Purpose: To compare between-tests changes in submaximal exercise heart rate (HRex, 3 min, 12 km/h) and the speed associated with 4 mmol/L of blood lactate (V4mmol) in soccer players to get insight into their level of agreement and respective sensitivity to changes in players’ fitness. Methods: A total of 19 elite professional players (23  y) performed 2 to 3 graded incremental treadmill tests (3-min stages interspersed with 1 min of passive recovery, starting speed 8 km/h, increment 2 km/h until exhaustion or 18 km/h if exhaustion was not reached before) over 1.5 seasons. The correlation between the changes in HRex and V4mmol was examined. Individual changes in the 2 variables were compared (>2 × typical error considered “clear”). Results: The changes in HRex and V4mmol were largely correlated (r = .82; 90% confidence interval, .65–.91). In more than 90% of the cases, when a clear individual change in HRex was observed, it was associated with a similar clear change in V4mmol (the same direction, improvement, or impairment of fitness) and conversely. Conclusions: When it comes to testing players submaximally, the present results suggest that practitioners can use HRex or V4mmol interchangeably with confidence. However, in comparison with a field-based standardized warm-up run (3–4 min, all players together), the value of a multistage incremental test with repeated blood lactate samplings is questionable for a monitoring purpose given its time, labor, cost, and poorer player buy-in.
Martin Buchheit, Ben M. Simpson, and Mathieu Lacome
Mathieu Lacome, Julien Piscione, Jean-Philippe Hager, and Christopher Carling
To investigate the patterns and performance of substitutions in 18 international 15-a-side men’s rugby union matches.
A semiautomatic computerized time–motion system compiled 750 performance observations for 375 players (422 forwards, 328 backs). Running and technical-performance measures included total distance run, high-intensity running (>18.0 km/h), number of individual ball possessions and passes, percentage of passes completed, and number of attempted and percentage of successful tackles.
A total of 184 substitutions (85.2%) were attributed to tactical and 32 (14.8%) to injury purposes respectively. The mean period for non-injury-purpose substitutions in backs (17.7%) occurred between 70 and 75 min, while forward substitutions peaked equally between 50–55 and 60–65 min (16.4%). Substitutes generally demonstrated improved running performance compared with both starter players who completed games and players whom they replaced (small differences, ES –0.2 to 0.5) in both forwards and backs over their entire time played. There was also a trend for better running performance in forward and back substitutes over their first 10 min of play compared with the final 10 min for replaced players (small to moderate differences, ES 0.3–0.6). Finally, running performance in both forward and back substitutes was generally lower (ES –0.1 to 0.3, unclear or small differences) over their entire 2nd-half time played compared with their first 10 min of play. The impact of substitutes on technical performance was generally considered unclear.
This information provides practitioners with practical data relating to the physical and technical contributions of substitutions that subsequently could enable optimization of their impact on match play.
Mathieu Lacome, Ben M. Simpson, Yannick Cholley, and Martin Buchheit
Purpose: To (1) compare the locomotor and heart rate responses between floaters and regular players during both small and large small-sided games (SSGs) and (2) examine whether the type of game (ie, game simulation [GS] vs possession game [PO]) affects the magnitude of the difference between floaters and regular players. Methods: Data were collected in 41 players belonging to an elite French football team during 3 consecutive seasons (2014–2017). A 5-Hz global positionning system was used to collect all training data, with the Athletic Data Innovation analyzer (v188.8.131.524) used to derive total distance (m), high-speed distance (>14.4 km·h−1, m), and external mechanical load (MechL, a.u.). All SSGs included exclusively 1 floater and were divided into 2 main categories, according to the participation of goalkeepers (GS) or not (PO) and then further divided into small and large (>100 m2per player) SSGs based on the area per player ratio. Results: Locomotor activity and MechL performed were likely-to-most likely lower (moderate to large magnitude) in floaters compared with regular players, whereas differences in heart rate responses were unclear to possibly higher (small) in floaters. The magnitude of the difference in locomotor activity and MechL between floaters and regular players was substantially greater during GS compared with PO. Conclusions: Compared with regular players, floaters present decreased external load (both locomotor and MechL) despite unclear to possibly slightly higher heart rate responses during SSGs. Moreover, the responses of floaters compared with regular players are not consistent across different sizes of SSGs, with greater differences during GS than PO.
