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In this study, we compared the reliability of short-term resting heart rate (HR) variability (HRV) and postexercise parasympathetic reactivation (i.e., HR recovery (HRR) and HRV) indices following either submaximal or supramaximal exercise. On 4 different occasions, beat-to-beat HR was recorded in 15 healthy males (21.5 ± 1.4 yr) during 5 min of seated rest, followed by submaximal (Sub) and supramaximal (Supra) exercise bouts; both exercise bouts were followed by 5 min of seated recovery. Reliability of all HR-derived indices was assessed by the typical error of measurement expressed as a coefficient of variation (CV,%). CV for HRV indices ranged from 4 to 17%, 7 to 27% and 41 to 82% for time domain, spectral and ratio indices, respectively. The CV for HRR ranged from 15 to 32%. Spectral CVs for HRV were lower at rest compared with Supra (e.g., natural logarithm of the high frequency range (LnHF); 12.6 vs. 26.2%; P=0.02). HRR reliability was not different between Sub and Supra (25 vs. 14%; P=0.10). The present study found discrepancy in the CVs of vagal-related heart rate indices; a finding that should be appreciated when assessing changes in these variables. Further, Supra exercise was shown to worsen the reliability of HRV-spectral indices.

This study analysed motor control during front crawl swimming starts by elite and trained swimmers, based on comparisons of: 1) kinematic and kinetic parameters of the start and 2) variability of these parameters across 3 trials per swimmer. Given that the start time to the 15-m mark is greatly influenced by the swimming phase, the study also compared the stroking and coordinative parameters from water entry to 25-m in the 2 skill groups. The swimmers performed 3 x 25-m at the 50-m race-pace and used their preferential start technique (grab start). The elite swimmers showed better start organization as reflected by higher impulse values in the direction of intended displacement despite similar block phase durations. They then spent more time in the water entry, gliding and leg kicking phases, with shorter swimming phase duration and 15-m start time than the trained swimmers (p

An imbalance in the agonist/antagonist ratio has been identified as a pathologic factor. Using an isokinetic dynamometer, several studies have investigated the loss of quadriceps strength due to fatigue, but few have explored this phenomenon in the hamstrings. This study assessed the decline in strength of the hamstring and quadriceps muscles with fatigue. The goal was to determine whether a divergence in the decline in strength occurs that would affect the hamstring to quadriceps ratio of endurance. Twenty-seven professional soccer players were selected for endurance testing to evaluate fatigue on an isokinetic dynamometer. The decline in hamstring strength was significantly greater than that of the quadriceps after 15 repetitions for the dominant leg and after 40 repetitions for the nondominant leg. This study also revealed a decline in the endurance ratio compared with the maximal strength ratio in the dominant leg after 30 repetitions. In fatigue states, the decline in hamstring strength diverges from that of the quadriceps in both legs. This difference in resistance to fatigue provokes an imbalance that may affect the stabilizing function of the thigh muscles. These results can be considered as indicators of an increased risk of injury during exhausting effort.

The aim of this paper is to review the current knowledge about degenerative and repair process of articular cartilage, and relationship between osteoarthritis and physical activities. Data Pubmed, ScienceDirect data base are interrogated for the period 1994 - 2003. Key words are: cartilage, osteoarthritis, exercise, rehabilitation. The mechanical biology of the cartilage and the chondrocytes, the effects of physical activity on the cartilage, the main studies on clinical trials on rehabilitation are reviewed. Chondrocyte and cartilage structure and function change with mechanical stresses. Mechanical loads can modulate cartilage matrix turnover. Joint injury increases the risk of osteoarthritis, and sports that subjects joints to repetitive high levels of impact loading increase the risk of injury and degeneration. In human, intensive physical exercises seem associated with osteoarthritis development. None of the current procedures for repairing articular cartilage restores a normal articular zone, however, selected procedures can predictably benefit selected subjects. This article presents the biology and discusses the alteration of cartilage as well as the osteoarthritis process which is not yet well understood. Current medical approaches to the treatment of osteoarthritis also are presented. Rehabilitation programme could be beneficial in the therapeutic management of osteoarthritis.

