Three of the most popular methods to increase lower-body strength and power are the squat, deadlift, and the Olympic-style lifts (5,17,18). These methods are frequently used by strength and conditioning coaches to enhance the physical qualities of athletes in hopes to transfer to sporting actions such as sprinting speed, change of direction (COD) speed, and jumping performance. These lifts have been supported in many cases in past literature (9–11,18–21,26,32,35,40,44,46–48) but may be limited in their transfer in advanced athletes because of their vertically loaded nature (1,6,12,14,23,41,43,49,50). A possible shortcoming of these exercises is that they are all vertically loaded; the load is applied in a vertical manner to the body. This differs from horizontally loaded movements, where the load is applied perpendicular to the body. Horizontally loaded movements may be beneficial for more horizontally based movements such as horizontal jumping, acceleration, and sprinting (2,6,12,41), whereas vertical-based movements may be better for vertically oriented movements. Athletes must be able to express strength, power, and speed in multiple directions, and it may be beneficial to emphasize horizontally based movements in strength and conditioning programs. This literature review addresses this contention by (a) investigating the literature on the back squat, deadlift, and Olympic-style lifts, (b) investigating the literature on shortcomings of the back squat, deadlift, Olympic-style lifts, and potential for horizontally loaded exercises, and (c) suggestions for coaches and future research.
The back squat is regarded as one of the most effective exercises to enhance athletic performance because of it being a multijoint movement that strengthens the prime movers needed to express explosive athletic movements (17). Recently, Seitz et al. (44) conducted a meta-analysis on the transfer of back squat training to sprinting. This meta-analysis included 15 studies, consisting of 510 subjects [no sex or age restrictions]. Inclusion based on (1) randomized control studies, (2) studies using instruments with high reliability and validity, (3) studies where the sprint test was conducted pretraining and posttraining, and (4) studies where the strength test was conducted using a free-weight [full, parallel, or half] back squat exercise) and found that back squat strength significantly correlated (r = −0.77; P = 0.0001) with sprinting speed. The researchers concluded lower-body strength, via the back squat, should be a relevant training regimen for athletes (44). López-Segovia et al. (32) studied 14 under-21 soccer players and showed power produced in the full squat is an important factor to explain short sprint performance (r = −0.79; P ≤ 0.01). Also, McBride et al. (35) performed a study with 17 male Division I-AA football athletes and recorded 1-repetition maximum (1RM) in the back squat in comparison with sprint times in the 5-, 10-, and 40-yard sprints. The overall results suggest that athletes with a 1RM/body mass of 2.10 or higher had significantly faster sprint times than those with a 1RM/body mass of 1.90 or below. These findings support other cross-sectional studies showing a close association between relative strength in the back squat and sprinting speed (10,11,48). The back squat has also been shown to be effective at improving vertical jump and COD speed (9,11,26,40,48). Chelly et al. (9) demonstrated training with heavy half back squats, twice a week for 2 months, increased jump performance, sprint performance (0–40 m), and peak power output in junior soccer players. Keiner et al. (26) studied 112 soccer players, aged 13–18, in a 2-year long-term strength development program. Subjects in the control group only participated in normal soccer training, whereas the experimental group performed strength training (back squats, front squat, and deadlifts) in addition to normal soccer training. After 2-years, the strength trained group showed significantly faster COD times, and the researchers concluded that long-term strength development in the squat is related to improved performance in COD sprints for adolescent athletes. Peterson, Alvar, and Rhea (40) investigated 54 men and women freshman collegiate athletes (men's and women's basketball, baseball, softball, and volleyball) and compared 1RM strength in the back squat with vertical jump, standing broad jump, cone t test, 20-yard acceleration, and 40-yard sprint. Peterson, Alvar, and Rhea determined that there was correlation between relative back squat strength and all the performance tests. Peterson, Alvar, and Rhea concluded that the relative strength in the back squat and measures of power, jumping ability, agility, linear sprint acceleration, and sprinting speed were strong.
The deadlift is popular among powerlifters and is regarded as an important exercise for athletes seeking to improve strength and power (5). A recent study by Laffaye et al. (28) examined 273 elite (college and professional) athletes (primarily football, basketball, baseball, and volleyball players) and the different variables that make up a successful vertical jump. The researchers determined that concentric force and eccentric rate of force development are the 2 most important qualities to determine jumping height, and therefore, suggested the deadlift as being a major exercise in improving concentric force development. This supports Robbins (42) who concluded that peak muscle activation in the deadlift is very similar to the peak muscle activation of a countermovement jump. Swinton et al. (46) studied 30 male rugby union players and demonstrated that relative strength in the deadlift was associated with faster sprinting speeds and higher vertical jumps. In fact, the researchers concluded that for the 30-m sprints and vertical leap, as much as 90% of the performance variation can be explained by relative strength and average/peak power output in the deadlift. Last, Thompson et al. (47) studied 34 novice subjects through a 10-week, twice per week, deadlift training protocol. Posttraining testing resulted in a 7.4% increase in vertical jump and an 18.8–49.0% increase in rate of torque development (47).