Mathieu Lacome, Ben Simpson, Nick Broad, and Martin Buchheit
Purpose: To examine the ability of multivariate models to predict the heart-rate (HR) responses to some specific training drills from various global positioning system (GPS) variables and to examine the usefulness of the difference in predicted vs actual HR responses as an index of fitness or readiness to perform. Method: All data were collected during 1 season (2016–17) with players’ soccer activity recorded using 5-Hz GPS and internal load monitored using HR. GPS and HR data were analyzed during typical small-sided games and a 4-min standardized submaximal run (12 km·h−1). A multiple stepwise regression analysis was used to identify which combinations of GPS variables showed the largest correlations with HR responses at the individual level (HRACT, 149  GPS/HR pairs per player) and was further used to predict HR during individual drills (HRPRED). Then, HR predicted was compared with actual HR to compute an index of fitness or readiness to perform (HRΔ, %). The validity of HRΔ was examined while comparing changes in HRΔ with the changes in HR responses to a submaximal run (HRRUN, fitness criterion) and as a function of the different phases of the season (with fitness being expected to increase after the preseason). Results: HRPRED was very largely correlated with HRACT (r = .78 [.04]). Within-player changes in HRΔ were largely correlated with within-player changes in HRRUN (r = .66, .50–.82). HRΔ very likely decreased from July (3.1% [2.0%]) to August (0.8% [2.2%]) and most likely decreased further in September (−1.5% [2.1%]). Conclusions: HRΔ is a valid variable to monitor elite soccer players’ fitness and allows fitness monitoring on a daily basis during normal practice, decreasing the need for formal testing.
Julien Robineau, Mathieu Lacome, Julien Piscione, Xavier Bigard, and Nicolas Babault
To assess the impact of 2 high-intensity interval-training (HIT) programs (short interval vs sprint interval training) on muscle strength and aerobic performances in a concurrent training program in amateur rugby sevens players.
Thirty-six amateur rugby sevens players were randomly assigned to strength and short interval training (INT), strength and sprint interval training (SIT), or a strength-only training group (CON) during an 8-wk period. Maximal strength and power tests, aerobic measurements (peak oxygen uptake [VO2peak] and maximal aerobic velocity), and a specific repeated-sprint ability (RSA) test were conducted before and immediately after the overall training period.
From magnitude-based inference and effect size (ES ± 90% confidence limit) analyses, the current study revealed substantial gains in maximal strength and jump-height performance in all groups. The difference in change of slow concentric torque production was greater in CON than in SIT (0.65 ± 0.72, moderate). VO2peak and, consequently, mean performance in the RSA test were improved in the SIT group only (0.64 ± 0.29, moderate; –0.54 ± 0.35, moderate).
The study did not emphasize interference on strength development after INT but showed a slight impairment of slow concentric torque production gains after SIT. Compared with INT, SIT would appear to be more effective to develop VO2peak and RSA but could induce lower muscle-strength gains, especially at low velocity.
Martin Buchheit, Mathieu Lacome, Yannick Cholley, and Ben Michael Simpson
Purpose: To examine the reliability of field-based running-specific measures of neuromuscular function assessed using global positioning system (GPS)–embedded accelerometers and their responses to 3 typical conditioned sessions (ie, strength, endurance, and speed) in elite soccer players. Methods: Before and immediately after each session, vertical jump (countermovement jump [CMJ]) and adductor squeeze strength (groin) performances were recorded. Players also performed a 4-min run at 12 km/h followed by four ∼60-m runs (run = 12 s, r = 33 s). GPS (5 Hz) and accelerometer (100 Hz) data collected during the 4 runs and the recovery periods, excluding the last recovery period, were used to derive vertical stiffness (K), peak loading force (peak force over all the foot strikes [F peak]), and propulsion efficiency (ie, the ratio between velocity and force loads [Vl/Fl]). Results: Typical errors were small (CMJ, groin, K, and Vl/Fl) and moderate (F peak), with moderate (F peak), high (K and Vl/Fl), and very high ICCs (CMJ and groin). After all sessions, there were small decreases in groin and increases in K, but changes in F were all unclear. By contrast, the CMJ and Vl/Fl ratio responses were session dependent. There was a small increase in CMJ after speed and endurance, but unclear changes after strength; the Vl/Fl ratio increased substantially after strength, but there were a small and a moderate decrease after endurance and speed, respectively. Conclusions: Running-specific measures of neuromuscular function assessed in the field via GPS-embedded accelerometers show acceptable levels of reliability. Although the 3 sessions examined may be associated with limited neuromuscular fatigue, changes in neuromuscular performance and propulsion efficiency are likely session-objective dependent.
