Work, Training and Life Stress in ITU World Olympic Distance Age-Group Championship Triathletes.

We assessed the training, work and Life Stress demands of a mixed gender group of 48 top amateur short-distance triathletes using an online retrospective epidemiological survey and the Life Events Survey for Collegiate Athletes. On superficial inspection, these mainly masters athletes appeared to undergo all the types of training that are recommended for the aging athlete. However, there were significant scheduling differences between their weekday vs. their weekend training, suggesting that age-groupers' outside sports commitments may affect their training efficacy. The triathletes claimed to periodize, to obtain feedback on and to modify their training plans when appropriate-and some evidence of this was obtained. Over the year preceding the ITU World Age-Group Championships, they averaged 53%, 33% and 14% of their combined swim, cycle and run training time, respectively, within intensity zones 1, 2 and 3. Although the triathletes specifically stated that their training was focused on preparation for the ITU World Age-Group Championships, the way that they modified their training in the month before the event suggested that this aim was not necessarily achieved. Sports-related stress accounted for most-42.0 ± 26.7%-of their total Life Stress over the preceding year (vs. 12.7 ± 18.6% for Relationship-, 31.3 ± 25.9% for Personal- and 14.0 ± 21.1% for Career-related Stress). It affected most athletes, and was overwhelmingly negative, when it related to failure to attain athletic goal(s), to injury and/or to illness.

Mood profiles of amateur triathletes: Implications for mental health and performance.

Moods have been shown to be predictive of athletic performance and a reflection of mental health status. The aims of our study were (a) to compare pre-race mood scores of triathletes with population norms; (b) to compare pre-race mood scores of triathletes grouped by gender and age bands; (c) to explore whether six distinct mood profile clusters reported in the literature were evident among triathletes and their respective prevalence; (d) to determine if pre-race mood scores predicted triathlon performance; and (e) to interpret our findings in terms of the risk of mental health issues for triathletes. Participants were 592 age-group triathletes (also referred to as recreational or amateur triathletes) who completed the Brunel Mood Scale pre-race and recorded their time goal for the race. Mean mood scores deviated significantly from population norms, with Tension and Vigor scores at the 55th and 54th percentile, respectively, and Depression, Anger, Fatigue, and Confusion scores between the 42nd and 46th percentile. Females reported higher Tension scores than males (p < 0.001), and those in the 18-25 years and 26-35 years age bands reported higher Tension scores than those in the 46-55 years age band (p < 0.008). Using k-means cluster analysis, six distinct mood profiles were identified, the distribution of which approximated the general population, except for a low prevalence of very negative profiles. Mean scores for Depression and Anger were exceptionally low and only 1.5% of triathletes, compared to the normal prevalence of ~5%, reported an "inverse Everest" profile, which is associated with elevated risk of psychopathology. Mood scores did not predict triathlon performance, assessed by finish time as a percentage of time goal. Results showed an association between triathlon participation and psychological well-being. Findings will inform future investigations of mood responses among triathletes and provide a relevant point of reference for applied practitioners who work with triathletes.

How to Form a Successful Team for the Novel Olympic Triathlon Discipline: The Mixed-Team-Relay.

The triathlon Mixed-Team-Relay (MTR) is a new race format present for the first time at the Tokyo Olympic Games in 2021. The results of the ITU Triathlon Mixed Relay World Championship from 2014 to 2019 were collected to provide practical suggestions for forming a successful MTR, such as the importance of each leg and discipline on MTR and Super-Sprint performance. The total relay time (Trelay), the time of each team member (leg-from 1 to 4) (Tleg), and the time of each single discipline (swim, T1, cycle, T2, run) were collected from the official website. Inferential analysis was performed to assess prediction and differences between variables. Leg 3 was shown to be the most important to predict Trelay (0.41), which is also the slower. For both Trelay and Tleg, cycling resulted as the most important (>0.60) and longer (~52%) portion, followed by running and swimming. However, higher importance in swimming was found in successful teams compared to running. For a successful MTR, we suggest: (a) use short-distance specialized triathletes; (b) strengthen cycling and swimming; (c) position in legs 1 and 2 athletes capable of racing in a group; in legs 3 and 4 athletes capable of racing in a non-drafting situation.

