Sprinting on a curve is significantly slower than on a straightaway. Although the dimensions vary from track to track, indoor track curves are among the tightest curves that athletes will sprint at maximal speed. Previous studies have provided theories for how speed attenuation occurs when running on a curve. Yet, no previous research has determined how the variability of indoor track curve radii affects trained sprinters at maximal speeds. Purpose: To determine the differences in running speeds, ground time (GT), and medio-lateral (ML) impulse, with different indoor track radii. A secondary purpose was to understand the between-leg differences in GT and ML impulse during maximal sprinting on a curve. Methods: 10 male intercollegiate sprinters performed 45-m maximal sprints on a straightaway, 15-m track curve and 21-m track curve. A force platform embedded under an indoor track surface measured ground reaction forces while timing lights measured running speed. Analysis: A mixed models analysis of variance blocking on subjects was performed testing the main effects of the track curve on sprinting speed, GT and ML impulse (p<0.01). Results: Sprinting speed was significantly slower when running on a curve. GT increased for inside leg on both curved path conditions compared to straight. ML impulses increased as the radius of the track curve decreased. Discussion: If a 200m race were performed on both our track curves, the track with 21m curve would be 0.12s faster than the track with the 15m curve. GT and ML impulse results support leading explanations that the inside leg is the limiting factor during curve running. Tighter track curves require greater ML forces, but for a shorter period of time compared to larger track turns. Coaches and athletes should consider the radius of the track curve as they prepare for training and performance and consider injury risk. The speed differences observed due to the track curve radius may provide the first step to understanding how the radius of the indoor track curve affects sprinting speed and ultimately, performance.

The purpose of this study was to compare strength and physical activity (PA) changes in postpartum women randomly assigned to either a four-month progressive resistance training (RT) program or a four month flexibility program. Sixty healthy women between six weeks and eight months postpartum initiated the study and 43 completed the entire study. The women tended to be overweight, were all non-smokers, and most were breastfeeding (97%) at the beginning of the study. Both groups (RT and flexibility) completed training exercises twice weekly. Both groups improved in all measures of strength (RT group: leg press, P < 0.001; bench press, P < 0.001; curl-ups, P < 0.001. Flexibility group: leg press, P = 0.009; bench press, P < 0.001; curl-ups, P = 0.005); however, the RT group had higher strength gains compared to the flexibility group over time (leg press, P < 0.005; bench press, P < 0.001; curl-ups, P < 0.007). In addition, both groups increased in low back flexibility but the group*period interaction did not reach significance (P = 0.096). Light-intensity PA increased in the RT group but not the flexibility group (P < 0.05). A group*period interaction was significant for light-intensity PA time (P = 0.031) and borderline significant for sedentary time (P = 0.054). However, controlling for the number of months postpartum and weight gain during the previous pregnancy resulted in a significant interaction for sedentary time (P < 0.05). No changes were found in moderate, vigorous, or moderate to vigorous PA within or between groups over time. In conclusion, twice-weekly RT increases strength and is associated with improvements in several PA outcomes in postpartum women; however, the mechanisms for this are unclear. The training sessions and/or increased spontaneous activity may have contributed.

