Several studies utilizing adult subjects have indicated that static stretching may reduce subsequent strength and power production, possibly for as long as an hour following the stretch. This observation has not been evaluated in children, nor in athletes accustomed to performing static stretches during strength/power type training sessions. The purpose of this investigation was to determine if an acute bout of passive, static stretching of the lower extremity would affect jumping performance in a group of young, female gymnasts. Thirteen competitive gymnasts (age 13.3 − 2.6 yrs) performed drop jumps under two conditions: immediately following stretching and without prior stretching. The jumps were performed on separate days. The conditions were randomly ordered among the subjects. Time in the air (AIR) and ground contact time (CT) were measured during the drop jumps using a timing mat. Three different stretches of the lower extremity were conducted on each gymnast twice, each stretch being held for 30 seconds. Following the stretching condition, AIR was significantly reduced (.44 vs .46 sec, p < .001), while CT was not different (.130 for both conditions, p > .05). This study demonstrates that children’s lower extremity power is reduced when the performance immediately follows passive, static stretching, even in children accustomed to static stretching during training sessions involving explosive power.
Jeni R. McNeal and William A. Sands
Jeni R. McNeal, William A. Sands and Michael H. Stone
The aim of this study was to investigate the effects of a maximal repeated-jumps task on force production, muscle activation and kinematics, and to determine if changes in performance were dependent on gender.
Eleven male and nine female athletes performed continuous countermovement jumps for 60 s on a force platform while muscle activation was assessed using surface electromyography. Performances were videotaped and digitized (60 Hz). Data were averaged across three jumps in 10-s intervals from the initial jump to the final 10 s of the test.
No interaction between time and gender was evident for any variable; therefore, all results represent data collapsed across gender. Preactivation magnitude decreased across time periods for anterior tibialis (AT, P < .001), gastrocnemius (GAS, P < .001) and biceps femoris (BF, P = .03), but not for vastus lateralis (VL, P = .16). Muscle activation during ground contact did not change across time for BF; however, VL, G, and AT showed significant reductions (all P < .001). Peak force was reduced at 40 s compared with the initial jumps, and continued to be reduced at 50 and 60 s (all P < .05). The time from peak force to takeoff was greater at 50 and 60 s compared with the initial jumps (P < .05). Both knee fexion and ankle dorsifexion were reduced across time (both P < .001), whereas no change in relative hip angle was evident (P = .10). Absolute angle of the trunk increased with time (P < .001), whereas the absolute angle of the shank decreased (P < .001).
In response to the fatiguing task, subjects reduced muscle activation and force production and altered jumping technique; however, these changes were not dependent on gender.
William A. Sands, Ashley A. Kavanaugh, Steven R. Murray, Jeni R. McNeal and Monèm Jemni
Athlete preparation and performance continue to increase in complexity and costs. Modern coaches are shifting from reliance on personal memory, experience, and opinion to evidence from collected training-load data. Training-load monitoring may hold vital information for developing systems of monitoring that follow the training process with such precision that both performance prediction and day-to-day management of training become adjuncts to preparation and performance. Time-series data collection and analyses in sport are still in their infancy, with considerable efforts being applied in “big data” analytics, models of the appropriate variables to monitor, and methods for doing so. Training monitoring has already garnered important applications but lacks a theoretical framework from which to develop further. As such, we propose a framework involving the following: analyses of individuals, trend analyses, rules-based analysis, and statistical process control.
William A. Sands, Cindy Slater, Jeni R. McNeal, Steven Ross Murray and Michael H. Stone
The lay press, scientists, and physicians appear to believe that gymnasts are continually getting smaller and that their “smallness” is a health risk.
To assess the historical changes in the size and age of the US women’s Olympic gymnastics teams from 1956 to 2008.
The official records from the US Olympic Committee and USA Gymnastics of Olympic team members were assessed at 2 levels: individual height, mass, age, and body-mass index (BMI) and the team performance scores and rankings. Fourteen Olympic teams with a total of 106 team members, including the alternates, were included. Trend analyses were conducted using linear and polynomial models.
Simple linear correlations indicated that since 1956, height, mass, age, BMI, and team Olympic rank have been declining. However, second-order polynomial curve fits indicated that in the last 4 Olympic Games the members of the US women’s gymnastics teams have been getting larger.
Women Olympic gymnasts were getting smaller through approximately the 1980s and early 1990s. Since then the size of these gymnasts has increased. The minimum-age rule modifications may have played a role in athlete size changes along with a shift from the near dominance of the former communist Eastern Bloc.
William A. Sands, Jeni R. McNeal, Michael H. Stone, G. Gregory Haff and Ann M. Kinser
Serious stretching in many sports involves discomfort and is often an early ceiling on improvements.
To continue investigation of the use of vibration to enhance acute range of motion while assessing the influence of vibration and stretching on pressure-to-pain threshold perception.
Ten young male gymnasts were assessed for split range of motion. One side split was randomly assigned as the experimental condition, and the other side split was assigned as the control. Both side splits were performed on a vibration device; the experimental condition had the device turned on and the control condition was performed with the device turned off. In addition, the athletes were assessed for pressure-to-pain transition using an algometer on the biceps femoris (stretched muscle) and vastus lateralis (nonstretched muscle) bilaterally.
Pre-post difference scores between the vibrated split (most improved) and the nonvibrated split were statistically different (P = .001, 95% confidence interval of the difference 2.3 to 5.8 cm). Following the stretching protocol, the force values for the pressure-to-pain threshold comparing the vibrated and nonvibrated biceps femoris muscle were not statistically different. The nonstretched vastus lateralis muscle also showed no statistical difference in pressure-to-pain threshold between the vibration and nonvibration conditions.
This study showed that vibration improved split range of motion over stretching alone, but did not show a difference in pressure-to-pain perception in either the stretched or nonstretched muscles.