This study evaluated the respiratory effects of a single dive in children. Eighteen young divers and 18 controls participated in our study (age range: 9 - 13 years). Volumes and expiratory flow rates were measured 20 minutes before and 10 minutes after one air dive (3 meters, 25 minutes). Before the dive, no differences were noted regarding pulmonary parameters. Ten minutes after the dive, decreases were noted in forced expiratory volume in 1 s (FEV1) and maximal voluntary ventilation (- 8 %, - 5.3 %, respectively; p < 0.01), peak expiratory flow, maximal expiratory flow rates at 50 % of FVC (MEF(50 %)) and MEF(25 %), forced mid-expiratory flow rate (FEF(25 - 75 %)), and FEV1/FVC(- 5.9 %, - 14.3 %, - 21.4 %, - 4.2 %, - 3.5 %, respectively; p < 0.05). The respiratory pattern observed 10 minutes after a single dive to three meters indicated airway narrowing. However, no association between diving experience and lung function was obtained.

The aim of this study was to compare the arm coordination of 14 elite men swimmers and 10 elite women swimmers at eight different velocities, from the usual 3000 m velocity to their maximal velocity (V (max)). Each stroke phase was identified by video analysis and the Index of Coordination (IdC) was established. Three modes of coordination have been identified: catch-up (IdC0); opposition (IdC = 0); and superposition (IdC0). This study shows that at a greater individually imposed swim pace (ISP) elite men spontaneously adapt by opposing their arms during sprint time (IdC = +2.57 +/- 6 % at Vmax), whereas elite women (IdC = -3.88 +/- 6.1 % at V (max)) adapt more slowly, remaining in catch-up coordination. Elite men favoured the increase of propulsive actions by increasing the propulsive phases (pull and push phases) and decreasing the entry + catch phase, even if the recovery phase increased. Elite women generated less propulsive actions during sprint, i. e. shorter push and pull phases and a longer entry + catch phase. The biomechanical constraints (effective velocity: EV) could explain that men switched coordination at high velocity (sprint), whilst the differences between men and women at a similar EV related more to their motor organisation than to biomechanical constraints. Anthropometric data could partially explain this difference between genders. Height (171.6 +/- 5.8 cm vs. 185.5 +/- 4.2 cm) and arm span (177.12 +/- 6.24 cm vs. 192.75 +/- 1.83 cm) were smaller in women than in men. The women catch-up coordination was not a "worse coordination" when compared with that of men, but it reflected a different motor organisation resulting from different anthropometric properties and swimming technique. Therefore, catch-up coordination could be an individual response to different constraints.

Although many professionals have produced books or videotapes which offer a novel approach to the game, a review of the scientific literature reports limited research evaluating the actual biomechanics of the golf swing in comparison with other sports. The aim of this study was to investigate the influence of kinematic pattern in golf swing using three different clubs: driver, five-iron, pitching-wedge. These three golf clubs have been chosen for their available range of ball flight. The measures of kinematic data during swing were established with the optoelectronic system VICON (Oxford's Metrics, Oxford, UK) with five cameras operating at 50 frames per second. Clubhead speed was measured using a swing made detector (Bell-Tronics, Ltd, Covington, USA). Seven right-handed male golfers with a high level of skill participated in the study. The results showed that there was an identical timing (movement time and proportion for each phase of the swing) between the three clubs tested, but the kinematics and the clubhead speed were different depending on the three different clubs used.

