significantly under predicted actual steps taken. For study 2, there was no statistical difference between measured EE and Actical-recorded EE. The Actical provides valid estimates of step counts at self-selected pace and walking at constant speeds of 1.56 and 2.01 m · s^–1. The Actical underestimates EE of walking at constants speeds ≥1.38 m · s^–1.