André Geyssant

Modeled responses to training and taper in competitive swimmers

This study investigated the effect of training on performance and assessed the response to taper in elite swimmers (N = 18), using a mathematical model that links training with performance and estimates the negative and positive influences of training, NI and PI. Variations in training, performance, NI, and PI were studied during 3-, 4-, and 6-wk tapers. The fit between modeled and actual performance was significant for 17 subjects; r2 ranged from 0.45 to 0.85, P < 0.05. Training was progressively reduced during tapers. Performance improved during the first two tapers: 2.90 +/- 1.50% (P < 0.01) and 3.20 +/- 1.70% (P < 0.01). Performance improvement in the third taper was not significant (1.81 +/- 1.73%). NI was reduced during the first two tapers (P < 0.01 and P < 0.05, respectively), but not during the third. PI did not change significantly during tapers. Thus, the present results show that the model used is a valuable method to describe the effects of training on performance. Performance improvement during taper was attributed to a reduction in NI. PI did not improve with taper, but it was not compromised by the reduced training periods.

Creatine supplementation does not improve sprint performance in competitive swimmers

This study was conducted to examine the effects of creatine (Cr) supplementation on sprint swimming performance and energy metabolism. Twenty highly trained swimmers (9 female, 11 male) were tested for blood ammonia and for blood lactate after the 25-, 50-, and 100-m performance in their best stroke on two occasions 7 d apart. After the first trial, subjects were evenly and randomly assigned to either a creatine (5 g creatine monohydrate 4 times per day for 5 d) or a placebo group (same dosage of a lactose placebo) in a double-blind research design. No significant differences in performance times were observed between trials. Post-exercise blood ammonia concentration decreased in the 50- and 100-m trials in the creatine group and in the 50-m trial in the placebo group. The supplementation period had no effect on post-exercise blood lactate. Therefore, creatine supplementation cannot be considered as an ergogenic aid for sprint performance in highly trained swimmers although adenine nucleotide degradation may be reduced during sprint exercise after 5 d of creatine ingestion.

Ergometric and metabolic adaptation to a 5-s sprint training programme

SummaryThe effects of 7 weeks of sprint training (repeated 5-s all-out sprints) on maximal power output (Wν, max) determined during a force-velocity test and a 30-s Wingate test (Wpeak) were studied in ten students [22 (SD 2) years] exercising on a cycle ergometer. Before and after training, muscle biopsies were taken from vastus lateralis muscle at rest for the ten subjects and immediately after a training session for five of them. Sprint training induced an improvement both in peak performances by 25% (Wν, max and Wpeak) and in the 30-s total work by 16%. Before sprint training, the velocity reached with no load (ν0) was related to the resting muscle phosphocreatine (PCr) stores (r=0.87, P < 0.001). The training-induced changes in ν0 were observed only when these PCr stores were lowest. This pointed to a possible limiting role of low PCr concentrations in the ability to reach a high velocity. The improvement in performances was linked to an increase in the energy production from anaerobic glycolysis. This result was suggested in muscle by the increase in lactate production measured after a training session associated with the 20% higher activity of both phosphofructokinase and lactate dehydrogenase. The sprint training also increased the proportion of slow twitch fibres closely related to the decrease in fast twitch b fibres. This result would appear to demonstrate an appropriate adaptive reaction following high-intensity intermittent training for the slow twitch fibres which exhibit a greater oxidative capacity.

Central and peripheral contributions to neuromuscular fatigue induced by a 24-h treadmill run

This experiment investigated the fatigue induced by a 24-h running exercise (24TR) and particularly aimed at testing the hypothesis that the central component would be the main mechanism responsible for neuromuscular fatigue. Neuromuscular function evaluation was performed before, every 4 h during, and at the end of the 24TR on 12 experienced ultramarathon runners. It consisted of a determination of the maximal voluntary contractions (MVC) of the knee extensors (KE) and plantar flexors (PF), the maximal voluntary activation (%VA) of the KE and PF, and the maximal compound muscle action potential amplitude (Mmax) on the soleus and vastus lateralis. Tetanic stimulations also were delivered to evaluate the presence of low-frequency fatigue and the KE maximal muscle force production ability. Strength loss occurred throughout the exercise, with large changes observed after 24TR in MVC for both the KE and PF muscles (-40.9+/-17.0 and -30.3+/-12.5%, respectively; P<0.001) together with marked reductions of %VA (-33.0+/-21.8 and -14.8+/-18.9%, respectively; P<0.001). A reduction of Mmax amplitude was observed only on soleus, and no low-frequency fatigue was observed for any muscle group. Finally, KE maximal force production ability was reduced to a moderate extent at the end of the 24TR (-10.2%; P<0.001), but these alterations were highly variable (+/-15.7%). These results suggest that central factors are mainly responsible for the large maximal muscle torque reduction after ultraendurance running, especially on the KE muscles. Neural drive reduction may have contributed to the relative preservation of peripheral function and also affected the evolution of the running speed during the 24TR.

