Weightlifting load effect on intra-limb coordination of lower extremity during pull phase in snatch: Vector coding approach

ABSTRACT

This study examined the weightlifting load effects on the lower extremity coordination pattern during a snatch pull movement. Twenty male elite weightlifters performed snatch trials in each of the three load conditions [light (30%), medium (65%) and heavy (90%) of their maximum weightlifting capacities]. Kinematic data for the transition, second pull and take-off phases of a snatch were collected at 200 Hz using an eight-camera motion capture system. Angle-angle plots and coupling angles were calculated for further analyses. The results indicate that participants utilised knee flexion control-strategy in light and medium load conditions during the transition phase, but not for in-phase strategy in heavy load condition. In the second pull phase, participants utilised concurrent ankle dorsiflexion and knee extension, followed by hip extension strategy. The heavy load condition exhibited the distinct coordination strategies before knee extension. In the take-off phase, light and medium load conditions appeared to use thigh-phase strategy (right ankle-knee: p = 0.788, left: p = 0.035, right knee-hip: p = 0.012, left: p = 0.017, right ankle-hip: p = 0.029, left: p = 0.011). This suggests that the heavy load condition requires the use of two-joint coordination patterns (in-phase or anti-phase) as compared to the other lighter load conditions.     

Relationships between lower-limb kinematics and block phase performance in a cross section of sprinters

Abstract

This study investigated lower-limb kinematics to explain the techniques used to achieve high levels of sprint start performance. A cross-sectional design was used to examine relationships between specific technique variables and horizontal external power production during the block phase. Video data were collected (200 Hz) at the training sessions of 16 sprinters who ranged in 100 m personal best times from 9.98 to 11.6 s. Each sprinter performed three 30 m sprints and reliable (all intraclass correlation coefficients, ICC(2,3) ≥ 0.89) lower-limb kinematic data were obtained through manual digitising. The front leg joints extended in a proximal-to-distal pattern for 15 sprinters, and a moderate positive relationship existed between peak front hip angular velocity and block power (r = 0.49, 90% confidence limits = 0.08–0.76). In the rear leg, there was a high positive relationship between relative push duration and block power (r = 0.53, 90% confidence limits = 0.13–0.78). The rear hip appeared to be important; rear hip angle at block exit was highly related to block power (r = 0.60, 90% confidence limits = 0.23–0.82), and there were moderate positive relationships with block power for its range of motion and peak angular velocity (both r = 0.49, 90% confidence limits = 0.08–0.76). As increased block power production was not associated with any negative aspects of technique in the subsequent stance phase, sprinters should be encouraged to maximise extension at both hips during the block phase.     

System approach to games and competitive playing: Reply to Lebed (2006)

Abstract

The maximal step length test has been proposed to evaluate the risk of falls among the elderly, although the test is confusing and prone to errors due to two types of test methods. The maximal double-step length test may be used to evaluate both leg function and the functional difference between the left and right legs, but its measurement and evaluation methods have not been studied extensively. The aims of the present study were to compare the maximal single- and double-step length tests, and to highlight differences between the sexes and between the dominant and non-dominant legs. Fifty healthy adults free from lower-limb disorders conducted the above step tests twice, once with the dominant and once with the non-dominant leg. The former test requires individuals to return the stepping leg to the original position or to draw the other leg to the step leg after stepping out maximally with either leg from a standing posture while maintaining body stability with the supporting leg. The latter test requires individuals to step forward with either leg maximally, after similarly stepping with the other leg and to draw the first stepping leg to the second stepping leg. The above tests are defined as the single- and double-step length test, respectively. Step lengths were measured in both tests, and these values were used for analysis. Correlations among step length tests conducted with the dominant and non-dominant legs were very high (r=0.82–0.97). Significant sex differences were found in all step length tests, and males were superior to females. No significant difference between legs was found in any test. In summary, the relationship between the maximal single- and double-step length tests was very high and step lengths showed a significant sex difference.     