Discovering the sluggishness of triathlon running - using the attractor method to quantify the impact of the bike-run transition.

Running in a triathlon, a so-called brick run, is uniquely influenced by accumulated load from its preceding disciplines. Crucially, however, and irrespective of race type, the demands of a triathlon always exceed the sum of its parts. Triathletes of all levels commonly report subjectively perceived incoordination within the initial stages of the cycle run transition (T2). Although minimizing it, and its influence on running kinematics, can positively impact running and overall triathlon performance, the mechanisms behind the T2 effect remain unclear. In the present study, we assessed the influence of the pre-load exercise mode focusing on the biomechanical perspective. To analyze inertial sensor-based raw data from both legs, the so-called Attractor Method was applied. The latter represents a sensitive approach, allowing to quantify subtle changes of cyclic motions to uncover the transient effect, a potentially detrimental transient phase at the beginning of a run. The purpose was to analyze the impact of a pre-load on the biomechanics of a brick run during a simulated Olympic Distance triathlon (without the swimming section). Therefore, we assessed the influence of pre-load exercise mode on running pattern (δM) and precision (δD), and on the length of the transient effect (tT) within a 10 km field-based run in 22 well-trained triathletes. We found that δD, but not δM, differed significantly between an isolated run (IRun) and when it was preceded by a 40 km cycle (TRun) or an energetically matched run (RRun). The average distance ran until overcoming the transient phase (tT) was 679 m for TRun, 450 m for RRun, and 29 4 m for IRun. The results demonstrated that especially the first kilometer of a triathlon run is prone to an uncoordinated running sensation, which is also commonly reported by athletes. That is, i) the T2 effect appeared more linked to variability in running style than to running style per se ii) run tT distance was influenced by preceding exercise load mode, being greater for a TRun than for the RRun condition, and iii) the Attractor Method seemed to be a potentially promising method of sensitively monitoring T2 adaptation under ecologically valid conditions.

Benefits to Performance and Well-Being of Nature-Based Exercise: A Critical Systematic Review and Meta-Analysis.

Prior reviews point to the superior benefits of exercising in nature vs in conventional indoor venues, particularly in terms of well-being. However, physical exercise performance, neither in terms of efficacy nor efficiency, has not been sufficiently addressed by past reviews of this topic. Therefore, we conducted both a systematic review and meta-analysis of the experimental literature that relates to differences in exercise performance and well-being between exercising in nature and in conventional indoor venues. Forty-nine relevant studies─the outcome data of which were used for the systematic review─were located within the Web of Science, PubMed, and Scopus databases. The meta-analyses, using data from twenty-four of the relevant studies, revealed no significant overall environmental effect on task performance efficacy outcomes (p = 0.100). For nature-based exercise, however, marginally positive cognitive performance outcomes (p = 0.059), lower ratings of perceived exhaustion (p = 0.001), and higher levels of vigor (p = 0.017) were observed, indicating higher performance efficiency. As for the effects of environment on well-being, positive affect was significantly higher for nature-based exercise (p = 0.000), while perceived stress was significantly higher for indoor exercise (p = 0.032). These results must, however, be interpreted with caution. High levels of bias and between-study heterogeneity were observed. Nonetheless, given several noticeable trends in the results, it may be that exercising in nature enhances the efficiency of exercise task performance to a greater extent than does indoor exercise.

Gender Effect on the Relationship between Talent Identification Tests and Later World Triathlon Series Performance.

BACKGROUND: We examined the explanatory power of the Spanish triathlon talent identification (TID) tests for later World Triathlon Series (WTS)-level racing performance as a function of gender. METHODS: Youth TID (100 m and 1000 m swimming and 400 m and 1000 m running) test performance times for when they were 14-19 years old, and WTS performance data up to the end of 2017, were obtained for 29 female and 24 male "successful" Spanish triathletes. The relationships between the athletes' test performances and their later best WTS ranking positions and performance times were modeled using multiple linear regression. RESULTS: The swimming and running TID test data had greater explanatory power for best WTS ranking in the females and for best WTS position in the males (R2a = 0.34 and 0.37, respectively, p ≤ 0.009). The swimming TID times were better related to later race performance than were the running TID times. The predictive power of the TID tests for WTS performance was, however, low, irrespective of exercise mode and athlete gender. CONCLUSIONS: These results confirm that triathlon TID tests should not be based solely on swimming and running performance. Moreover, the predictive value of the individual tests within the Spanish TID battery is gender specific.

