Speed Modulation in Swimming Frogs

Swimming movements of 7 European green frogs (Rana esculenta) were studied, starting from the detailed analysis of the speed and timing of the propulsive, glide, and recovery phases of their intermittent swimming behavior. First, the authors identified the spatiotemporal factors used by the frogs to modulate their swimming behavior. None of the gait variables correlated strongly with average swimming speed, and no significant correlations were found between variables belonging to different phases. There did not seem to be an obvious control strategy. Instantaneous speeds at the transition of the different phases all increased significantly with average speed, however. The strong correlation between maximal speed at the end of propulsion and the speed averaged over a cycle might reflect the dominance of the propulsive phase in the determination of the overall swimming speed. The modulation of swimming speed thus seemed largely comparable with the regulation of jumping distance. That finding was confirmed in a mathematical model, in which the positive correlations between both glide and recovery speeds, on the one hand, and average speed, on the other, were shown to be only mathematical consequences of the strong impact of the propulsive phase on overall swimming performance. That finding suggests that the correlations did not result from an active control strategy.     

Effect of aerobic training on inter-arm coordination in highly trained swimmers

The effect of three months of aerobic training on spatio-temporal and coordination parameters was examined during a swim trial at maximal aerobic speed. Nine male swimmers swam a 400-m front crawl at maximal speed twice: in trial 1, after summer break, and trial 2, after three months of aerobic training. Video analysis determined the stroke (swimming speed, stroke length, and stroke rate) and coordination (Index of Coordination and propulsive phase duration) parameters for every 50-m segment. All swimmers significantly increased their swimming speed after training. For all swimmers except one, stroke length increased and stroke rate remained constant, whereas the Index of Coordination and the propulsive phase duration decreased (p < .05). This study suggests that aerobic training developed a greater force impulse in the swimmers during the propulsive phases, which allowed them to take advantage of longer non-propulsive phases. In this case, catch-up coordination, if associated with greater stroke length, can be an efficient coordination mode that reflects optimal drag/propulsion adaptation. This finding thus provides new insight into swimmers’ adaptations to the middle-distance event.     

Perception and action in swimming: Effects of aquatic environment on upper limb inter-segmental coordination

This study assessed perception–action coupling in expert swimmers by focusing on their upper limb inter-segmental coordination in front crawl. To characterize this coupling, we manipulated the fluid flow and compared trials performed in a swimming pool and a swimming flume, both at a speed of 1.35 m s⁻¹. The temporal structure of the stroke cycle and the spatial coordination and its variability for both hand/lower arm and lower arm/upper arm couplings of the right body side were analyzed as a function of fluid flow using inertial sensors positioned on the corresponding segments. Swimmers’ perceptions in both environments were assessed using the Borg rating of perceived exertion scale. Results showed that manipulating the swimming environment impacts low-order (e.g., temporal, position, velocity or acceleration parameters) and high-order (i.e., spatial-temporal coordination) variables. The average stroke cycle duration and the relative duration of the catch and glide phases were reduced in the flume trial, which was perceived as very intense, whereas the pull and push phases were longer. Of the four coordination patterns (in-phase, anti-phase, proximal and distal: when the appropriate segment is leading the coordination of the other), flume swimming demonstrated more in-phase coordination for the catch and glide (between hand and lower arm) and recovery (hand/lower arm and lower arm/upper arm couplings). Conversely, the variability of the spatial coordination was not significantly different between the two environments, implying that expert swimmers maintain consistent and stable coordination despite constraints and whatever the swimming resistances. Investigations over a wider range of velocities are needed to better understand coordination dynamics when the aquatic environment is modified by a swimming flume. Since the design of flumes impacts significantly the hydrodynamics and turbulences of the fluid flow, previous results are mainly related to the characteristics of the flume used in the present study (or a similar one), and generalization is subject to additional investigations.     