Substrate oxidation during incremental arm and leg exercise in men and women matched for ventilatory threshold

Abstract

The aim of this study was to determine the variations in substrate utilization between men and women matched for ventilatory threshold (T _vent) during incremental arm cranking and leg cycling exercise at 70, 85, 100 and 115% of the mode-specific T _vent. Recreationally active men (n = 12) and women (n = 10) with similar values for percentage of peak oxygen consumption at T _vent participated in the study. Ventilatory equivalence, excess CO₂ and modified V-slope methods were used concurrently to determine T _vent. The participants performed 5 min of exercise at each of 70, 85, 100 and 115% T _vent during both arm cranking and leg cycling exercise. The females were tested during the early follicular phase for all trials. A two-way mixed-design analysis of variance was performed to test for differences between the sexes. When carbohydrate and fat oxidation were expressed relative to total fat-free mass, carbohydrate oxidation during arm cranking and leg cycling was significantly higher in men than women at each percentage of T _vent. In contrast, women showed significantly higher fat oxidation across intensities during both arm cranking and leg cycling. Our results suggest that when substrate utilization is expressed relative to total fat-free mass, women appear to maintain a higher rate of fat and lower rate of carbohydrate oxidation than men during both incremental arm cranking and leg cycling exercise relative to T _vent.     

The relationship between muscle cross-sectional area and strength in various isokinetic movements among soccer players

Abstract

The aim of the present study was to examine the relationships between muscle cross-sectional area (CSA) and muscular strength in terms of knee extension and flexion, hip extension and flexion, and hip abduction and adduction among well-trained soccer players. Fourteen university soccer players participated in the study, who had previously been divided into two groups based on ability (Group A: above-average ability; Group B: average ability). Maximal isokinetic and concentric muscular strength was measured in knee extension/flexion, hip extension/flexion and hip abduction/adduction using an isokinetic dynamometer at 1.57 and 4.19 rad·s^?1 (3.14 rad·s^?1) in both the dominant and non-dominant leg. The CSAs of the thigh, gluteus muscles and iliopsoas muscles were calculated based on magnetic resonance imaging. There was no significant difference between the two groups in muscle CSA and isokinetic strength. Although there were some statistically significant differences between the dominant and non-dominant leg in terms of CSA and strength (P<0.05–0.01), these were small and negligible. Apart from a non-significant relationship between the CSAs of the adductor muscles and hip adductor strength (r<0.26, n.s.), the CSA of the other muscle groups correlated with maximal isokinetic strength (r=0.38–0.64, P<0.05). These results suggest that no difference in muscle characteristics (in terms of muscle CSA and strength) was apparent among well-trained soccer players, even between the dominant and non-dominant leg. There is also a case that the anatomical function of a single (or group of) muscle(s) may not be reflected by the strength—CSA relationship depending on the movements (such as hip adduction-adductor muscle CSA). Thus, further studies are required to develop methods to assess neuromuscular function in relation to muscle morphology among soccer players.     

Comparison of kinematics in skilled and unskilled arms of the same recreational baseball players

Abstract

We examined mechanisms of coordination that enable skilled recreational baseball players to make fast overarm throws with their skilled arm and which are absent or rudimentary in their unskilled arm. Arm segment angular kinematics in three dimensions at 1000 Hz were recorded with the search-coil technique from the arms of eight individuals who on one occasion threw with their skilled right arm and on another with their unskilled left arm. Compared with their unskilled arm, the skilled arm had: a larger angular deceleration of the upper arm in space in the forward horizontal direction; a larger shoulder internal rotation velocity at ball release (unskilled arms had a negative velocity); a period of elbow extension deceleration before ball release; and an increase in wrist velocity with an increase in ball speed. It is suggested that some of these differences in arm kinematics occur because of differences between the skilled and unskilled arms in their ability to control interaction torques (the passive torque at one joint due to motion at adjacent joints). It is proposed that one reason unskilled individuals cannot throw fast is that, unlike their skilled counterparts, they have not developed the coordination mechanisms to effectively exploit interaction torques.     