Optic fibre as a transducer of tendomuscular forces

Direct in vivo tendon force measurements open up new possibilities for understanding of muscletendon loads during natural locomotion. The present report presents a new optic fibre method for such applications. The method is based on light intensity modulation by mechanical modification of the geometric properties of the optic fibre. A special optic fibre with a plastic covering buffer and with a total diameter of either 265 μm or 500 μm was carefully prepared at both ends for receiving and transmitting light. The fibre was inserted through the rabbit common calcaneal tendon with a 20 gauge needle. By removing the needle the optic fibre remained in situ. Static loading demonstrated that the voltage output of the optic fibre transducer showed a good linear fit of r =.999 with added loads. In dynamic loading conditions the optic fibre followed well the response of a strain gauge transducer, which was also attached to the tendon. The optic fibre method seems suitable for many applications for tensile and possibly ligament force measurements.

Influence of training on NIRS muscle oxygen saturation during submaximal exercise

PURPOSE Endurance training improves the oxygen delivery and muscle metabolism. Muscle oxygen saturation measured by near infrared spectroscopy (IR-SO(2)), which is primarily influenced by the local delivery/demand balance, should thus be modified by training. We examined this effect by determining the influence of change in blood lactate and muscle capillary density with training on IR-SO(2) in seven healthy young subjects. METHODS Two submaximal exercise tests at 50% (Ex1) and 80% pretraining VO(2max) (Ex2) were performed before and after a 4-wk endurance-training program. RESULTS VO(2max) increased only slightly (+8%, NS) with training but the training effect was confirmed by the increased capillary density (+31%, P < 0.01) and citrate synthase activity (50%, P < 0.01), determined from muscle biopsy samples. Before training, blood lactate increased during the first 5 min of Ex1 and then remained constant (3.8 +/- 0.5 mmol x L(-1), P < 0.01), whereas it increased continuously during Ex2 (8.9 +/- 1.8 mmol x L(-1), P < 0.001). After training, lactate decreased significantly and remained constant during the two bouts of exercise (2.0 +/- 0.4 and 3.7 +/- 1.2 at the end of Ex1 and Ex2, respectively, both P < 0.001). During Ex1, IR-SO(2) dropped initially at the onset of exercise and recovered progressively without reaching the resting level. Training did not change this pattern of IR-SO(2). During Ex2, IR-SO(2) decreased progressively during the 15 min of exercise (P < 0.05); IR-SO2 kept constant after the initial drop after training. We found a significant relationship (r = 0.42, P = 0.03) between blood lactate and IR-SO(2) at the end of both bouts of exercise; this relationship was closer before training. By contrast, IR-SO(2) or IR-BV was not related to the capillary density. CONCLUSION The training-induced adaptation in blood lactate influences IR-SO(2) during mild- to hard-intensity exercise. Thus, NIRS could be used as a noninvasive monitoring of training-induced adaptations.

Wet suit effect: a comparison between competitive swimmers and triathletes.

The purpose of the present investigation was to examine the wet suit effect on 8 swimmers and 8 triathletes. For swimmers, the performances of a 400-m swim with and without wet suit were not statistically different (4 min 12.5 +/- 8 s vs 4 min 13.9 +/- 4 s) while for triathletes the swim times were reduced by 19 s (4 min 45.8 +/- 34 s vs 5 min 04.7 +/- 30 s, P < 0.01). For swimmers, VO2max and blood lactate measured with the wet suit were lower than without (P < 0.01), while for triathletes stroke rate was significantly higher with the wet suit (P < 0.01). For the whole group, the individual differences of performance were related to the blood lactate differences (r = -0.68; P < 0.01) and to the hydrostatic lift (r = 0.63; P < 0.01). For swimmers, the energy cost of swimming and the gliding ability were not statistically different with or without wet suit, while for triathletes they were significantly lower and decreased with velocity. It is concluded that the wet suit effect improves performance more in inefficient swimmers with low buoyancy, swimming at low speeds.