The Training Characteristics of Recreational-Level Triathletes: Influence on Fatigue and Health.

Little is known about how recreational triathletes prepare for an Olympic distance event. The aim of this study was to identify the training characteristics of recreational-level triathletes within the competition period and assess how their preparation for a triathlon influences their health and their levels of fatigue. During the 6 weeks prior to, and the 2 weeks after, an Olympic distance triathlon, nine recreational athletes (five males, four females) completed a daily training log. Participants answered the Daily Analysis of Life Demands Questionnaire (DALDA), the Training Distress Scale (TDS) and the Alberta Swim Fatigue and Health Questionnaire weekly. The Recovery-Stress Questionnaire (REST-Q) was completed at the beginning of the study, on the day before the competition, and at the end of week 8. Training loads were calculated using session-based rating of perceived exertion (sRPE). The data from every week of training was compared to week 1 to determine how athletes' training and health changed throughout the study. No changes in training loads, duration or training intensity distribution were seen in the weeks leading up to the competition. Training duration was significantly reduced in week 6 (p = 0.041, d = 1.58, 95% CI = 6.9, 421.9), while the number of sessions was reduced in week 6 (Z = 2.32, p = 0.02, ES = 0.88) and week 7 (Z = 2.31, p = 0.02, ES = 0.87). Training was characterized by large weekly variations in training loads and a high training intensity. No significant changes were seen in the DALDA, TDS or REST-Q questionnaire scores throughout the 8 weeks. Despite large spikes in training load and a high overall training intensity, these recreational-level triathletes were able to maintain their health in the 6 weeks of training prior to an Olympic distance triathlon.

Wetsuit Use During Open Water Swimming. Does It "Suit" Everybody? A Narrative Review.

PURPOSE: Although wearing a wetsuit while swimming, when permitted, is primarily for safety reasons (ie, to protect against hypothermia), changes in buoyancy, biomechanics, and exercise performance have been reported. This narrative review covers the benefits of different wetsuit models on performance in swimming and triathlon. METHODS: A computer search of online databases was conducted to locate relevant published research until March 2021. After the screening process, 17 studies were selected for analysis. RESULTS: Most of the selected studies involved pool swimmers or triathletes completing short or middle distances in a pool while using a full or a long sleeveless wetsuit. Swimming with wetsuit elicited significant improvements in performance (maximum 11%), mainly by decreasing drag and energy cost, by increasing buoyancy, and by affecting technique. Different rates of change in each factor were found according to swimming ability and wetsuit model. In addition, wearing a wetsuit was often rated as uncomfortable by athletes. CONCLUSIONS: Although improvement in swimming performance by wearing a wetsuit has been reported in the literature, the amplitude of the improvement remains questionable. The enhancement in swimming performance is attributable merely to improvements in propulsion proficiency and buoyancy, as well as a reduction in drag. The extent to which athletes are familiar with the use of a wetsuit, their swimming ability, and the wetsuit model may play important roles in this improvement. More studies simulating competition and comparing elite versus nonelite athletes are needed.

The "Journal of Functional Morphology and Kinesiology" Journal Club Series: PhysioMechanics of Human Locomotion.

We are glad to introduce the Third Journal Club of Volume five, the third issue. This edition is focused on relevant studies published in the last years in the field of PhysioMechanics of Human Locomotion, chosen by our Editorial Board members and their colleagues. We hope to stimulate your curiosity in this field and to share with you the passion for the Sports Medicine and Movement Sciences seen also from the scientific point of view. The Editorial Board members wish you an inspiring lecture.