The aim of this study was to compare the arm coordination in 19 elite triathletes and 15 elite swimmers at six different velocities between 80 % and 100 % of their maximal velocity (Vmax). The different phases of the stroke (A: entry; B: pull; C: push; D: recovery) were identified by video analysis. An index of coordination (IdC) was calculated. It was the time that separated the beginning of the propulsive phase of one arm from the end of the propulsive phase of the other arm. IdC allows to express the mode of arm coordination: catch-up, IdC0; opposition, IdC = 0; superposition, IdC0. Between 80 % and 98 % Vmax, elite triathletes showed similar increases in IdC than swimmers (from -8.8 % to 2.6 % vs from -8.6 % to 0.3 %) switching from a catch-up to a superposition coordination. Between 88 % and Vmax, triathletes increased the propulsive phase (B+C) less (p0.01) than swimmers (3.4 % vs 8.5 %) and increased the recovery phase (0.8 %) when swimmers reduced it (-1.6 %). Between V5 and Vmax, both triathletes and swimmers had a significant (p0.01) difference in IdC change (-1.7 % vs 2.3 %). Moreover, triathletes reduced the propulsive phase when swimmers increased it (-0.6 % vs 3.2 %). The lower velocity of the triathletes was associated to a shorter stroke length when compared to the swimmers (1.70 m vs 2.15 m at Vmax). The stroke rates were not statistically different (55.1 vs 51.2 stroke x min(-1) at Vmax). Thus, monitoring IdC and stroke length is recommended for triathletes mainly at maximal velocity.

The relationship between breathing laterality and motor coordination symmetry as a function of the symmetry of medial rotator muscle force in the shoulders was investigated. The principal objective was to distinguish swimmer profiles. Thirteen expert male swimmers performed the front crawl and were assessed for: (i) inter-arm coordination with the IdC and arm coordination symmetry with the Symmetry Index, (ii) breathing laterality, and (iii) the symmetry of the isokinetic force in the shoulder medial rotators. The results indicated that the relative duration of catch+pull was greater for the dominant arm (51.7%) than for the non-dominant arm (48.4%) for the swimmers with force asymmetry (p

The aim of this study was to compare the intra-cyclic velocity graphs of breaststroke swimmers at two skill levels in relation to their movement phases. Two groups of nine male swimmers were videotaped underwater at three swimming race paces corresponding to their actual competitive times for the 200-m, 100-m and 50-m breaststroke. Their forward intra-cyclic hip velocity was recorded with a velocity-meter. The breaststroke cycle was divided into four phases: leg propulsion, leg-arm lag phase, arm propulsion, and arm and leg recovery. From the velocity-time data, the following parameters were computed: an index of velocity fluctuations (IVF), the distance covered during each stroke phase, and an acceleration-deceleration time ratio (ADTR). The main results showed that in both groups of swimmers, when the race pace increased, the distance covered during the leg-arm lag phase decreased, while the other swimming phases remained stable. When expressed in relative values, the percentage of distance covered during the leg-arm lag phase decreased. In nonelite swimmers, the percentage of distance covered in the other stroke phases increased significantly, while only a tendency was noted in the elite group. Elite swimmers demonstrated a higher ADTR at the 50-m pace than at their 100-m and 200-m paces. An inter-group comparison showed that elite swimmers had higher values for the IVF and ADTR, which indicated their capacity to accelerate to boost the swim and highlighted the relevancy of these factors to discriminate skill level.

The link between modifications in arm coordination (IdC) and intracyclic velocity variation (IVV) as a function of swim pace and gender is investigated. Twelve elite swimmers performed 5 different swim paces. Video analysis allowed IdC determination. The IVV was determined with a velocity-metre system. Results showed (i) a significant increase in IdC with swim pace (p < 0.05) but no significant change in IVV, and (ii) a gender effect for the mean values of both IdC and IVV (p < 0.05). This suggests that (i) the increase in IdC with swimming velocity helps to maintain IVV stability, and (ii) the mean IdC and the IVV level are determined by the relationship between anthropometric parameters and mechanical power output. Indeed, compared to males, the females generally had a lower mechanical power output, and lower drag to overcome, which explains the lower IVV found. It was concluded that increasing IdC could be a strategy adopted by elite swimmers to maintain IVV at a constant level, despite increases in both propulsive and drag forces and in relation to individual characteristics. Thus, the IVV-IdC relationship may be an interesting tool to determine a swimmer's misadaptation to the swim pace and to orient individual coaching in coordination analysis.