“When you’re down,stay down”:A lesson for all competitive alpine skiers supported by an ACL rupture measured in vivo

Background:During an experiment,a ski racer equipped with various measurement devices suffered an anterior cruciate ligament(ACL)rupture in his right knee.The aim of this study was to describe the underlying injury mechanism from a functional perspective.Methods:Eight giant slalom turns(i.e.,4 left turns),followed by 1 left turn at which the ACL injury occurred,were recorded by 2 video cameras,electromyography of 4 relevant muscle groups,inertial measurement units to measure knee and hip angles,and pressure insoles to determine ground reaction forces.Results:Due to a loss of balance,the ski racer began to slide sideways at the apex of a left turn.During sliding,his right(outside)leg was actively abducted upward without touching the ground.The ski racer then attempted to stand up again by dropping his leg back towards the snow surface.The end of this dropping was accompanied by a decrease in electromyographic activity in the knee stabilizing muscles.Once the inside edge of the outer ski caught the snow surface,a rapidly increasing peak force,knee flexion,and an aggressive sudden activation of the vastus medialis muscle were observed,while biceps femoris and rectus femoris further decreased their activation levels.This likely resulted in excessive anterior translation of the tibia relative to the femur,causing damage to the ACL.Conclusion:Our example emphasizes that ski racers should not get up until they stop sliding.Remember:“When you’re down,stay down.”     

Kinematic analysis of the shot-put: A method of assessing the mechanical work of the hand action force

The aims of this study were to (1) propose a method for evaluating shot-putters mechanical power, (2) investigate the relationship between mechanical work of hand action force (W_HAF), peak power output (PPO) of different limbs and shot-put performance and (3) show which of these two parameters (W_HAF, PPO) were the most appropriate to characterize the explosive abilities of the shot-putter. Twelve junior right-handed shot-putters, practised glide technique shot-put throwers (personal best?=?13.57 ± 1.72 m), participated in this study. Arm and leg force-velocity tests were performed to measure PPO. Kinematic analysis was conducted during a shot-putting event in regular conditions to quantify the W_HAF at the release moment and shot-put performance. Significant correlations were found between absolute arm and leg PPO with upper and lower muscle volumes (r?=?.67; p?=?.03; r?=?.76; p?=?.01; r?=?.74, p?=?.01; r?=?.65, p?=?.04). Positive relationships were recorded between absolute arm and leg PPO and shot-put performance (r?=?.67, p?=?.02; r?=?.81, p?=?.004, respectively). Shot-put performance was also closely related to the W_HAF (r?=?.93, p?=?.0001) and release velocity parameter (r?=?.86, p?=?.001). The present results confirm that force-velocity test and W_HAF constitute useful tools for assessing mechanical power in throwing. The W_HAF could be considered as more suitable than force-velocity test.     

The influence of variable resistance moment arm on knee extensor performance

Abstract

To enhance muscular strength, resistance training machines with a cam, incorporating a variable resistance moment arm, are widely used. However, little information is available about the influence of the variable resistance moment arm on torque, velocity, and power during muscle contraction. To address this, a knee extensor machine was equipped with a cam or with a semi-circular pulley that imposed a variable or a constant resistance moment arm, respectively. Fourteen physically active men performed two full knee extensions against loads of 40–80 kg in both conditions. Participants developed significantly higher torque with the pulley than with the cam (P < 0.001). The relative differences between pulley and cam conditions across all loads ranged from 8.72% to 19.87% (P < 0.001). Average knee extension velocity was significantly higher in the cam condition than in the pulley condition. No differences were observed in average and peak power, except at 50 and 55 kg. Torque–velocity and power–velocity relationships were modified when the resistance moment arm was changed. In conclusion, whatever the link, namely cam or pulley, the participants produced similar power at each load. However, the torque–velocity and power–velocity relationships were different in the cam and pulley conditions. The results further suggest that the influence of the machine's mechanism on muscular performance has to be known when prescribing resistance exercises.     