Evidence for generalized motor programs using gait pattern analysis

Human intra limb gait kinematics were analyzed via statistical and structural pattern recognition methods to determine the role of relative timing of limb segments within and between modes of gait. Five experienced runners were filmed while walking (3-6 km/hour) and running (8-12 km/hour) on a motor driven treadmill. Kinematic data consisted of relative timing of the four phases of the Philippson step cycle and intersegmental limb trajectories, determined from angle-angle diagrams. Despite marked decreases in absolute time durations within gaits remained constant over the speeds which were studied. Although a 2-fold increase in locomotor speed occurred in walking and a 1.5-fold speed increase occurred within running, the percentage of time spent in each of the Philippson phases was not significantly changed. However, significant differences in the time percentages and sequences of the step cycle phases were found between walking and running. Correlations between limb segment trajectories occurring in the different gaits showed strong coherence for overall step cycle patterns, but within step cycle phases and across speeds, selective phases displayed little correspondence.     

Coordination in arm movements during crawl stroke in elite swimmers with a loco-motor disability

The purpose of this study was to investigate selected kinematics parameters of the arm stroke in crawl swimmers with disabilities and to examine the potential use of an index of arm coordination (IdC) to evaluate the stroking technique of swimmers with diverse functional abilities. The degree of overlap in the propulsive phases (superposition model) and lag time between the propulsive phases (catch-up model) was examined in 18 well-trained swimmers with loco-motor disabilities, 9 females and 9 males, from functional classes S3-S10 with S10 being most functional. Based on the results, correct coordination appears to be fundamental to swimming crawl stroke in both able-bodied swimmers as well as swimmers with a disability. Some swimmers with disabilities examined here exhibited extreme values at both ends of the index scale. This might be essential to maintaining balance while swimming when not all limb activity contributes to the forward movement.     

Application of regression and neural models to predict competitive swimming performance

This research problem was indirectly but closely connected with the optimization of an athlete-selection process, based on predictions viewed as determinants of future successes. The research project involved a group of 249 competitive swimmers (age 12 yr., SD = 0.5) who trained and competed for four years. Measures involving fitness (e.g., lung capacity), strength (e.g., standing long jump), swimming technique (turn, glide, distance per stroke cycle), anthropometric variables (e.g., hand and foot size), as well as specific swimming measures (speeds in particular distances), were used. The participants (n = 189) trained from May 2008 to May 2009, which involved five days of swimming workouts per week, and three additional 45-min. sessions devoted to measurements necessary for this study. In June 2009, data from two groups of 30 swimmers each (n = 60) were used to identify predictor variables. Models were then constructed from these variables to predict final swimming performance in the 50 meter and 800 meter crawl events. Nonlinear regression models and neural models were built for the dependent variable of sport results (performance at 50m and 800m). In May 2010, the swimmers' actual race times for these events were compared to the predictions created a year prior to the beginning of the experiment. Results for the nonlinear regression models and perceptron networks structured as 8-4-1 and 4-3-1 indicated that the neural models overall more accurately predicted final swimming performance from initial training, strength, fitness, and body measurements. Differences in the sum of absolute error values were 4:11.96 (n = 30 for 800m) and 20.39 (n = 30 for 50m), for models structured as 8-4-1 and 4-3-1, respectively, with the neural models being more accurate. It seems possible that such models can be used to predict future performance, as well as in the process of recruiting athletes for specific styles and distances in swimming.     

Relationships between coordination,active drag and propelling efficiency in crawl

This study examines the relationships between the index of coordination (IdC) and active drag (D) assuming that at constant average speed, average drag equals average propulsion. The relationship between IdC and propulsive efficiency (e_p) was also investigated at maximal speed. Twenty national swimmers completed two incremental speed tests swimming front crawl with arms only in free condition and using a measurement of active drag system. Each test was composed of eight 25-m bouts from 60% to 100% of maximal intensity whereby each lap was swum at constant speed. Different regression models were tested to analyse IdC–D relationship. Correlation between IdC and e_p was calculated. IdC was linked to D by linear regression (IdC = 0.246 · D − 27.06; R² = 0.88, P < .05); swimmers switched from catch-up to superposition coordination mode at a speed of ∼1.55 m s⁻¹ where average D is ∼110 N. No correlation between IdC and e_p at maximal speed was found. The intra-individual analysis revealed that coordination plays an important role in scaling propulsive forces with higher speed levels such that these are adapted to aquatic resistance. Inter-individual analysis showed that high IdC did not relate to a high e_p suggesting an individual optimization of force and power generation is at play to reach high speeds.     

