C. Matthew Laurent

Downhill ski injuries in children and adolescents.

Downhill skiing is considered to be an enjoyable activity for children and adolescents, but it is not without its risks and injuries. Injury rates now range between 3.9 and 9.1 injuries per 1000 skier days, and there has been a well documented increase in the number of trauma cases and fatalities associated with this sport. Head and neck injuries are considered the primary cause of fatal injuries and constitute 11–20% of total injuries among children and adolescents. Cranial trauma is responsible for up to 54% of total hospital injuries and 67% of all fatalities, whereas thoracoabdominal and spine injuries comprise 4–10% of fatalities. Furthermore, there has been an increase in the proportion of upper extremity trauma with acromioclavicular dislocations, and clavicle and humeral fractures accounting for the majority (22–79%) of the injuries. However, the most common and potentially serious injuries in children and adolescents are those to the lower extremity, with knee sprains and anterior cruciate ligament tears accounting for up to 47.7% of total injuries. Knee sprains and grade III ligament trauma associated with lower leg fractures account for 39–77% of ski injuries in this young population.Approximately 15% of downhill skiing injuries among children and adolescents are caused by musculoskeletal immaturity. Other factors include excessive fatigue, age, level of experience, and inappropriate or improperly adjusted equipment. Collisions and falls constitute a significant portion (up to 76%) of trauma, and are commonly associated with excessive speed, adverse slope conditions, overconfidence leading to carelessness, and behavioural patterns within and among gender. The type and severity of injuries are typically functions of biomechanical efficiency, skiing velocity or slope conditions; however, a multiplicative array of intrinsic and extrinsic factors may simultaneously be involved. Despite extensive efforts to provide a comprehensive picture of the aetiology of injury, limitations have hampered reporting. These limitations include age and injury awareness, data collection challenges, lack of uniformity in the definition or delineation of age classification and lack of knowledge of predisposing factors prior to injury.Since skill level is the primary impetus in minimising ski injuries, formal instruction focusing on strategies such as collision avoidance and helmet use, fall training minimising lower extremity trauma, altering ski technique and avoiding behaviours that lead to excessive risk are, therefore, highly recommended. Skiing equipment should be outfitted to match the young skier’s height, weight, level of experience, boot size and slope conditions. Additionally, particular attention should be paid to slope management (i.e. overcrowding, trail and obstacle marker upkeep) and minimising any opportunity for excessive speed where children are present. Whether increases in knowledge, education and technology will reduce predisposition to injury among this population remains to be seen. As with all high-risk sports, the answer may lie in increased wisdom and responsibility of both the skier and the parent to ensure an adequate level of ability, self-control and simply common sense as they venture out on the slopes.

Sex-specific responses to self-paced, high-intensity interval training with variable recovery periods.

Abstract Laurent, CM, Vervaecke, LS, Kutz, MR, and Green, JM. Sex-specific responses to self-paced, high-intensity interval training with variable recovery periods. J Strength Cond Res 28(4): 920–927, 2014—This study examined sex-specific responses during self-paced, high-intensity interval training (HIIT). Sixteen (8 men and 8 women) individuals completed a peak oxygen uptake test and 3 treadmill HIIT sessions on separate days. The HIIT sessions consisted of six 4-minute intervals performed at the highest self-selected intensity individuals felt they could maintain. Recovery between intervals was counterbalanced and consisted of 1-, 2-, or 4-minute recovery during each trial. Relative measures of intensity, including percentage of velocity at VO2peak (vVO2peak), %VO2peak, %HRmax, and blood lactate concentration ([La]), were observed during the trials. Perceived readiness was recorded immediately before and ratings of perceived exertion (RPE) were recorded at the end of each interval with session RPE recorded after each trial. Results revealed a significant effect of sex on %vVO2peak (p < 0.01) and %HRmax (p < 0.01). Data show that across trials, men self-select higher %vVO2peak (84.5 vs. 80.7%), whereas women produce higher %HRmax (96.9 vs. 92.1%) and %VO2peak (89.6 vs. 86.1%) with no difference in [La] or perceptual responses. These findings support the notion that women may demonstrate improved recovery during high-intensity exercise, as they will self-select intensities resulting in greater cardiovascular strain. Moreover, results confirm previous findings suggesting that a 2:1 work-to-rest ratio is optimal during HIIT for both men and women.