Muscle cross-sectional areas and performance power of limbs and trunk in the rowing motion

Although it is clear that rowers have a large muscle mass, their distribution of muscle mass and which of the main motions in rowing mediates muscle hypertrophy in each body part are unclear. We examine the relationships between partial motion power in rowing and muscle cross-sectional area of the thigh, lower back, and upper arms. Sixty young rowers (39 males and 21 females) participated in the study. Joint positions and forces were measured by video cameras and rowing ergometer software, respectively. One-dimensional motion analysis was performed to calculate the power of leg drive, trunk swing, and arm pull motions. Muscle cross-sectional areas were measured using magnetic resonance imaging. Multiple regression analyses were carried out to determine the association of different muscle cross-sectional areas with partial motion power. The anterior thigh best explained the power demonstrated by leg drive (r ² = 0.508), the posterior thigh and lower back combined best explained the power demonstrated by the trunk swing (r ² = 0.493), and the elbow extensors best explained the power demonstrated by the arm pull (r ² = 0.195). Other correlations, such as arm muscles with leg drive power (r ² = 0.424) and anterior thigh with trunk swing power (r ² = 0.335), were also significant. All muscle cross-sectional areas were associated with rowing performance either through the production of power or by transmitting work. The results imply that rowing motion requires a well-balanced distribution of muscle mass throughout the body.     

Normal training response in skeletal muscle of post-infarction heart failure patients

Abstract

Congestive heart failure (CHF) patients experience reduced muscle fatigue resistance and exercise capacity. The aim of this study was to assess whether skeletal muscle in CHF patients has a normal training response compared to healthy subjects. We compared the effect of one-legged knee extensor (1-KE) endurance training in CHF patients (n=10), patients with coronary artery disease (CAD, n=9) and healthy subjects (n=13). The training response was evaluated by comparing trained leg and control leg after the training period. The fall in peak torque during 75 maximal 1-KE isokinetic contractions revealed that CHF patients were less fatigue resistant than healthy subjects in the control leg, but not in the trained leg. Peak power and peak oxygen uptake during dynamic 1-KE exercise was ~10–16% higher in trained leg than control leg. This training response was not significant different between groups. Muscle biopsies of vastus lateralis showed that fibre type composition was not different between trained leg and control leg. Capillary density was 6.5% higher in trained leg than control leg when all groups were pooled. In conclusion, the more fatigable skeletal muscle of CHF patients responds equally to endurance training compared to skeletal muscle of CAD patients and healthy subjects.     

“When you're down,stay down”: A lesson for all competitive alpine skiers supported by an ACL rupture measured in vivo

BackgroundDuring an experiment, a ski racer equipped with various measurement devices suffered an anterior cruciate ligament (ACL) rupture in his right knee. The aim of this study was to describe the underlying injury mechanism from a functional perspective.MethodsEight giant slalom turns (i.e., 4 left turns), followed by 1 left turn at which the ACL injury occurred, were recorded by 2 video cameras, electromyography of 4 relevant muscle groups, inertial measurement units to measure knee and hip angles, and pressure insoles to determine ground reaction forces.ResultsDue to a loss of balance, the ski racer began to slide sideways at the apex of a left turn. During sliding, his right (outside) leg was actively abducted upward without touching the ground. The ski racer then attempted to stand up again by dropping his leg back towards the snow surface. The end of this dropping was accompanied by a decrease in electromyographic activity in the knee stabilizing muscles. Once the inside edge of the outer ski caught the snow surface, a rapidly increasing peak force, knee flexion, and an aggressive sudden activation of the vastus medialis muscle were observed, while biceps femoris and rectus femoris further decreased their activation levels. This likely resulted in excessive anterior translation of the tibia relative to the femur, causing damage to the ACL.ConclusionOur example emphasizes that ski racers should not get up until they stop sliding. Remember: “When you''re down, stay down.”     