Is the Bike Segment of Modern Olympic Triathlon More a Transition towards Running in Males than It Is in Females?

In 2009, the International Triathlon Union created a new triathlon race format: The World Triathlon Series (WTS), for which only athletes with a top 100 world ranking are eligible. Therefore, the purpose of this study was to analyze the influence of the three disciplines on performance within all the WTS Olympic distance races within two Olympic cycles, and to determine whether their relative contribution changed over the years. Methods: For each of a total of 44 races, final race time and position as well as split times (and positions), and summed time (and position) at each point of the race were collected and included in the analysis. Athletes were divided into 4 groups according to their final race placing (G1: 1st⁻3rd place; G2: 4⁻8th place; G3: 8⁻16th place and G4: ≥17th place). Two-way multivariate ANOVAs were conducted to compare the main effects of years and rank groups. For females, there were significant differences in the swim and bike segment only between G4 and the other groups (p range from 0.001⁻0.029), whilst for the run segment each group differed significantly from each other (p < 0.001). For males, there were significant differences in swim only between G4 and the other groups (p range from 0.001⁻0.039), whilst for the running segment each group differed significantly from the others (p < 0.001). Although we found running to be the segment where there were significant differences between performance groups, it is apparently important for overall success that a good runner be positioned with the first cycling pack. However, bike splits were not different between either of the four male groups or between the first 3 groups of the females. At this very high level of performance, at least in the males, the bike leg seems to be a smooth transition towards running.

Correction: Does growth path influence beef lipid deposition and fatty acid composition?

[This corrects the article DOI: 10.1371/journal.pone.0193875.].

Does growth path influence beef lipid deposition and fatty acid composition?

Despite the recent advances in transcriptomics, gene expression studies addressing cattle´s skeletal muscle adaptations in response to compensatory growth are warranted, particularly regarding lipid metabolism due to its impact in meat sensory and nutritional traits. In the present study, in comparison to ad libitum feeding, a period of feed restriction was used in order to understand the changes in bull´s lipid metabolism and gene expression of the adipogenic and lipogenic pathways after re-alimentation. Thus, 40 young Alentejana bulls were either fed ad libitum (CG group) from 9 to 18 months of age or subjected to food restriction from 9 to 15 months of age, and fed ad libitum until 24 months of age (DG group). The intramuscular fat (IMF) and total fatty acids (FA) contents were similar between groups. The major FA (>2%) contents were similar (16:0, 16:1c9, 18:1c9 and 18:2n-6) between treatments with the exception of 18:0 content that was 15% lower in DG than in CG and 20:4n-6 that tended to be greater on DG bulls. Regarding minor FA (<2%), the DG group presented greater proportions (P<0.01) of 17:1c9, 18:1t9, 18:1t10 (, 18:1c11), 18:1c13, 18:3n-6, 22:0, 22:4n-6 and 22:6n-3 and lower (P<0.05) proportions of 20:0, 18:1t16+c14, and branched chain FA (iso-15:0, anteiso-15:0, iso-16:0 and anteiso-17:0) than the CG group. Delta-9 desaturase activity indices were consistently greater (P<0.05) in DG, when compared to the CG group. Regarding microarray analysis, differentially expressed genes between CG and DG bulls were grouped in 5 main biological functions: lipid and nucleic acid metabolisms, small molecule biochemistry, molecular transport and translational modification. Discontinuous growth down-regulated the expression of ACACB (FC (fold-change) = 1.32), FABP3 (FC = 1.45), HADHA (FC = 1.41) and SLC37A4 (FC = 1.40) genes, when compared to the CG system (FDR<0.05). In contrast, in the CG bulls, the expression of ELOVL5 (FC = 1.58) and FASN (FC = 1.71) was down-regulated when compared to DG bulls. These results were confirmed to be significant (P<0.05) in the case of ELOVL5, FASN and SLC37A4, and almost significant for FABP3 by qRT-PCR analysis. The SCD1 and SCD5 gene expressions were not found to be affected by growth path. These results contribute to the still scarce knowledge about the mechanisms involved in fatty acid metabolism during compensatory growth which have decisive role on meat quality produced in Mediterranean areas.