The Rodeo Athlete: Injuries - Part II

A previous instalment to this review focused on the sport science for rodeo, the history behind the sport and what is currently known about the physical and physiological status, coronary risk profile, strength and power levels, event-specific kinesiological and biomechanical aspects, nutritional habits and psychological indices associated with the rodeo athlete. In regards to injury, rodeo is well known for its high-velocity, high-impact atmosphere where athletes compete against the clock and uncooperative livestock. Considered by many to be a dangerous sport with high vulnerability towards trauma and frequent injuries, animal/human contact events comprise ∼80% of reported injuries. Severe trauma includes fractures, dislocations, subluxations concussions, ligament ruptures, pneumothorax and various neurapraxias. Head and neck trauma account for 10–29% of total trauma and up to 63% of upper body injuries, with concussion incidence rates of 3.4 per 1000 competitive exposures. The incidence of thoracic, back and abdominal injuries comprise 11–84% of trauma, while shoulder injuries, involving anterior/ posterior arthralgia, inflammation, instability and increasing weakness, account for 8–15% of upper extremity cases. Lower extremity trauma accounts for 26–34% of cases, with the majority involving the knee. Many believe that the incidence of trauma is underestimated, with studies hampered by numerous limitations such as a lack of injury awareness, missing data, poor injury recall, an array of reporting sources, delays in subject response and treatment, no uniform definition of injury or reporting system and predisposing factors prior to injury. Primary mechanisms of injuries are attributed to physical immaturity, fatigue, age and experience, behaviour, the violent nature of the sport and lack of adequate medical intervention. Although there is limited adherence to organized conditioning programmes, when properly planned, sport-specific conditioning may enhance athletic potential, minimize predisposition to injury and enhance recovery. Education in care and rehabilitation should be spearheaded by the medical community to reduce injury, as several studies have linked trauma to poor technique, inexperience and poor judgement. Medical services should encompass emergency medical oversight for trauma at all levels and press toward preventive care. Competitors should also be cognizant of the signs and symptoms of overtraining, a condition exacerbated by overuse and minimal recovery. The use of helmets, taping, bracing, protective vests, cervical collars and mouthpieces is gaining popularity but has not been thoroughly studied. Guidelines requiring padding of chutes, gates or equipment essential for performance may also avert trauma. Whether increases in knowledge, education and technology are able to reduce predisposition to injury among this population, remains to be seen. As with all high-risk sports, the answer may lie in increased wisdom and responsibility of coaches and athletes to ensure an adequate level of ability, self-control and common sense as they compete in this sport.

Validity of the VmaxST portable metabolic measurement system

Abstract The aim of this study was to assess and compare the validity of the portable VmaxST telemetry metabolic measurement device with that of a standard measurement system (Vmax29). Thirty asymptomatic, moderately active males provided written, informed consent and completed two maximal graded treadmill exercise tests (Bruce) using the VmaxST and the Vmax29 metabolic measurement systems. Tests were performed in random order on separate days to obtain peak values for time to exhaustion, heart rate, systolic and diastolic blood pressure, oxygen consumption ([Vdot]O2), carbon dioxide production ([Vdot]CO2), ventilation ([Vdot] E), and respiratory exchange ratio (RER). Multivariate analysis of variance revealed no significant main effect (P = 0.88) between the two systems across any variable, suggesting similar measurement capabilities between the two systems. Linear regression analyses revealed moderate to high coefficients of determination for [Vdot]O2 (r 2 = 0.99), [Vdot]CO2 (r 2 = 0.99), [Vdot] E (r 2 = 0.99), and RER (r 2 = 0.89). Furthermore, Bland-Altman analyses demonstrated that the VmaxST yielded similar values to the Vmax29, suggesting good agreement between the two systems. Agreement was confirmed when the differences between the methods resulted in a small range as identified by the 95% limits of agreement. Findings from the current study confirm that the VmaxST is a valid device for measuring metabolic and physiological variables during exercise within a controlled laboratory setting.

Comparison of V[combining Dot Above]o2peak Performance on a Motorized vs. a Nonmotorized Treadmill