Physical and Physiological Characteristics of Elite Volleyball Players

Abstract

The purpose of this study was to characterize the body fat, maximum aerobic power and maximum anaerobic power of elite junior wrestlers. The study was conducted in conjunction with an elite wrestler training camp. Wrestlers (n = 39) from ages 14 to 18 qualified for the camp and volunteered as subjects. Measurements were made for body composition (skinfold thickness), maximal aerobic power (treadmill run), and maximal anaerobic power of the arms and legs (Wingate test). Body fat averaged (±SD) 7.2% (±2.4), whereas the means (±SD) for maximal aerobic power, arm power, and leg power were 51.2(±9.3) ml/kg min^-1, 390.7 (±92) watts, and 549.1 ± 101 watts, respectively. Elite junior wrestlers appear to have a similar percentage of body fat, lower maximum aerobic power and higher relative anaerobic power compared to elite collegiate and senior wrestlers.     

BASES 2006: “From education to application”

The dependence of power on aerobic and anaerobic energy metabolism and on force production was studied in maximal leg exercise. National and international level male rowers (n = 9) performed four modified (legs‐only) rowing ergometer exercises: a progressive test, 2‐min (T2), 12‐min (T12) and 6‐min (T6) all‐out tests. In T2, significant correlations were observed between power in T2 (P_T2) and oxygen debt (r = 0.83, P<0.05) and between P_T2 and average force production (F_av) during the last 30 s (r = 0.85, P<0.05). These parameters explained 93% of the variation in P_T2. The highest correlations between power in T6 (P_T6) and physiological parameters were as follows: maximal oxygen uptake (VO₂ max: r = 0.87, P<0.01), blood bicarbonate concentration before the test ([HCO^‐ _3before]: r=0.85, P<0.05) and blood lactate concentration on anaerobic threshold (BL_anT: r= —0.82, P<0.05). Together, these parameters explained 92% of the variation in P_T6. In T12, the total power (P_T12) correlated with power of anaerobic threshold #OPP_ANT’. r = 0.95, P< 0.001) and with the highest VO₂ value in this test (VO₂ peak: r = 0.92, P<0.001). These two parameters explained 96% of the variation in P_T12.

The decrease of at least one of the force parameters during each test was taken as a sign of fatigue. The decline in force was compensated for by an increase in stroke rate at the end of T6 and T12 (P<0.01, P<0.001). Consequently, the power remained unchanged or even increased at the end of T6 and T12. The term ‘power endurance’ is introduced to describe the ability to resist and to compensate for local muscular fatigue.     

Force-velocity characteristics of upper limb extension during maximal wheelchair sprinting performed by healthy able-bodied females

The aim of this study was to determine the relationship between force and velocity parameters during a specific multi-articular upper limb movement--namely, hand rim propulsion on a wheelchair ergometer. Seventeen healthy able-bodied females performed nine maximal sprints of 8 s duration with friction torques varying from 0 to 4 N x m. The wheelchair ergometer system allows measurement of forces exerted on the wheels and linear velocity of the wheel at 100 Hz. These data were averaged for the duration of each arm cycle. Peak force and the corresponding maximal velocity were determined during three consecutive arm cycles for each sprint condition. Individual force-velocity relationships were established for peak force and velocity using data for the nine sprints. In line with the results of previous studies on leg cycling or arm cranking, the force-velocity relationship was linear in all participants (r = -0.798 to -0.983, P < 0.01). The maximal power output (mean 1.28 W x kg(-1)) and the corresponding optimal velocity (1.49 m x s(-1)) and optimal force (52.3 N) calculated from the individual force-velocity regression were comparable with values reported in the literature during 20 or 30 s wheelchair sprints, but lower than those obtained during maximal arm cranking. A positive linear relationship (r = 0.678, P < 0.01) was found between maximal power and optimal velocity. Our findings suggest that although absolute values of force, velocity and power depend on the type of movement, the force-velocity relationship obtained in multi-articular limb action is similar to that obtained in wheelchair locomotion, cycling and arm cranking.     