Sex and Exercise Intensity Do Not Influence Oxygen Uptake Kinetics in Submaximal Swimming.

The aim of this study was to compare the oxygen uptake ([Formula: see text]) kinetics in front crawl between male and female swimmers at moderate and heavy intensity. We hypothesized that the time constant for the primary phase [Formula: see text] kinetics was faster in men than in women, for both intensities. Nineteen well trained swimmers (8 females mean ± SD; age 17.9 ± 3.5 years; mass 55.2 ± 3.6 kg; height 1.66 ± 0.05 m and 11 male 21.9 ± 2.8 years; 78.2 ± 11.1 kg; 1.81 ± 0.08 m) performed a discontinuous maximal incremental test and two 600-m square wave transitions for both moderate and heavy intensities to determine the [Formula: see text] kinetics parameters using mono- and bi-exponential models, respectively. All the tests involved breath-by-breath analysis of front crawl swimming using a swimming snorkel. The maximal oxygen uptake [Formula: see text] was higher in men than in women [4,492 ± 585 ml·min-1 and 57.7 ± 4.4 ml·kg-1·min-1 vs. 2,752.4 ± 187.9 ml·min-1 (p ≤ 0.001) and 50.0 ± 5.7 ml·kg-1·min-1(p = 0.007), respectively]. Similarly, the absolute amplitude of the primary component was higher in men for both intensities (moderate: 1,736 ± 164 vs. 1,121 ± 149 ml·min-1; heavy: 2,948 ± 227 vs. 1,927 ± 243 ml·min-1, p ≤ 0.001, for males and females, respectively). However, the time constant of the primary component (τp) was not influenced by sex (p = 0.527) or swimming intensity (p = 0.804) (moderate: 15.1 ± 5.6 vs. 14.4 ± 5.1 s; heavy: 13.5 ± 3.3 vs. 16.0 ± 4.5 s, for females and males, respectively). The slow component in the heavy domain was not significantly different between female and male swimmers (3.2 ± 2.4 vs. 3.8 ± 1.0 ml·kg-1·min-1, p = 0.476). Overall, only the absolute amplitude of the primary component was higher in men, while the other [Formula: see text] kinetics parameters were similar between female and male swimmers at both moderate and heavy intensities. The mechanisms underlying these similarities remain unclear.

Ventilatory and Physiological Responses in Swimmers Below and Above Their Maximal Lactate Steady State.

The purpose of this study was to understand the ventilatory and physiological responses immediately below and above the maximal lactate steady-state (MLSS) velocity and to determine the relationship of oxygen uptake (VO2) kinetics parameters with performance, in swimmers. Competitive athletes (N = 12) completed in random order and on different days a 400-m all-out test, an incremental step test comprising 5 × 250- and 1 × 200-m stages and 30 minutes at a constant swimming velocity (SV) at 87.5, 90, and 92.5% of the maximal aerobic velocity for MLSS velocity (MLSSv) determination. Two square-wave transitions of 500 m, 2.5% above and below the MLSSv were completed to determine VO2 on-kinetics. End-exercise VO2 at 97.5 and 102.5% of MLSSv represented, respectively, 81 and 97% of VO2max; the latter was not significantly different from maximal VO2 (VO2max). The VO2 at MLSSv (49.3 ± 9.2 ml·kg(-1)·min(-1)) was not significantly different from the second ventilatory threshold (VT2) (51.3 ± 7.6 ml·kg(-1)·min(-1)). The velocity associated with MLSS seems to be accurately estimated by the SV at VT2 (vVT2), and vVO2max also seems to be estimated with accuracy from the central 300-m mean velocity of a 400-m trial, indicators that represent a helpful tool for coaches. The 400-m swimming performance (T400) was correlated with the time constant of the primary phase VO2 kinetics (τp) at 97.5% MLSSv, and T800 was correlated with τp in both 97.5 and 102.5% of MLSSv. The assessment of the VO2 kinetics in swimming can help coaches to build training sets according to a swimmer's individual physiological response.

An informational framework to predict reaction of constraints using a reciprocally connected knee model.

