Longitudinal Analysis of Cardiovascular Risk Factors in Active and Sedentary Kidney Transplant Recipients.

Background: Despite the benefits of physical activity on cardiovascular risk in kidney transplant recipients (KTRs), the long-term effects of exercise have been poorly investigated. This is a three-year observational study comparing graft function and cardiovascular risk factors in active KTRs (AKTRs) vs. sedentary KTRs (SKTRs). Methods: KTRs with stable renal function were assigned to active or sedentary group in relation to the level of daily physical activity based on World Health Organization (WHO) recommendations (<150 or >150 minutes/week, respectively). Complete blood count, renal function indices, lipid profile, blood pressure and anthropometric measures were collected yearly for an observation period of three years. The comparisons between the two groups were performed by repeated measures analyses of covariance (ANCOVAs), with age as a covariate. Results: Fifty-four subjects were included in the study. Thirty of them were identified as AKTRs (M/F 26/4, aged 45 ± 12 years) and 24 as SKTRs (M/F 18/6, aged 51 ± 14 years). Baseline characteristics were similar between the groups except body mass index (BMI) that was significantly higher in SKTRs (p = 0.043). Furthermore, over the three-year observation period, BMI decreased in AKTRs and increased in SKTRs (p = 0.006). Graft function was stable in AKTRs, while it showed a decline over time in SKTRs, as indicated by the rise in serum creatinine levels (p = 0.006) and lower eGFR (p = 0.050). Proteinuria, glucose and uric acid levels displayed a decrease in AKTRs and an increase in SKTRs during the three-year period (p = 0.015, p = 0.004 and p = 0.013, respectively). Finally, concerning lipid profiles, AKTRs had a significant reduction over time of triglycerides levels, which conversely showed a clinically relevant increase in SKTRs (p = 0.014). Conclusions: Our findings indicate that regular weekly exercise training may counteract the increased cardiovascular risks and also prevent graft function decline in KTRs.

Height prediction in elite Italian rugby players: A prospective study.

OBJECTIVES: We investigated the validity of the Mirwald equation as an estimate of height in a cohort of rugby players. METHODS: This was a prospective study with agreement analysis of height assessments conducted in 39 male youth rugby players (mean age 15.1 ± 0.9 years). During the 2007/2008 season, 151 young athletes were selected by rugby coaches using subjective decisions based on current performance and future potential. The rugby players were measured by physician experts and their height was estimated using the Mirwald formula (MF). Only 39 athletes were finally selected because they reached an elite level, allowing actual adult height to be collected from the official team websites in June 2018. Method agreement was assessed by intraclass correlation coefficient, regression, and plotted by Bland and Altman analysis. RESULTS: Twenty athletes played in the Italian National team and 19 in the First Italian Division (Eccellenza). Overall, they presented an early maturation and the MF was able to accurately estimate height. The MF underestimated height (187.4-189.1 cm) and showed a high association with actual adult players' height (r = 0.925, P < .001). CONCLUSIONS: Our results demonstrate that the MF, whose estimation of stature is based on height, sitting height, body mass, and leg length is able to predict stature in rugby players.

Physiological and Sport-Specific Comparison Between Division I and Division II Italian Male Field Hockey Players.

Bartolomei, S, Nigro, F, Gubellini, L, Ciacci, S, Merni, F, Treno, F, Cortesi, M, and Semprini, G. Physiological and sport-specific comparison between Division I and Division II Italian male field hockey players. J Strength Cond Res 33(11): 3123-3128, 2019-The purpose of this study was to compare the anthropometric and performance profiles of Division I (D1) and Division II (D2) Italian field hockey players. Fifteen DI players and 15 D2 players (age = 25.4 ± 5.2 years; body mass = 78.5 ± 9.0 kg; and body height = 179.6 ± 7.8 cm) were assessed on one occasion for anthropometry, body composition, physiological measurements, and sport-specific skills. Differences between the 2 groups were evaluated using a 1-way analysis of variance. Pearson correlations were used to examine relationships between the different measurements. Significantly (p = 0.039) lower percentages of body fat were found on D1 group compared with D2 group (-3.5%). A significant difference between the groups were noted for shooting accuracy (p = 0.013), with the D1 group performing 14.5% better than the DII group. No significant differences between the groups were found for shooting speed (p = 0.103) and slalom and dribbling performances (p = 0.292 and p = 0.416, respectively). Physiological assessments did not show any significant differences between the groups. Large correlations (r = 0.73; p < 0.001) were found between shooting speed and accuracy. Moderate correlations were observed between the shooting speed and the hand grip strength, in particular of the left hand (r = 0.61; p = 0.007). Results of this study indicate that the difference between D1 and D2 players may be more related to technical factors than to physical fitness. Ball control, however, may not be a limiting factor in D2 players.