The Olympic-style lifts are programmed to improve power and speed as they are performed at very high speeds and produce high-power outputs that are thought to have good transfer to athletic movements (18,21). A classic study by Garhammer (18) determined that peak power output during the Olympic-style lifts, specifically the second pull, produced far greater peak power outputs (400% greater) than the back squat, deadlift, or bench press. Hackett et al. (19) performed a systematic review to compare the effects of weightlifting, traditional resistance training, and plyometrics on vertical jump height. The researchers included 232 subjects (175 athletes and 57 physical education students) with resistance training experience and concluded that weightlifting results in an average of 5.1% greater vertical jump when compared with traditional resistance training. Hoffman et al. (20) explored 20 Division III collegiate football players on the effects of a 15-week training program of lifting compared with a program of powerlifting on 40-yard sprint times, vertical jump, agility, and strength. The researchers concluded that the weightlifting group improved 40-yard sprint (0.07 ± 0.22 seconds versus 0.04 ± 0.19 seconds), vertical jump (6.8 cm ± 6.1 versus 0.5 ± 6.8), and lower-body strength (22.5 ± 31.5 kg versus 18.9 ± 33.1 kg) to a greater extent than the powerlifting group (20). In another study, McBride et al. (34) recruited national level Olympic weightlifters (n = 6), powerlifters (n = 8), and sprinters (n = 6) and tested each group in 1RM back squat, jump squat tests, and vertical jumps with various loads performed. The researchers suggested that the weightlifting group produced significantly higher peak forces, power outputs, velocities, and jump heights in comparison with the powerlifting group and were significantly stronger than the sprinter group (34). The researchers concluded that strength and power characteristics are specific to each group and are influenced by the training protocols used (34).
SHORTCOMINGS OF VERTICAL EXERCISES
Direct transfer to improve sports performance using the back squat, deadlift, or Olympic-style lifts may be limited by the nature of the exercise and/or by the experience level of more advanced athletes (1,6,12,14,23,41,43,49,50). Young (50) reviewed the transfer of traditional strength exercises, such as the back squat, deadlift, and Olympic-style lifts, on sports performance. Young (50) stated that exercises involving bilateral contractions of the leg muscles resulting in vertical movement, such as squats, deadlifts, and Olympic-style lifts, have minimal transfer to performance in advanced athletes. Although general strength training might be beneficial for athletes because of the potential to enhance the force-generating capabilities of muscle, direct transfer to improve sports performance might be limited in experienced athletes (50). To maximize transfer to on-field performance, training should be as specific as possible, especially with regard to movement pattern and contraction velocity (6,14,50). The efficiency and effectiveness of bilateral, vertical exercises have been questioned as it has been shown that it takes exceptionally large increases in 1RM back squat strength (∼23 to 27%) to only slightly increase sprinting speed (2–3%) (14,23). Rumpf et al. (43) performed a review looking at the effects of various types of training on sprint performance in highly trained athletes (international level) versus recreational athletes. They grouped training methods into specific (sprinting or resisted sprinting) and nonspecific (resistance training). Although nonspecific training methods were found to be effective, mainly for recreational subjects, they were much less effective for highly trained athletes. Specific training methods proved to be superior for high-level athletes, leaving the researchers calling for the use of specific training methods to enhance performance in highly trained subjects (43). Barr et al. (1) showed that significant increases in power clean strength in elite rugby players over the course of 1 year did not yield any improvements in sprinting speed. They concluded that while increasing strength is likely important for players with low training experience, it may not have the same effect with highly trained athletes (1). When it comes to transfer to sporting movements such as COD speed, Jullien et al. (24) demonstrated that lower-body strengthening, via the back squat, failed to improve COD when compared with technique and coordination work in young professional male soccer athletes. These findings support the Brughelli et al. (6) review of training studies on COD ability. This review concluded that traditional strength and power training, performed bilaterally in the vertical direction, have mostly failed to elicit improvements in COD performance. Instead, utilization of exercises that more closely mimic the demands of COD, such as horizontal jump training, lateral jump training, and specific COD training have shown to be effective at improving COD performance (6). Hori et al. (22) investigated whether the athlete who has high performance in hang power clean also has high performances in sprinting, jumping, and COD. Twenty-nine semiprofessional Australian rules football players were tested for 1RM strength in the hang power clean and were separated into 2 groups—strongest 14 into the higher performance group; weakest 14 into the lower performance group (excluded the middle athlete). Overall, there was no significant difference between groups in 5-5 COD time. The researchers concluded that strength characteristics of the hang power clean differ from those needed for successful COD performance (22). Young et al. (49) studied 15 males aged 18–28 and compared various COD speed cuts with lower-body strength and power, measured by an isokinetic squat. The authors deduced that there was no significant correlation between the 2 measures and therefore suggested that training designed to increase leg strength and power as a means to enhance COD is not conclusively supported (49).