Pauline Clavel, Eve Tiollier, Cédric Leduc, Marina Fabre, Mathieu Lacome, and Martin Buchheit
Purpose: To assess the concurrent validity of a continuous blood-glucose-monitoring system (CGM) postbreakfast, preexercise, exercise, and postexercise, while assessing the impact of 2 different breakfasts on the observed level of validity. Methods: Eight nondiabetic recreational athletes (age = 30.8 [9.5] y; height = 173.6 [6.6] cm; body mass = 70.3 [8.1] kg) took part in the study. Blood glucose concentration was monitored every 10 minutes using both a CGM (FreeStyle Libre, Abbott, France) and finger-prick blood glucose measurements (FreeStyle Optimum) over 4 different periods (postbreakfast, preexercise, exercise, and postexercise). Two different breakfasts (carbohydrates [CHO] and protein oriented) over 2 days (2 × 2 d in total) were used. Statistical analyses included the Bland–Altman method, standardized mean bias (expressed in standardized units), median absolute relative difference, and the Clarke error grid analysis. Results: Overall, mean bias was trivial to small at postbreakfast (effect size ± 90% confidence limits: −0.12 ± 0.08), preexercise (−0.08 ± 0.08), and postexercise (0.25 ± 0.14), while moderate during exercise (0.66 ± 0.09). A higher median absolute relative difference was observed during exercise (13.6% vs 7%–9.5% for the other conditions). While there was no effect of the breakfast type on the median absolute relative difference results, error grid analysis revealed a higher value in zone D (ie, clinically unsafe zone) during exercise for CHO (10.5%) compared with protein (1.6%). Conclusion: The CGM device examined in this study can only be validly used at rest, after both a CHO and protein-rich breakfast. Using CGM to monitor blood glucose concentration during exercise is not recommended. Moreover, the accuracy decreased when CHO were consumed before exercise.
Cédric Leduc, Julien Robineau, Jason C. Tee, Jeremy Cheradame, Ben Jones, Julien Piscione, and Mathieu Lacome
Purpose: To explore the effects of travel related to international rugby sevens competition on sleep patterns. Methods: A total of 17 international male rugby sevens players participated in this study. Actigraphic and subjective sleep assessments were performed daily during 2 separate Sevens World Series competition legs (Oceania and America). The duration of each competition leg was subdivided into key periods (pretour, precompetition, tournament 1, relocation, tournament 2, and posttour) lasting 2 to 7 nights. Linear mixed models in combination with magnitude-based decisions were used to assess (1) the difference between preseason and key periods and (2) the effect of travel direction (eastward or westward). Results: Shorter total sleep time (hours:minutes) was observed during tournament 2 (mean [SD], 06:16 [01:08]), relocation (06:09 [01:09]), and the pretour week (06:34 [01:24]) compared with the preseason (06:52 [01:00]). Worse sleep quality (arbitrary units) was observed during tournament 1 (6.1 [2.0]) and 2 (5.7 [1.2]), as well as during the relocation week (6.3 [1.5]) than during the preseason (6.5 [1.8]). When traveling eastward compared with westward, earlier fall-asleep time was observed during tournament 1 (ES − 0.57; 90% CI, −1.12 to −0.01), the relocation week (−0.70 [−1.11 to −0.28]), and the posttour (−0.57 [−0.95 to −0.18]). However, possibly trivial and unclear differences were observed during the precompetition week (0.15 [−0.15 to 0.45]) and tournament 2 (0.81 [−0.29 to 1.91]). Conclusion: The sleep patterns of elite rugby sevens players are robust to the effects of long-haul travel and jet lag. However, the staff should consider promoting sleep during the tournament and relocation week.