High level swimming performance and its relation to non-specific parameters: a cross-sectional study on maximum handgrip isometric strength

The relationship between handgrip isometric strength and swimming performance was assessed in the four competitive swimming strokes in swimmers of different age groups and of both sexes. 78 national-level Portuguese swimmers (39 males, 39 females) were selected for this study. Grip strength, previously used as a marker of overall strength to predict future swimming performance, was measured using a hand dynamometer. The best competitive time at 100 and 200 m in all four swimming strokes were converted into 2010 FINA points. Non-parametric tests were used to evaluate differences between groups. Pearson product-moment correlations were computed to verify the association between variables. Handgrip maximum isometric strength was significantly correlated with swimming performance, particularly among female swimmers. Among female age group swimmers, the relationship between handgrip and 100-m freestyle was significant. Handgrip isometric strength seems to be related to swimming performance, especially to 100-m freestyle and in female swimmers. For all other distances and strokes, technique and training probably are more influential than semi-hereditary strength markers such as grip strength.     

Influence of swimming speed on inter-arm coordination in competitive unilateral arm amputee front crawl swimmers

This study examined the effect of swimming speed on inter-arm coordination and the inter-relationships between swimming speed, inter-arm coordination, and other stroke parameters, in a group of competitive unilateral arm amputee front crawl swimmers. Thirteen highly-trained swimmers were filmed underwater during a series of 25-m front crawl trials of increasing speed. Arm coordination for both arms was quantified using an adapted version of the Index of Coordination. Inter-arm coordination of the amputee swimmers did not change as swimming speed was increased up to maximum. Swimmers showed significantly more catch-up coordination of their affected-arm compared to their unaffected-arm. When sprinting, the fastest swimmers used higher stroke frequencies and less catch-up of their affected-arm than the slower swimmers. Unilateral arm-amputees used an asymmetrical strategy for coordinating their affected-arm relative to their unaffected-arm to maintain the stable repetition of their overall arm stroke cycle. When sprinting, the attainment of a high stroke frequency is influenced mainly by the length of time the affected-arm is held in a stationary position in front of the body before pulling. Reducing this time delay appears to be beneficial for successful swimming performance.     

Effects of speed feedback signs and law enforcement on driver speed

This study analyzes the effects of implementing three speed management strategies, namely speed feedback signs, periodic law enforcement, and speed feedback sign supported with periodic law enforcement on driver speed behavior and compliance. To analyze the effectiveness of each strategy, nine locations in Pima County, Arizona, were studied in a cross-sectional framework. For each study site, the driver’s speed, date, time, and vehicle’s length were collected at a location prior to the speed management zone as the baseline, at the speed management zone, and downstream of the speed management zone. The general effect showed that all the strategies were effective in reducing average speed and the proportion of drivers exceeding the speed limit. In addition, the results of the robust heteroscedastic ANOVA test showed that among all the strategies, the speed feedback sign supported with periodic law enforcement was the most effective one. Moreover, it was shown that by supporting the speed feedback sign with periodic law enforcement, the reduction in average speed and proportion of drivers exceeding the speed limit would last, even after passing the speed management strategy. In other words, the existence of periodic law enforcement could potentially modify drivers’ behaviors and increase the spatial effectiveness of speed feedback signs. Comparing the behavior of truck and passenger car drivers also revealed similar results. That is, both truck and passenger car drivers tend to slow down after observing the speed management strategy. The experimental evidence indicates positive benefits for reducing excessive speeding behaviors at the sites.     