A potential reason for the gap between strength in vertically oriented exercises, such as the squat, deadlift, and Olympic-style lifts, is the lack of specificity to horizontal planar movement. Several research studies have concluded that horizontal force application is related to faster sprinting speeds (7,15,25,37,38,41). Buchheit et al. (8) analyzed the horizontal forces of 86 elite youth soccer players during sprinting. The researchers found that horizontal force was significantly correlated with acceleration speed (10 m), suggesting that horizontal forces may be important for acceleration performance. Lockie et al. (31) echoed this by summarizing, in order to increase acceleration speed, it is important to develop specific horizontal strength and power. Randell et al. (41) highlighted the concern to the possible shortcomings of vertically loaded exercises, such as the back squat, deadlift, and Olympic-style lifts, and noted that the effectiveness of a gym-based lower-body resistance-training program with a horizontal component has not been fully investigated, citing a gap in strength and conditioning research. This gap in the literature, potentially, means that horizontally loaded movements may have greater transfer and benefit for acceleration and sprinting speed than vertically loaded exercises.
A training quality of both horizontally and vertically oriented exercises is full hip extension, which has been proposed as a key factor for improved sprinting, jumping, and lateral movement speed (3,12,45). The gluteal and hamstring musculature are the main drivers of powerful hip extension, and increasing strength and power in these muscles, may help horizontal-based movements (13). This may be of importance because as sprinting speeds increase, the activity of the gluteal and hamstring musculature also increase (2,3,7,16,27,30). It is proposed that horizontally loaded movements may be superior to vertically oriented movements in eliciting gluteal and hamstring activation, which may lead to greater transfer to horizontal strength and power (12). Recently, a study recorded electromyography (EMG) in 13 trained females during a horizontally based exercise, the hip thrust, and a vertically based exercise, the back squat (13). The barbell hip thrust elicited significantly greater mean (69.5 versus 29.4%) and peak (172 versus 84.9%) upper gluteus maximus, mean (86.8 versus 45.4%) and peak (216 versus 130%) lower gluteus maximus, and mean (40.8 versus 14.9%) and peak (86.9 versus 37.5%) biceps femoris EMG activity than the back squat. The researchers concluded the need for further investigation to see if this increased activation of muscle tissue would lead to greater hypertrophy, strength, and performance benefits (13). McGill et al. (36) demonstrated a horizontally based exercise, the kettlebell (KB) swing, with just 16 kg elicited as a maximal voluntary contraction of 80% for the gluteal muscles. The KB swing has also been shown to be equally effective as Olympic-style lifts and squats at improving vertical jump, despite using lighter loads (29,39). Lake et al. (29) determined that peak and mean power during the KB swing were greater than the back squat and comparable with the jump squat. The KB swing also recorded the highest net impulse with 32 kg (276.1 ± 45.3 N·s versus 60% 1RM back squat: 182.8 ± 43.1 N·s, and 40% jump squat: 231.3 ± 47.1 N·s). These findings indicate that the large mechanical demand during the KB swing could make the KB swing a useful addition to strength and conditioning programs that aim to develop the ability to rapidly apply horizontal force (29). Not only is horizontal hip extension good for sagittal plane-based movements, but Shimokochi et al. (45) assessed 28 female college basketball players and concluded that greater hip extension velocity explained better lateral cutting and sliding maneuvers, and training hip extension velocity may be crucial for better lateral acceleration and deceleration. Finally, McGill et al. (36) also noted that the unique horizontal loading pattern during the KB swing puts forces on the spine which is opposite to traditional lifts such as deadlift, back squat, and Olympic-style lifts. This may be why many individuals credit KB swings with restoring and enhancing back health and function (36).
Although general strength training, such as vertically oriented exercises, is beneficial for athletes because of the potential to enhance the force-generating capabilities of muscle, the direct transfer of such exercises to improve sports performance might be limited in experienced athletes or athletes requiring horizontally dominated movements (50). Young (50) reviewed the transfer of traditional strength training on sports performance and stated that exercises in the vertical plane, such as squats, deadlifts, and Olympic-style lifts, have minimal transfer to performance in advanced athletes (50). To maximize transfer to on-field performance, training should be as specific as possible, especially with regard to movement pattern and contraction velocity (6,14,50).