Researchers have used screw theory to describe the motion of the knee in terms of instantaneous axes of the knee (IAK). However, how geometric change to the dynamic alignment of IAK may affect stance phase of foot loading has not yet been fully explained. We have tested our informational framework through readily accessible benchmark data (Fregly et al. 2012): muscle contraction and ground reaction force are compounded into a wrench that is reciprocal to the IAK and resolved into component wrenches belonging to the reciprocal screw system. This revealed the special screw system that defines the freedom available to the knee and more precisely revealed how to measure this first order of freedom. After this step, we determined the reciprocal screw system, which involves the theory of equilibrium. Hence, a screw system of the first order will have a screw system of the fifth order as its reciprocal. We established a framework the estimation of reaction of constraints about the knee using a process that is simplified by the judicious generation of IAK for the first order of freedom in equilibrium.

The impact of triathlon training and racing on athletes' general health.

Although the sport of triathlon provides an opportunity to research the effect of multi-disciplinary exercise on health across the lifespan, much remains to be done. The literature has failed to consistently or adequately report subject age group, sex, ability level, and/or event-distance specialization. The demands of training and racing are relatively unquantified. Multiple definitions and reporting methods for injury and illness have been implemented. In general, risk factors for maladaptation have not been well-described. The data thus far collected indicate that the sport of triathlon is relatively safe for the well-prepared, well-supplied athlete. Most injuries 'causing cessation or reduction of training or seeking of medical aid' are not serious. However, as the extent to which they recur may be high and is undocumented, injury outcome is unclear. The sudden death rate for competition is 1.5 (0.9-2.5) [mostly swim-related] occurrences for every 100,000 participations. The sudden death rate is unknown for training, although stroke risk may be increased, in the long-term, in genetically susceptible athletes. During heavy training and up to 5 days post-competition, host protection against pathogens may also be compromised. The incidence of illness seems low, but its outcome is unclear. More prospective investigation of the immunological, oxidative stress-related and cardiovascular effects of triathlon training and competition is warranted. Training diaries may prove to be a promising method of monitoring negative adaptation and its potential risk factors. More longitudinal, medical-tent-based studies of the aetiology and treatment demands of race-related injury and illness are needed.

The stationary configuration of the knee.

BACKGROUND: Ligaments and cartilage contact contribute to the mechanical constraints in the knee joints. However, the precise influence of these structural components on joint movement, especially when the joint constraints are computed using inverse dynamics solutions, is not clear. METHODS: We present a mechanical characterization of the connections between the infinitesimal twist of the tibia and the femur due to restraining forces in the specific tissue components that are engaged and responsible for such motion. These components include the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments and cartilage contact surfaces in the medial and lateral compartments. Their influence on the bony rotation about the instantaneous screw axis is governed by restraining forces along the constraints explored using the principle of reciprocity. RESULTS: Published kinetic and kinematic joint data (American Society of Mechanical Engineers Grand Challenge Competition to Predict In Vivo Knee Loads) are applied to define knee joint function for verification using an available instrumented knee data set. We found that the line of the ground reaction force (GRF) vector is very close to the axis of the knee joint. It aligns the knee joint with the GRF such that the reaction torques are eliminated. The reaction to the GRF will then be carried by the structural components of the knee instead. CONCLUSIONS: The use of this reciprocal system introduces a new dimension of foot loading to the knee axis alignment. This insight shows that locating knee functional axes is equivalent to the static alignment measurement. This method can be used for the optimal design of braces and orthoses for conservative treatment of knee osteoarthritis.

Rating of perceived exertion during cycling is associated with subsequent running economy in triathletes.