Physiological and biological factors associated with a 24 h treadmill ultra-marathon performance

The purpose of this study was to examine the physiological and biological factors associated with ultra‐endurance performance. Fourteen male runners volunteered to run on a treadmill as many kilometers as possible over a 24‐h period (24TR). Maximal oxygen uptake (V̇O2max), velocity associated with V̇O2max () and running economy (RE) at 8 km/h were measured. A muscle biopsy was also performed in the vastus lateralis muscle. The subjects ran 149.2 ± 15.7 km in 18 h 39 ± 41 min of effective attendance on the treadmill, corresponding to 39.4 ± 4.2% of . Standard multiple‐regression analysis showed that performance was significantly (R2=0.82; P=0.005) related to V̇O2max and specific endurance, i.e. the average speed sustained over the 24TR expressed in . V̇O2max was associated with a high capillary tortuosity (R2=0.66; P=0.01). Specific endurance was significantly related to RE and citrate synthase activity. It is concluded that a high V̇O2max and an associated developed capillary network are essential for ultra‐endurance running performance. The ability to maintain a high %V̇O2max over a 24TR is another factor associated with performance and is mainly related to RE and high mitochondrial oxidative capacity in the vastus lateralis.

Performance and fibre characteristics of human skeletal muscle during short sprint training and detraining on a cycle ergometer

Abstract The ergometric effect of sprint training and detraining was studied in relation to muscle fibre changes in seven students trained during 9 weeks on a cycle ergometer. Before and after training and after 7-week detraining, they performed a force-velocity test on a friction-loaded cycle ergometer. On these three occasions, muscle samples were taken from vastus lateralis muscle at rest for histochemical analysis. The training-induced shift of the force-velocity relationship was such that the increase in maximal velocity (vmax) was greatest against high braking forces (FB) with unchanged vmax with no load. This was associated with higher maximal power output (28%) and peak force (16%). The increased maximal mean power output to reach a maximal velocity during a short sprint was obtained against a 23% higher optimal FB(FB,¯˙Wmax). At the same time, a considerable hypertrophy in fast twitch b (FTb) fibres was observed. All these changes were maintained after detraining. The training-induced changes in vmax reached against FB,¯˙Wmax(vm, ¯˙Wmax) allowed us to produce evidence for two particular sub-groups in which inverse fibre conversions were observed. In subgroup A, the lowered post-training vm, ¯˙Wmax was associated with a decrease in both FTa and FTb fibres. Conversely, the vm, ¯˙Wmax increase in subgroup B was associated with a higher percentage of FT fibres as the result of increased FTa fibres and decreased FTb fibres. Thus, the fibre hypertrophy associated with a unidirectional fibre translation [FTb→FTa→ slow twitch (ST)] toward fibres with a high thermodynamic efficiency would result mainly in increased force qualities, whereas the bidirectional fibre translation (ST→FTa←FTb) would allow enhancement of both force and velocity properties.

Characterization of the mechanical properties of backpacks and their influence on the energetics of walking

The objectives of the experiment were (i) to characterize the mechanical properties of backpacks and (ii) to study the influence of a flexible backpack on the energetics and kinematics of walking. Twelve subjects walked at different speeds on a treadmill with each of two backpacks loaded with 25% bodyweight, with either a rigid or a flexible link between the body attachment and the suspended loads. A single degree of freedom linear model of the link between the pack and the trunk was used to calculate the stiffness and damping coefficient of the two backpacks. The oxygen consumption (VO2) and the vertical acceleration of both the backpack and trunk were measured. The vertical excursion of the pack given by the model was significantly correlated with that actually measured (R=0.87, p<0.001). At 3.7 and 4.5 km h(-1) the flexible pack induced lower acceleration peaks (respectively -22% and -8%; p<0.05) and tended to reduce VO2 (p=0.055 at 4.5 km h(-1)) compared with the rigid one. At 5.2 and 6 km h(-1) both the accelerative forces and VO2 increased with the flexible pack (p<0.05) mainly because of the high vertical movement of the pack. It was concluded that a simple model can be used to predict the vertical excursion of the pack and that a flexible backpack can provide energetic benefits when its oscillations are nearly in phase with those of the trunk. However, any resonance effect can lead to a modified walking pattern and an increased metabolic cost.