Characteristics of Lower Extremity Work During the Impact Phase of Jumping and Weightlifting

Below is a great article from the latest issue of the Journal of Strength and Conditioning Research from Loren Chiu and his research group at the University of Alberta. This is very important as most only focus on the concentric explosive triple extension, but must remember that Olympic lifts also teach us to resist triple flexion.

Many sports, such as basketball and volleyball, include jumping activities. Jumping involves 3 general phases: (a) propulsion, (b) flight, and (c) landing. The landing phase is also described as the impact phase, as it involves a collision between the falling body and the ground. At impact, the body possesses kinetic energy as a result of the conservation of energy from the initial drop height potential energy. After impact, work is performed using eccentric muscle loading to absorb this kinetic energy (Devita and Skelly, 1992; Fry et al., 2003).
Previous research found the technique used to land from a jump influences the work performed at the hip, knee, and ankle. Bobbert et al., (1987) compared the impact phase of bounce and countermovement drop jumps, where bounce drop jumps had less ankle dorsiflexion and knee flexion than countermovement drop jumps. In bounce drop jumps, more work was performed at the ankle, whereas in countermovement drop jumps, work performed at the knee was greater. Similarly, Devita et al. (12) compared landings with greater and less than 90-degree angle of knee flexion. Landings with greater knee flexion required more work to be performed at the knee.
Impact is not unique to landing from a jump. Movements in the sport of weightlifting also involve propulsion, flight, and impact phases. In weightlifting, impact is a result of (a) the feet returning to the ground after a momentary separation and (b) receiving the barbell on the shoulders (i.e. clean) or overhead (i.e. snatch) which occurs when the feet contact the ground (8). Similar to landing from a jump, eccentric muscle loading is required to perform work and absorb energy present at impact during weightlifting.
Chiu 1

Methods
Ten women athletes (volleyball and weightlifting) participated in the investigation.  Athletes were involved in the following: (a) sports with jumping activities and (b) strength and conditioning training involving weightlifting exercises. All participants had been taught to perform the clean and power clean by a certified weightlifting coach. Further, they had a minimum of 6 months experience performing these exercises under the supervision of the coach.

Participants completed 2 sessions, spaced approximately 1 week apart. During the first session, maximal countermovement jump height was determined. Jump height was used to determine the height of the drop landing. Drop landings were performed by standing on a box adjusted to the maximum jump height, stepping off the box, and landing on 2 feet. Participants watched an instructional video followed by performing 5 jump and five drop landing trials. The video instructed participants to do the following:

  • Land with feet symmetrical
  • Land with knees and ankles bent
  • Land with feet flat
  • Land with the body upright; avoid leaning forward
  • Absorb the landing using muscle tension

In the second session, participants performed jump and drop landings, power cleans, and cleans while data were collected using 3D motion capture techniques. Participants performed 4 repetitions of maximal effort block jumps with landings, followed by 4 repetitions of drop landings from a height equal to their previously determined maximum vertical jump height. Power clean and clean exercises were performed with a barbell load of 80% of the participant’s 1RM clean. Three sets of 2 repetitions were performed for each of the power clean and clean. Sets of power cleans and cleans were alternated to prevent an ordering effect.
Chiu 2

Motion Analysis
Work performed at the hip, knee, and ankle were calculated during the landing and receiving phases of jumping and weightlifting tasks, respectively. Additionally, segment and joint kinematics and net joint moments were determined.

Chiu 3

Results
The most lower extremity work was performed in the clean and drop landing, followed by landing from a jump, and the least work was performed in the power clean (p < 0.05). For all tasks, work performed by the knee extensors was the greatest contributor to lower extremity work. Knee extensor net joint moment was greater in the power clean than jump and drop landings, and greater in the clean than all other tasks (p < 0.05). Knee flexion angle was not different between the power clean and jump landing (p > 0.05) but greater in the drop landing and clean (p < 0.05).

Chiu 4
Conclusion
To absorb the kinetic energy present at contact, work must be performed ideally by muscles. If muscles are not able to perform work, energy may be absorbed by connective tissue, including ligaments and bones, which may result in injury (Mills et al., 2009). To absorb energy in landing activities, strength of the knee extensors is critical. Weightlifting tasks share similar biomechanics to landing from a jump but require greater knee extensor effort. Thus, the power clean and clean may be used to develop knee extensor strength appropriate for landing from a jump. In particular, the clean requires greater knee extensor loading than the power clean, which is a similar comparison to the knee extensor loading in full versus partial squat exercise (Bryanton et al., 2012). Weightlifting exercises such as the snatch, clean, and variations of these lifts are commonly used in strength training programs; however, there is an emphasis on the propulsion or pulling phase (Chiu and Schilling, 2005). The present research finds that there are benefits to receiving the barbell in weightlifting exercises, especially in the deep squat position. Strength and conditioning professionals should be aware of the benefits of weightlifting exercises such as the clean and snatch performed through a full range of motion. Athletes in sports involving impact activities, such as jumping and landing, should incorporate the clean exercise to develop the strength and flexibility required to absorb energies during impact.