Abstract Morgan, AL, Laurent, CM, and Fullenkamp, AM. Comparison of V[Combining Dot Above]O2peak performance on a motorized vs. a nonmotorized treadmill. J Strength Cond Res 30(7): 1898–1905, 2016—Despite growing popularity of nonmotorized treadmills (NMTs), little data exist regarding responses during exercise testing using this equipment, which is important when providing an appropriate exercise prescription. The purpose of this study was to evaluate physiological and perceptual responses during peak graded exercise tests (GXTs) on a motorized treadmill (MT) vs. NMT. Volunteers (12 men and 12 women aged 18–35 years) performed 2 peak GXT sessions (1 MT and 1 NMT). Respiratory gases and heart rate (HR) were collected each minute; perceptual response was estimated (Borgs 6–20 rating of perceived exertion [RPE] scale) during the final 10 seconds of each stage. Peak values (i.e., V[Combining Dot Above]O2, HR, speed) were determined during the final 10 seconds of each test; ventilatory threshold (VT) was assessed using the V-slope method. Paired t-tests matching variables measured at each stage of the GXT identified significantly higher values on the NMT for V[Combining Dot Above]O2 83% of the time, HR 67% of the time, and RPE 25% of the time. Interestingly though, neither peak V[Combining Dot Above]O2 (48.6 ± 9.2 ml·kg·min−1 vs. 47.8 ± 8.9 ml·kg·min−1), peak HR (185 ± 9 b·min−1 vs. 188 ± 10 b·min−1; p = 0.90), nor VT (72.7 ± 5.7% vs. 73.8 ± 5.4%) were significantly different on the NMT vs. the MT. However, significant differences were identified between NMT and MT tests for time to exhaustion (9:55 ± 1:49 vs. 12:05 ± 2:48; p < 0.01) and peak speed (8.0 ± 0.9 mph vs. 9.2 ± 1.4 mph; p < 0.01). Thus, although peak values obtained were similar between testing sessions on the NMT and MT, the majority of submaximal data were significantly different between trials. These differences are important when designing exercise prescriptions using submaximal values from NMT testing that may be inappropriately high or low at corresponding intensities during training.

The rodeo athlete: sport science: part I

Based on the tradition, history and lore of the American West, as well as the individualistic nature and lifestyle of the sport of rodeo, the rodeo athlete has achieved iconic status in sport, literature, art and entertainment. For over half a century, rodeo has become a staple of organized sport programmes in high schools, universities and international competitions. The origins of rodeo grew from ranch work dating back to the Spanish vaqueros in the 1700s. The sport was officially organized in 1929 and, by the 1930s, championships were determined and the sport of rodeo surpassed baseball and auto racing in spectator attendance. Since then, sponsorship has grown, resulting in extensive worldwide popularity through major media outlets. Despite growing popularity, few investigations exist regarding the scientific aspects of the sport. Rodeo competition is an activity that is basically intermittent in nature, with short periods of highly intense activity. When considering that experience and, thus, improvement in rodeo is achieved solely through constant and punishing practices involving actual and repetitive, human versus livestock competition, the practices closely imitate a sport-specific form of interval training. Studies, which address the anthropometric and performance characteristics of rodeo competitors, reveal that they are comparable to athletes in more traditional sports. The psychological constructs conducive to performance in rodeo have been varied and limited, with most research efforts focused on personality characteristics, sensation seeking and competitive anxiety. Nevertheless, when evaluated relative to higher levels of traditional sport performance, rodeo participants closely resemble their mainstream counterparts. Although efforts to quantify this non-traditional sport are still in the initial stages, information concerning what the optimal fitness level of rodeo athletes should be for maximal performance levels, in a basically anaerobic sport, remains to be determined and is an area for future study. Rodeo performance, as with all sports, is based on a multifactorial array of variables and, therefore, interdisciplinary efforts encompassing expertise across medicine, science and coaching are encouraged. Taking a comprehensive approach in the assessment of athletes, as well as the development and quantification of event-specific training protocols, may ultimately enhance athletic potential, minimize opportunity for injury and possibly provide information to coaches and allied health professionals for the appropriate development and optimal medical care of these athletes.

STABILITY OF RPE INCREASE DURING REPEATED INTERMITTENT SPRINTS

The current investigation examined the potential teleoanticipatory effect on perceptual response during repeated bouts of maximal sprint work. To determine the consistency of ratings of perceived exertion (RPE) increase during identical exercise bouts following variable recovery periods, 16 (8 men, 8 women) participants completed four separate trials of repeated maximal sprinting on 4 separate days utilizing different recovery periods. Following completion of the baseline trial, participants were given variable, counter-balanced recovery periods of 24, 48 and 72 hours, whereupon they repeated the intermittent exercise protocol. To determine the degree of similarity among trials, each individuals rate of RPE progression during each cycle of eight sprints throughout the recovery trials were compared to the rate of progression during the baseline exercise session. A series of 4 (trial) × 3 (cycle of sprints) repeated measures ANOVA were performed to identify significant main effects between trials and among cycles while session RPE was analyzed using one-way repeated measures ANOVA. Fishers least significant difference post-hoc procedures were performed to identify where significant differences occurred when appropriate. Results revealed an inconsistency in the stability of RPE across repeated bouts of sprint exercise, with at least 50% of individuals having a substantial difference in RPE (i.e. ± 1 unit change) in at least one subsequent trial. These variations in perceptual responses were observed despite a concomitant stability of physiological and performance responses between sessions. Results suggest that rate of RPE increase correspond more closely to increased or decreased physiologic strain than to an anticipatory, feed-forward mechanism following variable recovery durations.