The Relationship of Isokinetic Torque at Two Speeds to the Vertical Jump

Abstract

The relationship between the ability to develop leg torque and performance in the vertical jump was investigated in 29 female athletes. Each subject's leg flexion, leg extension, and foot plantar flexion peak torque was determined isokinetically on a Cybex at angular velocities of 30 degrees/second and 180 degrees/second. The vertical jump was determined for each subject and correlations among the measures of torque and the vertical jump were calculated. Although the ability to produce leg power as exemplified by the vertical jump was significantly correlated with peak torque at the fast angular velocity but was not significantly correlated with peak torque at the slow angular velocity, the correlations were so low it was concluded that there was little if any relationship between torque at a fast or slow angular velocity and the ability to vertically jump.     

Bilateral leg extension power and fat-free mass in young oarsmen

We evaluated the impact of bilateral leg extension power and fat-free mass on 2000?m rowing ergometer performance in 332 young oarsmen (age 21±2 years, height 1.76±0.05?m, body mass 62±6?kg; mean±s). The 2000?m rowing performance time was correlated with height (1.62–1.93?m; R ²?=?0.23, P?<0.001), body mass (53–95?kg; R ²?=?0.53, P?<0.001), fat-free mass (47–82?kg; R ²?=?0.58, P?<0.001) and bilateral leg extension power (1202–3302?W; R ²?=?0.38, P?<0.001). Multiple regression analysis selected fat-free mass and bilateral leg extension power as regressor variables. Fat-free mass explained 58% of the variability in rowing performance and the inclusion of bilateral leg extension power improved the power of prediction by 5%. The results suggest that rowing involves almost every muscle in the body and that bilateral leg extension power is very important during this activity.     

Rhythmic Isometric Fatigue Patterns of the Elbow Flexors and Knee Extensors

Abstract

Twenty-seven male subjects performed two 5-min bouts of rhythmic, isometric elbow flexion and two similar bouts of knee extension at a rate of 30 maximal contractions per min. Exponential analyses revealed that the pattern of fatigue for each limb followed a single component curve of the form: Y_t = a₀e ^?Kot + c. An analysis of variance comparing the results from the two limbs revealed that (a) the strength scores for the leg were significantly (p < .05) higher than those for the arm throughout the exercise bouts; (b) both limbs experienced a significant strength decrement; and (c) there was significant interaction between trials and limbs. It appeared that the greater loss of strength by the knee extensors was reponsible for this interaction. It was concluded that during a rhythmic, all-out task, the rates of fatigue experienced by the two muscle groups tend to differ, with the elbow flexors fatiguing more rapidly initially but reaching a plateau at a relatively higher level than the knee extensors.     

Muscle cross-sectional areas and performance power of limbs and trunk in the rowing motion

Although it is clear that rowers have a large muscle mass, their distribution of muscle mass and which of the main motions in rowing mediates muscle hypertrophy in each body part are unclear. We examine the relationships between partial motion power in rowing and muscle cross-sectional area of the thigh, lower back, and upper arms. Sixty young rowers (39 males and 21 females) participated in the study. Joint positions and forces were measured by video cameras and rowing ergometer software, respectively. One-dimensional motion analysis was performed to calculate the power of leg drive, trunk swing, and arm pull motions. Muscle cross-sectional areas were measured using magnetic resonance imaging. Multiple regression analyses were carried out to determine the association of different muscle cross-sectional areas with partial motion power. The anterior thigh best explained the power demonstrated by leg drive (r2 = 0.508), the posterior thigh and lower back combined best explained the power demonstrated by the trunk swing (r2 = 0.493), and the elbow extensors best explained the power demonstrated by the arm pull (r2 = 0.195). Other correlations, such as arm muscles with leg drive power (r2 = 0.424) and anterior thigh with trunk swing power (r2 = 0.33 5), were also significant. All muscle cross-sectional areas were associated with rowing performance either through the production of power or by transmitting work. The results imply that rowing motion requires a well-balanced distribution of muscle mass throughout the body.