Moolyk, AN, Carey, JP, and Chiu, LZF. Characteristics of lower extremity work during the impact phase of jumping and weightlifting. J Strength Cond Res 27(12): 3225– 3232, 2013

Advertisements

The Back Squat and the Power Clean Elicit Different Degrees of Potentiation

Thirteen elite junior rugby league players took part in the investigation. All participants  were engaged in a regular training program that utilised combined maximal strength and power training for at least one year and were able to squat a minimum of 1.5 x their body mass.

The study required the participants to complete one familiarisation and three experimental sessions in order to compare the acute effects of the back squat and the power clean on PAP responses during a sprint test. During the familiarisation session the subject 1RM in the power clean and back squat were determined. The three experimental testing sessions were then completed in a randomised order, at the same time of day over a 2-week period. During the experimental sessions, the participants were required to perform 20-m sprints before and 7 minutes after one of the two conditioning activities (one set of three back squat at 90 % 1RM, one set of three power cleans at 90 % of 1RM) or after a control condition.

Potentiation and Control Protocols
Two minutes after the determination of the baseline sprint, the participants performed one of the following activity: 1) one set of three back squats at 90 % 1RM, 2) one set of three power cleans at 90 % 1RM or 3) a control condition (one 20-m sprint). Following a 7-min recovery period, the post-measurement 20-m sprint was performed.

Results

  • There was a significant interaction (time × condition) effect for PAP during the sprint test (p <0.05). Post-hoc analyses revealed a significant improvement in 20-m sprint time, velocity and average acceleration after both the set of back squats and the set of power cleans with no significant changes observed after the control condition.
  • The set of power cleans induced a significantly (p= 0.042; ES= 0.83) greater improvement in 20-m sprint time (3.05 ± 1.08 %) when compared to the set of back squats (2.16 ± 1.07 %).
  • The improvement in velocity was significantly greater (p= 0.047; ES= 1.17) after the set of power cleans (3.22 ± 1.15 %) than after the set of back squats (2.25 ± 1.11 %). The improvement in average acceleration was also significantly greater (p= 0.05; ES= 0.87) after the set of power cleans (6.61 ± 2.36 %) than after the set of back squats (4.59 ± 2.26 %).
  • The percent improvement in 20-m sprint time (i.e., PAP) had a large correlation with the relative 1RM back squat (r= 0.56; p= 0.04) and the relative 1RM power clean (r= 0.63; p= 0.02). Conversely, the absolute 1RM back squat (r= 0.49; p= 0.09) and the absolute 1RM power clean (r= 0.54; p= 0.06) were not significantly correlated to the improvement in the 20-m sprint time.
  • 20-m sprint time displayed a large correlation to the relative power clean strength (r= -0.64; p= 0.02) and the relative back squat strength (r= -0.57; p= 0.04). The 20-m sprint time also displayed a large correlation to the absolute power clean strength (r= -0.62; p= 0.02) and the absolute back squat strength (r= -0.60; p= 0.03).

Conclusion

  • Both the back squats and powers clean resulted in a significant PAP effect during a 20-m sprint performance test.
  • Additionally, the magnitude of PAP response was significantly greater following the power clean conditioning activity. One set of three power cleans performed at 90 % 1RM resulted in a significantly (p= 0.042; ES= 0.83) greater PAP response (3.05 ± 1.08 %) when compared to the PAP response (2.16 ± 1.07 %) to three back squats performed at 90 % 1RM.
  • The magnitude of PAP during a 20-m sprint was greater following the set of power cleans than the set of back squats may potentially be explained by the sprint start used and the kinematics associated with sprinting. The sprint start is thought to be highly dependent on ‘speed strength’ and maximal power production and the power clean allows for the production of high-forces at high-velocities resulting in higher power outputs. Conversely, the back squat allows the production of high-forces at low-velocities resulting in lower power outputs. Therefore, the execution of the set of power cleans might have allowed the participants to acutely produce a better acceleration than after the set of back squats, allowing them to run the 20-m distance quicker.
  • 20-m sprint performance can be improved if one set of three back squats or power cleans performed at 90 % 1RM is performed 7 minutes prior to a maximal 20-meter sprint effort. Additionally, the magnitude of improvement is greater following a set of power cleans in comparison to a set of back squats.