Stability and variability may respond differently to changes in walking speed

In gait research it has often been assumed that variability and stability are negatively correlated, where increases in variability are assumed to equate with increases in instability. The purpose of this paper is to illustrate that variability does not always equate with stability. To proof this point, a method was developed to directly assess stability and variability during the application of a visual perturbation at different walking speeds. Walking variability was measured by using the average standard deviation of the knee joint angle across the gait cycle. Walking stability was measured by the recovery time of the knee joint angle trajectory from the distortion induced by a visual perturbation that was delivered at the beginning of the stance phase. Five participants were required to walk at six different velocities on a treadmill (0.67, 0.80, 0.94, 1.07, 1.21, and 1.34 m/s). The coefficients of intraclass correlations for the experiment were 83% and 80% for the calculated stability and variability, respectively. The calculated stabilities were not sensitive to changes in walking speed (p>0.98). The calculated variability however decreased with increases in walking speed (p=0.004). No significant correlation between variability and stability was observed (r=-0.002). We suggest that gait stability is independent of variability during locomotion and should thus be measured independently.     

Adaptation of neuromuscular synergies during intentional constraints of space-time relationships in human gait

Tight frequency-to-amplitude relationships are observed in spontaneous human steady gait. They can be modified, if required; that flexibility forms a fundamental basis of the intentional adaptive capabilities of locomotion. In the present experiments, the processes underlying that flexibility were investigated at both the level of joint kinematics and the level of neuromuscular synergies. Subjects (N = 4) walked at the same speed either with a preferred or a nonpreferred frequency-to-amplitude relationship (i.e., constrained, short steps at a high frequency [COS condition] or constrained, long steps at a low frequency [COL condition]); their swing and stance phases were separately analyzed. In the COS condition, increases in EMG activity were specifically required during the swing phase. In the COL condition, several muscles required increases in EMG activity during the stance phase, but decreases of the hamstring muscles were needed during the swing phase. Whereas, in preferred walking, modification of the frequency affects the EMG patterns globally (the gain increasing with the frequency in both the stance and swing phases), the present results show that changing the frequency in a constrained manner either affects the swing phase specifically or affects both phases, but in the opposite direction. That finding indicates that a separate control is needed in both the swing and the stance phases.     

Adaptation of Neuromuscular Synergies During Intentional Constraints of Space-Time Relationships in Human Gait

Tight frequency-to-amplitude relationships are observed in spontaneous human steady gait. They can be modified, if required; that flexibility forms a fundamental basis of the intentional adaptive capabilities of locomotion. In the present experiments, the processes underlying that flexibility were investigated at both the level of joint kinematics and the level of neuromuscular synergies. Subjects (N = 4) walked at the same speed either with a preferred or a nonpreferred frequency-to-amplitude relationship (i.e., constrained, short steps at a high frequency [COS condition] or constrained, long steps at a low frequency [COL condition]); their swing and stance phases were separately analyzed. In the COS condition, increases in EMG activity were specifically required during the swing phase. In the COL condition, several muscles required increases in EMG activity during the stance phase, but decreases of the hamstring muscles were needed during the swing phase. Whereas, in preferred walking, modification of the frequency affects the EMG patterns globally (the gain increasing with the frequency in both the stance and swing phases), the present results show that changing the frequency in a constrained manner either affects the swing phase specifically or affects both phases, but in the opposite direction. That finding indicates mat a separate control is needed in both the swing and the stance phases.     

Daily variation of multiple behaviors in Aplysia fasciata: integration of feeding, reproduction, and locomotion

Daily variations in feeding, reproductive behaviors, and activity level were examined under three conditions: (1) animals had access to food and mates; (2) there was access only to food; (3) neither food nor mates were present. Behaviors differed in amplitude of variations from their daily mean value. Egg-laying had the strongest tendency to be clustered. Amplitude of variations in courtship and swimming was larger than those of immobility, crawling, and feeding, while moving in place was the least clustered behavior. Changes in state affected the tendency to be clustered. When food and mates were present, amplitude of variations became progressively larger for immobility, moving in place, crawling, and swimming. Behaviors differed in the degree to which variations were patterned as a 1/day oscillation. Relatively little of the variability in crawling, moving in place, courtship, and egg-laying was due to a 1/day oscillation under any condition. By contrast, a large proportion of the variability of immobility, swimming, mating, and eating was modulated by a 1/day oscillation in at least one condition. The contribution of a 1/day oscillation to variability differed in the conditions examined. For immobility and swimming, when food and mates were present, the 1/day component of variability became smaller. By contrast, presence of mates led to an increase in the 1/day component of variability modulating feeding. Daily peaks of swimming and feeding were in phase with one another, and out of phase with mating and feeding. The ratio of locomotion to inactivity is constant, independent of change in external conditions. However, this ratio varied throughout the day. When food and mates were absent, variations of immobility and swimming were strongly related to variations in the inactivity ratio. When food and mates were added, this tendency decreased. The data suggest that daily variations in occurrence of behaviors can be accounted for by interactions between oscillators affecting Aplysia behavior and motivational variables. A 1/day oscillator has strong effects on mating, swimming, and immobility. The effect of the oscillator is modified by changes in motivational state.     