This study was a randomized control trial. The purpose of this study was threefold: 1) to determine if intramuscular temperature (IMt) increases in the semitendinosus (ST) are similar to the vastus lateralis (VL) during standard WBV static squatting; 2) to determine if changes in intramuscular temperature of the hamstrings is different from a standard static semi-squat when undergoing WBV in a static stretching position; and 3) to determine if shorter overall durations as is typically used for stretching protocols (i.e. 5 repetitions of 30s each), will result in IMt increases. Twelve subjects (all males), with tight hamstrings completed this study (age 23.5 ± 1.5 years; body mass 76.3 ± 17.7 kg; height 177.8 ± 15.2 cm). Subjects were randomly assigned to treatment order of three groups: semi squat vibration (SQ), vibration with static stretch (VS), and static stretch only (SS). Subjects reported to the lab 3x, each visit separated by one week to receive all treatments. Each treatment day consisted of baseline temperature measurements in the VL and ST and following each of 2 sets (5x60-second for SQ, 5x30-second for VS and SS, with 30 seconds rest in between reps). Post-hoc comparisons revealed that VL temperature increases were significantly greater from baseline than the hamstrings at all three time periods (p<.0001). There were no significant differences found in ST IMt when comparing 5-minutes of total WBV in the VS condition (both sets of 2.5 minute bouts) to 5-minutes of vibration in the SQ condition (p=1.000), or between VS and SS after 5 minutes (p=.9827). Post-hoc comparisons between SS and VS conditions revealed no significant differences after 2.5 minutes (p=1.000), 5 minutes (p=.8812), and 10-minutes post vibration (p=.9844) in ST or VL (p=1.000, p=.0540, and p=.1815 respectively) temperature. The results of our study show that the ST does not exhibit similar increases in IMt as the VL when performing standard semi-squat WBV training. The IMts seen in the static stretch both with and without vibration seem to suggest that factors other than IMt most likely contribute to flexibility changes seen in prior WBV flexibility studies.

The purpose of this study was to describe kinematic changes that occur during an actual marathon. We hypothesized that (1) certain running kinematic measures would change between miles 5 and 25 of a marathon and (2) fast runners would demonstrate smaller changes than slow runners. Subjects (n = 179) were selected according to finish time (Range = 2:20:47 to 5:30:10). Two high-speed cameras were used to measure sagittal-plane kinematics at miles 5 and 25 of the marathon. The dependent variables were stride length, ground time, peak knee flexion during support and swing, and peak hip flexion and extension during swing. Two-tailed paired t-tests were used to compare dependent variables between miles 5 and 25 for all subjects, and regression analyses were used to determine whether faster runners exhibited smaller changes (between miles 5 and 25) than slower runners. For all runners, every dependent variable changed significantly between miles 5 and 25 (p < 0.001). Stride length increased 1.3%, ground time increased 13.1%, peak knee flexion during support decreased 3.2%, and peak hip extension, knee flexion, and hip flexion during swing decreased 27.9%, increased 4.3%, and increased 7.4%, respectively (p<0.001). Among these significant changes, all runners generally changed the same from miles 5 to 25 except that fast runners decreased peak knee flexion during support less than the slow runners (p < 0.002). We believe these kinematic changes were an attempt by all runners (fast and slow) to decrease energy expenditure and enhance performance at the late stage of the race. The fact that fast runners maintained knee flexion during support more consistently might be due to their condition on the race day. Strengthening of knee extensor muscles may facilitate increased knee flexion during support throughout a marathon.

The purpose of this study was to compare the effectiveness of two free throw shooting methods, the Ed Palubinskas Method (PM) and the Free Shoot Method (FSM), and their ability to improve free throw shooting accuracy. The experimental group, using the PM, and the control group, using the FSM, shot the same amount of free throws over a 13 week period. Subjects were 33 male intermediate basketball students at Brigham Young University. Subjects in both groups shot 26 free throws twice a week. Subjects were tested once every other week by shooting and recording the amount made out of nine attempts. There was no significant improvement for trials for both groups over the 13 weeks (F=1.583, p=.154). There was also no significant difference between groups (F=.445, p=.510) nor any interaction between groups (F=.642, p=.696). There was no significant difference in free throw shooting accuracy between the PM and FSM for the selected groups.

Skin blood flow (SKBF) demonstrates a biphasic response to innocuous, local heating. Much about the mechanism of the first phase is unknown. A type of ion channel (TRPV3) sensitive to and increasingly activated by temperatures from ~33 to ~45°C may be involved. TRPV3 channels are abundantly located in the keratinocytes and are believed to elicit the release of ATP, a putative cutaneous vasodilator, upon activation. This study investigated the possibility that TRPV3 channels and ATP have a role in the first phase of the SBKF response to local heat. Fifteen young, healthy subjects participated in the study. Two microdialysis probes were inserted into the dermis on the forearm. Using a peltier module, the skin above the probes (3cm x 3cm) was heated to 31, 35, 39, and 43°C to manipulate the level of activation of TRPV3 channels for eight minutes each. The probes were perfused with 0.9% saline at 2µl/min. Dialysate from each phase was analyzed for the concentration of ATP ([ATP]d). Cutaneous vascular conductance (CVC), measured by laser Doppler flowmetry, was monitored throughout. The [ATP]d decreased significantly when the skin was heated to temperatures known to strongly activate TRPV3 channels (i.e 39 and 43°C). [ATP]d demonstrated no relationship with CVC and only a very weak relationship with peltier temperature (r2 = 0.02, p<0.05). These data indicate that local heating and presumably heat-induced activation of the TRPV3 channels results in the decrease, not increase, of the release of ATP in human skin, and that the [ATP]d is not related to changes in skin blood flow. Significant dilation was observed at 35°C. This threshold, which is several degrees lower than the threshold previously reported, suggests that the TRPV3 channels may be involved in the dilator response in some way independent of interstitial ATP.