The Back Squat and the Power Clean elicit Different Degrees of Potentiation. Seitz LB, Trajano GS, Haff GG. International Journal of Sports Physiology and Performance

 

Relationship Between Functional Movement Screen and Athletic Performance

Tests such as the functional movement screen (FMS) and maximal strength (repetition maximum strength [1RM]) have been theorised to assist in predicting athletic performance capabilities. Some data exist concerning 1RM and athletic performance, but very limited data exist concerning the potential ability of FMS to assess athletic performance.

Functional movement screen (FMS) to assess performance in a series of self-described physical activities (unloaded deep squat, hurdle step, in-line lunge, shoulder mobility, active straight leg raise, trunk stability push-up, rotary stability). The 7 movement patterns are claimed to be conceptualized on the basis of the complex movement patterns found in sport such as jumping, running, and agility (Minick et al., 2010). A 4-point scale (0 = pain was associated with movement pattern, 1 = unable to perform movement pattern, 2 = compensation was present to complete movement pattern, and 3 = movement pattern was performed as described) is used based on the subjective analysis of each movement pattern with specific characteristics listed for each score.

1RM has been shown to relate to jumping, sprinting, and agility capabilities, including sport-specific skills (Keogh et al., 2009; McBride et al., 2009). Nuzzo et al., (2008) reported a significant correlation between 1RM in the squat and countermovement jump peak power, velocity, and jump height. McBride et al., (2009) found significant correlations between 1RM in the squat and 10- and 40-yd sprint times. Wisloff (2004) also reported significant correlations between 1RM in the squat and 10- and 30-m sprint times (r = 20.9, r = 20.7). In relation to sport-specific skills, Keogh et al., (2004) reported that the 1RM in the back squat was significantly correlated to club head velocity in golfers. The 1RM has also been shown to be related to performance in other sports such as basketball, baseball, tennis, and football (Kraemer et al., 2003; Hoffman et al.,2009; McBride et al., 2009).

Methods
Twenty-five National Collegiate Athletic Association (NCAA) Division I golfers (15 men, age = 20.0 ± 1.2 years, height = 176.8 ± 5.6 cm, body mass = 76.5 ± 13.4 kg, 1RM back squat = 97.1 ± 21.0 kg) (10 women, age = 20.5 ± 0.8 years, height = 167.0 ± 5.6 cm, body mass = 70.7 ± 21.5 kg, 1RM back squat = 50.3 ± 16.6 kg) participated in the investigation.

  • FMS – unloaded deep squat, hurdle step, in-line lunge, shoulder mobility, active straight leg raise, trunk stability push-up, and rotary stability. Each of the 7 movements was scored from 0 to 3.
  • 1RM Back Squat (thigh parallel to the floor)
  • VJ
  • 10 and 20-m sprint times
  • Agility T-test
  • Club Head Swing Velocity

Results

  • No significant correlations were found between FMS and any of the performance variables (10 and 20-m sprint, VJ, and T-test).
  • The 1RM was significantly correlated to CHSV (r = 0.805, p = 0.0001). The 1RM was also significantly correlated to VJ (r = 0.869, p = 0.0001), 10-m sprint (r = 20.812, p = 0.0001), 20-m sprint (r = 20.872, p = 0.0001), and T-test (r = 20.758, p = 0.0001).
  • The FMS score from each individual test (unloaded deep squat, hurdle step, in-line lunge, shoulder mobility, active straight leg raise, trunk stability push-up, rotary stability) were also compared with 10 and 20-m sprint, VJ, T-test, and CHSV. No significant relationships existed between any of the individual test and the athletic performance tests.

Conclusion
Based on the data from the current investigation, the FMS is not a useful tool for determining possible athletic capabilities, specifically in golf. In fact, higher FMS scores may falsely lead a practitioner to assume increased athletic capabilities when in actuality higher scores relate to poorer performances in tests such as the medicine ball throw or agility T-test times. The squat 1RM was a very strong predictor of athletic performance such as sprinting, jumping, and agility performance. It is likely that the FMS fails to relate to athletic performance in that it does not assess strength, which has been shown to be a major component of athletic performance. In conclusion, FMS should not be used to assess
athletes and strength and conditioning coaches should use 1RM squat determination as a very important assessment tool as a component for the determination of athletic performance.

Parchmann, CJ and McBride, JM. Relationship between functional movement screen and athletic performance. J Strength Cond Res 25(12): 3378–3384, 2011