We investigated the validity of a new portable system and the feasibility of the method for gait analysis as the assessment of gait has clinical relevance in the study of locomotor pathologies. This system is composed of a data logger, triaxial accelerometers, and software. Measurements of the pelvis kinematics during gait were performed on five hip osteoarthritic subjects and 15 healthy subjects using the portable system and a reference system (Vicon). The healthy subjects were studied in conditions of normal gait and gait altered by a heelpiece. The studied variables were the vertical amplitude of the sacrum, the time of gait cycle and the vertical trajectories of the spines. The new system corresponded with the reference system for the studied variables. The small differences between the two systems in the vertical amplitude of the sacrum (0.53 +/- 6.39 mm), time of the gait cycle (0.002 +/- 0.05 s), and the vertical trajectories of the spine (coefficient correlation of 0.06 +/- 0.05) confirmed the validity of the portable system data. The results showed a distortion of the pelvis trajectory when the gait was impaired. The portable system provides an objective method to discriminate normal from limping gait and is easy to use outside of the laboratory.

Spatio-temporal, metabolic and psychometric responses during and after a 400-m freestyle swim trial were investigated for gender and skill-level effects. Thirty-four men and women, 18 national and international competitors and 16 recreational swimmers, were compared. Mean speed, stroke rate (SR), and stroke length (SL) were obtained from video recordings. Peak heart rate (HR) and the lactate value (Hla) were determined, as were the recovery kinetics, i.e., the recovery time index (RTI) for heart rate and %Hla (r) for the lactate values. Well-being was assessed with the Profile of Mood States questionnaire (POMS). Subjective workload was assessed with the NASA-TLX questionnaire. The experts showed less variation in their swim speed than the recreational swimmers. The male experts showed greater SL and the female experts showed greater SL and SR. No significant difference was noted between the experts and recreational swimmers for peaks of HR and Hla, POMS (157.3 +/- 15.1 vs. 163.1 +/- 21.5), or subjective workload (32.4 +/- 6.7 vs. 31.6 +/- 6.1). The experts exhibited higher RTI (- 38.5 +/- 5.5 % vs. - 31.1 +/- 5.4 %) and %Hla (r) (8.6 +/- 7.18 % vs. 1.65 +/- 8.2 %). They also showed an improvement of 7.8 +/- 2.6 % for men and 6.02 +/- 1.6 % for women between the performance time for the trial and the best competitive time of the season. Last, our results suggest that the 400-m freestyle trial is a valid field test to evaluate the maximal aerobic speed (MAS) of swimmers with different training status. The systemic analysis herein described can be used to set the end-of-season target time for expert competitors. Attention should focus on SL, race management, and the physiological recovery for training prescription.

Golf has become an increasingly popular sport, which is enjoyed by both men and women. This paper addresses the question what differences may exist between men and women golfers. The purpose of this study is to analyze the kinematic pattern of the golf swing in both men and women experienced golfers. Seven male and five female golfers participated in the study. The measurements of kinematic data during swing were obtained with the optoelectronic system VICON (Oxford's Metric, Oxford, UK) with five cameras operating at 50 frames per second. Clubhead speed was measured using a radar system (Bell-Tronics, Ltd, Covington, USA). A Mann-Whitney test (p = 0.05) showed that the women seem to produce a wide swing with larger hip and shoulder joint rotation angles at the top of the backswing. Men flexed their left knee more during the backswing, this may promote a greater weight transfer to the right side. Nevertheless, these two kinematic patterns showed no significant differences in the clubhead speed. Men probably used their increased knee flexion to compensate for their muscular and articular suppleness which is less than that of the women. The results of this study show that there is a specific swing for women.