Joint assessment of handedness and footedness through latent class factor analysis.

Recently, some studies have demonstrated the effectiveness of two latent variable approaches in which hand preferences are analysed using either latent class methods or latent class factor (LCF) methods. The main aims of this study are: (i) to establish whether these approaches are adequate for assessing footedness, (ii) to evaluate their appropriateness when hand and foot preferences are jointly analysed, and (iii) to measure the association between handedness and footedness based on the examined latent variable models. To this end, a dataset providing information about the limb used to perform ten hand actions and three foot movements by 2236 young Italian sportspeople is analysed. The first aim is pursued through an exploratory analysis of the observed foot preferences; according to this analysis, footedness patterns are adequately described by two latent levels of footedness. As far as the second aim is concerned, a confirmatory analysis of foot and hand preferences is carried out; the best fit to the dataset is obtained using a two-dimensional LCF model with four latent levels of handedness and two latent levels of footedness. Finally, the association between handedness and footedness resulting from the employed methods is remarkably lower than that registered in other studies.

Effect of Lower-Body Resistance Training on Upper-Body Strength Adaptation in Trained Men.

Bartolomei, S, Hoffman, JR, Stout, JR, and Merni, F. Effect of lower-body resistance training on upper-body strength adaptation in trained men. J Strength Cond Res 32(1): 13-18, 2018-The aim of this study was to examine the effect of 2 different lower-body strength training schemes on upper-body adaptations to resistance training. Twenty resistance-trained men (4.25 ± 1.6 years of experience) were randomly assigned to either a high intensity (HI; n = 9; age = 24.9 ± 2.9 years; body mass = 88.7 ± 17.2 kg; height = 177.0 ± 5.6 cm) or a mixed high volume and HI resistance training program (MP; n = 11; age = 26.0 ± 4.7 years; body mass = 82.8 ± 9.1 kg; height = 177.54 ± 5.9 cm). High-intensity group followed a HI training for both upper and lower body (4-5 reps at 88%-90% of 1 repetition maximum (1RM)), whereas the MP group performed high-volume training sessions focused on muscle hypertrophy for lower body (10-12 reps at 65%-70% of 1-RM) and a HI protocol for the upper body. Maximal strength and power testing occurred before and after the 6-week training program. Analysis of covariance was used to compare performance measures between the groups. Greater increases in MP groups compared with HI groups were observed for bench press 1RM (p = 0.007), bench press power at 50% of 1RM (p = 0.011), and for arm muscle area (p = 0.046). Significant difference between the 2 groups at posttest were also observed for fat mass (p = 0.009). Results indicated that training programs focused on lower-body muscle hypertrophy and maximal strength for upper body can stimulate greater strength and power gains in the upper body compared with HI resistance training programs for both the upper and lower body.

Acute Effects of Ammonia Inhalants on Strength and Power Performance in Trained Men.