Behavior of larval and juvenile bullfrogs (Rana catesbeiana) following chronic spinal transection

The behavior of larval and juvenile bullfrogs (Rana catesbeiana) was examined for 32 days following cervical spinal transection. The threshold for cutaneously elicited hindlimb withdrawal was not changed at either stage of development but righting reflexes were abolished. Forelimb postural support of juveniles was abolished by the transection but recovered within 3 days. Hindlimb posture was normal and hopping could be elicited by stimulation of the rump with a blunt wire probe. Undulatory swimming of larvae was abolished by the transection but began to recover approximately 1 week later. The hindlimbs of larvae were very active following the transection and displayed long sequences of coordinated stepping in response to a variety of stimuli. Gross examination of the spinal cord in situ after 32 days suggested that fibers may have grown across the transection site. Retransection at the site of the original transection on Postoperative Day 33 had no discernable effect on the behavior juveniles or on the stepping of larvae, but it abolished recovered swimming of larvae. Deafferentation of lumbar segments of larvae eliminated stepping but had no effect on swimming. Deafferentation of cervical segments eliminated forelimb support in juveniles. These results suggest that recovery of larval swimming depends at least in part upon the growth of fibers across the transection site. Stepping of spinal larvae appears to be mediated by proprioceptive reflexes rather than by central pattern generators, and in the normal animal is probably under the control of descending inhibition. Recovery of posture and hopping in juveniles was much more rapid than that described for adult frogs and does not depend on growth across the transection site.     

Coordination and timing of spine and hip joints during full body reaching tasks

Coupling of spine and hip joints during full body reaching tasks was investigated in 16 participants (8 male and 8 female) who performed reaching tasks at comfortable and fast-paced movement speeds to three targets located in a para-sagittal plane. The participants paused at target contact for 500ms and then returned to an upright posture. Three-dimensional joint motions of the spine and hip were recorded using an electromagnetic tracking device. We found an effect of movement phase (i.e., reach and return) on the onset timing of the spine and hip joints. For most target locations and movement speeds, spine motion onset preceded hip motion onset during the reaching phase of the movement task. In the reach phase, when averaged across all movement conditions, spine joint motion preceded hip joint motion by an average of 48.9ms. In contrast, in the return phase, hip joint motion preceded spine joint motion by an average of 63.0ms. Additionally, when participants were instructed to use either a knee flexion or knee extension strategy to perform the reaching tasks there was no effect of movement strategy on timing of the spine and hip. There was also no effect of target height on the spine-hip ratio, but as movement speed increased, the spine/hip ratio decreased for all target locations due primarily to an increase in hip joint excursion. The findings indicate clear differences in onset timing of the spine and hip joints during reaching tasks that necessitate some forward bending of the trunk and that onset timing is reversed for the return to an upright posture.     