This study analysed the spatial-temporal and coordinative structures in 12 elite male 100-m front crawl swimmers. Swim performance was analysed over each length of a 25-m pool divided into five zones of 5 m. Velocity (V), stroke rate (SR), and stroke length (SL) were calculated for each zone and each length. Four stroke phases were identified by video analysis and the Index of Coordination (IdC) was established. Three modes of coordination were identified: catch-up (IdC0), opposition (IdC = 0), and superposition (IdC0). The swimmers tended to reduce the decrease in V and SR over the course of the 100 m by maintaining a stable SL. In fact, these spatial-temporal values were stable during the time spent stroking and were higher or lower during the start, the turns (in and out), and the finish. Thus the spatial-temporal changes did not occur within the lengths, but between them. Conversely, the evolution in the IdC showed that the swimmers had to install the stroke at the beginning and only reached a stable coordination in the second part of the race. Moreover, the IdC increased throughout the different zones of each 25-m length, indicating changes in motor organisation, particularly increases in the push or pull phases. The IdC values corresponded to a superposition of the arms, linked to a six-beat leg kick. Achievement of an effective superposition coordination occurred by boosting the stroke just after the turn-out until the end of the length. Regarding the spatial-temporal and coordinative structures of a 100-m front crawl, great swimming skill was reflected by both high and stable data.

Breath-holding induces cardiovascular responses, notably bradycardia and peripheral vasoconstriction, which are known collectively as the diving response. This response is oxygen-conserving, i.e. an augmented response attenuates arterial oxygen desaturation, and is enhanced by apnoea training. To test this hypothesis, we compared heart rate (HR) and arterial oxygen saturation (SaO (2)) in breath-hold divers (BHD) and non-divers (ND). Nine BHD and nine healthy ND performed two static apnoeas (for 30 s and 45 s) and two dynamic apnoeas (for 30 s and 45 s) while swimming underwater at 0.7 m . s (-1). The pool temperature was 26 degrees C. The apnoeas were performed at 60 % of forced vital capacity. Heart rate (HR) and SaO (2) were recorded before breath-holding and at its end and are expressed in % change from rest values (DeltaHR and DeltaSaO (2)). Comparisons between BHD and ND showed that DeltaSaO (2) were lower in divers after both static apnoeas for 30 s and 45 s (- 2.8 % vs. - 5.5 %; - 3.2 % vs. 6.3 %; p < 0.05, respectively) and dynamic apnoeas (- 6 % vs. - 10.1 %; - 7.2 % vs. - 12.3 %; p < 0.05, respectively). The change in HR did not differ between the two groups and negative linear relations were found between DeltaHR and DeltaSaO (2) in both divers and ND (r = 0.66 and 0.61, respectively; p < 0.001). Moreover, the slope was lower for the divers (- 0.785 vs. - 0.1429; p < 0.001). Our results suggest that apnoea training explained the greater oxygen conservation seen in the divers in both static and dynamic conditions.

This study proposes a new method to evaluate arm-leg coordination in flat breaststroke. Five arm and leg stroke phases were defined with a velocity-video system. Five time gaps quantified the time between arm and leg actions during three paces of a race (200 m, 100 m and 50 m) in 16 top level swimmers. Based on these time gaps, effective glide, effective propulsion, effective leg insweep and effective recovery were used to identify the different stroke phases of the body. A faster pace corresponded to increased stroke rate, decreased stroke length, increased propulsive phases, shorter glide phases, and a shorter T1 time gap, which measured the effective body glide. The top level swimmers showed short time gaps (T2, T3, T4, measuring the timing of arm-leg recoveries), which reflected the continuity in arm and leg actions. The measurement of these time gaps thus provides a pertinent evaluation of swimmers' skill in adapting their arm-leg coordination to biomechanical constraints.