Comparison of velocity and power output data derived from an inertial based system and an optical encoder during squat lifts in a weight room setting.

AIM: The purpose of this study was to assess a new wireless, light and portable inertial measurement system (FreePower; Sensorize, Rome, Italy), by comparing the measures of velocity and power it provides to the same measures derived from a high resolution optical encoder (Ergotest Technology a.s., Langesund, Norway). METHODS: Fifteen male tennis and soccer players performed back squat lifts at the Smith Machine at loads ranging from 30% to 90% of their established 1RM load. The two devices measured the kinematics of the barbell simultaneously. The mean and peak velocity of the barbell and the mean and peak power applied to the barbell-body system were extracted and used for the comparison. RESULTS: Measures of velocity and power, both in mean and peak values evidenced significant correlations (P<0.05) between the two systems. Linear regression r-squared values ranged from 0.978 for mean velocity to 0.993 for peak power, showing high-shared variance between the FreePower and the encoder values. Peak velocity, peak power and mean power values showed an absolute percentage difference of 2.8%, 3%, and 3.8%, respectively. The greatest discrepancy between the two systems was found in mean velocity values, where significantly lower values (P<0.05) were measured with the inertial system (-5.3%). CONCLUSION: The FreePower® inertial system can provide practitioners with measures of velocity and power that are consistent, within reasonable error limits, with a high resolution optical encoder, when it is used in a standard weight room setting and a significant number of lifts are included in the analysis.

Effect of a five-toed minimal protection shoe on static and dynamic ankle position sense.

AIM: The main aim of this study was to test the hypothesis that the VibramFivefingers model, with its minimal structure, cushioning and finger separation, allows a more accurate estimate of static and dynamic foot position compared to wearing a standard cushioned running shoe. METHODS: Static ankle joint position sense was assessed in the sagittal and frontal plane by asking fourteen healthy experienced amateur runners to estimate the perceived direction and amplitude of a support slope surface board placed under their right foot while standing. The dynamic measures were performed with the subjects running on a treadmill at 12 km/h and asking them to evaluate the treadmill surface slope. Two footwear (Fivefingers and a cushioned protective running shoe) and the barefoot condition were compared. RESULTS: Plantarflexion, dorsiflexion, eversion and inversion movements were underestimated in all the experimental conditions. In the static trials there was significantly more angle error underestimation (P<0.05) with the running shoe, while no significant differences were found between Fivefingers and barefoot condition. While running, the treadmill surface slope was significantly better estimated with Fivefingers than in the other two conditions (P<0.05). CONCLUSION: The data support the assumption that with Fivefingers is more likely to get a more correct estimation of the surface slope while standing and running compared to using a standard cushioned running shoe. The finding that the cushioned shoes significantly impair foot position awareness compared to less structured shoes is consistent with the results of some previous studies on healthy and unhealthy subjects.

Biomechanical and physiological comparison of barefoot and two shod conditions in experienced barefoot runners.

AIM: The first aim of this study was to assess how changes in the mechanical characteristics of the foot/shoe-ground interface affect spatio-temporal variables, ground pressure distribution, sagittal plane kinematics, and running economy in 8 experienced barefoot runners. The second aim was to assess if a special lightweight shoe (Vibram Fivefingers) was effective in mimic the experience of barefoot running. METHODS: By using an instrumented treadmill, barefoot running, running with the Fivefingers, and running with standard running shoe were compared, analyzing a large numbers of consecutive steps. Foot/shoe-ground interface pressure distribution, lower limb kinematics, V.O(2) and heart rate data were simultaneously collected. RESULTS: Compared to the standard shod condition when running barefoot the athletes landed in more plantarflexion at the ankle. This caused reduced impact forces and changes in stride kinematics. In particular, significantly shorter stride length and contact times and higher stride frequency were observed (P<0.05). Compared to standard shod condition, V.O(2) and peak impact forces were significantly lower with Fivefingers (P<0.05) and much closer to barefoot running. Lower limb kinematics with Fivefingers was similar to barefoot running with a foot position which was significantly more plantarflexed than in control shoe (P<0.05). CONCLUSIONS: The data of this study support the assumption that changes in the foot-ground interface led to changes in running pattern in a group of experienced barefoot runners. The Fivefingers model seems to be effective in imitating the barefoot conditions while providing a small amount of protection.

Anaerobic contribution to the time to exhaustion at the minimal exercise intensity at which maximal oxygen uptake occurs in elite cyclists, kayakists and swimmers.

Using 23 elite male athletes (8 cyclists, 7 kayakists, and 8 swimmers), the contribution of the anaerobic energy system to the time to exhaustion (t(lim)) at the minimal exercise intensity (speed or power) at which maximal oxygen uptake (VO2max) occurs (IVO2max) was assessed by analysing the relationship between the t(lim) and the accumulated oxygen deficit (AOD). After 10-min warming up at 60% of VO2max, the exercise intensity was increased so that each subject reached his IVO2max in 30 s and then continued at that level until he was exhausted. Pre-tests included a continuous incremental test with 2 min steps for determining the IVO2max and a series of 5-min submaximal intensities to collect the data that would allow the estimation of the energy expenditure at IVO2max. The AOD for the t(lim) exercise was calculated as the difference between the above estimation and the accumulated oxygen uptake. The mean percentage value of energy expenditure covered by anaerobic metabolism was 15.2 [(SD 6)%, range 8.9-24.1] with significant differences between swimmers and kayakists (16.8% vs 11.5%, P < or = 0.05) and cyclists and kayakists (16.4% vs 11.5%, P < or = 0.05). Absolute AOD values ranged from 26.4 ml.kg-1 to 83.6 ml.kg-1 with a mean value of 45.9 (SD 18) ml.kg-1. Considering all the subjects, the t(lim) was found to have a positive and significant correlation with AOD (r = 0.62, P < or = 0.05), and a negative and significant correlation with VO2max (r = -0.46, P < or = 0.05). The data would suggest that the contribution of anaerobic processes during exercise performed at IVO2max should not be ignored when t(lim) is used as a supplementary parameter to evaluate specific adaptation of athletes.