Some have suggested acute increases in musculotendinous stiffness (k) following whole body vibration (WBV). Others propose that chronic ankle instability (CAI) may alter k of the lower extremity. Changes in proprioceptive activity and/or gamma motoneuron activation post-WBV and/or due to CAI could lead to alterations in k. However, little is known about acute effects of WBV on k and less is known about changes in k with CAI. PURPOSE: Assess differences in vertical and joint k between healthy and CAI subjects during single-limb landings and detect alterations in k measures post-vibration. METHODS: Subjects were identified as CAI via the FAAM, MAII and special testing. Thirty-five CAI subjects (17 males, 18 females; age = 22 ± 7 yr; height = 1.73 ± 0.23 m; mass = 70 ± 30 kg) and 35 matched healthy subjects (17 males, 18 females; age = 23 ± 5 yr; height = 1.73 ± 0.21 m; mass = 70 ± 35 kg) qualified for this study. Kinetic (2000 Hz) and kinematic (250 Hz) data were recorded during several jump landings pre- and post-WBV. Five repetitions of WBV, at 26 Hz and 4 mm amplitude, were introduced between pre- and post-WBV jump trials. The jump task included a double-limb jump followed by a single-limb landing and a subsequent contralateral hop. Vertical k (∆vertical GRF/center of mass vertical displacement), hip, knee and ankle joint k (∆joint moment/∆joint angle) were calculated, averaged across five successful pre-WBV and across six post-WBV trials. An ANOVA was used to detect between-group differences, while an ANCOVA was used to analyze within-group differences post-WBV using pre-measures as covariates. A pseudo-Bonferroni adjustment was performed prior to statistical analysis (p < 0.01). RESULTS: No between-group differences were observed for any of the variables (F1,68 = 0.020 to 1.400, p = 0.240 to 0.890). A significant increase in vertical k was observed post-WBV for the healthy group (t67 = 2.760, p = 0.008), but not for the CAI group (t67 = 0.370, p = 0.720). The CAI group did demonstrate a decrease in ankle (t67 = -3.130, p = 0.003) and knee (t67 = -3.490, p = 0.001) joint k post-vibration. No other within-group differences were observed post-WBV (p > 0.01). CONCLUSIONS: It appears that WBV does acutely increase vertical k in healthy subjects. However, this treatment effect was not observed in CAI. Further research is needed to assess how k is regulated in CAI subjects and why CAI subjects responded differently to WBV.

Gymnasts must attain extreme ranges of flexibility to execute performance requirements, thus effective stretching proves vital to advancement in the sport. This study examined the acute effects of whole-body vibration (WBV) on passive and dynamic flexibility in young, female gymnasts. Participants (n = 27, Junior Olympic levels 5-10) served as their own control. Measurements of passive and dynamic flexibility were obtained using the TOPS forward split testing method to examine passive flexibility and dynamic flexibility was measured via split jumps that were analyzed with video and Dartfish software. According to randomized order, all participants completed a stretching protocol either with the WBV platform turned on (VIB) or off (C) separated by 48 h. Participants performed 4 sets of three stretches on the WBV platform. An ANCOVA was performed (using height, weight, age, years of experience, and gymnastics level as covariates). Significant improvements were found in passive flexibility for both VIB and C conditions, but there was no significant difference between the two stretching conditions (p = 0.17). The maximum split jump decreased significantly from pre to post measurement in both the VIB (p < 0.0001) and C (p = 0.04) conditions. VIB decreased the split jump significantly more than C. Based on the results of our study, an acute session of static stretching or stretching with WBV immediately before performance decreases split jump performance. Therefore, this WBV protocol is not recommended immediately prior to gymnastics competition.

