Functional hamstrings: quadriceps ratios in elite women's soccer players.

We compared starters and non-starters for various isokinetic strength variables in elite women's soccer players. A convenience sample of 10 starters (mean ± s; age = 20 ± 2 years; height = 170 ± 4 cm; body mass = 65 ± 5 kg) and 7 non-starters (age = 20 ± 1 years; height = 164 ± 3 cm; body mass = 63 ± 4 kg) performed maximal voluntary muscle actions of the leg extensors (concentric) and flexors (eccentric) on an isokinetic dynamometer in order to measure concentric peak torque for the leg extensors, eccentric peak torque for the leg flexors, and the functional hamstrings:quadriceps (H:Q) ratio at 1.047 rad · s(-1) and 4.189 rad · s(-1) concentric peak torque for the leg extensors was not different between starters and non-starters. However, it was greater at 1.047 rad · s(-1) than at 4.189 rad · s(-1) in both groups. Eccentric peak torque for the leg flexors was greater for the starters versus non-starters at 4.189 rad · s(-1). Eccentric strength of the leg flexors at fast movement velocities may be used as an effective physiological profile and may discriminate between playing status in elite women's soccer players.

Bodyweight support alters the relationship between preferred walking speed and cost of transport.

Humans tend to select a preferred walking speed (PWS) that minimizes the metabolic energy consumed per distance traveled, i.e. the Cost of Transport (CoT). The aims of this study were to: 1. compare PWS overground vs. on a treadmill at 100 and 50% of body weight, and 2. explore whether with body weight support, PWS corresponds to the speed that minimizes CoT. Fifteen healthy adults walked overground and on a lower body positive pressure treadmill with and without bodyweight support. Walking speeds (m.s-1) were recorded for each condition. Rate of energy expenditure (J.kg-1.min-1) and CoT (J.kg-1.m-1) were then determined from 5-min walking trials with 50% bodyweight support at PWS and ± 30% of the self-selected walking speed for that condition. PWS did not differ across conditions. With 50% body weight support, for each 30% increase in walking speed, rates of metabolic energy expenditure increased ∼15% while CoT decreased by ∼14%. Thus, with 50% body weight support, PWS did not correspond with the speed that minimized CoT. Bodyweight support decreases cost of maintaining an upright body but does not decrease the metabolic demand of limb advancement, contributing to the linear yet not proportional changes in rates of energy expenditure and CoT. We conclude that bodyweight support via an AlterG® treadmill disconnects the association between PWS and minimum CoT. These findings have implications for clinical populations (e.g., obese, elderly) who may benefit from walking on a bodyweight supporting treadmill but may select speeds incompatible with their physical activity goals.

The influence of ratio and allometric scaling procedures for normalizing upper body power output in division I collegiate football players.

The purpose of the present study was to examine the differences in upper body power output among lineman and nonlineman division I collegiate football players and to examine the influence of 2 normalization procedures: (a) simple ratio scaling and (b) standardized allometric scaling. Ten lineman (mean +/- SD: age = 19.3 +/- 1.6 years; height = 187.7 +/- 4.7 cm; mass = 127.7 +/- 13.3 kg) and 14 nonlineman (19.6 +/- 1.4 years; 181.8 +/- 5.2 cm; 92.3 +/- 10.6 kg) performed a multiple repetition bench press power test at 50% of their 1 repetition maximum. Peak power (PP) was determined from a Tendo weightlifting analyzer that was attached to the barbell. The PP values were then analyzed under 3 conditions that included: (a) no scaling (absolute values), (b) ratio scaling (PP body mass), and (c) allometric scaling (PP body mass). The results indicated that the larger lineman demonstrated greater absolute PP values (p = 0.02); however, ratio scaling favored the smaller nonlineman group (p = 0.04). There were no differences in PP values between positions after the standardized allometric scaling procedure (p = 0.60). These findings indicated that the standardized allometric scaling procedure may be a more effective method for normalizing PP values among elite division I collegiate football players.

Acute effects of different volumes of dynamic stretching on vertical jump performance, flexibility and muscular endurance.

The purpose of this study was to examine the acute effects of different volumes of a dynamic stretching routine on vertical jump (VJ) performance, flexibility and muscular endurance (ME). Twenty-six males (age 22.2 ± 1.3 years) performed three separate randomized conditions: (i) a control (CON) condition (5-min jog + 12 min of resting), (ii) a 5-min jog + a dynamic stretching routine (DS1; 6.7 ± 1.3 min) and (iii) a 5-min jog + a dynamic stretching routine with twice the volume (DS2; 12.1 ± 1.6 min). The dynamic stretching routine included 11 exercises targeting the hip and thigh musculature. VJ performance (jump height and velocity) and flexibility were measured prior to and following all conditions, while ME was measured following all conditions. The DS1 and DS2 conditions increased VJ height and velocity (P<0.01), while the CON condition did not change (P>0.05). When compared to the CON condition, the DS1 condition did not improve ME (P>0.05), whereas the DS2 condition resulted in a significant (15.6%) decrease in the number of repetitions completed (P<0.05). Flexibility increased following all conditions (P<0.01), while the DS1 condition was significantly greater (P<0.01) than the CON condition at post-testing. These results suggest that dynamic stretching routines lasting approximately 6-12 min performed following a 5-min jog resulted in similar increases in VJ performance and flexibility. However, longer durations of dynamic stretching routines may impair repetitive high-intensity activities.

The Effect of Energy Patches on Substrate Utilization in Collegiate Cross-Country Runners.

It is well established that an increased capacity of skeletal muscle to oxidize fatty acids can spare glycogen and delay the onset of fatigue in mild- to moderate-intensity exercise. The purpose of the following study was to examine the effect of LifeWave® energy patches on non-protein substrate utilization in Division-1 cross-country runners. To determine the effect of the patches subjects were pretested to establish baselines and randomly assigned to an experimental (EX) or placebo (PL) group. Twenty-two trained male (n = 11; mean ± SD, age = 21.1 ± 2.6years, height = 179.6 ± 4.2cm, body mass = 71.4 ± 7.4kg, VO2max = 72.6 ± 7.1mL·kg-1·min-1) and female (n = 11; mean ± SD, age = 21.5 ± 2.4years, height = 166.7 ± 5.7cm, body mass = 53.7 ± 3.2kg, VO2max = 63.6 ± 6.9mL·kg-1·min-1) cross-country runners volunteered to participate in the study. Dependent variables included maximal oxygen consumption (VO2max), rating of perceived exertion (RPE), respiratory exchange ratio (RER), maximum heart rate (HRmax), and time to exhaustion (TTE). Results indicated there were no significant differences between the EX and PL groups at posttesting for RPE, TTE, HRmax, or VO2max. RER was found to be significantly higher for the EX group compared to the PL group during stage 1 of the Bruce-protocol graded exercise test (p = 0.02). Based on the limited available research regarding LifeWave® energy patches effect on non-protein substrate utilization during aerobic exercise there appears to be no performance enhancing benefits.