Bartolomei, S, Nigro, F, Luca, G, Gabriele, S, Ciacci, S, Hoffman, JR, and Merni, F. Acute effects of ammonia inhalants on strength and power performance in trained men. J Strength Cond Res 32(1): 244-247, 2018-The aim of the present study was to investigate the influence of ammonia inhalants on lower body power and maximal isometric strength in trained men. Twenty experienced resistance trained men (age = 26.7 ± 3.7 years; body weight = 80.59 ± 9.0 kg; body height = 179.5 ± 5.7 cm) were tested for counter movement jump power (CMJP), maximal force, and peak rate of force development (pRFD20) expressed during an isometric midthigh pull (IMTP). Assessments were performed using either an ammonia inhalant (AI), a placebo (PL), or no inhalants (N). One-way analysis of variance (ANOVA) with repeated measures was used to compare strength and power performance between the different trials. A significant (p < 0.01) increase in pRFD20 was detected following the use of AI. No significant effects of trial were noted for CMJP and IMTP maximal force (p = 0.251 and p = 0.075, respectively). Results of the present study showed a potential ergogenic effect of AI on rate of force development (i.e., explosive force output), with a trend toward an improvement in maximal force production. The mechanism of action may be related to the stimulatory action of AI often reported by athletes as a "psyching-up" effect. The positive effect of AI on the rate of force development may represent an advantage in sports requiring high rates of force production.

Comparison Between Bench Press Throw and Ballistic Push-up Tests to Assess Upper-Body Power in Trained Individuals.

Bartolomei, S, Nigro, F, Ruggeri, S, Malagoli Lanzoni, I, Ciacci, S, Merni, F, Sadres, E, Hoffman, JR, and Semprini, G. Comparison between bench press throw and ballistic push-up tests to assess upper-body power in trained individuals. J Strength Cond Res 32(6): 1503-1510, 2018-The purpose of this study was to validate the ballistic push-up (BPU) test performed with hands on a force plate as a method to measure upper-body power. Twenty-eight experienced resistance-trained men (age = 25.4 ± 5.2 years; body mass = 78.5 ± 9.0 kg; body height = 179.6 ± 7.8 cm) performed, 2 days apart, a bench press 1 repetition maximum (1RM) test and upper-body power tests. Mean power (MP) and peak power (PP) were assessed using the bench press throw (BT) test and the BPU test performed in randomized order. The area under the force/power curve (AUC) obtained at BT was also calculated. Power expressed at BPU was estimated using a time-based prediction equation. Mean force and the participant's body weight were used to predict the bench press 1RM. Pearson product-moment correlations were used to examine relationships between the power assessment methods and between the predicted 1RM bench and the actual value. Large correlations (0.79; p < 0.001) were found between AUC and MP expressed at BPU. Large correlations were also detected between MP and PP expressed at BT and BPU (0.75; p < 0.001 and 0.74; p < 0.001, respectively). Very large correlations (0.87; p < 0.001) were found between the 1RM bench and the 1RM predicted by the BPU. Results of this study indicate that BPU represents a valid and reliable method to estimate the upper-body power in resistance-trained individuals.

The Energy Cost of Running with the Ball in Soccer.

Running with the ball is a soccer-specific activity frequently used by players during match play and training drills. Nevertheless, the energy cost (EC) of on-grass running with the ball has not yet been determined. The purpose of this study was therefore to assess the EC of constant-speed running with the ball, and to compare it with the EC of normal running. Eight amateur soccer players performed two 6- min runs at 10 km/h on artificial turf, respectively with and without the ball. EC was measured with indirect calorimetry and, furthermore, estimated with a method based on players' accelerations measured with a GPS receiver. The EC measured with indirect calorimetry was higher in running with the ball (4.60±0.42 J/kg/m) than in normal running (4.19±0.33 J/kg/m), with a very likely moderate difference between conditions. Instead, a likely small difference was observed between conditions for EC estimated from GPS data (4.87±0.07 vs. 4.83±0.08 J/kg/m). This study sheds light on the energy expenditure of playing soccer, providing relevant data about the EC of a typical soccer-specific activity. These findings may be a reference for coaches to precisely determine the training load in drills with the ball, such as soccer-specific circuits or small-sided games.

Sprint start kinematics during competition in elite and world-class male and female sprinters.