Mathieu Lacome, Simon Avrillon, Yannick Cholley, Ben M. Simpson, Gael Guilhem, and Martin Buchheit
Aim: To compare the effect of low versus high volume of eccentric-biased hamstring training programs on knee-flexor strength and fascicle length changes in elite soccer players. Methods: A total of 19 elite youth soccer players took part in this study and were randomly assigned into 2 subgroups. For 6 weeks in-season, the groups performed either a low-volume (1 set per exercise; 10 repetitions in total) or a high-volume (4 sets; 40 repetitions) eccentric training of their knee flexors. After 6-weeks midtraining (MID), players performed the alternate training regimen. Each training set consisted of 4 repetitions of the Nordic hamstring exercise and 6 repetitions of the bilateral stiff-leg deadlift. Eccentric knee-flexor strength (NordBord) as well as biceps femoris long head and semimembranosus fascicle length (scanned with ultrasound scanner) were assessed during pretraining (PRE), MID, and posttraining (POST) tests. Results: Knee-flexor eccentric strength very likely increased from PRE to MID (low volume: +11.3% [7.8%] and high volume: 11.4% [5.3%]), with a possibly-to-likely increase in biceps femoris long head (+4.5% [5.0%] and 4.8% [2.5%]) and semimembranosus (+4.3% [4.7%] and 6.3% [6.3%]) fascicle length in both groups. There was no substantial changes between MID and POST. Overall, there was no clear between-group difference in the changes from PRE to MID and MID to POST for neither knee-flexor eccentric strength, biceps femoris long head, nor semimembranosus fascicle length. Conclusions: Low-volume knee-flexor eccentric training is as effective as a greater training dose to substantially improve knee-flexor strength and fascicle length in-season in young elite soccer players. Low volume is, however, likely more appropriate to be used in an elite team facing congested schedules.
Mathieu Lacome, Ben M. Simpson, Yannick Cholley, Philippe Lambert, and Martin Buchheit
Purpose: To compare the peak intensity of typical small-sided games (SSGs) with those of official matches in terms of running demands and mechanical work (MechW) over different rolling average durations and playing positions. Methods: Data were collected in 21 players (25  y, 181  cm, and 77  kg) belonging to an elite French football team. SSG data were collected over 2 seasons during typical training sessions (249 files, 12  per player) and official matches (n = 12). Players’ locomotor activity was recorded using 5-Hz Global Positioning System. Total distance (m), high-speed distance (HS, distance above 14.4 km·h−1, m), and MechW (a.u.) were analyzed during different rolling average periods (1–15 min). The SSGs examined were 4v4+goalkeepers (GKs), 6v6+GKs, 8v8+GKs, and 10v10+GKs. Results: Peak total distance and HS during 4v4, 6v6, and 8v8 were likely-to-most likely lower than during matches (effect size: −0.59 [±0.38] to −7.36 [±1.20]). MechW during 4v4 was likely-to-most likely higher than during matches (1–4 min; 0.61 [±0.77] to 2.30 [±0.64]). Relative to their match demands, central defenders performed more HS than other positions (0.63 [±0.81] to 1.61 [±0.52]) during 6v6. Similarly, central midfielders performed less MechW than the other positions during 6v6 (0.68 [±0.72] to 1.34 [±0.99]) and 8v8 (0.73 [±0.50] to 1.39 [±0.32]). Conclusion: Peak locomotor intensity can be modulated during SSGs of various formats and durations to either overload or underload match demands, with 4v4 placing the greatest and the least emphasis on MechW and HS, respectively. Additionally, in relation to match demands central defenders and central midfielders tend to be the most and least overloaded during SSGs, respectively.