During ambulation, lower-extremity joint angles and net moments influence knee joint load. It is unclear which mechanical variables most strongly correlate with acute articular cartilage (AC) catabolism in response to ambulation. Purpose: To determine which mechanical variables are most strongly correlated to acute AC catabolism, and to test the acute effect of ambulation speed on AC catabolism, while controlling for load frequency. Methods: 18 able-bodied subjects (9 male, 9 female; age = 23 ± 2 y; mass = 68.3 ± 9.6 kg; height = 1.70 ± 0.08 m) completed three separate ambulation sessions: slow (preferred walking speed), medium (+50% of walking speed), and fast (+100% of walking speed). For each session, subjects completed 4000 steps on an instrumented treadmill while ten high-speed cameras recorded synchronized video data. Various, discrete, three-dimensional joint kinematic and kinetic variables were averaged across 20 total stance phases (5 stance phases at 1000, 2000, 3000, and 4000 steps). Blood samples were collected pre-, post-, 30-min post-, and 60-min post-ambulation. Serum cartilage oligomeric matrix protein (COMP) concentration was determined using an enzyme-linked immunosorbent assay. A stepwise multiple linear regression analysis was used to evaluate the relationships between serum COMP change and lower-extremity joint angles and moments. A mixed model ANCOVA was used to evaluate serum COMP concentration between sessions across time. Results: Peak ankle inversion, knee extension, knee abduction, hip flexion, hip extension, and hip abduction moment, and knee flexion angle at impact, explained 61.4% of the total variance in serum COMP change (p < 0.001), due to ambulation. COMP concentration increased 28%, 18%, and 5% immediately after ambulation for the running, jogging, and walking sessions, respectively. All sessions were significantly different immediately post-ambulation (p < 0.01). Conclusion: Certain lower-extremity joint mechanics are associated with acute AC catabolism, due to ambulation. Several key mechanical variables (e.g., peak knee extension, knee abduction, and hip abduction moments) explain much regarding the variance in serum COMP increase. These lower-extremity variables can be used to predict acute AC catabolism, allowing researchers and clinicians to better predict and/or understand AC catabolism. Additionally, when load frequency is controlled, increased ambulation speed acutely results in increased AC catabolism. Ambulation speed does not, however, influence serum COMP elevation duration. Joint mechanics and load frequency appear to be responsible for the magnitude of COMP increase, while duration of COMP elevation post-ambulation is dictated by load frequency.

In the shot put throw, the primary power is generated in the form of ground reaction forces as a result of action of the lower extremities (Coh, Stuhec, & Supej, 2008). The purpose of this study was to determine how the ground reaction force and ground contact time during the delivery phase of rotational shot put relates to the predicted distance of the throw. This will allow us to determine the optimal approach of force application for maximum throwing distance (Linthorne, 2001). Eight male subjects were used in this study (age 23 ± 4 y; body mass 123 ± 14 kg; height 190 ± 4 cm; all right handed). Subjects threw three attempts in a custom-built shot put ring where two force plates were located where both feet were expected to land in the delivery. The throws were also filmed using two high-speed cameras at 120 frames/s. These videos gave us the speed, angle and height of release for predicting distance thrown. Results: Peak right leg force during delivery was correlated with throwing distance (R2 = 0.450, p = 0.001). Also, left leg ground time was significant with predicted throwing distance (R² = 0.516, p < 0.001). Because increased strength leads to greater throwing distances (Zaras et al., 2013) and peak right leg force was significant, it would be useful to perform proper strength training exercises that can increase a thrower's ability to increase the peak ground forces during a throw. If the thrower can produce greater peak force into the ground with the right leg during the delivery phase, this should cause the thrower to come off their left leg sooner, resulting in greater speed of release and thus distance thrown.