The start kinematics has been reported to differ between male and female sprinters. This study aimed to determine whether kinematic differences between the sexes are attributable to an effect of sex per se, or rather to the absolute performance level of the sprinters, quantified by the 100-m time. A total of 20 sprinters (10 M, 10 F), including world-class and elite athletes, were assessed. Start phases from the "set" position to the first two steps were analysed. Linear regression analyses showed a few significant differences between sexes when taking into account the effect of performance level: M had shorter pushing phase duration, higher horizontal velocity at block clearing, and shorter contact times of the first two steps. Conversely, the performance level affected most of the examined parameters: faster sprinters showed the centre of mass (CM) closer to the ground and a more flexed front knee in the "set" position, longer pushing phase duration, lower vertical velocity of the CM at block clearing, and longer contact times and shorter flight times in the first two steps. These findings suggest that the start kinematics is only partially affected by the sex of sprinters, whereas a bigger role is played by their performance level.

Block vs. Weekly Undulating Periodized Resistance Training Programs in Women.

The aim of this study was to compare the effects of resistance training using block periodization (BP) and weekly undulating (WUD) model on maximal strength and hypertrophy in recreationally strength trained women. Seventeen recreationally trained women were randomly assigned to either a BP group (n = 9; age = 24.7 ± 4.2 years; body mass = 62.1 ± 5.3 kg; height = 166.4 ± 6.0 cm) or a WUD group (n = 8; age = 23.2 ± 2.2 years; body mass = 59.8 ± 11.9 kg; height = 160.1 ± 4.1 cm). Participants of both groups trained 3 days a week for 10 weeks. The BP and WUD programs used the same exercises, and the difference between the 2 programs was in the distribution of the training volume within each training phase. Anthropometric measures and strength testing were performed before (PRE) and after 10 weeks (POST) of training. The results revealed that both BP and WUD groups made significant increases in strength and power, but improvements in lower-body strength were significantly (p = 0.039) greater in the WUD group (+27.7%) compared with the BP group (+15.2%). Both groups significantly increased arm muscle hypertrophy (p < 0.001), whereas improvements in thigh muscle size were significant in the WUD group only (+5.8%, p = 0.001). Results of this study indicate that the WUD model is more effective than the BP model for increasing maximal strength and muscle size in the lower body in women.

EFFECTS OF SELF-SELECTED MUSIC ON MAXIMAL BENCH PRESS STRENGTH AND STRENGTH ENDURANCE.

Listening to music during strength workouts has become a very common practice. The goal of this study was to assess the effect of listening to self-selected music on strength performances. Thirty-one resistance-trained men (M age = 24.7 yr., SD = 5.9; M height = 178.7 cm, SD = 4.7; M body mass = 83.54 kg, SD = 12.0) were randomly assigned to either a Music group (n = 19) or to a Control group (n = 12). Both groups took part in two separate sessions; each session consisted in a maximal strength test (1-RM) and a strength-endurance test (repetitions to failure at 60% 1-RM) using the bench press exercise. The music group listened to music in the second assessment session, while the control group performed both tests without music. Listening to music induced a significant increase of strength endurance performance and no effects on maximal strength. These findings have implications for the use of music during strength workouts.

Assessment of handedness using latent class factor analysis.

Recently several studies in which handedness was evaluated as a latent construct have been performed. In those studies, handedness was modelled using a qualitative latent variable (latent class models), a continuous latent variable (factor models), or both a qualitative latent variable and a continuous latent trait (mixed Rasch models). The aim of this study was to explore the usefulness and effectiveness of an approach in which handedness is treated as a qualitatively scaled latent variable with ordered categories (latent class factor models). This aim was pursued through an exploratory analysis of a dataset containing information on the hand used by 2236 young Italian sportspeople to perform 10 tasks. For comparison purposes, a latent class analysis was carried out. A cross-validation procedure was implemented. The results of all the analyses revealed that the best fit to the observed handedness patterns was obtained using a latent class factor model. Through this model, individuals were assigned to one of four ordered levels of handedness, and a quantitative index of left-handedness for each individual was computed by taking into account the different effect of the 10 tasks. These results provide support for the use of the latent class factor approach for handedness assessment.

A comparison of traditional and block periodized strength training programs in trained athletes.