It is proposed that horizontally oriented movements may be superior to vertically oriented movements in eliciting gluteal and hamstring activation, which may lead to greater transfer to horizontal strength and power (12). Contreras et al. (2015) demonstrated that a horizontal-based movement elicited significantly greater mean (69.5 versus 29.4%) and peak (172 versus 84.9%) upper gluteus maximus, mean (86.8 versus 45.4%) and peak (216 versus 130%) lower gluteus maximus, and mean (40.8 versus 14.9%) and peak (86.9 versus 37.5%) biceps femoris EMG activity than the back squat. This is important as several previous research studies have shown that as sprinting speeds increase, the activity of gluteal and hamstring musculature also increases (2,3,7,16,27,30). In addition, several research studies have concluded that horizontal force application is related to faster sprinting speeds and COD (7,15,25,37,38,41,45). This leads to the need for further investigation whether these relationships exist in training studies with high-level athletes.
In conclusion, the effectiveness of a gym-based lower-body resistance-training program with a horizontal component has not been fully investigated (41). Further research needs to be conducted to determine whether recent EMG research showing increased muscle activation during horizontally oriented movements (13) leads to superior strength, power, speed, and on-field transference compared with vertically loaded exercises.
The use of a horizontally based training regimen has yet to be investigated and compared against a vertically based training regimen. Vertically oriented exercises have been demonstrated to be effective (9–11,18–21,26,32,35,40,44,46–48), but this effectiveness is diminished in experienced athletes and in transfer to specific physical qualities (1,6,12,14,23,41,43,49,50). This does not mean that vertically loaded movements should be omitted. They are important and have their place in any strength and conditioning program, but the use of horizontal-based movements may have greater transfer to certain aspects of sports performance. It should be noted that athletes who require specific performance in the horizontal, vertical, lateral, and/or rotational planes, engage in exercises containing those specific movements.
The following are practical exercises to maximize horizontal strength, power, and speed. Further research needs to be conducted in athletic populations to continue to distinguish differences in performance of horizontal movements versus vertical movements. These weight room exercises would be in addition to movement exercises such as sprinting, bounding, horizontal jumping, and sled pushing/towing.
- Hip thrust/barbell glute bridge—Contreras et al. (13) performed EMG on the hip thrust and back squat and demonstrated that the hip thrust activated greater levels of gluteal and hamstring musculature compared with the back squat, giving reason for future research to continue investigation of the hip thrust's effects on performance.
Just as the back squat and deadlift are loaded for various goals, the same is applied for the hip thrust. It should be loaded and subscribed volume for various goals from hypertrophy, strength, and even power, just as one would for the back squat or deadlift (see Video, Supplemental Digital Content 1, http://links.lww.com/SCJ/A200).
- KB swings—KB swings may be a great alternative to Olympic-style lifts in their ability to create violent hip extension (29,33,36,39).
The KB swing is an explosive movement and should be performed at high velocities for 3–6 sets for 5–12 reps with adequate recovery (90–120 seconds) between sets. The use of bands can also be applied to provide higher eccentric forces and greater power output.
- Reverse hyperextensions—Reverse hyperextensions are unique and they are open chained, and the hip extensors must work “in the air” not through the ground. In sprinting, the hip extensors are vitally important during flight to accelerate the leg-to-ground contact (4), so training the hip extensors without ground support may be a valuable tool to carryover to this action.
Reverse hyperextensions can be performed with both legs or a single leg for 2–5 sets of 8–15 reps with 60–90 seconds of rest between sets. They can be loaded using a traditional reverse hyperextension machine or can be loaded with bands or manual resistance by a partner.
- Hip extension—Commonly known as back extensions, but the intent of this movement is hip extension by gluteal and hamstring contraction rather than using the erectors to extend the lumbar spine.
The hip extension is great for addressing strength at length for the hamstrings and is optimal for 2–5 sets of 8–20 with 60–90 seconds of rest between sets.
- Pivot press—The pivot press uses the common landmine bar positioning to allow a horizontal bar path to occur. The pivot press expresses horizontal force transmission from the lower body to the upper body and closely mimics the demands of blocking and tackling in football and rugby.
The pivot press should be performed for sets of 2–5 for reps of 4–8 with 2 minutes of rest between sets. The intent should be to move the weight as fast as possible (see Video, Supplemental Digital Content 2, http://links.lww.com/SCJ/A201).
- Jammer sprint—The jammer machine allows horizontal resistance in a single leg action that mimics acceleration action. The jammer sprint should be used for 4–6 reps each leg for 2–4 sets with full recovery (2+ minutes) between sets (see Video, Supplemental Digital Content 3, http://links.lww.com/SCJ/A202).
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