OBJECTIVES: To determine which commonly measured variables of cycling intensity are related to subsequent running economy in triathletes. DESIGN: Cross-sectional laboratory study. METHODS: Running economy was compared between a control run (no preceding cycle) and a run performed after a 45 min high-intensity cycle in eighteen triathletes. Power output, heart rate, rating of perceived exertion (RPE) and blood lactate concentration were monitored throughout the cycle. The relationship between measures of cycle intensity and the change in running economy was evaluated using Pearson's product moment correlation. Changes in running economy were also interpreted using the smallest worthwhile change (>2.4%) and grouped accordingly (i.e. impaired, no change, or improved running economy). RESULTS: Triathletes' RPE at the end of the cycling bout was significantly associated with the change in running economy after cycling (r=0.57, p=0.01). Average RPE of the cycle bout and RPE at the end of the cycling bout were significantly different between groups, with higher RPE scores being related to impairments in running economy (p=0.04 and p=0.02 respectively). CONCLUSIONS: RPE during cycling is associated with subsequent running economy in triathletes. RPE is a simple, cost-effective measure that triathletes and their coaches can use in competition and training to control cycling intensity without the need for specialist equipment such as crank systems or blood analysers.

The natural shock absorption of the leg spring.

When a human being runs, muscles, tendons, and ligaments together behave like a single linear spring. This "leg spring" can be described remarkably well by spring/mass models. Although leg-stiffness during running (and logically, therefore, in hopping) has been shown to be adjusted in line with the individual characteristics of the external contact surface, the relative contribution of each of the sub-components of the leg spring to the mechanics of running is unclear. We proposed the three-degree-of-freedom leg spring chain in a position of stable equilibrium under the action of the leg stiffness. If the leg spring receives a displacement in hopping, the forces will no longer equilibrate, but the system will be exposed to the action of a force on a leg spring chain. We thus have two corresponding sets of modes, one set being the mode about which the chain is displaced, the other set for the forces which are evoked in consequence of the displacement. We found that if the leg has been displaced from a position of equilibrium about one of harmonic modes, then a vibration about this harmonic mode evokes a system of forces in the leg spring which in its turn tends to produce a motion on the original harmonic mode, and thus produce oscillation about the same harmonic mode. Our results suggest that the desired harmonic mode can be explained in terms of the natural shock absorption ability of the leg.

Reliability and validity of physiological data obtained within a cycle-run transition test in age-group triathletes.

This study examined the validity and reliability of a sequential "Run-Bike-Run" test (RBR) in age-group triathletes. Eight Olympic distance (OD) specialists (age 30.0 ± 2.0 years, mass 75.6 ± 1.6 kg, run VO2max 63.8 ± 1.9 ml· kg(-1)· min(-1), cycle VO2peak 56.7 ± 5.1 ml· kg(-1)· min(-1)) performed four trials over 10 days. Trial 1 (TRVO2max) was an incremental treadmill running test. Trials 2 and 3 (RBR1 and RBR2) involved: 1) a 7-min run at 15 km· h(-1) (R1) plus a 1-min transition to 2) cycling to fatigue (2 W· kg(-1) body mass then 30 W each 3 min); 3) 10-min cycling at 3 W· kg(-1) (Bsubmax); another 1-min transition and 4) a second 7-min run at 15 km· h(-1) (R2). Trial 4 (TT) was a 30-min cycle - 20-min run time trial. No significant differences in absolute oxygen uptake (VO2), heart rate (HR), or blood lactate concentration ([BLA]) were evidenced between RBR1 and RBR2. For all measured physiological variables, the limits of agreement were similar, and the mean differences were physiologically unimportant, between trials. Low levels of test-retest error (i.e. ICC <0.8, CV<10%) were observed for most (logged) measurements. However [BLA] post R1 (ICC 0.87, CV 25.1%), [BLA] post Bsubmax (ICC 0.99, CV 16.31) and [BLA] post R2 (ICC 0.51, CV 22.9%) were least reliable. These error ranges may help coaches detect real changes in training status over time. Moreover, RBR test variables can be used to predict discipline specific and overall TT performance. Cycle VO2peak, cycle peak power output, and the change between R1 and R2 (deltaR1R2) in [BLA] were most highly related to overall TT distance (r = 0.89, p < 0. 01; r = 0.94, p < 0.02; r = 0.86, p < 0.05, respectively). The percentage of TR VO2max at 15 km· h(-1), and deltaR1R2 HR, were also related to run TT distance (r = -0.83 and 0.86, both p < 0.05).