The purpose of this study was to compare 2 different periodization models in strength and power athletes. Twenty-four experienced resistance trained men were randomly assigned to either a block periodization training program (BP; age = 24.2 ± 3.1 years, body mass = 78.5 ± 11.0 kg, height = 177.6 ± 4.9 cm) or to a traditional periodization program (TP; age = 26.2 ± 6.0 years, body mass = 80.5 ± 13.3 kg, height = 179.2 ± 4.6). Participants in both training programs performed 4 training sessions per week. Each training program consisted of the same exercises and same volume of training (total resistance lifted per session). The difference between the groups was in the manipulation of training intensity within each training phase. Strength and power testing occurred before training (PRE) and after 15 weeks (POST) of training. Magnitude-based inferences were used to compare strength and power performance between the groups. Participants in BP were more likely (79.8%) to increase the area under the force-power curve than TP. Participants in BP also demonstrated a likely positive (92.76%) decrease in the load corresponding to maximal power at the bench press compared with TP group, and a possible improvement (∼60%) in maximal strength and power in the bench press. No significant changes were noted between groups in lower-body strength or jump power performance after the 15-week training period. Results of this study indicate that BP may enhance upper-body power expression to a greater extent than TP with equal volume; however, no differences were detected for lower-body performance and body composition measures.

Effects of combined strength and endurance training on exercise capacity in kidney transplant cyclists and runners.

INTRODUCTION: After transplantation, engaging in regular physical activity (PA) or sport is recommended for health. Participation to competitive sports is increasingly common among kidney transplant recipients while little is known on how training affects the physical performance in transplanted athletes. AIM: The purpose of this case study was to assess the effects of a tailored training program on exercise parameters in kidney transplant cyclists (CKTRs) and runners (RKTRs). METHODS: Twelve male transplanted athletes were enrolled. The workload at aerobic and anaerobic thresholds, the submaximal aerobic power (V'O2 stage) and rate of perceived exertion (RPE) during an incremental cycling or running test, and the peak instantaneous force (PIF) during a countermovement jump were assessed at baseline (T0) and after 6 months of tailored training (T6) consisting in strength and aerobic exercises. Exercise adherence, blood lipid profile and renal function were also investigated. RESULTS: Eight CKTRs and 4 RKTRs completed the 6-month training period, with a significant increase of training volume (minutes/week). The exercise adherence was met by 90% in both groups. At T6, there were significant (p<0.05) improvements of maximum workload attained, the workload corresponding to the aerobic threshold and PIF, while workloads at anaerobic threshold, V'O2 stage and RPE were unchanged. Blood cholesterol significantly decreased (p<0.01), while the other blood parameters were unchanged. CONCLUSIONS: These findings indicate that the combined strength and endurance training is well tolerated and may improve exercise performance in this selected population of KTRs.

Estimation of the anaerobic threshold from heart rate variability in an incremental swimming test.

This study aimed to evaluate, in swimming, the agreement between the anaerobic threshold (AT) as determined from the analysis of blood lactate concentration ([La]) and from a new method based on the heart rate (HR) variability (HRV). Fourteen high-level swimmers completed an incremental 7 × 200-m front crawl test, during which the HRV was measured continuously and [La] was collected after each step. To individuate the AT, the trends of the high-frequency HRV spectral power (HFPOW) and of the fraction of HFPOW relative to the respiratory sinus arrhythmia (HFPOW-RSA) were analyzed. In all the subjects, an abrupt increase of both HFPOW and HFPOW-RSA was observed and associated with the AT. The AT parameters determined, respectively, from [La] and HFPOW-RSA were similar (p > 0.05) and highly correlated (HR: 182.0 ± 8.1 vs. 181.1 ± 8.2 b·min, r = 0.93, 95% limits of agreement [LoA]: -6.7 to 4.9 b·min; velocity: 1.47 ± 0.11 vs. 1.47 ± 0.11 m·s, r = 0.98, 95% LoA: -0.05 to 0.05 m·s). Instead, the AT HR and velocity obtained from HFPOW (179.2 ± 8.4 b·min; 1.45 ± 0.11 m·s) were correlated to the corresponding parameters determined from [La] (HR: r = 0.84; velocity: r = 0.94) but underestimated them slightly (95% LoA: -11.9 to 6.3 b·min and -0.11 to 0.05 m·s). These results demonstrate that the AT can be assessed from the HRV in swimming, providing an important testing tool for coaches. Furthermore, using the actual respiratory spectral component, rather than the total HF spectral power, allows us to obtain a more accurate estimate of AT parameters.