The effect of using paddles on hand propulsive forces and Froude efficiency in arm-stroke-only front-crawl swimming at various velocities

Through pressure measurement and underwater motion capture analysis, this study aimed to elucidate the effects of hand paddles on hand propulsive forces, mechanical power, and Froude efficiency in arm-stroke-only front-crawl swimming at various velocities. Eight male swimmers swam under two conditions in randomized order, once using only their hands and once aided by hand paddles on both hands. Each participant swam 10 times a distance of 16 m in each condition, for a total of 20 trials. To elucidate the relationship between propulsive forces and swimming velocity, each participant was instructed to swim each of the two sets of 10 trials at an arbitrarily different swimming velocity. During the trials, pressure sensors and underwater motion capture cameras were used together to analyze the pressure forces acting on the hand and hand kinematics, respectively. Six pressure sensors were attached to the right hand, and pressure forces acting on the right hand were estimated by multiplying the areas with the pressure differences between the palm and dorsal side of the hand. Acting directions of pressure forces were analyzed using a normal vector perpendicular to the hand or hand paddle, calculated from coordinates obtained using underwater motion capture analysis. As a result, there were no differences in propulsive forces and mechanical power to overcome water resistance (P_D) with or without hand paddles at the same swimming velocities. However, the use of hand paddles decreased stroke rate and hand velocities, so mechanical power to push the water at the hand (P_K) decreased. Using hand paddles thus increased Froude efficiency (η_F). These results suggest that training load decreases when swimmers swim at the same velocities while using hand paddles. This insight could prove useful for coaches and swimmers when using hand paddles for training to help ensure that they are used in accordance with their intended training purpose. If swimmers use hand paddles increasing propulsive force or P_K, they should swim at a higher swimming velocity with hand paddles than without.     

The number of active sweat glands (PSI, palmar sweat index) in stress caused by blood donation

The number of active sweat glands (PSI), heart rate, systolic (SBP) and diastolic blood pressure (DBP) were assessed every 2 minutes in 109 male blood donors. Three measurements were taken at the beginning (adaptation phase), three later but before blood donation (baseline), one during the venous puncture (phase 3), three thereafter but still during donation (phase 4), and four after removal of the cannula (phase 5). Analysis of variance yielded significant differences between phases; PSI and SBP behaved similarly, decreasing from adaptation to baseline, rising during puncture, and decreasing again thereafter. Mean within-subject correlations between variables were significantly above 0. Between-subjects correlations were significantly negative for PSI and DBP. This is best explained by the influence of age on both variables. Correlations of PSI values as determined by three raters had a mean of 0.90. The study shows that the PSI is a very sensitive indicator of stress that is easily accessible also in field studies.     

Effects of gait speed on the body’s center of mass motion relative to the center of pressure during over-ground walking

Preferred walking speed (PWS) reflects the integrated performance of the relevant physiological sub-systems, including energy expenditure. It remains unclear whether the PWS during over-ground walking is chosen to optimize one’s balance control because studies on the effects of speed on the body’s balance control have been limited. The current study aimed to bridge the gap by quantifying the effects of the walking speed on the body’s center of mass (COM) motion relative to the center of pressure (COP) in terms of the changes and directness of the COM-COP inclination angle (IA) and its rate of change (RCIA). Data of the COM and COP were measured from fifteen young healthy males at three walking speeds including PWS using a motion capture system. The values of IAs and RCIAs at key gait events and their average values over gait phases were compared between speeds using one-way repeated measures ANOVA. With increasing walking speed, most of the IA and RCIA related variables were significantly increased (p < 0.05) but not for those of the frontal IA. Significant quadratic trends (p < 0.05) with highest directness at PWS were found in IA during single-limb support, and in RCIA during single-limb and double-limb support. The results suggest that walking at PWS corresponded to the COM-COP control maximizing the directness of the RCIAs over the gait cycle, a compromise between the effects of walking speed and the speed of weight transfer. The data of IA and RCIA at PWS may be used in future assessment of balance control ability in people with different levels of balance impairments.     

Self-Concept and School Adjustment

This study attempted to relate self-concept to several dimensions of the child's experience that are deemed fundamental to effective academic adjustment. It was hypothesized that a child's conception of school would be related to his conception of himself, and thus might be construed as an extension of his self-concept. 80 6th-grade students were used as subjects for all phases of the investigation. Significantly positive correlations were obtained between self-concept measures and the following variables: conception of school, social status at school, emotional adjustment, mental ability, reading achievement, and mathematical achievement.