Placebo Effect: Influence on Repeated Intermittent Sprint Performance on Consecutive Days.

Abstract Tolusso, DV, Laurent, CM, Fullenkamp, AM, and Tobar, DA. Placebo effect: influence on repeated intermittent sprint performance on consecutive days. J Strength Cond Res 29(7): 1915–1924, 2015—Despite the available literature addressing the placebo effects role in mediating human performance, there is a paucity of research addressing the possibility of a placebo effect both within and between bouts of repeated sprint performance on consecutive days. Therefore, the purpose of this study was to determine whether the administration of a placebo influences recovery during sessions of intermittent sprinting. Ten subjects performed 4 repeated sprint tests under 2 different conditions; 2 while being administered a control beverage separated by 24 hours of recovery and the other 2 with a placebo beverage separated by 24 hours of recovery. Before each sprint test, subjects provided perceived recovery status (PRS). Ratings of perceived exertion were recorded within 5 seconds after each sprint. After each repeated sprint protocol, subjects were asked to provide a rating of perceived exertion (RPE), rate their pain, and provided a blood lactate sample. Power was recorded throughout each session from a nonmotorized treadmill to analyze changes in sprinting performance. Repeated-measures analysis of variance was used to determine significant differences in peak and mean power, PRS, RPE, pain, and blood lactate. The placebo trial produced significantly higher peak (p < 0.001) and mean power (p = 0.002) vs. the control in later sprints absent of any other significant difference in metabolic or perceptual strain (p > 0.05). In conclusion, it seems that the administration of a placebo can attenuate the decline in performance as fatigue increases during repeated sprinting bouts.

The Contribution of Trunk Axial Kinematics to Poststrike Ball Velocity During Maximal Instep Soccer Kicking.

To date, biomechanical analyses of soccer kicking have focused predominantly on lower-extremity motions, with little emphasis on the trunk and upper body. The purpose of this study was to evaluate differences in trunk axial kinematics between novice (n = 10) and skilled (n = 10) participants, as well as to establish the relationship of trunk axial motion and sagittal plane thigh rotation to poststrike ball velocity. Three-dimensional body segmental motion data were captured using high-resolution motion analysis (120 Hz) while each participant completed 5 maximal instep soccer-style kicks. The results demonstrate that skilled participants use 53% greater axial trunk range of motion compared with novice participants (P < .01), as well as 62% greater peak trunk rotation velocity (P < .01). The results also show a moderate, positive correlation of peak trunk rotation velocity with poststrike ball velocity (r = .57; P < .01), and peak hip flexion velocity with poststrike ball velocity (r = .63; P < .01). The current study highlights the potential for trunk rotation-specific training to improve maximum instep kick velocity in developing soccer athletes.

A Comparison of Both Motorized and Nonmotorized Treadmill Gait Kinematics to Overground Locomotion

CONTEXT Motorized treadmills (MTs) present an altered motor task compared to overground (OG) locomotion in that MT belt surfaces are motor-driven, whereas individuals walking/running OG must propel themselves. A possible solution may lie with novel nonmotorized treadmill (NMT) devices as the belt surface is propelled by the user. OBJECTIVE The purpose of this study was to compare gait performance during both MT and NMT locomotion to OG. DESIGN Crossover study. SETTING A university research laboratory. PATIENTS A total of 20 healthy adults (10 women) participated in the study. INTERVENTION Each participant performed self-selected walking and running OG, and on both an MT and NMT. MAIN OUTCOME MEASURE Shoulder, trunk, and lower-extremity kinematics were analyzed for each treadmill condition and compared to OG. RESULTS The analyses demonstrated that there were no differences between MT and OG gait kinematics during either walking or running. However, NMT gait showed increased hip, knee, and ankle flexions in late swing and early stance compared to OG during both walking and running. For example, during walking, the NMT elicited hip-, knee-, and ankle-flexion/extension angles of 34.7°, 8.0°, and 3.6° at foot strike compared to 24.8°, -3.1°, and -5.8° in the OG condition (P < .05). There was also a significant reduction in trunk-flexion/extension range of motion during running compared to OG (7.7° in NMT vs 9.8° in OG). CONCLUSIONS These differences may have implications for both training and rehabilitation on an NMT. Future studies should consider the influence of NMT familiarization on gait performance and should emphasize the assessment of neuromuscular performance.