Landing techniques in volleyball.

Knee injuries such as anterior cruciate ligament lesions and patellar tendonitis are very frequent in volleyball, and are often attributed to micro traumas that occur during the landing phase of airborne actions. The aim of the present study was to compare different jumping activities during official men's and women's volleyball games. Twelve top-level matches from the Italian men's and women's professional leagues were analysed. The jumps performed during the games were classified according to the landing technique used by the player (left or right foot or both feet together), court position, and ball trajectory. Chi-square analyses were performed to detect differences in landing techniques between the sexes, court positions, and trajectories when serving, attacking, blocking, and setting. Significant differences (P < 0.05) were found between the sexes for block, set, and spike but not for the jump serve. The frequency of landings on one foot was related to court position and the trajectory of the sets: when spiking faster sets, the players were more likely to use a one-footed landing. The present results should help coaches and physiotherapists to devise appropriate training and prevention programmes, and reveal the need for further detailed biomechanical investigations of the relationships between landings and knee injuries.

Comparison of physiological responses to an incremental running test on treadmill, natural grass, and synthetic turf in young soccer players.

This study aimed to compare the physiological responses to a running test often used to assess lactate thresholds in soccer players when performed with an identical protocol on treadmill (Tr), natural grass (Nat), and synthetic turf (Synt). Eighteen young soccer players (mean +/- SD: age, 17.4 +/- 0.8 years; body mass, 66.2 +/- 6.7 kg; height, 175.8 +/- 5.7 cm) performed on each surface a multistage running test, including 4-minutes stages separated by a 1-minute rest, with initial speed set at 8 kmxh and increased of 2 km.h after each stage. Blood lactate concentration (La) and heart rate (HR) were assessed. The test ended when La exceeded 4 mmolxL. At each of the stages completed in the three conditions by all the subjects (8, 10, 12, and 14 kmxh), La was higher in Synt vs. both Nat and Tr with differences of at least 0.6 mmolxL (p < 0.05), whereas HR was higher (p < 0.05) in Synt vs. Nat with differences from 4.3 bxmin (at 10 kmxh) to 6.4 bxmin (at 8 kmxh). Running speed at the 4 mmolxL La threshold was lower (p < 0.05) in Synt (13.1 +/- 1.1 kmxh) than in Nat (13.9 +/- 1.2 kmxh) and Tr (14.4 +/- 1.3 kmxh). The La/HR curve obtained in Synt was shifted upward compared with the Nat and Tr curves, indicating higher La values at given HRs. These results could be mostly explained by adaptations of running mechanical patterns to surface properties that affect the energy requirements of running. This study emphasized the importance of testing soccer players on the specific surface used for training activities when assessing lactate threshold indices to prescribe and monitor field training.

Renal function and physical fitness after 12-mo supervised training in kidney transplant recipients.

AIM: To evaluate the effect of a 12-mo supervised aerobic and resistance training, on renal function and exercise capacity compared to usual care recommendations. METHODS: Ninety-nine kidney transplant recipients (KTRs) were assigned to interventional exercise (Group A; n = 52) and a usual care cohort (Group B; n = 47). Blood and urine chemistry, exercise capacity, muscular strength, anthropometric measures and health-related quality of life (HRQoL) were assessed at baseline, and after 6 and 12 mo. Group A underwent a supervised training three times per week for 12 mo. Group B received only general recommendations about home-based physical activities. RESULTS: Eighty-five KTRs completed the study (Group A, n = 44; Group B, n = 41). After 12 mo, renal function remained stable in both groups. Group A significantly increased maximum workload (+13 W, P = 0.0003), V'O2 peak (+3.1 mL/kg per minute, P = 0.0099), muscular strength in plantar flexor (+12 kg, P = 0.0368), height in the countermovement jump (+1.9 cm, P = 0.0293) and decreased in Body Mass Index (-0.5 kg/m2, P = 0.0013). HRQoL significantly improved in physical function (P = 0.0019), physical-role limitations (P = 0.0321) and social functioning scales (P = 0.0346). No improvements were found in Group B. CONCLUSION: Twelve-month of supervised aerobic and resistance training improves the physiological variables related to physical fitness and cardiovascular risks without consequences on renal function. Recommendations alone are not sufficient to induce changes in exercise capacity of KTRs. Our study is an example of collaborative working between transplant centres, sports medicine and exercise facilities.

The influence of isometric preload on power expressed during bench press in strength-trained men.

The purpose of this study was to compare the power expressed during the bench press exercise in resistance-trained men following different pre-activation conditions. Twenty-two trained men (age 24.1 ± 1.7 years, height 178.6 ± 6.1 cm, body mass 81.1 ± 10.6 kg) completed a maximal effort bench press (1-RM) test (100.0 kg ± 8.1 kg). In a subsequent assessment, each participant performed concentric bench press movements with loads of 20%, 30%, 40% and 50% of their 1-RM preceded by either a concentric contraction (CC), a low isometric preload (LIP; 70% 1-RM) or a high isometric preload (HIP; 100% 1-RM) conditions. All movements were performed in a Smith machine with a settable quick-release device. Participants performed all three conditions in randomized fashion. Results indicated that power outputs during the bench press exercise following HIP were significantly (p < 0.05) greater than CC at 20% 1-RM (+9%), 30% 1-RM (+16%) and 40% 1-RM (+14%), and LIP at 20% 1-RM (+4%), 30% 1-RM (+20%) and 40% 1-RM (+15%). No differences were found between conditions at 50% 1-RM. Area under the force-power curve with HIP was greater (p < 0.05) than with CC and LIP. In conclusion, results of this study indicate that the use of a HIP (100% 1-RM) in trained participants results in significantly greater power output during the concentric phase of a multi-joint exercise when compared to standard concentric movement.

The concurrent effects of strike pattern and ground-contact time on running economy.

OBJECTIVES: Running economy is a key determinant of endurance performance, and understanding the biomechanical factors that affect it is of great theoretical and applied interest. This study aimed to analyse how the ground-contact time and strike pattern used by competitive runners concurrently affect running economy. DESIGN: Cross-sectional. METHODS: Fourteen sub-elite male competitive distance runners completed a 6-min submaximal running trial at 14kmh(-1) on an outdoor track using their habitual strike pattern (n=7 rearfoot strikers: average age, 25.3 years old (SD=2.4); average weight, 64.7kg (SD=5.6); average height, 175.3cm (SD=5.2); n=7 midfoot strikers: average age, 25.0 years old (SD=2.8); average weight, 69.6kg (SD=4.0); average height, 180.1cm (SD=5.1). During the run, the oxygen uptake and ground-contact time were measured. RESULTS: Midfoot strikers showed a significantly shorter (p=0.015) mean contact time (0.228s (SD=0.009)) compared with rearfoot strikers (0.242s (SD=0.010)). Conversely, there was no significant difference (p>0.05) between the groups with respect to mean oxygen uptake (midfoot strikers: 48.4mlmin(-1)kg(-1) (SD=5.3); rearfoot strikers: 49.8mlmin(-1)kg(-1) (SD=6.4)). Linear modelling analysis showed that the effect of contact time on running economy was very similar in the two groups, with a 1ms longer contact time involving an approximately 0.51mlmin(-1)kg(-1) lower oxygen uptake. In contrast, when controlling for contact time, midfoot striking involved an approximately 8.7mlmin(-1)kg(-1) lower oxygen uptake compared with rearfoot striking. CONCLUSIONS: When adjusting the foot-ground contact biomechanics of a runner with the aim of maximising running economy, a trade-off between a midfoot strike and a long contact time must be pursued.